SCIENTIFIC SERVICES PROJECT
(USA Track & Field)
HIGH JUMP #32 (Men)
Jesus Dapena and Travis K. Ficklin
Biomechanics Laboratory, Dept. of Kinesiology, Indiana University IMPORTANT INFORMATION FOR THE COACH:
If one of your high jumpers was studied in our project, we hope yo u will find the information in this report helpful for the coaching of your athlete.
Although the hi gh jump has been one of the most intensely studied events in track and field, knowledge of it is st ill imperfect, and there is room for doubts and disagreements. We have tried to give you what we believe are the best poss ible recommendations, based on the biomechanical information that is presently available, but we do not pretend to have all the answers. We hope yo u do not feel that we are trying to force our ideas on yo u, because that is definitely not our intent. Use what you like, and ignore what you don't like. If you find any part of this report useful in any way, we will feel that it has served its purpose.
Here is how we suggest that you use the report:
• Read the main te xt of th e report (" Di scuss ion of high jumping technique, and general analysis of results"). Try to follow the logic that we used to arrive at our conclusions.
• If yo u feel comfortable with our logic, and it fits with your own ideas, try to implement our recommendations as described in "Specific recommendations for individual athletes". Throughout the report, keep in mind that "c.m." stands for "center of mass", a point that represents the average position of the whole body. This point is also called somet im es the "center of gravity".
• If yo u do not agree with our logic, we still hope that yo u will find our data useful for reaching yo ur own conc lusion s.
NOTE FOR PREVIOUS READERS OF THESE AND OTHER REPORTS: The masses or weights of the segments that make up the body of an individual athlete are not known exactly, and neither are the moments of inertia nor other important mechanical characteristics of the segments of the human body. Therefore, researchers have to work with estimates of those values, and different researchers work with different estimates. The methods used for the ca lculation of mechanical information (for instance: three-dimensional coordinates of body landm arks, center of mass position, angular momentum) also vary from one researcher to another. Because of this, it is often not advisable to compare the data from reports produced by different laboratories.
Even within our own laboratory, some definitions have changed from one report to another. Also, some of the data are calculated with progressively improved methods which give more accurate values. Therefore, the data in this report may not be strictly comparable with data presented in previous reports. However, all values given in the present report were computed usi ng the same method, because any data for jumps from prev ious years were re ca lcul ated. Therefore, all the data presented in this report, including data for jumps made in previous years, are compatible with each other.
Jesus Dapena Department of Kinesiology HPER 11 2 Bloomington , November 13, 2007 Indiana University Bloomington, IN 47405 U.S.A.
telephone: (8 12) 855-8407 email : dapena@indi ana .edu II
TABLE OF CONTENTS page
INTRODUCTION ...... I
GENERAL METHO DOLOGY ...... 1 Vid eotaping and se lecti on of tri als ...... ! Vid eo analys is ...... I Seq uences ...... I Subject characteri sti cs and meet res u Its ...... I
DISCUSSION OF HIG H JUMPING TECH NI QUE, AN D GENERAL ANALYSI S OF R ESULTS ...... ! General characteristics of th e run-up ...... 2 Approach angles ...... 2 Progression of th e run-up ...... 2 Horizontal velocity and height of th e c. m. at th e end ofthe run-up ...... 3 Vertical velocity of the c. m. at th e start of th e takeoff phase ...... !! Ori entati on of the takeoff foot, and potenti al for ankle injuries ...... 12 Trunk lean ...... 12 Arm and lead leg acti ons ...... 15 Takeoff tim e ...... 17 Change in hori zo ntal velocity during the takeoff ph ase ...... 17 Height and verti cal ve locity of th e c. m. at th e end of th e takeoff ph ase ...... 17 Height of th e bar, peak height of th e c.m ., and clearan ce height ...... 19 Takeoff distance ...... 20 Angul ar momentum ...... 20 Adj ustments in th e air ...... 28 The twist rotat ion; problems in its execution ...... 3 1 Co ntrol of airborne movements; computer simulation ...... 33
SPEC I FI C RECOMM ENDATIONS FOR IN DIV IDUAL ATHLETES ...... 35 Dilling ...... 35 Harri s ...... 44 Hutch in son ...... 52 Littleton ...... 6 1 Moffatt ...... 70 Nieto ...... 79 Se ll ers ...... 88 Shunk ...... 98 Willi ams ...... 107
REFERENCES ...... 120
ACKNOWLEDGEMENTS ...... 12 1
APP EN DIX 1: TECH N IQUES FOR LOWERING TH E CENT ER OF M ASS I N T HE LAST STEPS O F T H E RUN-UP ...... 122
APP EN DIX 2: EXERC ISES T O H ELP T H E LO W ERING OF TH E CENTER OF MASS I N T H E LAST ST EPS OF T H E RUN-UP ...... 127
APP EN DIX 3: PRO DUCTION O F LAT ER AL SOMER SAULTING ANGULAR MOM EN T UM ...... 129
APP EN DIX 4: DRAWING TH E PATH O F A HIG H JUMP RUN-UP ...... 131 I NTRODUCTION run-up, step lengths, and other in fo rmation.
This report contains a biomechanical analys is of Sequences the techniques used by some of the top athl etes in the Computer graphics were used to produce several final of the men's high jump event at th e 2007 motion sequences for each jump. They are in serted USATF Championships. Data from analyses made in in this report immediate ly after th e individua l previous years are a lso shown for some of these analysis of each athlete. There are three pages of athl etes. sequences for each trial. The report evalu ates the advantages and The first page is labe led " Run-up", and it shows disadvantages of the techniques used by the analyzed a double sequ ence of the end of the run-up and th e athl etes, and suggests how to correct some of the takeoff phase. The top of th e page shows a sid e technique problems fo und. The rationale used for the view; th e bottom of th e page shows a back view. The technique evalu ations stems from a comprehens ive back view is what would be seen by a hypotheti cal interpretation of the Fosbury-flop style of hi gh observer following the athlete a long th e curved path jumping that is based on the research of Dyatchkov of th e run-up; the s id e v iew is what would be seen by ( 1968) and Ozolin ( 1973), on basic research carried an observer standing at th e center of th e run-up out by the first author of this report (Dapena, 1980a, curve. The numbers at th e botton of the page indicate 1980b, 1987a, 1995a, 1995b; Dapena et at., 1988, time, in seconds. To facilitate th e compari son of one 1990, 1997a), and on the experience accumu Ia ted jump with another, the value t = I 0.00 second s was through the analysis of American and other high arbitrarily assigned in a ll tria ls to th e instant when the jumpers at Indiana University s ince 1982 (Dapena, takeoff foot first made contact with th e ground to 1987b, 1987c; Dapena eta! , 1982, 1983a, 1983b, start the takeoff phase. 1986a, 1986b, 1986c, 1991 , 1993a, 1993 b, 1993c, The next page of computer plots (labeled 1994a, 1994b, 1995a, 1995b, 1997b, 1997c, 1998a, "Takeoff Phase") shows sid e and back views of a 19 98b, 1999a, 1999b, 200 I a, 200 I b, 2002a, 2002b, deta il ed sequence of the takeoff phase. (The 2003~2003 b ,2 004 a,2 004b ,2 006~2006b , 20 0 7) in sequence usua lly extends somewhat beyond the loss the course of serv ice work sponsored by the United of contact of th e takeoff foot with the ground.) States Olympic Committee, USA Track & Field The third page (labeled " Bar Clearance") shows and/or the Internati ona l Olympic Committee. a double sequence of the bar c learance. The top of the page shows the view along the bar; th e bottom of GENERAL METHODOLOGY the page shows the view perpendicul ar to th e plane of the bar and the standards. Videotaping a nd selection of trials T he jumps were videotaped s imultaneously w ith Subject characteristics a nd meet resul ts two hi gh definition vid eo cameras shooting at 50 Table I shows general in formation on th e images per second. It was not possible to record all analyzed athletes, and th e ir results in th e the j umps in the meet. However, it was possible to competitions. All the jumpers used th e Fosbury-tlop find for a ll the athl etes presented in this report at least style. one tria l that was representative of the best jumps of the athlete during the competition. (The best jump of DISCUSSION OF HIG H JUMPI NG an athl ete is not necessarily a successful clearance.) TECHN I QUE, AND GENERAL A number was ass igned to each tria l. This ANAL YSIS OF R ESULTS number simply indicated th e order of appearance of that jump in our videos, and it is used here for A hi gh jump can be div ided into three parts: the id entification purposes. run-up phase, the takeoff phase, and th e flight or bar clearance phase. The purpose of the run-up is to set Video analys is the appropriate conditions for the beginning ofth e The locati ons of 2 1 body landmarks were takeoff phase. During the takeoff phase, the athl ete measured ("digiti zed") in the images obtai ned by the exerts forces th at determine the maximum height that two cameras. Computer programs were then used to the c. m. wi II reach after leaving th e ground and the calcu late the three-dimensiona l (3 D) coordinates of angul ar momentum (also call ed "rotary momentum") the body landmarks fro m the final part of th e run-up that th e body will have during the bar clearance. The through the takeoff phase and the bar clearance. onl y active movements that can be made after Another program used th ese 3 D coordinates to leaving the ground are intern al compensatory calcul ate the locati on of th e center of mass (c.m.) movements (for instance, one part of the body can be (also called the center of gravity, e.g.), speed ofthe 2
Table I
General informati on on th e analyzed jumpers, and meet results.
Athlete Standing Weight Personal best Best he ights c leared at meets(**) he ight mark (*) (m) (Kg) (m) (m)
Jim DILLING 1.95 86 2.30 2.27 (U07) Tora HARRIS 1.91 84 2.33 2.24 (UO I); 2.24 (U02); 2.22 (U03); 2.27 (T04); 2.33 (U06); 2.2 1 (U07) Eugene HUTCHINSON 1.89 76 2.26 2.2 1 (U07) Will LITTLETON 1.87 77 2.28 2. 18 (U07) Kei th MOFFATT 1.99 80 2.30 2.27 (T04); 2.30 (U06); 2.24 (U07) Jamie N IETO 1.94 84 2.34 2 .25 (U99); 2.2 1 (UO I); 2.24 (U02) 2.30 (U03); 2.33 (T04); 2. 19 (U06) 2 .24 (U07) Scott SELLERS 1.88 75 2.33 2 .19 (U06); 2. 18 (U07) Adam SHUNK 1.8 3 75 2.30 2 .24 (T04); 2.24 (U07) Jesse WILLIAMS 1.84 73 2.33 2 .24 (T04); 2.24 (U07)
(*) by th e end of th e last meet in which th e jumper was ana lyzed (**) U99 = 1999 USATF Ch.; UO I = 200 I USATF Ch.; U02 = 2002 USATF Ch.; U03 = 2003 USATF Ch.; T04 = 2004 U .S. O lympic Trials; U06 = 2006 USATF Ch.; U07 = 2007 USATF Ch.
li fted by lowering anoth er part; one part of th e body steps of the run-up, the takeoff phase and th e a irborn e can be made to rotate faster by making another part phase. Notice that the c.m . (e.g.) path is initia lly to slow down its rotation). th e left of th e footprints. This is because th e athlete The run-up serves as a preparation for th e takeoff phase, th e most important part of the jump. The is leaning toward th e left during th e curve. The c. m. actions of th e athlete during th e bar c learance are less path th en converges w ith th e footprints, and the c.m. important: Most of the probl ems found in th e bar is pretty much directly over th e takeoff foot at th e clearance actu all y originate in th e run-up or takeoff end of th e takeoff. phases. Figure 2 also shows angles t 1, p2, p 1 and p0 : t 1 is th e ang le between th e bar and th e lin e joining th e last
General characteristics of the run-up two footprints; p2 and p 1 are the angles between th e The typ ical length of th e run-up for experi enced bar and th e path of the c. m. in the ai rborne phases of hi gh jumpers is about I 0 steps. In th e Fosbury-flop th e last two steps; p0 is the ang le between the bar and technique, th e first part of the run-up usua lly follows th e path of th e c.m . during the a irborn e phase that a stra ight lin e perpendicular to th e plane of th e fo ll ows the takeoff. The angles are smaller in stand ard s, and th e last four or fi ve steps fo ll ow a athletes who move more para ll e l to th e bar. The curve (Figure 1). One ofthe main purposes of the valu es of th ese ang les are shown in Table 2. curve is to make the jumper lean away from the bar at the start of th e takeoff phase. The faster th e run or Progression of the run-up th e ti ghter th e curve, the greater th e lean toward th e To start th e run-up, the athlete can eith er take a center of the curve. (For more deta il s on th e shape of few walking steps and th en start running, or make a the run-up, see Appendix 4.) standing start. In th e early part of the run-up the athl ete needs to follow a gradua l progress ion in Approach angles which each step is a little bit longer and faster than Figure 2 shows an overhead view of the last two the previous one. After a few steps, the high j umper 3
Figure 1 Figure 2
Or------,0 takeoff point
19<>..----- ' / ' ..... , I ' / ~- 1 ' I ' G ~ ------... 8 -T-- I ' I ' I I i Too I I Po'··.. . / \ c. m. path ., ______j_ __ _
/ I I \ I .. ~P ······ ... sL , I I 1 I /"" I ', •••• ••• e. m. pos ition at the end / raJi LI S or ~ 1 I I - I k 'f I ,· •. 1 ott 1e ta eo t p 1ase ------.L.~ / the eur\'e
1 I I / 1 \I / n 1 ll start or / ______------___ , - ' the curve ' \ 'I ce nter of th e cun·e p ' opposite force. The upward force exerted by th e 'I I ground on th e ath lete is much larger than body Q I weight, and it changes the vertical velocity of the I I c. m . from a valu e th at is initiall y c lose to zero to a I p large upward verti cal velocity . The verti cal velocity I I of th e athlete at th e end of the takeoff phase I I determines th e peak height that th e c.m. will reach q after th e ath lete leaves th e ground, and is therefore of I I great importan ce for the result of th e jump. p To maximize th e verti cal velocity at the end of I start or the run -up-0 th e takeoff phase, th e product of th e verti cal fo rce 0 exerted by the athlete on th e ground and the time during which thi s force is exerted should be as large as poss ibl e. This can be achieved by making th e will be running pretty fast, with long, re laxed steps, verti cal force as large as possible and th e verti cal very similar to those of a 400-meter or 800-meter range of moti on through whi ch th e c. m . trave ls runner. In th e last two or three steps of th e run-up th e during th e takeoff phase as long as poss ible. athlete should gradua lly lower the hips. It must be A fas t approach run can he lp th e athlete to exert stressed here that this lowering of th e hips has to be a larger vertical fo rce on th e ground. This can be achi eved without in curring a s ignificant loss of achi eved in the fo ll owing way: When th e takeoff leg running speed. is planted ahead of th e body at the end of the run-up, the kn ee extensor muscles (quadriceps) resist against Horizonta l velocity and height of the c. m. at the the fl ex ion of th e leg, but the leg is fo rced to fl ex end of the run-up anyway, because of th e fo rward momentum of th e The takeoff phase is defin ed as th e peri od of jumper. In thi s process the takeoff leg's knee time between th e in stant when th e takeoff foot first extensor muscles are stretched. It is be li eved th at this touches th e ground (touchdown) and the in stant when stretching produces a stimu lation of the muscles, it loses contact w ith the ground (takeoff). During th e which in turn a ll ows th e foot of th e takeoff leg to takeoff phase, th e takeoff leg pushes down on th e press hard er again st the ground. In this way, a fas t ground. In reacti on, th e ground pushes upward on run-up helps to in crease th e vertical fo rce exerted the body through the takeoff leg w ith an equa l and during th e takeoff phase. (For a more extended 4
Table 2
Direction o f th e foo tprints o f th e last step (t 1) , d irectio n of the path of the c.m. in the last two steps (p2 and p 1) and after takeotT(p0) , directio n o f th e long itud in al axis of th e foo t with respect to th e bar (e 1) , w ith respect to the fi nal direction of th e run-up (e2) and with respect to th e hori zontal fo rce made on th e ground during th e takeoff ph ase (e1) , length of th e last step (S L1, expressed in meters and also as a percent of th e standing height of the corresponding athlete), and takeoff distance (TOD). Note : Some of the valu es in th is table may not fi t perfectl y with each other, because of ro unding off.
Athlete Trial and t , p, PI Po e, e, e, SL 1 TOD meet(*) (0) Cl n (0) Cl (0) (0) (m) (%) (m)
Di lling 97 U07 37 55 47 43 19 28 33 2.05 105 1.23
Harris 2 1 UOI 34 51 44 36 4 39 46 2.03 106 1.09 17 U02 27 50 39 40 6 33 33 1. 99 104 1. 09 II U03 27 49 4 1 39 II 30 32 1.85 97 1.1 4 30 T04 3 1 52 47 40 13 34 42 1.90 100 1. 08 38 U06 3 1 55 46 42 15 30 35 1. 94 10 1 1. 50 6 1 U07 30 53 43 39 2 1 22 26 1. 98 104 1.25
Hutchinson 72 U07 37 55 47 45 36 II 14 2. 12 11 2 0.95
Littleton 48 U07 34 56 45 41 16 29 34 1. 94 104 1.1 7
Moffatt 33 T04 28 52 39 35 12 26 3 1 2.17 109 0.98 40 U06 27 57 4 1 42 20 2 1 2 1 2.18 109 0.92 84 U07 33 57 45 40 24 22 28 2.09 105 1. 03
Nieto 17 U99 34 6 1 47 40 3 44 5 1 2.02 104 0.96 36 UO I 32 59 46 42 6 40 45 1. 9 1 98 I 13 13 U02 28 59 43 4 1 15 28 30 1. 90 98 1. 07 37 U03 26 55 43 38 7 35 40 1. 96 10 1 1.04 62 T04 24 53 39 39 9 3 1 32 2.02 104 1.0 1 24 U06 3 1 60 46 44 2 44 46 2.05 106 148 99 U07 32 58 46 38 4 42 52 1. 97 102 1. 05
Sell ers 03 U06 43 56 50 46 38 12 17 2. 14 11 4 1.25 42 U07 45 56 52 53 34 17 16 2.09 Ill 140
Shunk 28 T04 29 52 42 35 8 34 40 1. 94 106 0.79 95 U07 29 53 4 1 37 2 39 43 1.77 97 1.00
Wi ll iams 16 T04 19 48 37 37 2 35 35 1.8 1 99 0.94 82 U07 33 59 48 43 0 48 54 1. 76 96 143
(*) U99 = 1999 USATF Ch.; UO I = 200 I USATF Ch.; U02 = 2002 USATF Ch.; U03 = 2003 USATF Ch.; T04 = 2004 U.S. Olympic T ri als; U06 = 2006 USATF Ch.; U07 = 2007 USATF Ch. di scussion of th e mechanisms th at may be in volved and in a high position at th e end of the takeoff. Most in th e high jump takeoff, see Dapena and Chung, hi gh jumpers have no trouble achi evin g a reasonably 1988.) Tabl e 3 shows the values of vH2 , the hi gh position at th e end of th e takeoff; th e greatest hori zo nta l velocity of the athlete in th e next-to-last difficulty Ii es in the establishment of a low position at step of th e run-up, and of vH 1, th e hori zonta l velocity th e start of th e takeoff phase. T here are two ways to of th e athlete in th e last step of th e run-up, just produce a low positi on of th e c.m. at the start of th e before th e takeoff foot is pI anted on th e ground. The takeoff phase: (a) to run with bent legs in th e last valu e of VHt is the important one. couple of steps of th e run-up; and (b) to run on a To max imize th e verti cal range of moti on curve, which makes the athlete lean toward th e center through whi ch force is exerted on the body during th e of th e curve, and thus produces a further lowering of takeoff phase, it is necessary fo r th e center of mass to the c.m . The c. m .-lowering effects of th e two be in a low pos it ion at the start of the takeoff phase meth ods are additive, and high jumpers norma lly 5
Table 3
Height of th e c.m. at the start of th e takeoff phase (ilru, expressed in meters and also as a percent of th e standing height of each athl ete), hori zontal veloc ity in th e last two steps of th e run-up (v 11 2 and v111 ), hori zontal ve locity after takeoff(v1rro), change in hori zontal velocity during th e takeoff phase (t.v 11 ), vertical velocity at the start of the takeoff phase (vzm), and vertical velocity at the end of the takeoff ph ase (vl.To). Note: Some of th e va lu es in thi s tabl e may not fit perfec tl y with each oth er, because of rounding off.
Athlete Trial and h·m VHz V][J VJITO t.v" VzTD VzTo meet(*) (m) (%) (m/s) (m/s) (m/s) (m/s) (m/s) (m/s)
Dilling 97 U07 0.92 47.5 7.9 7.8 4.2 -3 .6 -0.6 4.40
Harris 2 1 UO I 0.84 44.0 8. 1 8.0 3.9 -4.1 -0.7 4.40 17 U02 0.86 45 .0 7.7 7.8 3.9 -3.9 -0.6 4.40 II U03 0.88 46.0 8.0 7.7 4.1 -3 .6 -0.3 4.40 30 T04 0.88 46.0 8. 1 7.7 4.0 -3.7 -0.4 4JO 38 U06 0.86 45 .0 8.2 8.0 4.5 -3 .6 -0.4 4.50 6 1 U07 0.85 44.5 8J 8.0 4.2 -3 .8 -0.3 4JO
Hutchinson 72 U07 0.82 43 .5 7J 7.2 3.5 -3 .7 -0.5 4JO
Littl eton 48 U07 0.86 46.0 7.8 7.9 4.6 -3 .3 -OJ 4.15
Moffatt 33 T04 0.97 48.5 7.9 7.7 4.2 -3 .5 -0.5 4JO 40 U06 0.94 47.0 7.2 7.3 3.6 -3 .7 -0.4 4.45 84 U07 0.96 48.5 6.9 7.2 3.8 -3J -OJ 4JO
Nieto 17 U99 0.9 1 47.0 7.2 7.0 3.6 -3.4 -OJ 4JO 36 UO I 0.88 45.5 7.7 7. 1 3.7 -3.4 -0.3 4JO 13 U02 0.88 45 .5 7.6 7.2 3.6 -3 .6 -0.2 4JO 37 U03 0.89 46.0 7.4 7.3 3.8 -3.5 -OJ 4.40 62 T04 0.92 47.5 7.2 6.9 3.4 -3 .5 -0.5 4.40 24 U06 0.90 46.5 7.6 7.4 4.0 -3.4 -0.2 4.25 99 U07 0.9 1 46.5 7. 1 7.3 4.0 -3.4 -OJ 4JO
Sellers 03 U06 0.89 47.5 7.8 8.0 4.5 -3.4 -0.5 4JO 42 U07 0.90 48.0 7.5 7.7 4J -3.4 -0.6 4.25
Shunk 28 T04 0.8 1 44 .5 7.8 7.0 3.5 -3.5 -0.2 4J5 95 U07 0.84 46.0 7.7 7.1 3.9 -3 .2 -0.1 4.40
Willi ams 16 T04 0.88 47.5 7.4 7.3 3.8 -3.4 -0.2 4.40 82 U07 0.88 48.0 7.8 7.7 4J -3.4 -OJ 4.50
(*) U99 = 1999 USATF Ch.; UO I = 200 I USATF Ch.; U02 = 2002 USATF Ch.; U03 = 2003 USA TF Ch.; T04 = 2004 U.S. Olympic Trials; U06 = 2006 USATF Ch.; U07 = 2007 USATF Ch.
lower th e c. m. through the combination of both necessary work to achieve this, since th e results will meth ods. be highly rewarding. Appendix 2 describes so me Running with bent legs requires th e body to be exercises that can help high jumpers to run with bent supported by a deepl y flexed non-takeoff leg during legs in the last steps of the run-up without los in g the nex t-to-last step of the run-up, and thi s requires a speed, and to produ ce a good pos ition for the body at very strong non-takeoff leg. A Iso, it is d ifficu It to th e start of the takeoff ph ase. learn the appropriate neuromu scul ar pattern s that will By running on a curve, the athlete can reduce the all ow th e ath tete to pass over the dee ply fl exed non amount of leg flexi on needed to attain any given takeoff leg without los in g speed. Still, it is poss ible amount of c. m. lowering. Therefore, th e cur ved run to learn how to run fast with bent legs. It requires a up makes it easier to maintain a fast running speed considerable amount of effort and training, but while lowering the c.m. Unfortunately, th e amount athl etes should be strongly encouraged to put in the of c.m. lowering that can be produced exclu sively 6
through curve-induced leaning is rath er limited. than the second one. However, if the two values of Therefore, hi gh jumpers normally need to combine hm were, for in stance, 46.5% and 48.0% it would not bent-legs running w ith the use of a curved run-up to be possible to be complete ly sure whi ch of th e produce th e necessary amount of lowering of the c.m. jumpers was lower, because th e 46.5% could be Table 3 shows th e value of hm , the height of th e reall y 47.5%, and th e 48.0% could be really 47.0% .) c.m. at the in stant w hen th e takeoff foot is planted on Let' s consider what would happen if all th e the ground to start the takeoff phase. It is the athl etes shown in Figure 3 had similar dynamic comb in ed result of running w ith bent legs and strength in th e takeoff leg. In such case, the athletes leaning toward th e center of th e curve. It is in th e upper left part of th e graph would be far from expressed in meters, but also as a percent of each th eir limit for buckling, the athletes in the lower right athlete' s standing he ight. The percent values are part of the graph would be closest to buckling, and more meaningful for the comparison of one athl ete th e athletes in th e center, lower left and upper right w ith anoth er. parts of the graph would be somewhere in between Let's say th at an athlete has learn ed how to run with respect to th e ri sk of buckling. Therefore, if a ll fast and low. A new problem could occur: The th e athletes shown in Figure 3 had s imilar dynamic athl ete could actu a ll y be too fast and too low. If th e strength , we would recommend th e athl etes in th e takeoff leg is not strong enough, it will be forced to upper left part of th e graph to learn how to run faster flex excessively during th e takeoff phase, and then it and lower (see Appendix 2), and th en experiment may not be able to make a forcefu I extens ion in th e with jumps using run-ups that are faster and/or lower final part of th e takeoff phase. In oth er words, th e than th e ir ori g inal ones. The athletes in th e center, takeoff leg may buckle (collapse) under the stress, lower left and upper ri ght parts of th e graph would and th e result will be a very low jump or an aborted also be advised to experiment with faster and lower j ump. Therefore, it is important to find th e optimum run-ups, possibly emphasizin g " faster" for the combinati on of run-up speed and c.m . height. We jumpers in the lower left part of the graph, and wi ll now see how this can be done. " lower" for the jumpers in the upper ri ght part of th e Figure 3 shows a plot ofhm versus VHJ· (At this graph . The athletes in the lower ri ght part of th e time, please ignore the diagonal lines; we will deal graph would be cautioned against the use of much with them later on.) Each po int on th e graph faster and/or lower run-ups th an their present ones, represents one jump by one athlete. A different because these athletes would already be closer to symbol has been ass igned to each athlete. This buckling th an the oth ers. symbol will be used for th at athlete in a ll graphs of The procedure just described would make sense this report. Po ints in th e left part of th e graph if a ll th e jumpers shown in Figure 3 had s imilar represent jumps w ith a s low speed at th e end of the dynamic strength in th e takeoff leg. However, this is run-up; points in the right part of the g raph represent not a good assumption: The takeoff legs of different jumps w ith a fast speed at th e end of th e run-up. hi gh jumpers will have different amounts of dynamic Points in th e upper part of the graph represent jumps strength , and more powerful athletes willa be ble to with a high c.m . at the end of the run-up; points in the handle faster and lower run-ups without buckling. lower part of the graph represent jumps with a low Therefore, it is possible that an athlete in th e upper c. m . at th e end of the run-up. This kind of graph left part of the g raph might be weak, and thus already permits to v isua li ze simultaneously how fast and how close to buckling, while an athlete farther down and hi gh an athlete was at the end of the run-up. For to th e ri ght in the graph might be more powerful, and in stance, a point in th e upper ri ght part of the graph actually farther from buckling. The optimum would indicate a jump with a fast run-up but a hi gh combination of run-up speed and c. m . height will be c.m . pos ition at th e end of th e run-up. different for different hi gh jumpers, and we w ill need (At this point, it is important to cons ider th e to know a hi gh jumper' s dynamic strength before we accuracy of these valu es. A II measurements have can predict how fast and how low th at high j umper some degree of erro r, and depending on what is be in g should be at th e end of the run-up. measured, the error may be larger or smaller. The It is not easy to measure the dynamic strength of errors in the vH 1 values are sma ll , typically less th an a hi gh jumper's takeoff leg. The personal record of 0.1 m/s; th e errors in th e hm values can be of greater an athl ete in a squat lift or in a vertical jump-and significance. It is easy for th e valu e of hm to be ha lf reach test are not good indicators of th e dynamic a percent point off for any jump, and occasionally it strength of th e takeoff leg. This is because these tests could be off by as much as one whole percent point. do not duplicate c losely enough th e conditions of th e Therefore, if two jumpers had, for instance, hm hi gh jump takeoff. The best indicator that we have valu es of46.5% and 49.0%, respectively, we could found of th e takeoff leg' s dynamic strength is the be pretty sure that the first jumper reall y was lower capabili ty of th e hig h jumper to generate lift in an 7
Figure 3
50
49
0 MOF 84 48
IL 16 }:{ NIE62 0 47 }:{ MO 40 NIE 17 }:{
46 SHU 95 ~
NIE 36
45 ~- .-~
44
43
7.0 7.2 7.4 7.6 7.8 8.0 8.2
VHI (m/s) 8
actu a l hi gh jump. Therefore, we use the vertical th at athl etes near th e regression line or below it were velocity achi eved by the hig h jumper at the end of th e running too slow ly at the end of th e run-up. takeoff ph ase (VzTO - see be low) to indicate the A similar rationa le can be followed with th e athl ete's dynamic strength or "takeoff power". graph of hm vs. Vzro, shown in Figure 5. Each of the To help us in our prediction of th e optimum small open circles in Figure 5 represents one jump by horizontal speed at the end of the run-up from the one of th e athletes in our statistical sample. The dynamic strength of th e takeoff leg, we made use of oth er symbo ls represent the athl etes ana lyzed for the stati sti cal inform ati on accumulated through film present report. The horizontal ax is of the graph again analyses of male and female high jumpers in th e shows vertical velocity at takeoff (vzTO): The most course of Scientific Support Services work sponsored powerful high jumpers are the ones who are abl e to at Indiana University by th e United States Olympic generate more lift, and they are to th e ri ght in th e Committee and by USA Track & Field (formerly The graph ; th e weaker jumpers are to the left. The Athletics Congress) in th e period 1982- 1987. The vertical ax is shows the he ight of the c.m. at the start athletes in vo lv ed in these studies were all elite hi gh of the takeoff phase (hm ), expressed as a percent of jumpers film ed at the fin a ls of nati ona l and th e athl ete's standing he ight. The diagonal regression internati ona l level competitions (USATF and NCAA lin e shows the trend of the statistical data. Although Championships; U.S. Olympic Trials; World Indoor the data are more "noisy" than in th e previous graph Championships). (i .e. , th ere is a wider " cloud" around th e regress ion Each of the sma ll open circles in Figure 4 lin e), th e graph in Figure 5 also agrees with our represents one jump by one of the athl etes in our genera l expectations: The more powerful jumpers ori g inal statistical sample. The other symbo ls (larger Vzro values) are able to be lower at the end of represent the athletes analyzed for the present report. th e run-up (smaller hm values) w ith out buckling The hori zontal ax is of th e g raph shows vertical during the takeoff phase. In Figure 5, jumpers on the velocity at takeoff (vzTO): The most powerful hi gh regression lin e or above it will have bad techniques in jumpers are the ones who are able to generate more this regard , and the optimum will be somewhere lift, and they are to the ri ght in the graph ; the weaker below th e regression lin e. jumpers are to th e left. The vertical axis shows th e When Figures 4 and 5 are used as diagnosti c final speed of th e run-up (vH 1). The diagonal tools, it is necessary to take into cons id erati on the "regression" line shows the trend of the statistical information from both graphs. For in stance, if a data. The graph agrees with our expectations: The g iven athlete is pretty much on the regression lin es of more powerful jumpers, those able to get more lift Figures 4 and 5, or below the regression line in (larger Vzro), can a lso handle faster run-ups (larger Figure 4 and above the regression line in Figure 5, we v~ 11 ) without buckling. should presume th at this athlete is not near th e So, what is th e optimum run-up speed for a given buckling po int. Therefore th e athlete should be high jumper? It seems safe to assume that most hi gh advised to in crease the run-up speed and/or to run jumpers will not use regularly a run-up that is so fast with lower hips at th e end of th e run-up. However, if that the takeoff leg will buckle. This is because it an athlete is sli ghtly below the regression lin e in takes intense concentrati on and effort for a hi gh Figure 4, but markedly be low it in Figure 5, the case jumper to use a fast run-up, and if the athlete feels is different. Since th e c.m . was very low during the th at the leg has buckled in one jump, an easier run-up, maybe th e athlete was close to the bu ckling (slower) run-up will be used in further jumps. Since po int, even th ough the run-up speed was not very bucklin g (or at least partial buckling) will begin to fast. In this case, it would not be appropriate to occur at run-up speeds immediately faster than the advise an increase in run-up speed, even if th e optimum, this means th at few hig h jumpers should be athlete's run-up speed was somewhat slow in expected to use regularl y run-ups that are faster th an compari son to what we would expect on the average. their optimum. On the other hand , we should expect By now, it should be c lear to the reader that the a larger number of high jumpers to use run-up speeds intensity of th e demands put on the takeoff leg during that are s lower th an their optimum. This is because a the takeoff phase depends mainly on th e combination fa ir number of high jumpers have not learned to use a of final run-up speed and c. m. height at the end of the fast enough run-up. Therefore, the diagonal run-up. Therefore, the advice given to an individual regression line which marks th e average trend in th e athlete needs to take into account both of these graph represents speeds that are s lower than the factors simultaneously. This is where the diagonal optimum. In sum, although th e precise value of th e lin es in Figure 3 come into play. Each diagonal line optimum run-up speed is not known for any g iv en indicates combinations of run-up speed and c.m. value of Vzro, we know that it will be faster than the height th at are equally demanding for the takeoff leg. value indicated by the diagona l regression lin e, and Diagona l lin es further down and toward the right on 8.8 VHI 8.6 (m/s) 8.4 8.2
HAR61 8.0 ~ "YO T""' SEL03 HAR"" 2 1 HAR 38 6. 0 LIT 48 OIL97 7.8 0 0 0 0 . HAR 17 + HAR 30 0 "" @ SEL42 MOF 33 ""HAR II W•IL8 7.6 0
0 0 0 0 0 NIE 24 0 ):!:> ,, ~ 7.4 99 WIL 16 ..,., 0 0 7.0 + 0~ NIE 17 ):! + sHU 28 ):! 6.8 ~ NIE 62 6.6 6.4 6.2 6.0 5.8 ~~~+-~-+--~+-~-+--~+-~-+--~~~-+--~+-~ 3.2 3.4 3.6 3.8 4.0 4.2 4.4 4.6 4.8 5.0 VZTO (m/s) \0 11 the graph represent progressively more demanding the bar e ither on the way up toward the peak of th e combinations. Each athlete's Vzro valu e (which jump or on the way down. needs to be obta in ed fro m Table 3) determines the It is important to keep in mind that the regress ion appropriate diagona l line for that athlete in Figure 3. lin es in F igures 4 and 5 represent average va lu es, not If an athlete is higher and/or to the left of the optimum valu es . They represent mediocre recommended diagonal lin e, as will often be the case, techniques that are not particul arly bad but also not we w ill advise the athlete to move his/her po int to the particul arl y good. For optimum technique, an athl ete recommended diagonal lin e. If the athlete is already needs to be higher than th e regression line ofFigure4 on the recommended di agonal line, we will advise the and/or lower than the regression lin e of Figure 5. In athl ete to retain the current combinati on of run-up contrast, the diagonal lines in Figure 3 have already speed and c. m . height. If th e athlete is somewhat been adjusted to represent optimum values in stead of lower and/or to the ri ght of the recommended average values. Therefore, if an athlete' s po int in diagonal line, we will a lso adv ise th e athlete to retain Figure 3 is on the diagonal line recommended for that the current combination of run-up speed and c.m. athlete (based on th e athlete' s Vzro valu e taken from height. T his is because our recommended diagonal Table 3), th e athlete is cons idered to be at his/her lin e is a rath er conservative cho ice with a safety optimum combinati on of speed and c.m. he ight at the marg in built into it. [Note f or other researchers end of th e run-up. (coaches and athletes can skip this) : In statistical (IMPORTANT CAUTION: Chang in g to a terms, the recommended diagonals were chosen to be faster and/or lower run-up wi II put a greater stress on only one standard deviation more demanding than the takeoff leg, and thus it may increase the ri sk of the average.] In the rare case that the athlete is much injury if the leg is not strong enough. Therefore, it is lower and/or much farther to the right than the always important to use caution in the adoption of a recommended diagona l line, we wi ll warn th e athlete faster and/or lower run-up. If the desired change is that such a combination might be excessively very large, it would be adv isable to make it gradually, demanding in relation to the athlete' s current leg over a peri od of time. In a ll cases, it may be wise to strength capability. further strengthen the takeoff leg, so that it can We have a reasonably good idea of which is the withstand the in creased force of the impact produced appropriate diagona l lin e for each athlete. However, w hen the takeoff leg is pl anted.) we do not know where the athlete's po int should be located along that diagonal line. Coaches who are Vertical velocity of the c.m. at the start of the advocates for so-call ed " power jumping" w ill prefer takeoff phase the athlete's point to be farther down and to the left The vertical velocity at the end of the takeoff a long th e diagona l lin e, whi le coaches who are phase, which is of crucial importance for th e he ight advocates for so-call ed "speed jumping" will prefer of the jump, is determined by the vertical velocity at the athlete's po int to be farther up and toward the the start of the takeoff phase and by the change that right along the diagona l line. We are neutral in this takes pl ace in its value during the takeoff phase. In dispute: As long as the ath lete is on the norm al high jumping, at th e end of the run-up (that is, recommended diagona l line, we consid er the athlete at the start of the takeoff phase) th e ath lete is movin g to have an appropriate combinati on of speed and c. m. fast forward, and a lso sli ghtly downward. In other height at th e end of th e run-up. The onl y caution th at word s, the vertical velocity at th e start of the takeoff we give is to avoid extreme valu es e ither far up and phase (vzm) usua lly has a small negati ve valu e ( i.e., to the right or far down and to the left a long th e downward). It is evident that for a given change in diagonal line, because both will tend to create vertical velocity during the takeoff phase, the athlete problems later for the bar c learance. An extremely with the smallest amount of negative vertical velocity fast speed and high c.m . position at the end of the at touchdown will jump the highest. The valu es of run-up w ill tend to leave the athlete with a lot of Vs zm are hown in Table 3 . The jumpers w ith the best leftover horizontal speed at th e end of the takeoff. techniques in thi s respect are those with th e least This will make it impossible for the ath lete to "drape" negative Vzm valu es. around the bar w ith out knocking it down with either In each step of the run-up th e c. m. norma lly the shoul ders or th e calv es. At the other extreme, a moves up s li ghtly as th e athlete takes off from the very slow speed and low c. m . pos ition at the end of ground, reaches a maximum height, and th en drops the run-up wi ll tend to leave the athl ete w ith only a down again before the athl ete plants the next foot on small amoun t of leftover hori zontal speed at the end the ground. In the last step of the run-up, if the of the takeoff. This will severe ly limit the amount of takeoff foot is p !anted on the ground early, the hori zonta l travel of the body after the end of the takeoff phase will start before the c. m . acquires too takeoff, and thus w ill make it difficult to avoid hitting much downward vertical velocity. To achi eve this, 12 the athlete has to try to make th e las t two foot of the run-up, but usually it is a lso dev iated sli ghtly contacts with the ground very quickly one after th e toward the landing pit (see Figure 6). (The reason for other. In other word s, th e tempo of the last two foot this deviation is explained in Appendix 3 .) supports should be very fast. Most hi gh jumpers plant th e takeoff foot on th e If the length of th e last step is very long, it could ground with its long itudinal ax is pointing in a contribute to a late planting of the takeoff fo ot, which directi on that generally is not a li gned with th e fin a l in turn could lead to a large negative valu e for Vzm. directi on of th e run-up nor with th e hori zontal force Tabl e 2 shows th e length of the last step of the run-up th at the athlete is about to make on th e ground: It is (S L 1). T his length is expressed in meters, but to more parall e l to the bar th an either one of them . fac ilitate comparisons among athletes it is also Since th e hori zontal reacti on force that the foot expressed as a percent of th e standing he ight of each receives from the ground is not a ligned with th e athlete. long itudinal ax is of the foot, th e force tends to make Another factor that has an influence on th e th e foot ro ll inward . (See the sequence in Figure 7, verti cal velocity at the start o f th e takeoff phase is th e obtained from a high-speed vid eotape taken during way in which th e c.m . is lowered in the fina l part of the 1988 International Golden High Jump Gala th e run-up. High jumpers can be c lassified into three competition in Genk, Belg ium - courtesy of Dr. Bart groups, depending on the way in which they lower Van Gheluwe.) In anatomical terminology, this the c.m. Many athletes lower the ir c. m . early (two or rotation is call ed " pronati on of the ankle jo int". It three steps before the takeoff), and th en th ey move stretches the media l s id e of th e joint, and produces relatively flat in th e last step. T hese athletes typicall y compression in the latera l sid e of th e jo int. If th e have a moderate amount of downward verti cal pronation is very severe, it can lead to injury of th e velocity at the in stant that th e takeoff phase starts. ankle. It a lso makes th e foot be supported less by th e The second group of athl etes keep th e ir hips high outside edge of the foot, and more by th e longitud in a! until almost th e very end of th e run-up, and then th ey (forward-backward) arch of th e foot on th e media l lower the c.m. in th e last step. These athletes have a side. According to Krahl and Knebe l (1979), this can large negative vertical velocity at the start of the lead to injury of the foot itse lf. takeoff phase, regardless of how early they plant the Pronation of the ankle joint occurs in th e takeoffs takeofffoot on th e ground. A third group of athletes of many high jumpers. However, it can bed ifficu It lower the c. m. in th e same way as th e first group, but to see, depending on th e pos ition of the camera and then th ey raise the c.m . again quite a bit as the non th e size of th e image. Because of thi s, pronation of takeoff leg pushes off into the last step. These th e ankle joint is often not c learl y v is ibl e in our athl etes ty pi cally have a very sma ll amount of standard films or vid eotapes of high jumping downward verti cal velocity at th e start of the takeoff competitions (and th erefore it does not show in our phase, and this is good, but th ey a lso waste part of computer graphics sequences eith er). This does not their previous lowerin g of th e c.m . necessarily mean th at there is no ankle pronati on; it The first and th e third techniques have both onl y means that we can't see it. advantages and disadvantages, but the second In an effort to diagnose the ri sk of ankle and foot technique seems to be less sound than the other two, injury for each analyzed hig h jumper, we measured because of th e large downward vertical velocity th at angles e 1 (the angle between th e longitudina l ax is of it produces at th e in stant of th e start of the takeoff th e foot and th e bar), e2 (between the longitudinal phase. There is a more deta il ed discuss ion of these ax is of th e foot and th e f in a l direction of th e run-up), three techniques in Appendix I. and e3 (between the longitudina l ax is of th e foot and A graph showin g the verti cal moti on of the c.m . the hori zonta l force) in each jump. (See Figure 6.) in the final part of th e run-up was produced for each The values of th ese ang les are reported in Table 2. athl ete, and these graphs are in serted in the report For diagnosis of the ri sk of injury, e3 is the most after th e individual ana lysis of each athlete. important ang le. Although th e safety limit is not well known, anecdotal evid ence suggests that e3 values O rientation of the ta keoff foot, a nd potentia l for sma ller than 20° are reasonably safe , that e3 values an kle a nd foot inj ur ies between 20° and 30° are somewhat risky, and th at e3 At the end of the run-up, th e high jumper's c.m. values larger th an 30° are dangerous. is movin g at an ang le p 1 w ith respect to th e bar (see "Approach angles"). During th e takeoff phase, th e Tru nk lean athl ete pushes on th e g round verti call y downward , Figure 8 shows BFTD, BFTO, LRTD and and also horizonta lly. T he hori zonta l force that the LRTO, the backward/forward and left/right ang les of foo t makes on th e ground during th e takeoff phase lean of th e trunk at the start and at th e end of th e points forward, a lm ost in lin e with th e final directi on takeoff phase, respectively. The va lu es of th ese 13 Figure 7 Figure 6 landing pit bar ,_ fin al direc tion , '•,, of th e run -up __;;;.. __ '•,,, ho11Zon tal f01 ce made on the ground /''--, __ ----:~~: longit udin al axJS ------t-- -~;- - __ or thdtx>t Pt ---- 1,_'------~-'-l--~~~--·::: ::o horizontal reac ti on force rece ived by th e foot Figure 8 '-..., BFTO ' \ ' I ------"- side view I I / I LRTD_. I / / I I I -'--- I -'---- back view (videotape courtesy of Bart Van Gheluwe) 14 Table 4 Angles of tilt of the trunk [backward/forward at th e start of th e takeoff phase (BFTD) and at th e end of the takeoff phase (BFTO), and th e change in this angle during th e ta keoflphase (t.BF); left/ri ght at the start of the takeoff phase (LRTD) and at th e end of th e takeoff phase (LRTO), and the change in this angle during th e takeoff phase (t.LR)], acti ve ness of th e ann nearest to th e bar (AAN) and of th e ann farthest from the bar (AAF), summed acti veness of the two arms (AA T), acti ve ness of the lead leg (LLA), and summed acti veness of th e three free limbs (FLA). Note: Some of the values in this tabl e may not fi t perfectly with each other, because of rounding off. Athlete T ri al and BFTD BFTO t.BF LRTD LRTO t.LR AAN AAF AAT LLA FLA meet (*) Cl (0) (0) (0) Cl (0) (mm/m) (mm/m) (mm/m) (mm/m) (mm/m) Dilling 97 U07 79 92 14 77 89 12 8.0 8.3 16.2 15.8 32.1 Harris 2 1 UO I 74 88 14 72 85 13 5.0 7.9 12.9 9.3 22.2 17 U02 76 85 9 73 96 23 7.9 9.0 17.0 I 0.4 27.4 II U03 75 86 II 76 92 15 I 1.1 9.5 20.6 11.6 32.2 30 T04 73 88 16 72 89 18 9.0 8.0 17.0 8.7 25.7 38 U06 77 87 10 74 94 20 5.6 7.2 12.8 11.9 24.7 6 1 U07 76 87 II 74 97 23 8.7 7.6 16.3 12.9 29.3 Hutchinson 72 U07 75 92 17 87 102 15 12.2 13. 1 25.3 25.5 50.8 Littleton 48 U07 84 90 6 79 10 1 2 1 8.2 7.2 15 .5 15.3 30.8 Mo ffat1 33 T04 88 84 -4 76 102 26 4.1 6.0 10. 1 16.9 27.0 40 U06 83 79 -4 76 103 27 5.4 7.7 13.2 2 1. 6 34.8 84 U07 87 83 -4 79 10 1 22 5.0 7.0 12.0 19.6 3 1. 6 Nieto 17 U99 80 89 10 74 96 22 5.0 9.9 14.9 17.4 32.3 36 UO I 68 83 15 75 100 25 4.0 11 . 1 15.1 13.4 28.4 13 U02 72 8 1 9 74 97 23 4.9 8.5 13.4 16.5 29.9 37 U03 75 85 10 72 100 28 5.0 8.7 13.6 16.3 30.0 62 T04 77 80 3 77 102 26 7.5 11 .5 19.0 20.2 39.2 24 U06 83 95 12 75 98 23 4.5 9. 1 13.6 16.1 29.7 99 U07 82 89 7 73 97 24 7.3 10.0 17.3 18 . 1 35.4 Se llers 03 U06 74 88 14 8 1 10 1 20 7.4 12 .8 20.2 20.8 4 1.0 42 U07 79 92 13 84 106 22 7.6 13.8 2 1.4 20.9 42.3 Shunk 28 T04 7 1 82 10 72 97 25 6. 1 10 .3 16.4 15.3 31.7 95 U07 73 81 7 74 100 26 6.4 9.7 16. 1 16.9 33 .0 Willi ams 16 T04 76 92 16 77 92 15 8.6 3.6 12.1 12. 1 24.2 82 U07 76 89 13 76 89 13 9.0 5. 1 14.2 12.4 26.5 (*) U99 = 1999 USATF Ch.; UO I = 200 I USATF Ch.; U02 = 2002 USATF Ch.; U03 = 2003 USATF Ch.; T04 = 2004 U.S. O lympic Trials; U06 = 2006 USA TF Ch.; U07 = 2007 USATF Ch. angles are g iven in Table 4 . The trunk normally has it is usually somewhat beyond the vertical (LRTO). a backward lean at the start of the takeoff phase Up to I 0° beyond the vertical (LRTO = I 00°) may be (BFTD). Then it rotates forward, and by the end of considered norma l. Table 4 a lso shows the values of th e takeoff it is c lose to vertical, and sometim es past ~BF and ~LR . T hese are th e changes that occur th e vertical (BFTO). Due to th e curved run-up, the during the takeoff phase in th e backward/forward and trunk norm ally has also a latera l lean toward the left/right ang les of ti It of the trunk, respectively. center of the curve at the start of th e takeoff phase Statistical inform ation has shown that th ere is a (LRTD). During the takeoff phase, the trunk rotates relationship of the trunk lean angles with the vertical toward the ri ght (toward the left in athl etes who take velocity of th e athlete at the end of the takeoff phase, off from the ri ght foot) , and by the end of the takeoff and consequently with the peak height of th e c. m.: If 15 two athletes have sim ilar run-up speed, he ight of the acce lerated upward during th e takeoff phase, th ey c.m. at th e end of th e run-up and arm acti ons during exert by reacti on a compressive force downward on th e takeoff phase (see below), the athlete w ith sma ll er the trunk. This force is transmitted through th e BFTD, t.BF, LRTD and t.LR valu es genera lly takeoff leg to th e g round. The in creased downward obtain s a larger vertical velocity by th e end of th e verti cal force exerted by th e foot on th e ground takeoff ph ase. This means th at athletes w ith greater evokes by reacti on an increased upward vertical force backward lean at th e start of the takeoff phase and exerted by th e ground on th e athlete. Thi s produces a greater lateral lean toward th e center of th e curve at larger vertical ve locity of th e c.m . of the athl ete by the start of the takeoff phase tend to jump hi gher. th e end of the takeoff phase, and consequently a Also, fo r a g iven amount of backward lean at th e start hi gher jump. of the takeoff phase, the athletes who experi ence There is no perfect way to measure how acti ve sma ll er changes in thi s ang le during th e takeoff phase th e arms and the lead leg were during th e takeoff genera lly jump higher, and for a g iven amount of phase of a high jump. In our reports we have latera l lean at th e start of th e takeoff phase, th e progressively improved our measurement of this athl etes who experience small er changes in this angle important technique factor; th e data in th e present during the takeoff phase a lso tend to jump hi gher. report were calculated with our latest meth od whi ch However, before j umping to conc lu sions and gives more meaningful valu es th an some of the deciding th at a ll hi gh jumpers should lean backward previous ones. and latera ll y as much as possible at th e start of th e [Note for other researchers (coaches and takeoff ph ase, and then change th ose angles of lean athletes can skip this paragraph): In this report, arm as little as poss ibl e during th e takeoff phase itself, it activeness was expressed as the vertical range of is necessary to take two po ints into consid erati on. motion of the c. m. ofeac h arm during the takeoff First of a ll , sma ll valu es of BFTD, t.BF, LRTD and phase (re lative to the upper end of the trunk), t.LR are not onl y statisti call y associated w ith larger multiplied by the fraction of the whole body mass that verti cal velociti es at th e end of th e takeoff phase corresponds to the arm, and divided by the standing (whi ch is good), but also with less angul ar height of the subject. Th e activeness of the lead leg momentum (see be low), and th erefore w ith a less was similarly measured as the vertical range of effecti ve rotati on during the bar clearance. motion of the c. m. of the lead leg during the takeoff A lso, we can't be complete ly certa in that small phase (relative to the lower end of the trunk), valu es of BFTD, t.BF, LRTD and t.LR produce a multiplied by the fraction of the whole body mass that takeoff that generates a larger amount of verti cal corresponds to the lead leg. and div ided by the velocity and therefore a hi gher peak he ig ht for the standing height of the subject. In effect, this means c. m . We don't understand well the cause-effect that the activeness ofeac h free limb was expressed as mechani sms behind th e stati sti cal re lati onships, and it the number of millimeters contributed by th e limb is poss ibl e to offer altern ati ve expl anati ons, such as motion to the lifting of the c. m. of the whole body this one: Weaker athletes are not able to generate during the takeoffp hase, per meter of standing much lift, mainly because th ey are weak. Therefore, height. Defined in this way, the activeness of each they are not able to jump very high. This makes f ree limb considers th e lim b's mass, its average them reach the peak of th e jump re lative ly soon after vertical velocity during the takeoffp hase, and the takeoff. Consequently, th ey will want to rotate faster duration of this vertical motion. It allows the in the ai r to reach a norma l hori zontal layout position comparison ofo ne j umper with anoth er, and also at th e peak of the jump. For thi s, they will generate direct comparison of the lead leg action with the arm more angul ar momentum during th e takeoff, which in actions.] turn w ill require larger values ofBFTD, t.BF, LRTD Table 4 shows the acti veness of th e arm nearest and t.LR. We can't be sure of which interpretati on is to th e bar (AAN) and o f th e arm farth est from th e bar th e correct one: Does the trunk til t affect the he ight (AAF), th e summed acti veness of th e two arms of th e jump, or does th e weakness of th e athlete affect (AAT), the acti veness of th e lead leg (LLA) and th e th e height of the jump and ( indirectly) th e trunk tilt? combined acti veness of a ll three free limbs (FLA). Or are both explanations partly correct? At this point, (As explain ed in th e previous paragraph, coaches and we don't know for sure. athletes don't need to worry about th e fin e deta il s of how th ese va lues w ere calculated ; th ey only need to Arm and lead leg actions keep in mind th at larger numbers ind icate greater The acti ons of th e arms and of th e lead leg ac tiveness of th e limbs during the takeoff.) during the takeoff phase are very important for th e Figure 9 shows a plot of AA F versus AAN for outcome of a high jump. When th ese free limbs are the ana lyzed tria ls. The farth er to th e ri ght th at a point is on the pl ot, the g reater th e acti veness of th e 16 Figure 9 AAF (mm/m) 14 0 SEL42 HUT 72 SEL 03 {:) • 12 }:{ NIE 36 NIE 62 SHU 28 10 + }:{ NIE I NIE 99 HAR I I SHU+ 95 ... }:{ HAR I7 37 ... NIE24 i E OIL 97 NIE 13 • HAR 30 8 ...... HAR 21 0 MO F 40 LIT 48 ... HAR 61 0 ... b. MOF 84 HAR 38 6 W•IL 82 4 WI•L 16 2 4 6 8 10 AAN (mm/m) 17 arm nearest to the bar; th e hig her up that a point is on detrimenta l. Short takeoffs go together with a strong the plot, the greater the activeness of the arm farthest acti on of the takeoff leg (good), but a lso with weak from the bar. The ideal is to be as far to th e ri ght and arm actions and w ith a high c.m. position at th e start as high up as possible on th e graph, as this g ives the of th e takeoff phase (bad). In sum , takeoff times are largest valu es for th e total arm action, AA T, also informative, but the length of th e takeoff time by shown in th e graph. itself does not necessarily indicate good or bad For a good arm acti on, both arms should swing technique. strongly forward and up during th e takeoff phase. The arm s should not be too fl exed at th e e lbow Change in horizonta l velocity during the takeoff during the swing - a good e lbow angle seems to be phase somewhere between full extens ion and 90° of It was explained before that the athlete should fl ex ion. have a large hori zontal velocity at the instant The diagonal lin e going from the lower left immediately before th e takeoff foot is planted on the corner of Figure 9 toward the upper right part of the ground to start the takeoff phase, and that therefore graph indicates the points for which both arms would no horizonta l velocity should be lost before that have the same activeness. T he positi ons of th e po ints in stant. However, th e hori zonta l velocity should be above the diagonal lin e reflect a well- established fact: reduced consid erably during the takeoff phase itself. High jumpers are genera lly more active w ith th e arm The losses of horizontal velocity th at all high jumpers that is farth est from th e bar. experi ence during the takeoff phase (see tlv1.1 in Table Some high jumpers ( in c luding many women) fail 3) are due to th e fact that th e jumper pushes forward to prepare their arms correctly in the last steps of the on the ground during the takeoff phase, and therefore run-up, and at the beginning of the takeoff phase the receives a backward reaction force from the ground. arm nearest to the bar is ahead of the body in stead of These losses of hori zonta l velocity during the takeoff behind it. From this position th e arm is not able to phase are an intrinsic part of the takeoff process, and swing strongly fo rward and upward during the th ey are associated with the generation of vertical takeoff, and these jumpers usua lly end up with small velocity . !fan athl ete does not lose much hori zo ntal AAN va lu es. These athletes should learn to bring velocity during the takeoff phase, this may be a sign both arm s back in the final one or two steps of the that the athlete is not mak in g good use of the run-up, so that both arms can later swin g hard hori zonta l velocity obtained during th e run-up. We forward and up during th e takeoff phase. Learning cou ld say that th e athlete should produce a lot of this kind of arm action will take some time and effort, hori zontal velocity during the run-up so that it can but it should he lp these athletes to jump higher. If a th en be lost during the takeoff phase while the athl ete jumper is unable to prepare th e arm s for a double-arm obtains vertical velocity . If not enough hori zontal action, the forward arm should be in a low pos ition at velocity is produced during the run-up, or if not the start of the takeoff phase. That way, it can be enough of it is lost during the takeoff phase, we can thrown upward during the takeoff, alth ough usuall y say that th e run-up is not being used appropriately to not quite as hard as with a double-arm action. help th e athlete to jump higher. Figure I 0 shows a plot of LLA versus AAT for the ana ly zed trials. T he farther to the ri ght th at a Height and vertical velocity of th e c.m. at the end point is on the plot, th e greater th e combined of th e takeoff phase acti veness of th e arms; th e higher up that a point is on The peak he ight th at the c.m . will reach over the the plot, the greater th e activeness of the lead leg. bar is complete ly determined by th e end of the The ideal is to be as far to th e right and as high up as takeoff phase: It is determined by th e height and the possibl e on the graph, as this g ives the largest values vertical velocity of the c.m . at th e end of the takeoff. for the total free limb action, FLA, a lso shown in the At the instant that th e takeoff foot loses contact graph . with the ground, the c.m . of a high jumper is usually at a height somewhere between 68% and 73 % of the Ta keo ff ti me standing height of th e athlete. This means that ta ll The duration of the takeoff phase (TTO ) is shown hi gh jumpers have a built-in advantage: Their in Table 5. (Due to the s low camera speeds used, the centers of mass will genera ll y be higher at the instant valu e ofTTO can eas il y be in error by 0.01 s, and that they leave th e ground. sometim es by as mu ch as 0.02 s.) This "takeoff The vertical velocity of th e c.m. at th e end of the tim e" is influenced by a seri es of factors. Some of takeoff phase (vzTO, shown in Table 3) determines them are beneficial for th e jump; oth ers are how much h ig her the c.m. wi ll travel beyond the takeoff height after the athlete leaves the ground . 18 Figure 10 LLA (mm/m) 30 HUT72 25 • ';\:) 0 SEL 03 MOF40 <> <> 20 }:{ SEL42 0 NIE 62 MOF 84 NIE 17 }:{ }:{ NIE99 0 NIE 13 + sHU95 MOF 33 NIE 37 NIE 24 A \.DIL97 15 Ll 8 SHU 28 NIE 36 }:{ WIL 16 T 1><\:1 I-IAR61 eT W•IL82 HAR 38 T HAR II T 10 HARI 7 T HAR 21 T HAR 30 ~~ '\:::_~ "'\:) ~-y"'?- 5 ry\:1 '\-\:) 0 0 5 10 15 20 25 AAT (mm/m) L9 Table 5 Takeo ff time (Tro), height of th e bar (hBAR ), o utcome of the jump, maximum he ight of the c.m. (h, K), clearance height in th e pl ane of th e stand ard s (hcLs), absolute clearance height (hcLA), effectiveness of th e bar cl earance in the plane of th e standards (~ h c L s ) , and absolute effecti veness o f th e bar clearance (~ h cLA ) ; tw istin g angul ar momentum (1-J.,- ), forward somersaulting angul ar momentu m (HF), lateral somersaulting angul ar momentum (HL) and total somersa ulting angul ar momentum (Hs) du ri ng th e airborne phase. Note: So me of the valu es in thi s table may not fit perfectl y with each oth er, because of ro unding off. Athl ete Trial and TTo hnAR O utcome hi'K hu .s hu .A ~h c1.s ~ h ci.A HT H,. H ~. Hs meet (*) (s) (m) (m) (m) (m) (m) (m) (**) (**) (**) (**) Dilling 97 U07 0. 17 2.27 clea rance 236 2.27 2.28 -0.09 -0.08 30 80 35 90 Harris 2 1 UO I 0. 18 2.24 clearance 234 2.25 2.28 -0. 09 -0.06 50 90 80 120 17 U02 0. 18 2.24 clearance 2.33 2.26 230 -0.07 -0.03 60 65 90 11 0 II U03 0. 17 2.22 clearan ce 2.33 2. 17 2.26 -0.14 -0.07 55 55 90 105 30 T04 0. 16 2.27 clearance 2.28 2.25 2.25 -0.03 -0.03 65 100 90 135 38 U06 0. 15 230 clearance 2.38 235 235 -0.03 -0.03 55 85 90 120 6 1 U07 0.18 2.2 1 clearance 2.28 2. 24 2.26 -0.04 -0.02 55 75 95 120 Hutchinson 72 U07 0.22 2.2 1 clearance 2.27 2.2 1 2.22 -0.06 -0.05 50 60 70 90 Littl eton 48 U07 0.16 2.18 clearance 2.20 2.20 2.20 0.00 0.00 45 90 90 125 Mo ffa tt 33 T04 0.17 2.27 clearan ce 235 2.26 230 -0.09 -0.05 40 50 90 100 40 U06 0. 18 230 clearance 2.41 232 233 -0.09 -0.08 50 45 95 110 84 U07 0. 18 2.24 clea rance 2.33 2.25 2.27 -0.08 -0.06 40 45 95 105 Nieto 17 U99 0.19 2.25 clearance 230 230 2.30 0.00 0.00 35 85 95 125 36 UO I 0.20 2.27 mi ss 23 1 2.25 2.28 -0.06 -0.03 40 55 100 11 5 13 U02 0.18 2.24 clearance 23 1 2.27 2.27 -0.04 -0.04 45 60 95 11 0 37 U03 0. 18 230 clearance 236 2.28 234 -0.08 -0.02 45 65 100 120 62 T04 0. 18 233 clearance 235 23 1 235 -0.04 0.00 55 70 95 11 5 24 U06 0.18 2.24 mi ss 2.28 2.2 1 2.23 -0.07 -0.05 40 65 95 11 5 99 U07 0. 19 2.25 clearance 2.30 2.28 2.29 -0.02 -0.0 1 35 65 100 11 5 Se ll ers 03 U06 0. 17 2. 19 clearance 2.27 2.20 2.2 1 -0.07 -0.06 45 80 70 105 42 U07 0. 18 2.18 clearance 2.24 2. 18 2. 18 -0.06 -0.06 45 70 75 105 Shunk 28 T04 0. 19 2.27 miss 2.25 2.2 1 2.22 -0.04 -0.03 60 75 90 11 5 95 U07 0. 19 2.27 miss 2.27 2.23 2.28 -0.04 +0.0 1 55 55 95 11 0 Willi ams 16 T04 0. 16 2.24 clearance 2.28 2.25 2.25 -0.03 -0.03 50 90 75 120 82 U07 0. 15 2.24 clearance 232 2.25 2.27 -0.07 -0.05 30 80 75 11 0 (*) U99 = 1999 USATF Ch.; UO I = 200 I USATF Ch.; U02 = 2002 USA TF Ch., U03 = 2003 USATF Ch.; T04 = 2004 US O lympic T ri als; U06 = 2006 USATF Ch., U07 = 2007 USATF Ch. (** ) Angul ar momentum units: s·' · 10·' Height of the bar, pea k height of the c.m., and been cleared successfu ll y ; if the bar stays up, th e clearance height athlete is credited with the height at which the bar The height of th e bar (h sAR), th e maximum was set, even if the jumper had room to spare over it. height reached by th e c.m . (hrK) and the outcome o f Usin g computer modeling and graphics, it is th e jump are shown in Table 5. possible to estimate the approximate maximum The true value of a high jump generally is not height that an ath lete would have been able to c lear kn own: If the bar is knocked down, the jump is ruled clean ly without touching the bar in a g iven jump a fou I and the ath lete gets zero credit, even though a ("clearance height"), regard less of whether the actual hypoth eti cal bar set at a lower height would have jump was offic ially a valid clearance or a foul. 20 Figure II shows three im ages of a high jumper's Takeo ff distance clearance of a bar set at 2.25 m . Figure 12 shows all The distance between the toe of the takeoff foot the im ages obta in ed through v id eo ana lysis of the bar and th e pl ane of the bar and th e standard s is call ed clearance. In Figure 13 th e drawing has been the "takeoff distance" (Figure 2). The va lu e of this saturated w ith interm ediate positions of the high di stance is shown in Tabl e 2, and it is important jumper, calcul ated through a process call ed because it determines th e pos it ion of the peak of the curvil inear interpo lation. The scale in th e "saturati on jump re lative to the bar: If an athlete takes off too fa r drawin g" shows th at in this jump th e athlete would from the bar, th e c. m . w ill reach its maximum he ight have been able to c lear a bar set in the plane of the before crossing th e p lane of th e standards, and th e standards at a he ight of 2.34 m (hc Ls) without jumper will probably fall on the bar; if the athlete touching it. A closer examinati on of Figure 13 a lso takes off too c lose to the bar, there w ill be a large ri sk shows that th e maximum he ight of th e " ho ll ow" area of hitting the bar w hile the c. m. is on the way up, left be low th e body was no t perfectl y centered over before reaching its max imum he ight. Different the bar: If this athlete had taken o ff c loser to the athl etes usually need different takeoff distances. The plane of th e stand ard s, he would have been able to optimum va lu e fo r the takeoff distance of each clear a bar set at an absolute maximum height of athl ete is th e one that wi ll make the c.m. of th e 2.35 m (hcLA) w ithout touching it. j umper reach its max imum he ight more or less Due to errors in the d ig iti zati on of the film s or directl y over th e bar, and it will depend primarily on v id eotapes, in the thicknesses of th e vari ous body the fin a l directi on of th e run-up and on th e amount of segments of the computer graphics model and in the residua l horizontal velocity th at the athlete has left degree of curvature of the trunk in th e drawings, th e after th e completion of the takeoff phase. valu e of the clearance he ight in the plane of the In genera l, athletes w ho travel more standards (hcLs) and the valu e of the absolute perpendicu Jar to the bar in the f in a l steps of the run clearance he ight (hcLA) obta ined us ing th is method up (indicated by large p2 and p 1 ang les in T able 2) are not perfectly accurate. A test showed that hcLs will also travel more perpendicular to the bar after the wi ll be over- or underestimated on the average by completion of th e takeoff phase (indicated by large p0 between 0.02 m and 0.03 m, but this w ill be larger or ang les in T able 2), and they will need to take off sma ll er in individua l cases. Therefore, the calcul ated farther from th e bar. In general, ath letes w ho run clearance he ight valu es should be consid ered onl y faster in the fin al steps of th e run-up (indicated by rough estimates. It is a lso necessary to keep in mind large values of v1-12 and V H 1 in T abl e 3) will also have th at high jumpers can generally depress the bar about more hori zontal velocity left after takeoff (indicated 0.02 m, sometimes 0.04 m, and occasional ly 0.06 m by large va lues ofvHro in Table 3); thus, they will or more w ithout knocking it down. trave l through larger hori zonta l distances after the T he differences between th e clearance he ights completion of the takeoff phase than s lower j umpers, and th e peak he ight of th e c.m . indicate the and th ey will a lso need to take off farther from th e effec ti veness of th e bar c learance in th e pl ane of th e bar in ord er for th e c.m . to reach its max imum he ight standard s (.::lhc Ls = hcLs - hrK) and th e absolute more or less directly over the bar. effecti veness of the bar c learance (.::lh cLA = he LA - High jumpers need to be able to judge after a hrK)· Larger negati ve numbers indicate less effecti ve miss whether th e takeoff po in t might have been too bar c learances. close or too far from the bar. This can be done by Tabl e 5 shows the max imum he ight that the paying attention to th e time when the bar was hit. If ath lete would have been able to clear without th e bar was hit a long time after the takeoff, this touching th e bar in th e plane of th e standard s (hcLs), probably means that the bar was hit as th e athlete was th e absolute max imum he ight that the athlete would coming down from the peak of the jump, imply in g have been able to c lear w ithout touching the bar that the athlete took off too far from the bar, and in (hcLA), th e effecti veness of the bar c learance in the that case the ath Jete should move th e starting po int of plane of th e standard s (.::lh c Ls )a, and the bsolute the run-up s li ghtly closer to th e bar; if th e bar was hit effecti veness of th e bar c learance (.::lh cLA) in th e very soon after takeoff, this probably means th at th e analyzed tria ls. bar was hit w hile th e athlete was still on the way up The most usua l reasons fo r an ineffecti ve bar toward th e peak of the jump, imply in g that th e clearance are: taking off too c lose or too far from th e takeoff po int was too c lose to the bar, and in th at case bar, in suffic ient amount of somersaulting angul ar the athlete should move the starting po int of th e run momentum, in sufficient twist rotati on, poor arching, up sli ghtly farther from the bar. and bad timing of th e arching/un-arching process. These aspects of high jumping technique w ill be Angular mo mentum discussed next. Angul ar mo mentum (also call ed " rotary 21 Figure 11 HARKEN #34 062787 2.25 M CLEARANCE 22 Figure 12 HARKEN ~34 062787 2 . 25 M CLEARANCE 23 Figure 13 HARKEN *34 062787 2 . 25 M CLEARANCE 24 momentum") is a mechanical factor that makes the during the takeoff phase. athl ete rotate. High jumpers need th e ri g ht amount of Statistics show th at jumpers w ith a very large angul ar momentum to make in th e air the rotations backward lean at th e start of the takeoff phase (s ma ll necessary for a proper bar clearance. The athlete BFTD ang les) do not get quite as much forward obtains th e angular momentum during the takeoff somersaulting angular momentum as other jumpers. phase, through the forces that the takeoff foot makes The reasons for this are not completely clear. on the ground; the angular momentum cannot be The forward somersaulting angular momentum changed after the athlete leaves the g round. can also be affected by the actions of the arms and The bar c learance technique of a Fosbury-flop lead leg. Wide swings of the arm s and of th e lead can be described roughly as a twisting somersault. leg during the takeoff can help the athl ete to jump To a great extent, th e twist rotation (whi ch makes the hi gher (see "Arm and lead leg actions" above). athl ete turn the back to the bar during the ascending However, in a v iew from the sid e (top sequence in part of the fli ght path) is generated by swin g in g the Figure 16) they also imply backward (clockwise) lead leg up and somewhat away from th e bar during rotations of these limbs, which can reduce th e total the takeoff, and sometimes also by actively turning forward somersaulting angular momentum of the the shoulders and arms during the takeoff in the body. desired direction of th e twist. These actions create To diminish this problem, some hi gh jumpers angu lar momentum about a vertical ax is . This is turn their back toward th e bar in the last step of the call ed th e twisting angul ar momentum, Hr. The Hr run-up, and then swing the arms diagonally forward valu es of the analyzed athletes are shown in Table 5. and away from th e bar during the takeoff phase (see Most hi gh jumpers have no difficulty obtaining an Figure 17). Since this diagonal arm swin g is not a appropriate amount of Hr . (However, we will see perfect backward rotation, it interferes less with the later that the actions that the athlete makes in th e a ir, generati on of forward somersaulting angul ar as well as other factors, can a lso s ignificantly affect momentum. wheth er the hi gh jumper will be perfectl y face-up at the peak of th e jump, or tilted to one s ide with one hip lower than the other.) Figure 14 The somersault rotati on, which will make the shoulders go down while the knees go up, results from two components: a forward somersaulting component and a latera l somersaulting component. (a) Forward somersaultin g ang ular momentum (H F) During the takeoff phase, the (a) (b) athl ete produces angul ar momentum about a horizontal ax is perpendicul ar to the final direction of the run-up (see Figure 14 a and the sequence at the '· top of Figure 15). This forward rotation is s imilar to the one produced when a person hops off from a movin g bus facing the direction of moti on ofthe bus: side view back view After the feet hit th e ground, the tend ency is to rotate forward and fall flat on one's face . It can be described as angular momentum produced by th e checking of a linear motion . -...... _ -...... _ final run- up direc1io n The tilt ang les of the trunk at the start and at th e end of the takeoff phase (see "Trunk lean") are ...... _/'...... _ 8 statisti cally related to the angular momentum G III. 1.\II.R,\I ·;Q obtain ed by th e athlete. Large changes of the trunk "1)\II ·R"'i\l il ll'\'i...l -V'...... I tilt from a backward position toward vertical during RUL\110' :::::-.... I the takeoff phase are associated with a larger amount --G---~ - of forward somersaulting angular mo mentum. This makes sense, because athletes with a large amount of (c) IliSl "IIA' I / ~"'P" ' Hs !\o, u ~ ~ riC;" ='"I I'D -Ul BACKVIEW N Vl 10 . 22 10.20 10 . 18 10 . 16 10.14 10 . 12 10.10 10 .08 10.06 10 .04 10.02 10.00 DIRECT FORWARDARM SWING SIDE VIEW ~ IJCI= ~ ..... 0'\ BACKVIEW N0\ 10.22 10 .20 10.18 10.16 10.14 10.12 10.10 10 . 08 10.06 10.04 10.02 10.00 DIAGONALARM SWING SIDE VIEW ~ dQ" ='"I ~ ..... -...J BACKVIEW N -...l 10 . 22 10.20 10.18 10 . 16 10.14 10 . 12 10.10 10.08 10.06 10.04 10.02 10.00 28 (b) Lateral somersaulting angular jumpers th at it is necessary to seek a compromise momentum (HL) During th e takeoff phase, angular between lift and rotati on. momentum is also produced abo ut a hori zontal ax is The bottom sequence in Figure 17 shows that in in Iin e w ith the f in a l directi on of th e run-up (see an athlete who takes off from th e left leg a d iagona l Figure 14 b and th e bottom sequence in Figure 15). In arm swing is associated with a clockw ise moti on of a rear view of an athlete who takes off from th e left th e arm s in a view from th e back, and th erefore it leg, this ang ul ar momentum component appears as a contributes to th e generati on of lateral somersaulting c lockwise rotati on. angul ar momentum . If th e j umper made use of a straight run-up, in a High jumpers usually have more lateral th an rear v iew th e athlete would be uprig ht at touchdown, fo rward somersaulting angul ar momentum. The sum and leaning toward th e bar at the end of th e takeoff. of th ese two angular momentum components adds up Since a leaning position would result in a low er to th e required total (or "resultant") somersaulting height of th e c.m . at th e end of th e takeoff phase, the angul ar momentum, Hs ( Figure 14c). (This is not a producti on of angul ar momentum would thus cause a simple addition; th e fo rmula is Hs = + .) reduction in the verti cal range of moti on of th e c.m . ~H ~ H ~ during th e takeoff phase. However, if th e athlete uses The fo rward (HF) , lateral (HL) and total (Hs) a curved run-up, the initia l lean of th e athlete to the somersaulting ang ul ar momentum valu es of th e left at the end of th e approach run may a ll ow th e analyzed athletes are shown in Table 5, and in athlete to be upright at th e end of th e takeoff phase graphical fo rm in Figure 18. (To fac ilitate (see Figure 14 b and th e bottom sequence in Figure compari sons among athletes, th e angul ar momentum 15). The fi nal upright positi on contributes to a higher valu es have been norma li zed for th e weight and c. m . pos ition at the end of the takeoff phase. Also, standing height of each athlete.) In genera l, athl etes th e initia l latera l tilt contributes to a lower c.m. w ith more angul ar momentum tend to rotate faster. positi on at the start of th e takeoff phase. Therefore Female high jumpers tend to acquire more the curved run-up, togeth er w ith the generation of angular momentum than male high jumpers. This is latera l somersaulting angul ar mo mentum, contributes because th e women don't jump quite as hig h, and to in crease the vertical range of motion of the c. m. th erefore th ey need to rotate faster to compensate for during the takeoff phase, and thus permits greater lift th e sma ll er amount of time th at they have availabl e th an if a stra ig ht run-up were used. (However, so me between th e takeoff and the peak of the jump. caution is necessary here, s in ce statisti cal informatio n suggests that j umpers w ith an excessive lean toward Adj ustm ents in the a ir th e center of th e curve at the start of th e takeoff phase Afte r the takeoff is completed, th e path of the tend to get a sma ll er amount of latera l somersaulting c. m . is totall y determined, and nothing can be done to angul ar momentum th an j umpers w ith a more change it. However, this does not mean th at th e moderate lean. The reasons forth is are not clear. ) paths of a ll parts of th e body are determined. What T here is some statisti cal associati on between cann ot be changed is th e path of th e point that large changes in the left/ri ght tilt angle of th e trunk represents th e average position of all body parts (th e during th e takeoff phase and large amounts of lateral c.m.), bu t it is possible to move one part of the body somersaulting angul ar momentum at the end of th e in one directi on if other parts are moved in th e takeoff phase. T hi s makes sense, because ath Ietes opposite directi on. Us in g this princ ipl e, after the w ith a large amount of latera l somersaulting angular shoulders pass over th e bar th e high jumper can ra ise momentum at the end of th e takeoff phase should the hips by lowering th e head and th e legs. For a also be expected to have a large amount of it already g iven position of th e c.m ., th e farther the head and during the takeoff phase, whi ch should contribute to a th e legs are lowered, the higher the hips will be lifted. greater rotati on of the trunk during th e takeoff phase Thi s is th e reason for the arched position on top of from its initial latera l directi on toward th e vertical. the bar. The reader should be reminded at this point that To a great extent, th e rotati on of th e high j umper alth ough large changes in tilt during th e takeoff phase in th e a ir is a lso determined once the takeoff phase is and, to a certain extent, sma ll backward and latera l completed, because th e angul ar momentum of the leans of the trunk at the start of th e takeoff phase athlete cannot be changed during the airborne phase. (i .e., large BFTD and LRT D valu es) are associated However, some a lterati ons of th e rotati on are still w ith in creased angul ar momentum, th ey are a lso possibl e. By s lowing down th e rotati ons of some stati sti cally associated wi th reduced vertical ve locity parts of the body, oth er parts of the body w ill speed at th e end of th e takeoff phase, and th erefore with a up as a compensati on, and vice versa. For instance, reduced max imum he ight of the c.m. at the peak of th e athlete shown in Fig ure 19a slowed down the the j ump. This supports th e intuitive feeling of high counterc lockw ise rotation of th e takeoff leg shortly 29 Figure 18 120 100 80 60 40 20 0 0 20 40 60 80 100 120 140 HF 30 Figure 19 ._.-..0 -._.() ~r r ~ --~ C c__ ~ F ~------~ ~ "'00 0 .-< "' 0 .-< 31 after th e takeoff phase was completed, by fl exing at somersaulted faster: Both jumpers had th e same tilt the kn ee and extending at the hip ( t = I 0.34 - at t = I 0.22 s, but at t = I 0.94 s the athlete in Figure 10 .58 s). In reacti on, this helped th e trunk to rotate 19c had a more backward-rotated position than th e faster counterc lockwise, and th erefore contributed to athlete in Figure 19b. The faster speed of rotati on of produce th e horizonta l position shown by th e trunk at th e jumper in Figure 19c was due to hi s more t = 10.58 s. Later, from t = I 0.5 8 tot = 10.82 s, the compact body configurati on in the peri od between t = athlete slowed down th e counterclockwise rotati on of I 0.46 s and t = 10.70 s. It was achi eved ma inly th e trunk, and even reversed it into a c lockwise through a greater fl exion of the knees. This rotati on; in reacti on, th e legs s imultaneously configurati on of th e body reduced th e athlete's in creased th eir speed of rotation counterc lockwise, moment of inertia about an ax is parall e l to the bar, and thus cleared th e bar (t = 10.58- I 0.82 s). and made him somersault fas ter. (The jumps shown The principl es of acti on and reacti on just in Figures 19b and 19c were artific ia l jumps described both for translation and rotati on result in produced usin g computer s imulati on - see below. th e typi cal arching and un-arch in g actions of high This ensured that th e athlete had exactl y th e same jumpers over the bar: The ath lete needs to arch in position at takeoff and th e same amount of angular order to lift the hips, and then to un-arch in ord er to momentum in both jumps. ) speed up th e rotati on of th e legs. As the body un The technique used by the athlete in Figure 19c arches , th e legs go up, but th e hips go down. can be very helpful for high jumpers with low or Therefore, timing is critical. If th e body un-arches moderate amounts of somersaulting angul ar too late, th e calves will knock th e bar down; if the momentum. Both jumps shown in Figures 19b and body un-arches too earl y, th e athlete w ill " sit" on th e 19c had the same amount of angular momentum (H s bar and w ill also kn ock it down. = I I 0), and th e center of mass reached a peak he ight There can be several reasons for an athlete's 0.07 m higher than the bar in both jumps. While th e weak arching. The athlete may be un aw are that athlete in Figure 19b hit th e bar with his calves (t = he/she is not arching enough. Or th e athlete is not I 0.82 s), the faster somersault rotati on of the athlete able to coordinate properl y th e necessary actions of in Figure 19c help ed him to pass all parts of th e body th e limbs. Or th e athlete is not flexib le enough. Or over th e bar with some room to spare. th e athlete is fl exible enough but has w eak abdominal In the rare cases in which a high jumper has a muscles and hip fl exor muscles (the muscles that pass very large amount of angular mo mentum, the in front of th e hip joint), and therefore is re luctant to technique shown in Figure 19c could be a li ability, arch very much sin ce he/she is aware th at the because it might accelerate th e rotati on so much th at necessary un-arching acti on that will be required later th e shoulders will hit the bar on the way up . For will be imposs ible to execute with th e necessary athletes with a large amount of angul ar momentum, it forcefulness due to th e weakness of th e abdominal will be better to keep the legs more extended on th e and hip fl exor muscles . way up to th e bar, fo ll owing the body configurati on Anoth er w ay in which rotati on can be changed is pattern shown in Figure 19b. This will temporarily by altering th e "moment of inertia" of the body . The slow down the backward somersau lt, and thus moment of in ertia is a number th at indicates whether prevent the athlete from hitting the bar with th e th e vari ous parts th at make up th e body are c lose to shoulders on the way up to th e bar. (Of course, th e th e ax is of rotation or far from it. When many parts athlete will still need to arch and un-arch with good ofthe body are far from the ax is of rotati on, th e timing over th e bar.) moment of inertia of th e body is large, and this decreases th e speed of turning about th e ax is of The twist rotation; problems in its execution rotation. Vi ce versa, if most parts of th e body are It was pointed out earli er th at th e tw ist rotati on kept close to th e ax is of rotati on, th e moment of in hi gh jumping is produced to a great extent by th e in ertia is sma ll , and th e speed of ro tati on in creases. tw isting component of angular momentum , HT. But This is what happens to fi gure skaters in a view from it was a lso mentioned th at oth er factors could affect overhead when th ey spin: As they bring th eir arms whether the jumper would be perfectl y face-up at th e closer to th e vertical ax is of rotation, th ey spin faster peak of th e jump, or tilted to one sid e with one hip about the vertical ax is. In high jumping, rotati on lower than the oth er. One of th e most important of about a hori zontal axis paralle l to th e bar (i.e., the these factors is th e proporti on between th e sizes of somersault) is genera lly more important th an rotation the forward and lateral components of th e about th e vertical ax is, but th e same princ iple is at somersaulting angul ar momentum. We w ill now see work . The jumps shown in Fig ures 19b and 19c both how this works. had th e same amount of somersaulting angul ar Figure 20 shows sketches of a hypoth eti cal high momentum. However, th e athlete in Fig ure 19c jumper at th e end of the takeoff phase and after three 32 Figure 20 lower th an th e hip of the lead leg. Another point that we have to take into account is th at, while th e twisting component of angular needs 90° twist momentum (Hr) is a major factor in the generati on of (b) th e twist rotation in high jumping, it is generall y not needs 135° twist needs 45° twist enough to produce th e necessary face-up pos ition on top of th e bar: In addition, the athlete a lso needs to (c) (a) use rotational action and reacti on about the longitudinal axis of th e body to increase the amount bar of twist rotati on th at occurs in the a ir. In a norma l high jump, th e athlete needs to achi eve about 90° of twist rotati on between takeoff and the peak of the jump. Approximately half of it (about 45 °) is initial body {I produced by the twisting angul ar momentum ; th e orientation at takeoff oth er half(roughl y anoth er 45°) needs to be produced through rotationa l action and reacti on. Rotati onal acti on and reaction is sometimes call ed "cattin g" because cats dropped in an upsid e-down position w ith no angu lar mo mentum use a mechanism of this kind to land on their feet. The catting that takes place in th e twist rotation of a hi gh jump is diff icult to see, because it is pure somersault rotations in different directions (with obscured by th e somersault and twist rotations no twist), a ll viewed from overh ead. For s implicity, produced by th e angular momentum. If we could we have assumed that the final directi on of the run-up "hide" the somersault and twist rotations produced by was at a 45° angle with respect to the bar. A normal th e angul ar momentum, we would be abl e to iso late combin ation of forward and latera l components of the catting rotation, and see it c learl y. To achieve somersaulting angular momentum would produce at that, we would need to look at th e hi gh jumper from the peak of the jump th e pos ition shown in image b, the viewpoint of a rotating camera. The camera which would require in addition 90° of twist rotati on would need to somersault with the athlete, stay in g to generate a face-up orientation. If instead an athlete aligned with the athlete's long itudinal ax is. The generated only lateral somersaulting angular camera would also need to twist with th e athlete, just momentum, the result would be th e position shown in fast enough to keep up with th e portion of the twist image a, whi ch wou ld require onl y about 45° of twist rotation produced by the twisting component of rotation to achi eve a face-up ori entation ; if the athlete angu lar momentum. That way, all that would be left generated only forward somersaulting angular would be th e rotation produced by the catting, and momentum, the result would be th e position shown in this rotati on is what would be visible in th e camera's image c, whi ch would require about 135° oftwist view. It is impossibl e to make a real camera rotate in rotation to achi eve a face-up orientation . It is very such a way, but we can use a computer to calculate unusual for hig h jumpers to have onl y lateral or how th e jump would have appeared in th e images of forward somersaulting angular momentum, but many such a camera if it had existed. This is what is shown jumpers have much larger amounts of one than of th e in Figure 2 1. oth er. The example shows that jumpers with The sequence in Figure 2 1 covers the peri od parti cul arly large amounts of forward somersaulting between takeoff and the peak of th e jump, and angu lar momentum and small amounts of latera l progresses from left to ri ght. All the im ages are somersaulting ang ul ar momentum will need to tw ist viewed from a directi on a ligned with th e longitudina l more in th e air if th e athl ete is to be face up at the axis of th e athlete. (The head is th e part of the athlete peak of th e jump. Otherwise, th e body will be tilted, nearest to the " camera".) As th e jump progressed, w ith th e hip of the lead leg lower than the hip of the the camera somersaulted with th e ath Jete, so it stayed takeoff leg. Conversely, jumpers with particul arly ali gned with th e athl ete's longitudinal ax is. The large amounts of latera l somersaulting angul ar camera a lso twisted counterc lockwise w ith th e momentum and small amounts of forward athl ete, just fast enough to keep up with th e portion somersaulting angul ar momentum wi ll need to twist of the twist rotati on produced by the twisting less in th e air than other jumpers in ord er to be component of angul ar mo mentum. Figure 21 shows perfectl y face up at th e peak ofthejump. Otherwise, a c lear counterclockwise rotati on of the hips (about the body will be tilted, with th e hip of th e takeoff leg 45°) between th e beginning and th e end of th e 33 Figure 21 actio ns rcactio{j-..._ f \ ~ sequence. This implies that the athlete rotated takeoff phase; a position th at is too tilted toward th e coun terc lockwise faster th an th e camera, i.e., faster ri ght at the end of the takeoff phase (toward the left than the part of th e twist rotati on produced by the in th e case of jumpers taking off fr om th e ri ght foo t); twistin g component of angular momentum. The premature lowering of th e lead leg soon after takeoff. coun terc lockwise rotation of the hips v isible in the When this kind of probl em occurs, it w ill be sequence is th e amoun t of twist rotation produced necessary to check th e cause of th e probl em in each th ro ugh catting. It occurred mainly as a reacti on to individua l case, and then decid e what would be the th e clockwise moti ons of the rig ht leg,m whi ch oved eas iest way to correct it. toward the ri ght, and th en backward . (These acti ons of the ri ght leg are subtle, but neverth eless vis ibl e in Control of airborne movements; computer the sequence.) In part, th e counterclockw ise catting simulation rotation of th e hips was a lso a reacti on to the We have seen th at th e c.m. path and th e angul ar clockwise rotation of the ri ght arm. Without th e momentum of a high jumper are determ ined by th e catting, th e tw ist rotati on of this athlete would have time th e athl ete leaves th e ground. We have also been redu ced by an amount equ ivalent to th e seen that in spite of th ese restricti ons on th e freedom approxim ate ly 45 ° of counterc lockwise rotation of the jumper, th e athlete sti II has a certain degree of visible in the sequence of Fig ure 2 1. control over th e movements of th e body during the Some j umpers emphasize th e tw isting ang ul ar airborn e phase. momentum more; others tend to emphasize th e Sometim es it is easy to predi ct in rough genera l catting more. If not enough twisting angular term s how th e acti ons of certain parts of the body momentum is generated during the takeoff phase, or during the a irborne phase will affect the moti ons of if th e athlete does not do enough catting in th e air, th e the rest of th e body, but it is difficult to judge through athl ete w ill not tw ist enough in th e a ir, which w ill simple "eyeba lling" wheth er th e amounts of moti on make th e body be in a tilted position at th e peak of w ill be suffic ient to achieve th e desired results. th e jump, with th e hip of th e lead leg lower than th e Other times, particularly in complex three hip of th e takeoff leg. T his will put the hip of the dimens ional a irborne motions such as th ose in vo lved lead leg ( i.e., th e low hip) in danger of hitting th e bar. in hi gh j umping, it is not even possible to predict th e T here are other ways in whi ch probl ems can kinds of moti ons th at w ill be produced by actions of occur in th e twist ro tati on. If at the end of th e takeoff oth er parts of the body, let alone th eir amoun ts. phase an athlete is tilting backward too far, or is To he lp solve this problem, a meth od for th e tilting too far toward th e ri ght (too far toward th e left computer s imulati on of human a irborne movements in th e case of a jumper who takes off from th e right was developed (Dapena, 1981 ). In this meth od, we foo t), or if the lead leg is lowered too soon after g ive the computer th e path of th e c.m . and th e takeoff, th e tw ist rotati on w ill be slower. This is due angul ar momentum of the body fro m an actu al j ump to interacti ons between th e somersault and twist th at was filmed or v id eotaped . We a lso g ive th e rotati ons that are too complex to expl a in here. computer th e pattern s of moti on (ang les) of a ll th e According to th e previous discussion, a tilted body segments relati ve to the trunk during the entire posit io n at th e peak of th ejump in whi ch the hip of airborn e phase. T he computer then calculates how the lead leg is lower than th e hip of the takeoff leg the trunk has to move during the a irborn e phase to can be due to a vari ety of causes: an in suffic ient mainta in th e path of th e c. m . and th e angul ar amount of tw isting angular momentum; a much momentum of the whole body the same as in th e larger amount of fo rward than latera l somersaulting orig in a l j ump. If we input to the computer the angul ar momentum ; in suffic ient catting in th e air ; a orig in a l pattern s of moti on of the segments (th at is, backward tilted position of th e body at th e end of th e th e pattern s of motion that occurred in the orig in a l 34 jump), th e computer will gen erate a jump that will be practi ca lly id enti ca l to th e ori g in al jump. But if we input to th e computer altered pattern s of moti on of th e segments, th e computer will generate an altered jump. This is th e jump that would have been produced if th e high jumper had used th e sam e run up and takeoff as in the ori gin al jump, but th en dec id ed to change th e moti ons of th e Iimb s after taking off from the ground . Once th e computer has generated the simu lated jump, thi s jump can be shown usin g graphi c representati ons just like any other jump. With th e simulati on meth od, it is also possibl e to input to th e computer an altered amount of angul ar momentum . This generates a simulated jump that shows how th e athlete would have moved in th e air if th e run -up and takeoff had been changed to produ ce a diffe rent amount of angul ar momentum than in th e ori gin al jump. The co mputer simulati on meth od just described can be used to test for vi able altern atives in th e airborn e ac ti ons of hi gh jumpers, and also to in ves tigate th e effects of different amounts of angul ar momentum. 35 SPEC I FIC R ECOMMEND ATIONS FOR takeoff phase. Then, hi s arm acti ons during th e INDIV IDUAL ATH LETES takeoff ph ase were strong (AAT = 16 .2 mm/m). However, th e acti on of his lead leg was weak (LLA = Jim DI LLING 15. 8 mm/m), and th erefore his overall combinati on of arm and lead leg actions was somewhat weak (FLA = Jump 97 was Dilling's last successful c learance 32. 1 mm/m). at th e 2007 USATF Championships (2.27 m). In jump 97, th e backward lean of Dilling' s trunk Based on Dilling's vertical velocity at takeoff in at th e start of th e takeoff phase was somewhat small j ump 97 (vzm = 4 .40 m/s), a technique of average (BFTD = 79°). Then he rotated fo rward, and by th e quali ty would have in cluded a fina l run-up speed of end of th e takeoff his trunk was 2 o beyond th e about 7.5 m/s and a c. m. he ight at th e end of th e run verti cal ( BFTO = 92°). In th e vi ew from th e sid e, th e up equa l to about 4 7% of his own standing height. trunk should be vertical ( i. e., at 90°) at th e end of the Dilling's actu a l c. m. height at th e end of the run-up takeoff, so Dilling's overrotati on probably produced was s imilar to what might have been expected for a a s li ght loss of li ft. Dilling was able to generate a technique of average quali ty (hm = 47.5%), but he good amount of forward somersaulting angular was faster (vH 1 = 7.8 m/s). The overa ll combinati on momentum (HF = 80). It would have been preferabl e of run-up speed and c. m. height that Dilling used in for Dilling to have a greater amount of backward lean jump 97 was reasonably good for a jumper capabl e of at the start of th e takeoff phase, and then rotated only generatin g 4.40 m/s of vertical velocity. up to th e vertical by th e end of the takeoff. That way, he would have been able to generate the same amount T he last step of Dilling's run-up was somewhat of angul ar momentum without incurring any loss of too long (S L 1 = 2.o 05 m , r I 05 % of hi s own standing li ft. height). This sli ghtly long length of the last step of the run-up probably contributed to Dilling's Dilling' s trunk had a good amount of lean toward somewhat large negative vertical ve locity at the start th e left at th e start of th e takeoff phase ( LRTD = of the takeoff phase (vzm = -0.6 m/s). A large 7r). Then, he rotated toward th e right, but by the negati ve Vzm valu e is not adv isable, because it end of th e takeoff he had not quite reached th e requires the athlete to make an extra effort to stop th e verti cal in th e view from th e back (LRTO = 89°). In downward moti on before producing th e needed th e v iew from th e back, it's norm al to go a few upward vertical ve locity. degrees past the vertical at th e end of the takeoff. We consider it acceptabl e ( indeed, desirable) to tilt up to At the end of th e run-up, Dilling planted th e 10° past the vertical at th e end of th e takeoff(in th e takeoff foo t too para ll e l to th e bar. Because of this, view from th e back) because we beli eve that this may th e angle between th e long itudina l ax is of th e takeoff be th e best compromise between th e generation of li ft foot and the horizontal force received by th e foot was and th e generati on of ro tati on (ang ul ar momentum). too large (e = 33°). This would norma lly lead us to 3 Thus, Dilling's position at th e end of th e takeoff in predict a risk of foot pronation, and injury to th e jump 97 was too conservati ve. Because of this, the ankle and foot. (See th e secti on on "Orientati on of amount of latera l somersaulting angular momentum the takeoff foot, and potentia l for ankle and foot th at he was able to generate was extremely small (HL inj uries" in th e main text of th e report.) However, = 35). (Figure 18 shows th e c learly th e difference direct examinati on of th e vid eos showed little or no between Dilling's HL valu es and those of th e oth er visible pronati on in any of Dilling's jumps. It is high jumpers.) necessary to keep in mind that, due to our cam era locations, it is hard er to actu a lly see pronation in Dilling's forward and latera l components of j umpers who approach from th e ri ght s ide ( lik e somersaulting angular momentum added up to a very Dilling), so it is conceivable th at he might be sma ll tota l amount of somersaulting angul ar pronating w ith out our noti c ing it, but we think this is momentum (Hs = 90). unlike ly. Dilling's small amount of latera l somersaulting Dilling started hi s arm preparati ons too many angular momentum produced two problems. The steps before th e takeoff. Therefore, he spent too most important one was that it redu ced his total many steps running w ith th e arms out of sync w ith amount of somersaulting angul ar mo mentum, which the legs. To some extent, this may have limited his in turn slowed down th e somersault rotation over th e ability to run fas t. But he did succeed in hav ing hi s bar. But in add it ion it also produced a large arm s in good (i.e., low) pos itions at th e start of the 36 / di sproportion between hi s forward and lateral components of somersaulting angu lar momentum . This disproportion prevented Dilling's body from being perpendicular to the bar during the bar clearance. In stead, he was slanted, with his head mu ch closer to th e left standard than his legs. (See above.) This slanted position made the left knee reach the bar earlier than the right knee, and thu s T !!A I X made it more difficult to avoid dislodgin g the bar T with th e legs. llt\R I T II IIR 61 The peak height reached by the c.m. in jump 97 was hpK = 2.36 m. The "saturation graph" shows that in this jump Dilling could have cleared cleanly a bar set at about hcLs = 2.27 m, and at he LA= 2.28 m if he had taken off slightly closer to the pl ane of the bar and the standards. In relation to the peak height of the c.m. (2.36 m), th e 2.28 m clean clearance height indicated that hi s bar clearance was not very effectiv e. This did not mean that D iII ing did anythin g wrong in th e air; in fa ct, his actions in the air were quite good. The lack of effectiveness of 7.6 7.8 8.0 8.2 Dilling's bar clearance was th e direct resu lt of his was reasonably good, better th an average quality. very small total amount of so mersaulting angu lar However, for a tru ly hi gh quali ty combinati on it momentum, and therefore the result of the extremely would be advisable for Dilling to use a still slightly small amount of lateral so mersaulting angu lar fas ter and /or lower run-up. In term s of Figure 3, momentum that he was able to generate during the Dilling's point should be moved to th e diagonal lin e takeoff. recomm end ed for Vzm = 4.40 m/s. (See th e graph above.) Possible co mbinations could be 8.0 m/s and We carried out several tests using computer 47.5%, or 7.9 m/s and 46.5%, or 7.8 m/s and 46%, as simulati on of th e bar clearance. In these tests we shown by the three arrows in th e graph . (See kept the pos ition at takeoff, the angu lar momentum Appendix 2 for exercises that will help to produce and th e path of th e c. m. th e same as in the ori ginal fast and low co nditions at th e end of th e run-up.) jump, but we made changes in th e acti ons th at Dilling made in th e air. In these simulations, we were not (Standard caution when increasing the run-up ab le to improve on the effectiveness of the bar speed and/or lowering the c.m. height at the end of clearance th at Dilling achi eved in the original jump. the run-up: Til e use of a Jaster and/or lower run This confirmed that the probl ems in Dilling's bar up will put a greater stress on til e takeoff leg, and clearance were due to his angular momentum, and thus it may increase tile risk of injury if tile leg is not to his actions in the air. not strong enough. Therefore, it is always important to use caution in the adoption of a Jaster Recommendations and/or lower run-up. If tile desired change is very large, it would be advisable to make it gradually, Dilling's combinatio n of speed and height at the over a period of time. In all cases, it may be wise to end of the run-up (7 .8 m/s and 47.5%, respectively) further strengthen til e takeoff leg, so that it can 37 withstand the increased force of the impact lead leg. But if Dilling lifted th e knee of his ri ght produced when the takeoff leg is planted.) knee hi gher at th e end of th e takeoff, he would be able to generate a little bit more li ft during the takeoff A small probl em in Dilling's technique was the phase. somewhat long length of th e las t step of his run-up. To co rrect thi s, he should try to increase the tempo of In summ ary, th e most seri ous problem in the last two foo t landings, i.e., he should try to plant Dilling's technique is probabl y his very small amount th e left foot on th e ground almost imm edi ately after of lateral so mersaulting angul ar momentum, which he pl ants th e right foot. By increasing the tempo of has an important detrimental effect on th e th e last two foot landings, Dilling will reduce the effectiv eness of hi s bar clearance. This needs to be length of th e las t step of th e run-up, but more co rrected by allowing th e trunk to rotate further importantly, he will redu ce the time that he spend s in toward the right by th e end of the takeoff ph ase . Of th e air during th at step. This will prevent him fr om lesser importance are the sli ghtly excessive length of accumulatin g too much downward (negativ e) verti ca l th e last step of his run-up, his so mewhat in suffi cient ve loc ity in th e air, so that he does not have an amount of backward lean at th e start of th e takeoff excessively large downward vertical ve locity when ph ase, and th e weakn ess of his lead leg acti on during he pl ants th e left foot on the ground to start th e th e takeoff ph ase. ta keoff ph ase . In the view from th e back, Dilling had a good lean toward th e left at th e start of th e takeoff ph ase, but th en he did not all ow his trunk to rotate enough toward the ri ght by the end of the takeoff. This is probably the most important problem in Dilling's technique. He needs to all ow his trunk to rotate much furth er toward th e ri ght, to a pos ition up to I oo beyond the ve rtical in th e view fro m th e back at th e end of th e takeoff ph ase. This will all ow him to generate a larger amount of lateral so mersaulting angul ar momentum , whi ch in turn will lead to a larger total amount of somersaulting angul ar momentum as well as better proportions betw een th e forward and lateral components of so mersaulting angul ar momentum . This will produce a better so mersault rotati on over the bar, and will thus improve th e effecti veness of Dilling's bar clearance. A mu ch small er probl em is Dilling's so mew hat small amount of bac kward lean at th e start of the takeoff ph ase. He should thrust his hips a little bit furth er forward in th e very last step of th e run-up. This will give his trunk a larger amount of backward lean at the start of th e tak eoff ph ase. Then, he should all ow hi s trunk to rotate forw ard during th e takeo ff ph ase, but only up to th e verti ca l by th e end of the takeoff. This should produ ce th e same amount of fo rward somersaulting angul ar momentum as in jump 97, while avo iding any loss of lift th at might have been produced through excess ive forward lean at th e end of th e takeoff. Whil e Dilling's arm acti ons during th e takeoff ph ase were good, th e acti on of his lead leg was not very strong. This is anoth er problem th at is relati ve ly min or, because to a great extent the strong acti ons of the arm s partl y co mpensate for the weakness of th e 38 .....0 "' "'..... "' N co "' co co "' q< "' (il uz "' ~ (il ...:l u 0 ::.: 0 0 ...... -< N N ..... 0 q< N 0 0 "' .-< ..... 0 '*""' .-< z(,!) H ~ ...:l ""I ...:l z H ~ 0 ~ 0 N 0 .-< DILLING #97 062407 2 . 27 M CLEARANCE TAKEOFF PHASE w 10.22 10.20 10.18 10.16 10 . 14 10.12 10.10 10.08 10.06 10 . 04 10 . 02 10 . 00 1.0 DILLING #97 062407 2 . 27 M CLEARANCE BAR CLEARANCE ~ ~ 10 . 94 10 . 82 10.70 10 . 58 10 . 46 10 . 34 10.22 ~ 41 0 0 0 0 L[) .... "' 0 I 0.... 0 co I "' I \ 0 - "' "' fil uz fil~ H u ::;: ..... N N ..... 0.... ~ N H .... "'0 {)) ..... :> "' .... :r: '"'<..? <..? z H H fil H :r: H 0 H Cl ::;: .... u "' 42 DILLING #97 062407 2.27 M CLEARANCE 43 DILLING #97 062407 2.27 M CLEARANCE 44 Tora HARRIS adequate for his needs, and possibly even too stro ng, given the extremely demanding co nditions produ ced Jump 61 was Harri s' last successful clearance at by hi s tremend ously fast and low run-up. th e 200 7 US A TF Championships (2.2 1 m) . Harris' trunk had a moderate backward lean at Based on Harris' vertical ve loc ity at takeoff in th e start of th e takeoff ph ase (BFTD = 76°). Then, he jump 61 (vzro = 4.3 0 m/s) , a technique of average rotated forward during the takeoff ph ase, but at th e quali ty would have includ ed a fin al run-up speed of end of th e takeo ff he was still somewhat short of the about 7.4 m/s and a c. m. height at th e start of th e verti ca l in a view fr om th e side (BFTO = 8r). The takeoff ph ase equal to about 47% of hi s own standing amount of forward so mersaulting angul ar momentum height. Harris' actual speed at th e end of th e run-up th at Harris was able to generate was somewhat small (vH 1 = 8.0 m/s) was mu ch faster th an wh at would be (HF = 75). ex pected for a technique of average quality, and his c.m. at th e end of th e run-up was in a mu ch lower Harris' trunk had a very good lean toward th e left position (hm = 44.5%) th an what would be ex pected. at th e start of the takeoff phase (LRTD = 74°). Th en Overall , th e co mbin ati on of run-up speed and c. m. he rotated toward th e ri ght, and at th e end of th e height th at Harri s used in jump 61 was ex tremely takeo ff he was r past th e verti ca l in a view fr om th e demanding - maybe too demanding if he was not in bac k (LRTO = 9r). In the view fr om th e back, it's peak ph ys ica l condition. normal to be up to I 0° pas t th e vertical at the end of the takeo ff. Th erefore, Harris' position at the end of At th e end of th e run-up, Harris pl anted th e th e takeo ff in jump 61 was very good. His good takeoff foo t too parall el to th e bar. Because ofthis, pos itions at th e start and at th e end of th e takeoff th e angle between the longitudinal ax is of th e takeoff phase enabl ed him to generate a large total amount of foot and the hori zo ntal force received by the foot was lateral somersaulting angular momentum (HL = 95). so mewhat too large (e 3 = 26°). This was actually a ve ry good improvement in comp ari so n with an y of Harris' forward and lateral components of his prev ious an alyzed jumps, but sti II it would somersaulting angul ar momentum add ed up to a large norm all y lead us to predi ct some ri sk of foot total amount of somersaulting angular momentum pronati on, and injury to th e ankle and foo t. (See th e (Hs = 120) . secti on on "Ori entation of th e takeoff foot, and potential fo r ankle and foo t injuries" in th e main text Harris' c.m . reached a max imum height hPK = of the report. ) However, direct examination of th e 2.28 m in jump 6 1. The "saturati on graph" shows videos showed little or no visibl e pronati on in any of th at in this jump he co uld have cl eared cleanly a bar Harris' jumps. It is necessary to keep in mind th at, set at about hCLs = 2.24 m, and at hcLA = 2.26 m if he due to our camera locati ons, it is harder to actually had taken off betw een 5 and I 0 em closer to th e pl ane see pronati on in jumpers who approach from th e ri ght of th e bar and th e stand ard s. In relati on to the peak sid e (like Harris) , so it is conce ivable that he might height of the c. m. (2 .28 m), the 2.26 m clean be pronating without our noti cing it, but we think this clearance height indicated a very effecti ve bar is highly unlikely. clearance . Harris' arm ac ti ons during th e takeo ff phase were Recommendations stro ng (AAT = 16 .3 mm/m), a good improvement relati ve to 2006. The acti on of his lead leg was weak All as pects of Harri s' technique were quite good. (LLA = 12.9 mm /m), alth ough it was better than in The ori entation of the takeoff foot does not seem to any of his previous analyzed jumps. The overall be a problem an ymore now th at we can observe it combinati on of arm and lead leg actions was weak more accurately with high-definition video . (FLA = 29.3 mm /m) , alth ough it was better than in most of his previous an alyzed jumps. Normally, we Harris' co mbination of speed and c. m. height at wo uld consider weakn ess in th e fr ee-limb actions a th e end of th e run -up was extremely good. He should problem in a jumper's technique. However, Harris' not go any faster or lower th an in jump 61 . We also run-up was so fast and so low th at it put a tremendous suspect th at he should not go quite so fast nor so low amount of stress on th e takeoff leg. The use of very unless he is in perfect phys ical condition. stro ng free-limb acti ons during th e ta keoff ph ase in addition to such conditions at the end of th e run-up The weakn ess of Harris' arm and lead leg acti ons might have produced the coll apse of th e takeo ff leg . might superfi cially seem to be a problem in his Therefore, Harris' free-limb actions may have been 45 technique. However, as explai ned before, we believe that Harris' arm and lead leg acti ons may actually have been too strong, g iven how fast and how low he was at the end of th e run-up. Harris' leans backward and toward th e left at the start of th e takeoff phase and at th e end of th e takeoff phase were all good in jump 61. This aspect of his technique needs no changes. Harris' bar c learance is unorthodox, as usua l, with a "s itting" body configurati on on th e way up to the bar (see the sequ ence of th e bar c learance at t = I 0.34 sand t = I 0.46 s) and a somewhat tilted position near th e peak of th e jump, with the ri ght hip lower th an th e left hip (see th e sequence of the bar clearance at t = I 0.70 s). However, this technique works well with Harris' conditions at th e end of th e takeoff. The technique is very effective for Harris, all owing him to clear c leanly a bar set only 2 em lower than th e peak height reached by his c.m. Therefore, we advise him to make no changes in it. One might then ask why Harris did not jump nearly as hi gh in the 2007 competition as in th e 2006 competition. A key element was hi s much small er amount of vertical velocity at th e end of the takeoff, Vzro = 4.50 m/s in 2006 but 4 .30 m/s in jump 61 from 2007, which produced a peak c.m . he ight of 2.3 8 m in 2006 but 2.28 min jump 61 from 2007. We do not know what caused this deteriorati on. Technique did not seem to be the problem. We suspect that Harris' physical condition was not good on th e day of th e 2007 meet, or that he was simply unable to coordinate his muscular efforts properly during th e takeoff phase - the c lassical " bad day" syndrome that all hi gh jumpers experience at one meet or anoth er. Harris may have compounded the problem by stickin g to an extreme ly demanding combination of very fast speed and very low height at the end of the run-up. If the physical condition of the athlete is not at its peak, it is better to back off slightly from making extreme demands on the takeoff leg, because the weakened takeoff leg will actually perform worse with a "better" (i .e., more demanding) combinati on of run-up speed and height. Another factor th at affected Harris ' performance at the 2007 meet was that, when th e bar was raised to 2.24 m he was unable to repeat th e jump that he had executed at the 2 .2 1 m he ight. His three attempts at 2.24 m were inferior to his jump at 2 .2 1 m, which would have allowed him to clear the 2 .24 m bar, and possibly (with a sli ght brush) even th e 2.27 m bar. 46 N 00 00 00 "' "'"" [il "' uz ~ [il o-1 0 u 0 ;:;: 0 rl rl N N .... 0 N "" 0 "'0 rl rl 0 rl 'lj,"' Ul H :::> ""I z :::> ~ p:; :c 0 N 0 rl HARRIS #61 062407 2.21 M CLEARANCE TAKEOFF PHASE 10.22 10.20 10.18 10.16 10.14 10.12 10.10 10.08 10 . 06 10 . 04 10.02 10.00 ::3 HARRIS #61 062407 2 . 21 M CLEARANCE BAR CLEARANCE +:>. 10.94 10.82 10 . 70 10.58 10 . 46 10 . 34 10 . 22 00 60 I C . M. HEIGHT VS TIME 50 ~ ~- ---- 40 9.40 9.60 9 . 80 10 . 00 HARRIS #61 062407 2.21 M CLEARANCE ~ 50 HARRIS #61 062407 2 . 21 M CLEARANCE 5 1 HARRIS #61 062407 2 . 21 M CLEARANCE 52 Eugene HUTCH INSON examinati on of the videos showed no visible pronation in any of Hutchinson's jumps. This was a ll Jump 72 was Hutchinson' s last successful very good. clearance at th e 2007 USATF Championships (2.2 1 m). Hutchinson's arm actions during the takeoff phase were very strong (AA T = 25 .3 mm/m). The Based on Hutchinson's vertical velocity at action of his lead leg was also strong (LLA = 25 .5 takeoff in jump 72 (vzTO = 4 .30 m/s), a technique of mm/m) . Not surprisi ng ly , th e overall combinati on of average quality would have included a final run-up arm and lead leg actions was very strong (FLA = 50.8 speed of about 7.4 m/s and a c.m. height at the start mm/m). This was a ll excell ent ofthe takeoff phase equal to about 47% of hi s own standing height. Hutchinson had a s lower speed at Hutchinson's trunk had a good backward lean at the end of the run-up (vH 1 = 7.2 m/s) than what would the start of th e takeoff phase (BFTD = 75 °). Then, he be ex pected for a technique of average quality, but rotated forward during th e takeoff phase, and at the his c.m. at th e end of the run-up was also in a much end of th e takeoff he was sli ghtly beyond th e verti cal lower position (hm = 43.5%) th an what would be in a view from the s ide (BFTO = 92°). This s lightly expected. Overall, the combination of run-up speed excessiv e forward lean at th e end of th e takeoff and c.m. height that Hutchinson used in jump 72 was probably made him lose a little bit of lift. In spite of good. th e large amount of forward rotation that Hutchinson went through during the takeoff phase, th e amount of The technique th at Hutch in son used for getting forward somersaulting angul ar momentum that he into pos ition in th e las t steps of th e run-up was was able to generate during th e takeoff phase was similar to the one used by athlete B of Appendix I sma ll (H F = 60). This was probably due to hi s strong (alth ough less extreme). This was not good. free-limb actions, which are good for generatin g lift Hutchinson ' s c.m. was in a moderately low position but can interfere with th e generation of forward two steps before the takeoff phase. After he pushed somersaulting angular momentum. (See th e secti on off with hi s left foot into the next-to-last step, his on "Angular momentum" in th e main text of the c.m. reached a height of about 50% of his own report.) standing height - in the pages of computer graphics that follow these comments, see Hutchinson's graph Hutchinson' s trunk had almost no lean toward of "e.g. height vs time" at about t = 9.68 s. Then, the left at th e start of the takeoff phase (LRTD = 8r; Hutchinson lowered hi s c. m. to a much lower vertical would have been 90°). Then he rotated position. For this, he simply did not stop the drop toward the right, and at the end of the takeoff his completely at any time during the period of support trunk was 12° past the vertical in a view from the over th e ri ght foot (t = 9.76- 9.97 s). When the ri ght back (LRTO = I 02°). In the view from the back, it's foot left the ground at t = 9.97 s, Hutchinson was in a normal to go a few degrees past the vertical at the end lower pos ition th an in the prev ious step, but th e c.m. of the takeoff. We cons ider it acceptable (indeed, was not goin g up at this time: It was still dropping. desirable) to tilt up to I oopa st the vertical at the end Then, th e speed of dropping became still larger in th e of the takeoff phase ( in th e view from the back) final non-support phase of the run-up (from t = 9.97 s because we beli eve th at this may be the best tot = I 0.00 s). By the time that Hutchinson planted compromise between the generation of lift and th e the left foot on the ground to start the takeoff phase, generation of rotation (angular momentum). But his c.m. was dropping at a somewhat large speed Hutchinson was 2° beyond the a ll owable limit for tilt (vzm = -0.5 m/s), and this was not good for th e at the end of the takeoff, and this may have cost him takeoff ph ase of th e jump. A large negative Vzm some additional lift. As in the forward rotation, valu e is not advisabl e, because it requires the athlete Hutchinson's overrotati on toward th e right during th e to make an extra effort to stop the downward moti on takeoff phase did not allow him to produce an before producin g the needed upward vertical adequate amount of angular momentum : His lateral velocity. Another factor that influenced somersaulting angular momentum was very small Hutchinson's rather large negative vertical velocity at (HL = 70). This was due to hi s almost complete lack the start of the takeoff phase was the long length of of lean toward th e left at the start of th e takeoff his last step (SL = 2.12 m, or 11 2% of his own 1 phase. standing height). Not surpris in gly, Hutchinson's forward and At the end of the run-up, Hutch in son planted th e lateral components of somersaulting angul ar takeoff foo t at a very safe angle (e3 = 14°), and direct 53 momentum added up to a very sma ll total amount of lean toward the left was th at Hutchinson's run-up somersaulting angul ar momentum (Hs = 90). was not curved enough: It was too straight. To acquire the necessary amount of lean toward th e left Hutchinson's c.m . reached a max imum he ight at the end of th e run-up, he will need to tighten th e hrK = 2.27 m in jump 72. The " saturation graph" run-up curve, i.e. , to use a curve with a shorter radius. shows that in this jump Hutchinson could have See Appendix 4 for more informati on on how to cleared c leanly a bar set at about hcLs = 2.2 1 m, and change th e shape of the run-up curve. at hcLA = 2.22 m if he had taken off s li ghtly farther from th e pl ane of the bar and th e standard s. In Also, hav ing the appropriate amount of curvature relati on to the peak he ight of th e c.m . (2.27 m), th e in th e run-up does not guarantee that th e athlete will 2.22 m clean clearance height indicated th at lean properly . The back view of Hutchinson at t = Hutchinson' s bar cl earance in jump 72 was 9.82/9.88 s shows that his trunk stayed upright while reasonably effective. Considering th at his angul ar the legs jutted out toward th e ri ght. This was not momentum was very small, this indicated that his good. It is important to lean with th e entire body, and acti ons in th e a ir were very good. not only with th e legs. Recommendations Once Hutchinson has managed to get th e appropriate amount of lean toward the left at th e start Most aspects of Hutchinson's technique were of the takeoff phase (by usin g a shorter curve radius quite good. His ma in technique problem was in th e and by leaning w ith the entire body), he w ill be abl e bar c learance. A lthough we c lassify his bar clearance to rotate toward th e ri ght through a very large angle as " reasonably effective", this is not the sam e as during the takeoff phase, to a pos ition up to 10° (but saying th at it was satisfactory: It wasn't. no more than th at) beyond the vertical by th e end of Hutchinson' s bar clearance can be made much more the takeoff. By do ing this, he w ill be able to generate effec ti ve th an it was in jump 72. The solution w ill a larger amount of latera l somersaulting angul ar require the generation of a larger tota l amount of momentum. This will in crease hi s tota l amount of somersaulting angul ar momentum. somersaulting angular momentum, which in turn w ill improve th e effectiveness of his bar clearance: With Hutchinson' s forward component of the same peak height of the c.m. , he w ill be able to somersaulting angular momentum was sma ll . The clear a bar set at a hi gher he ight. reason fo r this was that it is difficult to generate a lot of forward somersaulting angul ar mo mentum when A rath er sma ll problem in Hutchinson' s th e ath tete uses very intense arm and lead leg actions technique was that he had a somewhat too large during the takeoff phase. Weakening the arm and downward vertical velocity at th e time that th e left lead leg acti ons during th e takeoff phase would foot was planted on the ground to start the takeoff indeed help to increase th e forward somersaulting phase. To eliminate this problem, Hutchinson would angular momentum, but this would come at the cost first need to be a lready at a very low height two steps of quite a bit of li ft. Therefore this is not an before takeoff. Then he would need to travel rath er advisable way to in crease th e angular momentum. fl at in th ose fin al two steps, ne ith er ra is in g nor Hutchinson should reta in his current very good arm lowering his hips. Then, in th e last step of th e run-up and lead leg acti ons during the takeoff phase, even if he should not lift hi s left foot as high as he did in this Iim its the generati on of forward somersaulting jump 72 (see th e sid e v iew at t = 9.94 s), and he angul ar momentum. The so lution to the angular should try to increase th e tempo of th e last two foot momentum pro blem will need to come through the landings, i. e., he should try to plant th e left foot on latera l component of somersaulting angular the ground a lmost immediate ly after he plants the momentum, as we will see next. ri ght foot. By in creasing the tempo of th e last two foot landings, Hutchinson should be abl e to reduce The reason why Hutchinson was not able to the length of th e last step of th e run-up, but more generate a good amount of latera l somersaulting importantly, he will reduce the time that he spends in angul ar momentum (and th erefore th e ma in reason the air during th at step. This w ill prevent him from fo r the mediocre effecti veness of his bar clearance) accumulating too much downward (negati ve) verti cal was that he did not have enough lean toward the left velocity in the a ir, so th at he does not have an at th e start of th e takeoff phase. (See the view from excessively large downward vertical ve locity when the back at t = I 0.00 s in his run-up or takeoff he pl ants th e left foot on th e ground to start th e sequences, and compare it w ith th ose of Harris, N ieto takeoff phase. or Shunk.) In turn, th e reason for this in suff ic ient 54 Other than the changes described above fo r th e run-up curve and fo r the increase of th e tempo of the las t two footfa lls of the run-up, we propose no oth er changes for Hutchinson' s technique. His run-up was of the slow-but-very-low vari ety, which is a perfectly valid optio n. His arm and lead leg acti ons were very good, and so was the safe ori entation of his takeoff foot. Except fo r the in suffic ient curvature of Hutchinson's run-up curve (and th e problems that it produced in the bar clearance), and to a lesser extent hi s excessively long last step, his technique was overall very sound. 55 (X) "'a. "" "'a. .....0 a. "'..... a. N (X) a. (X) (X) a. u~ a."" z a. ..;~ ~ ...:l u ::;: ..... 0 N 0 0 N ...... 0 ""N "'0 N ..... 0 "*' ..... z 0 0 ..... Ulz H p.. 0::: ::> u I E-< z ::> ::> 0::: 11:: 0 N 0 ..... HUTCHINSON #72 062407 2 . 21 M CLEARANCE TAKEOFF PHASE Vl 10.22 10 . 20 10.18 10 . 16 10.14 10 . 12 10 . 10 10.08 10.06 10 . 04 10 . 02 10.00 0'1 HUTCHINSON #72 062407 2 . 21 M CLEARANCE BAR CLEARANCE 1t Vl 10 . 94 10.82 10.70 10.58 10 . 46 10.34 10.22 -..) 58 0 0 0 0 \0 L() ""' 0 I ....0 I 0 - CXl "' \ 0 - \0 "' I N r-- 0 N""' \0 0 ~ H N E-i r- % Ul :> z 0 E-i Ul :r: z H t!J :r: Hw u :r: E-i :::> 0 :r: i ""' u "' 59 HUTCHINSON #72 062407 2 . 21 M 60 1.00 m HUTCHINSON #72 062407 2.21 M 61 Will LITTLETON 2.18 m clearance (jump 48) Jump 48 was Littleton's last successful c learance at th e 2007 USATF Championships (2.18 m). Li tt leton' s vertical velocity at takeoff in jump 48 was VzTO = 4.15 m/s. However, th e USATF Championships were not a very good competition fo r him, and thus Littleton' s 4. 15 m/s VzTO value presents a di storted v iew of his physical condition during th e 2007 season. Littleton' s best mark of th e season was 2.28 m. Even though we have no hard data on his 2.28 m jump, we can estimate fa irly accurate ly that he must have generated about 4.35 m/s of vertical velocity in that j ump. T herefore, we w ill consid er Vzro = 4.3 5 m/s th e best indicator of Littleton' s physical conditio n. between the middle image and the image on the left, as indicated by the larger amount of bl ack sole vis ibl e Based on a verti cal velocity at takeoff of Vzr o = in th e im age on th e left. Other jumps by Littleton 4 .35 m/s, a technique of average quali ty would have during the competition showed similar s igns of in clud ed a fin al run-up speed of about 7.4 m/s and a pronati on. It is true th at the amount of pronati on c.m . height at the end of th e run-up equal to about does not seem very severe in these im ages, but we 4 7% of hi s own standing he ight. In j ump 48, need to keep in mind th at ne ith er one of these two Li tt leton was actua ll y sli ghtly lower at the end of the sequences were taken from th e best viewpoint for the run-up (hm = 46%) th an what would be expected in a observation of pronati on, so it is possible th at th e technique of average quali ty, and he was a lso much pronati on might be more severe th an what meets the faster (vH 1 = 7.9 m/s). This was a very good eye. combinati on fo r him . Littleton did not prepare his arms fo r a double At the end of the run-up, Littleton planted th e arm takeoff. (See th e s id e-view and back-view takeoff foo t too para ll e l to th e bar. Because of this, sequences of the run-up between t = 9.58 sand t th e angle between the long itudina l axis of th e takeoff = I 0.00 s.) Still, he managed to have both arm s in foot and the horizontal force received by the foot was moderately low positions at the start of th e takeoff too large (e3 = 34°). T his would norma lly lead us to phase (t = I 0.00 s), which raised th e possibil ity that predict a risk of foot pronati on, and injury to the he m ight still be able to use reasonably strong arm ankle and foot. (See the secti on on " Orientati on of acti ons during the takeoff phase. Indeed, Littleton th e takeoff foot, and potentia l for ankl e and foot lifted his right arm to a high positi on by th e end of inj uries" in th e main text of th e report.) However, the takeoff phase, so its action was fa irl y strong direct examinati on ofthe vid eos showed only (AAN = 8.2 mm/m). (See the detailed sequence of moderate amounts of pronati on in Littleton's jumps. the takeoff phase between t = I 0.00 s and t = I 0.16 s; see a lso Figure 9 in the main text of the report.) He Until last year we record ed th e jumps w ith movie also lifted his left e lbow to a high position by th e end cameras ( 16 mm fi lm ), and th e im ages of th e jumps of th e takeoff phase, but in addition he executed an were genera ll y not clear enough to actua lly see the intern al rotatio n of th e left upper arm th at put th e left pronati on of the foot during th e takeoff phase. This fo rearm in a hori zonta l orientation at th e end of th e year, we have switched to hi gh definition v id eo takeoff, which put th e left wrist bare ly higher than cameras, and th e im ages are c learer. This sometim es the left elbow and shoulder. (See th e sequence of th e all ows us to see the pronati on when it occurs. The takeoff phase at t = I 0.16 s.) This made th e acti on of images in this page show screen captures of two Littleton's left arm be very weak (AAF = 7.2 mm/m). separate views of Littleton's takeoff foot during th e Keep in mind that the arm farthest from the bar (th e takeoff phase in jump 48. Onlys a ma ll amount of left arm in Littleton' s case) is the one th at norma lly pro nati on is evident. Both views showed th at the makes a stronger acti on in most high jumpers. foo t ro ll ed: The left im age of the bottom sequence Because of the weak acti on of his left arm, Littleton' s shows th e tilted shoe; th e top sequence does not show tota l arm acti on was somewhat weak (AAT = 15.5 the tilt directl y, but it does show th at the outs id e edge mm/m). Littleton did not lift his right knee h ig h of th e shoe actua ll y lifted off from th e ground enough at th e end of the takeoff phase. Therefore, 62 the acti on of his lead leg was weak ( LLA = 15.3 was hrK = 2T.20 m. he "saturati on graph" shows that mm/m). His overall combination of arm and lead leg in this jump Littleton could have cleared cleanly a bar actions was also weak (F LA = 30.8 mm/m). set also at about hcLs = 2 .20 m. In relati on to th e peak height of th e c.m . (2.20 m), the 2.20 m clean In j ump 48, Littleton' s trunk had onl y a very clearance height indicated an extremely effective bar sma ll amount of backward lean at th e start of th e clearance. takeoff ph ase (BFTD = 84 °). Then he rotated forward, and by the end of the takeoff hi s trunk was Recommendations vertical ( BFTO = 90°). Thi s position at the end of th e takeoff phase was very good. But, g iven th at Almost all as pects of Littleton's technique were Littleton's backward lean at the start of the takeoff very good. He was reasonably low and very fast at phase was very sma ll , and that he did not rotate the end of the run-up. Then, w ithout producing forward through a very large ang le during the takeoff excessive leans fo rward nor toward the ri ght at th e ph ase (since he had not gone beyond th e verti cal by end of th e takeoff, he generated good amounts of th e end of th e takeoff), we expected him to generate angul ar momentum, whi ch contri buted to make his onl y a limited amount of fo rward somersaulting bar clearance extremely effective. These are some of angul ar momentum . However, he was able to the most important technique aspects of high generate a large amoun t of forward somersaulting jumping, and Litt leton d id th em a ll very well. angul ar momentum (HF = 90). It's not entirely clear how Litt leton managed to do this. In part, it may The onl y significant concern that we have about have been faci li tated by the weakness of his arm and Littleton' s technique is the ori entati on of his left foo t lead leg actions. (Weak arm and lead leg actio ns can during th e takeoff phase. He planted the takeoff foot hamper the generation of li ft, but th ey do fac il itate too parall el to th e bar. Based on this, we advise him the generatio n of fo rward somersaulting angular to plant the takeoff foot on th e ground w ith its momentum.) long itudinal ax is more in lin e w ith th e fin al direction of th e run-up, w ith th e toe po in t in g at least 15 o more Littleton' s trunk had a moderate amount of lean clockw ise than in jump 48. This technique change toward the left at the start of th e takeoff phase w ill help to prevent foot pro nation, and injury to the (LRTD = 79 °). Then he rotated toward the right, and ankle and foot. by the end of the takeoff he was I I o past the vertical 0 in th e view fro m th e back (LRTO = I 0 I ). In th e In the past, to advise hig h j umpers about the view fro m the back, it's normal to go a few degrees appropriate ori entation of th e takeoff foot, we re li ed past the vertical at th e end of th e takeoff We exclusively on th e orientati on of the takeoff foot consider it acceptable (indeed, desirable) to tilt up to relati ve to the direction of the horizontal fo rce made 10° pas t th e vertical at the end of th e takeoff ( in th e by the athlete on th e ground during th e takeoff phase view from th e back) because we beli eve th at this may (angle e3). This was because it was alm ost never be th e best compromise between th e generati on of lift possibl e to actu a lly see th e foot pronati on in th e and th e generati on of rotati on (angular momentum). im ages of the 16 mm movie film that we used. This Littleton was essentia lly at th e acceptabl e limit fo r has changed to some extent w ith our switch to high lean toward th e ri ght at th e end ofth e takeoff phase. definition v ideo. The im ages are much clearer, and That was very good. The fact that Littleton had only we have a better chance of actua lly seein g the a moderate amount of lean toward th e left at th e start pronati on in th e v id eo im ages. For athletes who of the takeoff phase limited somewhat th e amount of approach from the left, we can genera ll y see the rotation toward the right that he could go th rough pronati on quite well if it occurs . Unfo rtun ately, for during the takeoff phase w ithout being over-rotated at athl etes who approach fro m th e right (like Littl eton), the end of the takeoff Because of this, the amount of it is not so easy to see, due to the positions in which lateral somersaulting angul ar momentum that he was we have to pl ace our cameras. Still , we were abl e to detect some pronati on in most of Littleton's jumps. ab le to generate was somewhat small (HL = 90). Because of the rather large valu e of th e e3 angle in Littleton's fo rward and lateral components of jump 48 and th e existence of pronation in Littleton' s somersaulting angul ar momentum added up to a good jumps (even though we can' t judge very well how total amount of somersaulting angul ar momentum severe th at pronation was), our advice to Littleton is (Hs = 125). to pl ay it safe by planting th e takeoff foot more in lin e w ith the fi nal direction of the run -up. The peak height reached by the c.m . in j ump 48 63 Other than the just described change in th e w ill actu a lly produce more li ft fo r Littleton. (See the ori entati on of th e takeoff foot, we have no oth er previous two paragraphs.) Taking all of this into strong advice for Littleton. Sure, we could advise account, is it worth while to experiment w ith all these him to swing his left arm and th e knee of his right leg changes? We think th at it probably isn' t. O ur advice hard er forward and up, to higher positions by th e end is to work only on th e improved ori entati on of th e of th e takeoff phase. Such actions might a ll ow takeofffoot, and to leave everything e lse in Littleton to generate more lift. However, it is Litttleton's technique as it was in j ump 48. possibl e that, w ith his very fast and low run-up, Littleton might be already near his limit for buckling, Future improvements in Littleton's results w ill in which case a marked increase in his arm or lead probably need to be based on improvements in hi s leg actions might be counterproducti ve. physical condition rath er th an in hi s technique, because his technique is a lready very good. Even if in creased arm and lead leg acti ons would in crease Littleton's li ft (whi ch is something th at we are not sure of), th ey could also produce other probl ems unless oth er changes are a lso incorporated in to his technique, as w ill be expla in ed next. As we stated previous ly, it is possible that th e weakness of Littleton' s arm and lead leg acti ons might be what all ows him to generate a good total amount of somersaulting angul ar momentum, because th ey compensate for the problem created by the very sma ll size of his backward lean at th e start of the takeoff phase. If Littleton strengthened his arm and lead leg actions w ith out f irst correcting (i.e., increasin g) his backward lean at th e start of th e takeoff phase, it is possibl e that th e amount of forward somersaulting angul ar momentum th at he would be abl e to generate woul d become small er. This would reduce his to ta l amount of somersaulting angular mo mentum, whi ch in turn would probably deteri orate th e effecti veness of Littleton's bar c learance. Thus, what Littleton woul d gain in li ft (through his enhanced arm and lead leg acti ons) might be lost through reduced effecti veness in his bar clearance. T herefore, s imply making stronger use of the arms and lead leg during th e takeoff phase is probably not a good idea for Littleton. What would happen if Littl eton were to thrust his hips further fo rward in th e last step of th e run-up, and thus acquire a larger amount of backward lean at the start of th e takeoff phase? In such case, he would have avail able a larger range of motion of forward rotati on from th ere all the way to the vertical by th e end of th e takeoff phase, and this would favo r the generati on of a larger amount of forward somersaulting ang ul ar momentum . This would compensate for any angul ar mo mentum loss produced by th e use of stronger arm and lead leg actions. In this way, Littleton might be able to generate more li ft through stronger use of his arms and lead led without incurring any ill effects on th e effecti veness of his bar c learance. This sounds like a good idea. However, it brings us back to the fact that we don't know if enhanced arm and lead leg actions 64 00 Ll1 N 00 00 00 ~ "" u "' ~ "' ~ H u ::;: 0 00 0 .... 0 N .... r- 0 N"" \0 0 00 0 "" .... 0 '"'z ..-< 0 E-< ~ p.. ...:l :::> E-< I E-< z H :::> ...:l I>: 0 N ....0 LITTLETON #48 062407 2 . 18 M CLEARANCE TAKEOFF PHASE 0\ 10 . 22 10.20 10.18 10.16 10 . 14 10 . 12 10 . 10 10.08 10.06 10 . 04 10.02 10 . 00 Vl LITTLETON #48 062407 2 . 18 M CLEARANCE BAR CLEARANCE ~~ 0\ 10 . 94 10.82 10 . 70 10 . 58 10 . 46 10 . 34 10 . 22 0\ 60 C . M. HEIGHT VS TIME 50 ~~ / ~ 40 9.40 9.60 9.80 10.00 LITTLETON #48 062407 2 . 18 M CLEARANCE 0\ -..) 68 LITTLETON #48 062407 2.18 M CLEARANCE 69 LITTLETON #48 062407 2.18 M CLEARANCE 70 Keith MOFFATT 2.24 m clearance (jump 84) Jump 84 was Moffatt's last successful cl earance at th e 2007 USATF Championships (2.24 m). Based on Moffatt's vertical velocity at takeoff in j ump 84 (vzTO = 4.3 0 m/s), a technique of average quali ty would have included a fin a l run-up speed of about 7.4 m/s and a c. m. he ight at th e end ofthe run up equal to about 47% of his own standing height. At th e end of th e run-up, Moffatt's c.m . was actua lly hi gher th an what would be expected for a technique 2.27 m third miss of average qua lity (hro = 48.5%), and his speed was slower (vH 1 = 7.2 m/s). This overa ll combination of run-up speed and c.m. height th at Moffatt used in j ump 84 was a very weak challenge for a jumper capable of generating 4 .3 0 m/s of vertical velocity . In fact, it was worse than th e combinati ons th at he used in his previous ana lyzed jumps. O ver time, Moffatt has used progressively weaker combinations his 2.24 m clearance Uump 84) and in his third miss of fin a l speed and c.m. he ig ht at th e end of the run at 2 .27 m . Even th ough this camera view is not th e up. (See the graphic be low, based on Figure 3.) This best for th e observati on of takeoff foot pronati on, it is is th e most important performance-re lated problem in clear th at th ere was pronati on: In both jumps, the Moffatt's technique. outsid e edge of th e shoe lifted off from th e ground between th e middle image and the image on th e left. The effect was more marked in th e bottom jump. Moffatt's arm actions during th e takeoff phase were weak (AAT = 12 .0 mm/m). The action of the lead leg was strong (LLA = 19.6 mm/m). The overa ll combinati on of arm and lead leg acti ons was somewhat weak (FLA = 3 1.6 mm/m), weaker th an in . . 2006 . Moffatt had only a small amount of backward 11 , .iO l rl J)i A % lean at the start of th e takeoff phase in jump 84 (BFTD = 8r ). By itself, this presented a problem for At the end of th e run-up of jump 84, Moffatt th e generation of forward somersaulting angular planted the takeofffoot too parall e l to the bar. momentum. But th en th e problem was compounded: Because of this, the ang le between th e longitudinal As in 2004 and 2006, in stead of rotating forward ax is of th e takeoff foot and the hori zonta l force toward the vertical during th e takeoff phase, received by th e foot was too large ( e3 = 28°), and Moffatt' s trunk actu a lly rotated backward, so th at at created a ri sk of ankle pronati on, and injury to th e th e end of the takeoff hi s trunk had a larger backward ankle and foot. (See th e section on "Orientati on of lean th an at th e start (BFTO = 83°). Given this, it th e takeoff foot, and potentia l for ankle and foot was not surpris ing that Moffatt was only able to injuries" in the main text of th e report.) generate a very small amount of forward somersaulting angular momentum (H F = 45). Until last year we record ed the jumps with movie cameras ( 16 mm f ilm), and th e im ages ofthe jumps Moffatt's trunk had a moderate lean toward th e were genera ll y not clear enough to actu a lly see the left at the start of the takeoff phase (LRTD = 79°). pronati on of th e foot durin g the takeoff phase. T hi s Then, he rotated toward the right during the takeoff year, we have switched to high definition vid eo phase, and by th e end of the takeoff he was I I o past cameras, and th e im ages are c learer. This sometim es the vertical in th e view from th e back (LRTO = all ows us to see th e pronati on when it occurs. The 0 I 0 I ) . In the view from the back, it's normal to go a sequence im ages on this page show screen captures few degrees past the vertical at the end of th e takeoff. of Moffatt' s takeoff foot during the takeoff phase in 71 We consider it acceptable (indeed, desirable) to tilt Recommendations up to I 0° past th e vertical at the end of the takeoff phase ( in th e v iew fro m th e back) because we beli eve To a great extent, our recommendati ons to that this may be th e best compromise between th e Moffatt are the same as last year's. generati on of Ii ft and the generation of rotation (angular momentum). So Moffatt was essentia lly at In jump 84, Moffatt was very high and very slow the all owable Iim it fo r ti It at the end of th e takeoff. at th e end of the run-up. T hi s is th e most important T his was good, and an improvement re lati ve to 2006. performance-related problem in his technique. Moffatt was able to generate a good amount of lateral Moffatt needs to be much faster and/or lower. For somersaul tin g angul ar momentum (HL = 95). any jumper, th e optimum combination of run-up speed and c.m . he ight at th e end of the run-up is Moffatt's very sma ll forward and large latera l faster and/or lower th an the expected average components of somersaulting ang ul ar momentum ("ord inary") combination. In terms of Figure 3, all added up to a small total amount of somersaul ting so lutions to this probl em in volve moving Moffatt's angul ar momentum (Hs = I 05). point to th e diagona l lin e recommended fo r VzTO = 4.30 m/s. One possible option would be to combine The peak height reached by th e c.m . in jump 84 the height th at Moffatt had at th e end of the run-up in was hrK = 2.33 m. The "saturation graph" shows th at j ump 84 (hm = 4 8.5%) with a much faster speed (vH 1 in this j ump Moffatt could have cleared c leanly a bar = 8. 0-8.1 m/s). (See the horizonta l arrow in the graph set at about hcLs = 2 .25 m, and at hcLA = 2.27 m if he below.) This larger amount of fin al run-up speed had taken off about I 0 em c loser to th e bar. In should a ll ow Moffatt to generate more lift during th e relati on to th e peak he ight of th e c. m . (2.33 m), the takeoff phase, and thus to produce a larger height fo r 2.27 m clean c learance he ight indicated th at his c.m . at th e peak of the j ump. (See Appendix 2 for Moffatt's bar clearance was not very effecti ve. exerc ises that w ill help to produce fas t and low conditi ons at the end of th e run-up.) An a ltern ati ve option would be to put th e c. m . at the end of th e run-up in a lower pos ition, equivalent to about 47% of Moffatt's own standing he ight. This would be a f in a l run-up height si milar to the one used by Moffatt in jump 40 from 2006. W ith such a position at the end of th e run-up, a fin al hori zontal speed of about 7.8-7.9 m/s SIIU q5 would be suffic ient to ~ quali fy as optima l. (See }::{ th e interm ediate arrow in ~ I E J6 th e graph.) T llAI .o8 T A third possib ili ty liA R I T would be to put th e c. m . at liAR 61 the end of th e run-up in a still lower position, 1- R ~ I equivalent to about 46% of Moffatt' own standing height. This would be a III•IT ~ final run-up height sim ilar to those used by Littleton or Shunk at the 2007 USATF Championships. 7.2 7.4 7.6 7.8 8.0 8.2 With such a pos it ion at the 72 end of th e run-up, a fi nal hori zontal speed of about report; (d) use stronger arm actions during the takeoff 7.7 m/s would be sufficient to qua li fy as optima l. phase. (See the lowest of the three arrows in th e graph.) Among the athletes analyzed in this report, (Standard caution when increasing the run-up Moffatt is probably the one who is performing speed and/or lowering the c.m. height at the end of fa rth est from hi s potentia l. If he ever corrects hi s the run-up: The use of a faster and/or lower run many and important technique probl ems, he could up will put a greater stress on the takeoff leg, and make tremendous progress in his high jump results. thus it may increase the risk of injury if the leg is not strong enough. Therefore, it is always important to use caution in the adoption of a Jaster am/lor lower run-up. If the desired change is very large, it would be advisable to make it gradually, over a period of time. In all cases, it may be wise to further strengthen the takeoff Leg, so that it can withstand the increased force of the impact produced when th e takeoff leg is planted.) Based on th e angle between th e longitudinal ax is of th e takeoff foot and the hori zontal fo rce received by th e foo t (ang le e3) in jump 84, Moffatt's foot ori entation did not seem too dangerous. However, th e video im ages strongly suggested th at the problem may be more seri ous. Therefore, we advise Moffatt to pl ant th e takeoff foot on the ground w ith the long itudinal ax is of th e foot more in lin e with the fi nal directi on of the run-up: It should be planted on th e ground in a more clockw ise ori entati on, w ith th e toe po inting at least I 0° more toward th e landing pit th an in j ump 84. This technique change should help to prevent ankle pronati on, and injury to th e ankle and foot. In regard to Moffatt's forward/backward and left-right leans during th e takeoff phase, and to his bar clearance, th e changes in th ese aspects of his technique since last year have been quite small. Please refer to th e advice g iven in last year's report in regard to th ese aspects of Moffatt's technique. Moffatt's arm acti ons during th e takeoff phase suffe red some deteri orati on between 2006 and 2007. Moffatt needs to thrust his arms hard er forward and upward during the takeoff phase, to a higher position by the end of th e takeoff. These actions w ill help him to generate more lift. The acti on of Moffatt's lead leg during the takeoff phase is not bad, and therefore it does not need any changes. The changes proposed fo r Moffatt are, by order of importance: (a) correct the ori entati on of the takeoff foot - this is an important safety-related issue; (b) use a fas ter speed and a low er position at the end of the run-up - this is the most important perfo rmance-related issue; (c) make changes in the bar clearance technique, as explained in last year's 73 (X) U1 "' "' "' "'(X) "' (X) (X) "' "" w "' uz "' ..:~ w ...:1 u 0 ::;: 0 "' r-"' 0 "' "'ID 0 0 ..... "'(X) 0 'lj, ..... E-< E-< p.. ..: ~ r... I r... z 0 ~ ::;: 0:: 0 "' .....0 MOFFATT #84 062407 2.24 M CLEARANCE TAKEOFF PHASE -..) 10.22 10 . 20 10 .1 8 10 .1 6 10.14 10 .1 2 10.10 10.08 10.06 10.04 10 . 02 10.00 ~ MOFFATT #84 062407 2.24 M CLEARANCE BAR CLEARANCE ~ -..) 10.94 10.82 10.70 10.58 10.46 10.34 10.22 Vl 60 C.M . HEIGHT VS TIME v ~ / 50 --- ~ ~ 40 9.40 9.60 9.80 10.00 MOFFATT #84 062407 2 . 24 M CLEARANCE -..) 0\ 77 MOFFATT #84 062407 2.24 M CLEARANCE 78 MOFFATT #84 062407 2.24 M CLEARANCE 79 Jamie N I ETO Jump 99 was N ieto's last successful c learance in 2.15 m 2.27 m the "administrative ti ebreaker" to decid e 2nd place at clea rance miss #1 th e 2007 USATF Championships (2.25 m). Based on N ieto's vertica l velocity at takeoff in j um p 99 (vzm = 4.30 m/s), a technique of average quali ty would have in cluded a c.m. he ight equal to 2.18m 2.27 m clearance miss #2 about 4 7% of hi s own standing he ight at th e end of th e run-up, and a fin a l run-up speed of about 7.4 m/s. Nieto's actu al c.m. he ight and speed at th e end of th e run-up (hm = 46.5%; v 1.11 = 7.3 m/s) were s imilar to those expected for a technique of average qua li ty. Therefore, th e overall combination of f in a l run-up 2.2 1 m 2.27 m cleara nce mi ss #3 speed and c.m . he ight that Nieto used in jump 99 was not very bad, but a lso not parti cul arl y good. At the end of th e run-up, N ieto pl anted th e takeoff foot too para ll e l to the bar. Because of this, 2.24 m 2.27 m th e angle between th e long itudina l ax is of th e takeoff clearance tiebreaker foot and the horizontal fo rce received by the foot was miss #1 extre me ly large (e3 = 52°). T his would normally lead us to predict a very large risk of foot pronati on, and injury to th e ankle and foot. (See the section on "Ori entati on of th e takeoff foot, and potentia l for 2.25 m ankle and foot injuries" in th e main text of the tiebreaker report.) However, th ro ugh direct v iewin g of the clearance videos we noti ced th at there was onl y a moderate amount of pronation in N ieto's jumps. (See the images on this page.) takeoff phase, and it was r beyond th e verti cal by the end of the takeoff (LRTO = 9r). In th e view N ieto's arm acti ons during th e takeoff phase were fro m the back, it's norma l fo r high j umpers to go up strong (AAT = 17.3 mm/m), and the acti on of his to I 0° past the vertical at the end of the takeoff. This lead leg was somewhat weak (LLA = 18 .1 mm/m). seems to provid e an optimum compromise between In consequence, th e overall combinati on ofN ieto's th e generati on of lift and the generation of enough arm and lead leg acti ons in jump 99 w as somewhat lateral somersaulting angul ar momentum to permit a weak (FLA = 35.4 mm/m). This was not quite as good rotation over th e bar. Therefore, Nieto's good as in 2004, but better th an in any oth er of posit io n at the end of the takeoff was quite good. His N ieto's prev ious analyzed jumps. large amount of rotati on toward the left during th e takeoff phase a ll owed him to generate a good amoun t N ieto had onl y a sma ll amoun t of backward lean of lateral somersaulting angul ar momentum (HL = at th e start of th e takeoff phase in jump 99 ( BFTD = I 00). 82°). T hen he rotated fo rward during th e takeoff phase, and at th e end of th e takeoff he was essentia lly Nieto's somewhat sma ll amount of forward verti cal (BFTO = 89°). A problem w ith this was that, somersaulting angular momentum and large amount due to his small amount of backward lean at the start of lateral somersaulting angul ar momentum of the takeoff phase, Nieto did not rotate forward combined into a somewhat sma ll tota l amount of through a large enough ang le during th e takeoff somersaulting angul ar momentum (Hs = 11 5). phase. T his limited to a somewhat sma ll value the amount of forward somersaulti ng angular momentum N ieto's c.m. reached a maximum he ight hrK = that he was able to generate (HF = 65). 2.30 m in jump 99 . T he "saturation graph" shows that in this j ump he could have cleared cleanly a bar N ieto's trunk had a very good lean toward the set at about hcLs = 2.28 m, and at hc LA = 2.29 m if he rig ht at th e start of the takeoff phase (LRTD = 73 °). had taken off s lightly fa rther from the plane of th e T hen hi s trunk rotated toward th e left during th e bar and the standard s. In relati on to th e peak he ight of the c.m. (2.30 m), the 2 .29 m c lean c learance he ight 47 )::{ indicated a very effecti ve bar '>: II 17 c learance. This had parti cular merit in v iew of the fact th at N ieto's tota l amount 46 SIIUOl of somersaulting angular -+.; momentum was somewhat )::{ sma ll. \/1[ j(> 45 Overall , N ieto's leans at the pIan t and at the end of th e takeoff, his generation of + S l ~H angul ar momentum, and his 44 bar c learance were very good. Reco mmenda tions 43 II LIT• 1 The ma in problem in N ieto's technique was his 7.0 7.2 7.4 combin atio n of speed and c. m . height at the end of the run-up. He needs to be important to use caution in the adoption of a Jaster faster and/or lower than in j ump 99. T he optimum and/or lower run-up. If th e desired change is very combinati on for any j umper is faster and/or lower large, it would be advisable to make it gradually, th an th e expected average ("ordinary") combination. over a period of time. In all cases, it may be wise to In term s of Figure 3, all so lutions to th is problem f urther strengthen th e takeoff leg, so that it can in volve moving Nieto's point to the diagona l lin e withstand the increased force of the impact recommended for Vzm = 4 .30 m/s. One possib le produ ced when the takeoff leg is planted. ) option woul d be to combine th e height th at Nieto had at th e end of the run-up in jump 99 (hm = 46.5%) In spite of the very large ang le between th e w ith a much fas ter speed (vH 1 = 7.7-7.8 m/s). (See longitudinal ax is ofNieto's takeoff foot and the the horizontal arrow in th e graph shown in this page.) hori zonta l force received by the foot (angle e3) , direct This larger amoun t of fin a l run-up speed should observati on of th e v id eotape im ages indicate that all ow N ieto to generate more lift during the takeoff N ieto's ankle only experi enced a moderate amount of phase, and thus to produce a larger he ight for hi s c.m. pronati on. Angle e3 is not th e only factor th at at th e peak of th e jump. (See Appendix 2 for determines th e amount of pronati on, and it may be exercises that will help to produce fas t and low that Nieto's ank le musculature is strong enough to conditions at the end of th e run-up.) control the amount of pronati on of the foot in spite of th e very large e3 ang le. We sti ll think it would be An altern ati ve option would be to put the c.m. at good for Nieto to plant the takeoff foot on the ground the end of th e run-up in a lower position, equivalent in a more counterc lockw ise orientati on, w ith the toe to about 45.5% ofNieto's own standing he ight. This pointing more toward the landing pit than in jump 99. would be a fina l run-up height s imilar to those used However, due to th e in fo rmation g leaned from by N ieto in j umps 36 and 13 from 2001 /2002. With N ieto's vid eo images, we are not as concern ed about such a positio n at the end of th e run-up, a fin al N ieto' s ankle as we were in prev ious reports. hori zonta l speed of about 7.6 m/s would be suffic ient to qua lify as optima l. (See the arrow pointing Nieto's arm and lead leg acti ons in jump 99 were downward and toward the right in th e graph.) overall somewhat weak, but this was not a very important problem . T he problem would be (Sta ndard ca ution w hen in creasing the run-up completely e liminated if N ieto lifted his left knee a speed a nd/or lowering the c. m. height at the end of li ttle bit higher at the end of the takeoff phase. the run-up: The use of a f aster and/or lower run up will put a greater stress on the takeoff leg, and No changes should be made in N ieto's leans at thus it may increase the risk of injury if th e leg is the start and at the end of th e takeoff phase, in his not strong enough. Therefore, it is always generati on of angular momentum, nor in his actions 81 on top of the bar. These aspects of his technique are already very good. 82 0 N 0 ..... 0 ..... 0 0 .....0 00 00 0\ N 00 0\ 83 N N 0 ..... 0 N 0 CD ..... 0 ..... 0 ..... .....0 .....N 0 ..... 0 ..... 0 CD 0 0 ..... fil uz ;:1 "'0 ..: 0 fil ..... H u ::;: N ..,. "' 0 N 0 r- ..,.0 N fil U) "'0 ..: 0:: N 0"1 p., 0 0"1 ~ 0 ~ ..... *0 0 E-< fil fil H ::! z E-< 0 0 .....0 NIETO #99 062407 2 . 25 M CLEARANCE BAR CLEARANCE ~ 00 10.22 10 . 34 10 . 46 10 . 58 10 . 70 10 . 82 10 . 94 -+::- 85 0 0 0 L{) "" 0 I 0 0 - 00 "' \ 0 - "' I "' [ii uz ~ [ii ...:! u ~ L{) N N [ii r- ~ 0 H E-< N"" (fl "'0 :> E-< "' :r: ~"' <:!> H 0 [ii E-< :r: [ii 0 Hz ~ "" u "' 86 NIETO #99 062407 2.25 M CLEARANCE 87 NIETO #99 062407 2 . 25 M CLEARANCE 88 Scott SELLERS Jump 42 was Sell ers' last successful clearance at the 2007 USATF Championships (2 .18 m). Sell ers' verti cal velocity at takeoff in jump 42 was Vzro = 4.25 m/s. However, th e USATF Championships were a particul arly bad competition fo r him, and thus Sell ers' 4 .25 m/s Vzro valu e without any pronati on of the takeofffoot. However, presents a distorted view of his physical condition it is possible th at Sell ers' ankle may not be as safe as during the 2007 season. Sell ers' best mark of th e it seems. season was 2.33 m. Even though we have no hard data on hi s 2.33 m jump, we can estimate fairly Until last year we recorded the jumps with movie accurately that he must have generated about 4.55 cameras ( 16 mm film), and th e images of the jumps m!s of vertical velocity in th at jump. Therefore, we were generally not clear enough to actually see the wi ll consid er Vzro = 4.55 mls th e best indicator of pronation of the fo ot during the takeoff ph ase. This Sell ers' physical condition. year, we have switched to high definition vid eo cameras, and the im ages are clearer. This sometim es Based on a vertical velocity at takeoff of Vzro = all ows us to see the pronati on when it occurs. The 4.55 m/s, a technique of average quali ty would have im ages above show screen captures of Sellers' included a final run-up speed of about 7.6 m/s and a takeoff foot during the takeoff phase in jump 42 . c.m. height at the end of th e run-up equal to about Even th ough th is camera v iew is not the best for the 46.5% of his own standing he ight. In jump 42, observati on of takeoff foot pronation, some pronati on Sell ers was actually s li ghtly faster at the end of th e is ev id ent: The outside edge of th e shoe actua ll y run-up (vH 1 = 7.7 m/s) th an what would be expected lifted off from th e ground between th e middle im age in a technique of average quality, but his c.m. was and the image on the left, and other jumps by Sellers also clearly higher (hm = 48%). This was much during the competition showed similar evidence of worse than the 8.0/4 7.5 combinati on that he used in pronati on. It is not clear to us why Sellers' foot 2006, and a weak chall enge for a hi gh jumper with a pronated when hi s e3 ang le was so good. It is true takeoff leg capabl e of generating 4 .55 m/s of vertical th at the amount of pronation does not seem very velocity . The wet conditions of the track in th e 2007 severe in th ese images, but we need to keep in mind competition may have played a role in this problem, th at the images were not taken from the best but we don ' t know fo r sure. viewpoint for th e observati on of pronation, so it is possible that the pronati on might be more severe th an The last step of Sellers' run-up was somewhat what meets th e eye. too long (SL1 = 2 .09 m, or Ill % of hi s own standing height). This long length of the last step of th e run Sellers' arm actions during th e takeoff ph ase up probabl y contributed to Sellers' somewhat large were very strong (AAT = 2 1.4 mm/m), and the action negati ve vertical velocity at the start of the takeoff of his lead leg was also strong (LLA = 20.9 mm/m). phase (vzm = -0 .6 m/s) . A large negative Vzm value Therefore, hi s overall combination of arm and lead is not advisable, because it requires the athlete to leg actions was also strong (FLA = 42.3 mm/m). make an extra effort to stop th e downward motion This was a ll very good. before producing the needed upward vertical velocity. lnjump 42, Sellers' trunk had only a small amount of backward lean at th e start of the takeoff At the end of the run-up, Sellers planted the phase (BFTD = 79°). Then he rotated fo rward, and takeoff foo t at what we cons ider to be a very good by the end of the takeoff his trunk was 2° beyond the ori entation, not too paralle l to the bar. As expected, vertical (BFTO = 92°). In the view from th e s id e, the the angle that this produced between th e foot and the trunk should be vertical (i.e., at 90°) at th e end of the horizontal direction in which th e foot pushed against takeoff, so Sellers' overrotati on probably produced a th e ground during th e takeoff phase was small ( e3 = sli ght loss of lift. Also, due to Sellers' sma ll amount 16°). (See the section on "Orientation of the takeoff of backward lean at th e start of the takeoff phase, and foo t, and potential for ankl e and foot injuries" in the in spite of the fact that he was s lightly overrotated main text of the report.) This was similar to Sell ers' forward by the end of th e takeoff phase, th e amoun t e3 angle value from 2006, and we would expect such of forward somersaulting angul ar momentum that he a sma ll e3 angle to produce a very safe takeoff, was abl e to generate was somewhat sma ll (HF = 70). 89 T his limitatio n in th e amount of angular momentum Sell ers' marked was ultimately due to Sell ers' in sufficient backward lean toward th e bar at lean at th e start of th e takeoff phase. the end of the takeoff pu t his shoulders in Sell ers' trunk had onl y a very small amount of danger of hitting th e lean toward the left at th e start of the takeoff phase bar on th e way up, (LRTD = 84 °). Then he rotated toward th e ri ght, and even w ith hi s limited by the end of th e takeoff he was 16° pas t the vertical amount of in th e view from the back ( LRTO = I 06°). In th e somersaulting angul ar view from th e back, it's norma l to go a few degrees momentum. This may past the vertical at th e end of th e takeoff. We have been what led consid er it acceptable ( indeed, desirable) to tilt up to him to adopt a rather unusua l "sitting" body I oop ast the vertical at th e end of the takeoff ( in th e configurati on on the way up to the bar. As the athl ete view from th e back) because we be li eve th at this may gets into such a configurati on the legs rotate be th e best compromise between th e generation of li ft counterclockw ise (in th e view from th e left standard , and the generati on of rotati on (ang ul ar momentum). along th e bar) while th e upper trunk rotates clockw ise However, in his quest fo r th e generation of lateral and the hips drop down. (See th e graphic above.) somersaulting angular momentum, Sell ers went well T his is a good maneuver that he lps to keep th e beyond the acceptable limit fo r lean toward the ri ght shoulders away from the bar. It is generally not by the end of the takeoff phase. This probably necessary in normal jumps in whi ch th e athlete is produced a sizable loss of li ft for th e j ump. And still , closer to vertical at the end of the takeoff phase. (We he was only able to generate a small amount of latera l assume that th e purpose of th is "sitting" body configuration used by Sell ers was indeed to prevent somersaulting angular momentum (HL = 75). This limi ted amount of angular momentum, as well as the th e shoulders from hitting th e bar, and not an attempt loss of lift associated w ith the excessive lean toward at implementing the " knee bending" maneuver that th e ri ght at th e end of th e takeoff, were both we proposed in the 2006 report. The maneuver th at ultimate ly due to Sell ers' insufficient lean toward th e we proposed was to " bend the knees as if th e athlete left at th e start of the takeoff phase. T he wet were try in g to kick th e bar from below with his conditions of the track in the 2007 competition may heels", quite different from th e "s itting" position have played a ro le in this problem : Did the wet track described above, which Sell ers used in a ll of his make it impossibl e to use a curve tight enough to j umps at th e 2007 meet.) produce the necessary amount of lean toward th e left? We don't know. In j ump 42, Sell ers did not arch very much. The graphics below show his maxi mum arch in j ump 03 Sellers' fo rward and latera l components of from 2006 and in jump 42. (The image of j ump 03 somersaulting angul ar momentum added up to a has been rotated counterc lockw ise to faci litate the sma ll to tal amount of somersaulting angul ar compari son of th e amounts of arching.) T he graphics momentum (Hs = I 05). This was th e same amount show th at Sell ers used much less arching in j ump 42 th at he generated in 2006i , but n j ump 42 from 2007 from 2007 than in j ump 03 from 2006. Sell ers' leans backward and toward the left at th e jump 03 from 2006 jump 42 start of the takeoff phase were c learly worse (sma ll er) th an in 2006. This resul ted in larger leans forward and toward th e right at the end of th e takeoff, w ith consequently larger losses of li ft. The peak height reached by th e c. m. in jump 42 was hrK = 2.24 m. T he "saturati on graph" shows th at in this j ump Sell ers coul d have cleared c leanl y a bar set at about hc Ls = 2 .1 8 m. In re lati on to the peak height of th e c. m . (2 .24 m), the 2 .18 m c lean clearance he ight indicated a bar c learance th at was Recommendations not very effective. The effectiveness of Sell ers' bar c learance was sim ilar to that of2006. In part th e Sell ers' technique was much worse in 2007 than problem was due, as in 2006, to Sell ers' limited total in 2006. We do not know to what extent th e amount of somersaul ting ang ul ar mo mentum, but problems were due to the slippery conditio ns of the there were oth er complicating factors as we ll. track. (The track was wet in both meets, but it 90 seemed to dry off better toward the end of the meet in 2006 th an in 2007 .) / An important problem in Sell ers' technique w as his combination of speed and c.m. height at the end of the / run-up. He needs to be faster and/or lower th an in j ump 42. The optimum combinatio n for any j umper is faster and/or lower than the expected average ("ordin ary") combinati on. In terms of Figure 3, a ll so lutio ns to th is problem in vo lve moving Sell ers' point to th e diagonal lin e HAR II recomm ended fo r Vz TO = 4.55 m/s. (See the graph on th e ri ght. ) One possible option would be to combine the heights that Sell ers had at the end of the run-up in jumps 03 or 42 w ith a much larger amount of speed than what Se ll ers had in jump 42. We would suggest fo r him a fin al speed of about 8.3 or 8.2 m/s. (See the hori zonta l arrow and the arrow th at points s lightly downward in the graph shown to th e ri ght of these lin es.) These larger fi nal speeds of Sell ers' run- up should a ll ow him to generate more li ft during the takeoff phase, and thus to prod uce a larger height fo r his c.m. at th e peak of th e 7.6 7.8 8.0 8.2 j ump. (See Appendix 2 fo r exercises that wi ll help to produce fas t and low right in th e graph above.) condit io ns at the end of the run-up.) These recommended combinati ons of speed and An altern ati ve option would be to put th e c. m. at height at th e end of the run-up are based on the use of th e end of the run-up in a clearly lower position, average "run-of-the-mill" arm and lead leg actions equivalent, for instance, to about 46% of Sell ers' own during the takeoff phase. Athletes such as Sell ers stand in g height. Th is would be a fi nal run-up height who use very stro ng arm and lead leg actions during si milar to those used by Littleton or Shunk at th e th e takeoff phase should compensate by usin g 2007 USATF Championships. With such a position somewhat slower and/or higher run-ups; oth erw ise, at the end of the run-up, Sellers would not need to be th e takeoff leg might buckle during the takeoff ph ase. traveling at 8.2/8.3 m/s at the end of the run-up fo r hi s technique to be cons idered optimum: A fin al (Standard caution when increasing the r un- up horizontal speed of about 8.0 m/s would do. (See th e speed and/or lowerin g the c.m. height at the end of arrow pointing steeply downward and toward th e the r un-up: The use of a faster and/or Lower run- 91 up will put a greater stress on the takeoff leg, and As expl a in ed before, we do not know why thus it may increase the risk of injury if the leg is Sell ers' takeoff foot pronated, when it had such a not strong enough. Th erefore, it is always good ori entation during th e takeoff phase. Maybe th e important to use caution in the adoption of a faster musc les th at fi ght against pronati on are weak in am/lor lower run-up. If the desired change is very relati on to the oth er muscles of his takeoff leg. Or he large, it would be advisable to make it gradually, might have fl at feet, a lth ough we think that this is over a period of time. In all cases, it may be wise to unlike ly. We a lso are not sure how severe th e further strengthen the takeoff leg, so that it can amount of pronati on is. In any case, it may not be a withstand the increased force of the impact bad idea to have Sell ers be examined by a phys ician produced when the takeoff leg is planted.) or a physical therapist. Maybe there is nothing wrong w ith his foot or ankle, but maybe th ere is, and The most important problem in Sellers' an orth oti c might help to protect against inj ury . technique was probably the minimal amount of lean that he had toward th e left at the start of th e takeoff Sell ers' arm and lead leg acti ons during the phase. (See the back views of hi s run-up sequence or takeoff ph ase were very good. N o changes are of his takeoff sequence at t = I 0.00 s.) It led him to needed this aspect of his technique. In fact, as acquire a very large lean of his trunk toward the ri ght mentioned above, Sell ers' free limb acti ons were so at th e end of th e takeoff phase (see th e back view of strong th at, for optimum technique, he should th e takeoff sequence at t = I 0.18 s), whi ch in turn led probably use a sli ghtly s lower and/or higher run-up to a large loss of lift. T he fas ter run-up speed th at we than what was recommended in th e prev ious page. propose fo r Sell ers should he lp to produce a s li ght increase in hi s lean toward th e left at the end of th e In th e air, our advice to Sell ers is to implement run-up. However, to acquire th e necessary amount of the airborn e acti ons proposed in th e 2006 report: He lean he w ill probably also have to tighten th e run-up should bend th e knees as if he were try in g to ki ck th e curve, i.e., to use a curve w ith a shorter radius. See bar from be low with his heels. (See the 2006 report Append ix 4 for more information on how to change for further deta il s.) th e shape of th e run-up curve. In summary , Sell ers should use a faster and/or A small er problem is Sell ers' in suffic ient lower run-up. He should al so tighten (i.e., shorten) backward lean at th e start of the takeoff phase. He the radius of hi s curve, and he should thrust his hips should thrust hi s hips further fo rward in th e very last furth er forward in th e las t step of th e run-up. This step of the run-up. This w ill give his trunk a larger will produce good leans toward th e left and backward amount of backward lean at th e start of th e takeoff at th e start of the takeoff phase. He should try to phase. Then, he should a ll ow hi s trunk to rotate plant th e takeoff foot on th e ground immediately after forward during the takeoff phase, but only up to th e he plants th e ri ght foot on the ground. Then he vertical by the end of th e takeoff. This should should rotate during the takeoff phase fo rward all the produce a larger amount of forward somersaulting way to th e vertical, and toward the right to a position angul ar momentum, while avo iding any loss of lift no more th an I 0° beyond th e vertical in the view th at might have been produced through excessive from th e back. By do ing this, he will generate a good forward lean at th e end of the takeoff. amount of somersaulting an gul ar mo mentum w ith out losing any lift. In th e air, he needs to implement th e Anoth er sma ll probl em was the rath er long airborne acti ons proposed in th e 2006 report length of Sell ers' last step of th e run-up. To correct (in cluding th e bending of th e knees as if he were thi s, he should try to in crease th e tempo of th e last trying to ki ck th e bar from below w ith hi s heels: two foot landings, i.e., he should try to plant th e left mimic th e acti ons of s imulation #2 from th e 2006 foot on the ground almost immediately after he pl ants report). No changes should be made in Sell ers' arm th e ri ght foot. By in creasing the tempo of th e last or lead leg acti ons during th e takeoff phase, because two foot landings, Se llers should be able to reduce they are already very good. It may be a good id ea to the length of the last step of th e run-up, but more get his takeoff foot examined by a physician or a importantly, he will reduce th e time that he spends in physical therapist - maybe th ere isn't anything wrong the air during th at step. This w ill prevent him from w ith it, but maybe th ere is. accumulating too much downward (negati ve) vertical velocity in the a ir, so th at he does not have an excessively large downward vertical velocity when he pl ants th e left foot on the ground to start th e takeoff phase. 92 co "' "' "' "' \0 r- "' "'co "' co co "' .... "' w uz "' ~w ...:! u 0 0 ~ co ....0 r-"' 0.... "'\0 0 ....0 "'.... 0 'lj, .... Ul ~ p.. w ::> ...:! I ...:! z w ::> Ul ~ '!b 0 "' 0.... SELLERS #42 062407 2 . 18 M CLEARANCE TAKEOFF PHASE \!) 10.22 10.20 10.18 10 . 16 10 . 14 10.12 10 . 10 10.08 10 . 06 10.04 10 . 02 10 . 00 VJ SELLERS #42 062407 2 . 18 M CLEARANCE BAR CLEARANCE ~ 10.94 10.82 10 . 70 10 . 58 10 . 46 10 . 34 10.22 ~ 60 C . M. HEIGHT VS TIME ------ ~ 50 ~ ~ ------~ 40 9.40 9.60 9.80 10 . 00 SELLERS #42 062407 2 . 18 M CLEARANCE \0 Vl 96 SELLERS #42 062407 2 . 18 M CLEARANCE 97 SELLERS #42 062407 2 . 18 M CLEARANCE 98 Adam SHUNK at the end of th e takeoff. We consid er it acceptable (indeed, des irable) to tilt up to I 0° past the vertical at Jump 95 was Shunk's 2"d attempt at 2.27 m at th e the end of the takeoff phase (in th e view from th e 2007 USATF Championships. It was a c lose miss, back) because we be li eve th at this may be the best and probably hi s best jump of th e day. compromise between the generation of lift and the generation of rotation (angular momentum). So Based on Shunk's vertical velocity at takeoff in Shunk' s left/right lean ang les at the start and at the j ump 95 (vzm = 4.40 m/s), a technique of average end of th e takeoff phase were both very good. This quali ty would have included a final run-up speed of all owed him to generate a large amount of latera l about 7.5 m/s and a c.m. height at the end of the run somersaulting angu lar momentum during th e takeoff up equal to about 4 7% of his own standing height. phase (HL = 95). Shunk was actually in a s li ghtly lower position at the end of the run-up than what would be expected for a Shunk's forward and lateral components of technique of average qu ali ty (hm = 46%), but he was somersaulting angular momentum ad ded up to a also very s low (vH 1 = 7.1 m/s). Overall, th e somewhat sma ll total amount of somersaulting combination of run-up speed and c.m . height that angul ar momentum (Hs = II 0). Shunk used in j ump 95 was a weak chall enge for a hi gh jumper w ith a takeoff leg capable of generating T he peak he ight reached by th e c.m. in jump 95 4.40 m/s of vertical velocity . Shunk actually had a was hrK = 2.27 m. The "saturati on graph" shows that good amount of speed in the next-to-last step of the in this jump Shunk could have cleared cl eanly a bar run-up (v 11 2 = 7.7 m/s) , but lost a lot of it (0.6 m/s) as set at about hcLs = 2.23 m, and at hcLA = 2.28 m if he he passed over the right foot. had taken off about 5 em farther from th e pl ane of the bar and the standard s. Int relation o the peak he ight At th e end of the run-up, Shunk planted the of the c.m. (2 .27 m), the 2.28 m clean c learance takeoff foot too para ll e l to th e bar. Because of this, height indicated an extreme ly effective bar clearance. the angle between th e longitudina l ax is of th e takeoff Considering th at Shunk's angular momentum was foot and the hori zontal force received by th e foot was somewhat sma ll , this indicated that hi s acti ons in the very large ( e3 = 43 °). This produced a very large ri sk ai r were exceptiona lly good. of ankle pronation, an d injury to th e ankle and foot. (See the section on "Ori entation of th e takeoff foot, Recommendations and potential for ankle and fo ot injuries" in th e ma in text of the report.) Shunk had two ma in problems in his technique. The first one was his combination of speed and c.m. Shunk's arm actions during the takeoff phase height at the end of the run-up. The optimum were strong (AA T = 16. 1 mm/m). However, th e combinati on for any jumper is faster and/or lower acti on of his lead leg was somewhat weak (LLA = th an th e expected average ("ordinary") combinati on. 16 .9 mm/m). Because of this, his overall Although Shunk was in a reasonably low position at combination of arm and lead leg acti ons was th e end of th e run-up, his fin a l run-up speed was not somewhat weak (FLA = 33 .0 mm/m). fast enough. There are several ways in which Shunk can so lve this problem. In terms of Figure 3, all Shunk's trunk had a good backward lean at the options in volve moving his point to the diagonal lin e start of the takeoff phase ( BFTD = 73 °). But then he recommended for Vzro = 4.40 m/s. (See th e graph in did not rotate forward enough during th e takeoff the next page.) One possible option wou ld be to phase, and at th e end of the takeoff he was still far combine th e reasonably good (low) height that Shunk from the vertical in th e v iew from the sid e (BFTO = already had at the end of th e run-up in jump 95 with a 81 °). Because of this, the amount of forward much larger amount of speed. We would suggest for somersaulting angular momentum that Shunk was him a final speed of about 7.8 m/s. (See th e ab le to generate was sma ll (Hr = 55). hori zonta l arrow in the graph shown in the next page.) To achieve this, Shunk would not actu ally Shunk's trunk had a very good lean toward the have to run faster during the entire final part of the left at the start of the takeoff phase (LRTD = 74°). run-up. He already has a good amount of speed in Then, he rotated toward the right, and by th e end of the next-to-last step of th e run-up (vH 2 = 7.7 m/s), so the takeoff he was I 0° past th e vertical in the view he just needs to concentrate on not los in g any of this from th e back (LRTO = I 00°). In th e view from the speed as he passes over the last support on his right back, it's norma l to go a few degrees past the vertical foot. For this, Shunk needs to try to pull backward harder on th e ground w ith his right foot. A larger 99 fin aol speed f his run -up should allow Shunk to 0 0 generate more lift during th e ~101 · 8~ SlL 4~ <> takeo ff phase, and thus to produce a larger height for \VII. R2 his c.m . at th e peak of the VIL 16 jump . (See App endix 2 for 0 Ill •I. 97 exercises that wi ll help to ):{ ~ 1 0 . 40 NIE 17 ):{ produ ce fas t and low ):{ co nditions at th e end of th e N IL 99 run-up.) An altern ati ve option wo uld be to put th e c.m. in a slightly lower pos iti on, simi lar to th e lower height th at Shunk had at th e end of th e run-up in jump 28 from + 2004 . If Sh un k is able to $ I ~8 achi eve this, he would not need to be travelin g at 7.8 m/s at the end of th e run-up for his technique to be 111"1'• co nsidered optimum : A fin al horizo ntal speed of 7.5 m/s wo uld do. (See th e arrow pointin g downward and 7.0 7.2 7.4 7. 6 7.8 8. 0 8.2 toward th e right in the graph on this page.) exclu sively on th e ori entati on of the takeoff foot relative to the direction of th e horizontal force made (Sta nda rd ca ution w hen increasing the run-up by th e ath Jete on the ground during the tak eoff ph ase speed and/or lowering the c.m. height at the end of (an gle e3) . This was becau se it was almost never the run-up: Th e use of a Jaster and/or lower run poss ib le to actu all y see th e foot pronati on in the up will put a greater stress on th e takeoff leg, and images of the 16 mm movie fi lm th at we used. This thus it may increase the risk of injury if the leg is has changed to some extent with our switch to hi gh not strong enough. Th erefore, it is always definition video. The im ages are mu ch clearer, and important to use caution in the adoption of a Jaster we have a better chance of ac tua lly seeing the and/or lower run-up. If th e desired change is very pronati on in th e vid eo im ages . For athl etes who large, it would be advisable to make it gradually, approach from th e left , we can generally see th e over a period of time. In all cases, it may be wise to pronation quite well if it occurs. Unfortun ately, for further strengthen th e takeoff leg, so that it can athl etes who approach fr om the ri ght (li ke Shunk), it withstand the increased f orce of the impact is not so easy to see, du e to the pos itions in which we produced when lit e takeoff leg is planted. ) have to place our cameras. Sti ll , we were able to detect pronati on in most of Shunk 's jumps. Th e two The second major problem in Shunk's techniqu e seri es of im ages in th e nex t page show th e takeoff was the ori entation of th e left foot during th e takeo ff foot in two of Shunk's jumps. Th e fi rstjump was his ph ase . He planted th e takeoff foot too parall el to th e clearance at 2.2 1 m; th e second one was hi s second bar. Based on this, we advise him to plant the takeoff miss at 2.27 m Uump 95). The midd le photo of th e foo t on th e groun d with its longitudinal ax is more in first sequ ence (the 2.2 1 m clearance) shows what th e lin e with the fin al directi on of th e run-up, with th e toe takeoff foot loo ks like imm ediately aft er the entire pointing at least 25 °c more lockwise th an in jump 95. shoe so le establishes full contac t with th e ground , This technique change wi ll help to prevent foot before hard ly any pronati on has occurred. A pronati on, and injury to th e ank le and foot. co mparison of thi s photo with the left photo of th e sam e jump and with the middle and left photos ofthe In the pas t, to advise high jump ers about the second miss at 2.27 m (al l three of which appropriate ori entati on of th e takeoff foot, we reli ed corresponded to slightly later tim es within the takeoff 100 not to make any changes in his Jeans at th e start nor 2.21 m clearance at the end of th e takeoff phase, nor in his acti ons over the bar We do advise Shunk to take off a little bit farther from the bar th an he did in jump 95. This is necessary in order to center his body better over th e bar, and thus to reap th e full benefits of his excellent bar c learance. So our ma in advice to Shunk is to pass more smoothly over the right leg in the penultimate step of 2.27 m second miss th e run-up, losing little or no horizontal speed, and to (jump 95) plant th e takeoff foo t more in Iin e w ith th e f in a l directi on of th e run-up. He also needs to take care not to take off too c lose to th e bar. phase) shows th at, in the latter three photos, th e outs id e edge of th e shoe was li fted off from the ground. This indicated th at th ere was pronati on. G iven the very large valu e of th e e3 ang le in jump 95 and th e ex istence of pronati on in Shunk's jumps (even though we can' t judge very well how severe th at pronati on was), our advice to Shunk is to play it safe, and plant the takeoff foot more in lin e with th e fin al directi on of th e run-up. A minor problem in Shunk's technique was the somewhat weak acti on of his lead leg. It wou Jd be good to li ft th e knee of th e ri ght leg hig her by th e end of th e takeoff. T his should he lp Shunk to generate a sli ghtly larger amount of lift. Shunk should not make any changes in his leans at the start nor at the end of th e takeoff phase, nor in his acti ons over th e bar, because these aspects of his technique are a lready near-perfect. It is true th at Shunk did not rotate fo rward enough during the takeoff phase, and th at this limited his fo rward component of somersaulting angular momentum, and consequently also hi s tota l amount of somersaulting angul ar momentum. However, this was not a problem for hi m. The amount of somersaulting ang ul ar momentum that he generated, togeth er w ith his very good acti ons in th e a ir, produced an extreme ly effecti ve bar c learance: He would have been able to c lear a bar set I em higher than th e peak height reached by his c. m . This is th e most effecti ve bar c learance that we have ever measured in an American high jumper. That is why we advise Shunk 101 \D"" "' 0 r- "' \D r- "' N ro "' ro ro "' "'"" "' Ul Ul H 0 0 ~ 0 ~ ..... r- N N r- 0 N"" 0 \D ..... 0 0 "' ..... % "' P< ;.:: ::::> z I ::::> z :I: ::::> Ul ~ 0 N .....0 SHUNK #95 062407 2 . 27 M MISS TAKEOFF PHASE 0 10 . 22 10.20 10.18 10 . 16 10 . 14 10 . 12 10.10 10 . 08 10 . 06 10 . 04 10 . 02 10 . 00 N 103 "' "'0 ..-< 0 ..-< co "' 0 ..-< 0 ..-< CJJ CJJ H;:;: ;:;: co r- "' 0 "' ..-< r-"' 0 "' ~ "' u "'0 z "' ~ 'lj, ~ "' ...:l ;.: z u ::> "' 0:: ~ "' CJJ P'l 0 ..-< 104 0 0 0 0 "' Ll"l "" 0 0.... ) 0 - (X) 0 - "' "' (I) (I) H ~ ~ ..... N N ..... ~ 0 H E-< ""N (I) "'0 > Ll"l E-< :c %"' (.!) H :.:: ~ z :c :::> 0 :c i - "" (I) u "' 105 SHUNK #95 062407 2.27 M MISS L06 SHUNK #95 062407 2.27 M MISS 107 Jesse WILLIAMS Jump 82 was Williams' last successful c learance at th e 2007 USATF Championships (2.24 m). 2. 15 m 2. 21 m miss #1 cl ea rance Based on Williams' vertical velocity at takeoff in jump 82 (vzro = 4.50 m/s), a technique of average quality would have in cluded a c. m. he ight at th e end of the run-up equal to about 46.5% of hi s own standing height, and a fin a l run-up speed of about 7.6 2. 15 m 2.24 m m/s. Williams' actu a l speed at th e end of th e run-up mi ss #2 clearance (vH 1 = 7.7 m/s) was sli ghtly faster than what might have been expected fo r a technique of average quali ty, but he was also hi gher (hm = 48%). The overall combinati on of run-up speed and c.m . height th at Williams used in jump 82 was not very bad, but also not parti cul arly good. 2. 15 m 2.27 m cl earance miss #1 At th e end of th e run-up, Williams planted th e takeoff foo t too para ll e l to th e bar. Because of this, the ang le between the longitudina l ax is of th e takeoff foot and the horizontal fo rce received by the foot was extreme ly large (e3 = 54°). This produced a very large ri sk of foot pronati on, and injury to the ankle 2.18 m 2.27 m and foot. (See th e secti on on "Orientati on of the clea rance miss #2 takeoff foot, and potentia l for ankle and foot injuries" in th e ma in text of th e report.) The danger was confirmed th rough d irect viewing of th e vid eos, whi ch showed a large amount of pronation in a ll of Williams' jumps. (See the images on thi s page.) 2. 27 m mi ss #3 Williams did not prepare his arms for a double arm takeoff. (See th e s ide-v iew and back-view sequences of the run-up between t = 9 .64 s and t = 10 .00 s.) Still , he managed to have both arms in action was weak (AAT = 14.2 mm/m). Williams did low positi ons at the start of th e takeoff phase (t = not lift hi s left knee hig h enough at th e end of the I 0.00 s), and this raised the possibi lity that he m ight takeoff phase. Therefore, th e action of his lead leg still be able to execute reasonably strong arm acti ons was weak (LLA = 12.4 mm/m). His overall during th e takeoff phase. Indeed, Williams lifted hi s combinati on of arm and lead leg actions was also left arm to a hi gh positi on by th e end of the takeoff weak (FLA = 26.5 mm/m). phase, so its acti on was strong (AAN = 9 .0 mm/m). (See th e deta il ed sequence of th e takeoff phase Williams had a moderate amount of backward between t = I 0.00 sand t = I 0.16 s; see also Figure 9 lean at the start of th e takeoff phase in jump 82 in th e main text of th e report.) He a lso lifted hi s ri ght (BFTD = 76°). Then he rotated forward during th e elbow to a hi gh position by the end of th e takeoff takeoff phase, and at the end of the takeoff he was phase, but in addition he executed an intern al rotati on essentially vertical (BFTO = 89°). This was all very of th e ri ght upper arm that put the ri ght forearm in a good, and it all owed him to generate a large amount hori zonta l pos ition at the end of th e takeoff, which of forward somersaulting angul ar mo mentum (HF = pu t th e right hand in a lower position th an the ri ght 80). shoulder. (See the sequence of th e takeoff phase at t = 10 . 16 s.) This made the acti on of Williams' ri ght Williams' trunk had a good lean toward the right arm be very weak (AAF = 5.1 mm/m). Keep in mind at th e start of the takeoff phase (LRTD = 76°). Then that th e arm farth est from th e bar (th e ri ght arm in he rotated toward th e left, and at th e end of th e Williams' case) is th e one th at norma ll y makes a takeoff he was I o short of th e vertical in a view from stronger acti on in most high jumpers. Because of th e the back (LRTO = 89 °) . In th e v iew from the back, weak action of his ri ght arm, Williams' total arm 108 it's norm al to go a few degrees past the verti ca l at th e airborn e motions than the mai n sequence of jump end of th e takeoff. We co nsid er it acceptable 82 's bar clearance. Therefore, the reader can use (indeed, des irable) to tilt up to 10° pas t the vertical at them to check that Williams indeed started to un-arch the end of the takeoff ph ase (in th e view fr om th e too soon. See the view along th e bar of simulati on # I bac k) because we be li eve th at this may be th e best between t = I 0. 64 sand t = I 0.76 s. Th e sequence co mp ro mise between th e generati on of lift and th e shows th at Will iams started to un-arch before his hips generation of rotati on (angul ar momentum). had crossed over to the oth er sid e of the bar. ) Therefore, Williams' lack of lean toward th e left at the end of the tak eoff was very "conservati ve", and In simulati on #2 we kept th e position at takeoff, th e amount of lateral somersaulting angul ar th e angular momentum and the path of the c.m. th e momentum that he was able to generate was small same as in the origin al jump. In the air, we had (HL = 75). Williams execute, on the way up to the bar (up tot = I 0.64 s), th e same ac ti ons as in th e orig inal jum p 82 . Williams' large amount of fo rward But fro m th at point onward we had him change hi s somersaulting angul ar momentum and small amount ac ti ons. (See th e view along the bar in the sequence of lateral somersaulting angul ar momentum of simulati on #2.) We had him keep his knees combined into a somew hat small total amount of lowered fo r a littl e bit longer th an in the ori gin al somersaulting angular momentum (Hs = II 0). jump (between t = I 0.64 sand t = I 0.76 s) ; then we had him lift his knees very strongly (t = I 0.76 -1 0.88 Williams' c.m. reached a max imum height hrK = s) to avo id dragg ing th e bar down with his calves . 2.32 m in jump 82. The "saturati on graph" shows that in this jump he co uld have cleared cleanl y a bar The "satu rati on graph " of simulati on #2 showed set at about hcLs = 2.25 m, and at hcLA = 2.27 m if he that, with th ese alte rati ons in his actions over the bar, had taken off about 5 em closer to the pl ane of the Will iams wo uld have been able to clear cleanly a bar bar and th e stand ard s. In relati on to th e peak height set at a height of2.30 m. A height of2.30 m is 0.03 of th e c.m. (2 .32 m), the 2.27 m clean clearance m hi gher than th e 2.27 m height (hcLA) th at Will iams height indi cated a reasonably effecti ve bar clearance. co uld have cleared cleanly in th e ori gin al jump, and onlyl 0.02 m ower th an th e peak height reached by Alth ough we classify Willi ams' bar clearance as the c. m. (2.32 m). Thi s wo uld qu ali fy as a very "reasonably effecti ve", thi s is not th e same as say ing effecti ve bar clearance. th at he should be satisfi ed with it. Computer anim ati ons of jump 82 showed th at Williams started Recommendations his un-arch in g prematurely, and we wo nd ered if a change in the timing of Williams' un-arching might The main prob lem in Williams' technique was help him to produ ce a more effecti ve bar clearance. the orientati on of his takeoff foo t. He shoul d plant the ta keofffoot on th e ground with the longitudi nal To in vestigate this qu esti on furth er, we made ax is of th e foot more in lin e with th e fin al direction of tes ts usin g compu ter simulati on of the bar clearance. the run-up: The foot should be pl anted on th e ground We made two computer simulations. In the first one in a more co unterclockw ise ori entation, with the toe of these computer-generated jumps ("s imulati on # I") pointin g at least 35 ° more toward the landing pi t th an we kept the pos ition of th e body at takeoff, th e in jump 82. This technique change will help to angular momentum, the path of the c. m. and the prevent ankl e pronati on, and injury to th e ankle and moti ons of th e body segments relati ve to each other foot. This is a health-related issue rath er than a after takeoff th e sa me as in the ori gin al jump 82. perform ance-related issue, but nevertheless it is the Grap hi c sequences of this simulati on (v iew fro m most important problem in Willi ams' technique. overh ead; view perp endi cular to the pl ane of the bar and the standards; view in line with th e bar) are From a perfo rm ance standpoint, th e most shown in one of th e graphics pages th at follow these important probl em in Williams' technique was hi s comm ents. The result was a simul ated jump very co mbination of speed and c. m. height at th e end of si mil ar to the origi nal jump . This is a stand ard th e run-up. He needs to be fas ter and/or lower than pract ice in computer simulati on, to check th at th e in jump 82. The optimum combination fo r any simulation program is functi oning properl y. The jumper is faster and/or lower th an th e expected graphic sequences of this unaltered simulated jump average ("ordin ary") combinati on. In terms of Figure are shown here to prov id e a basis for co mp arison 3, all so lutions to thi s pro blem in vo lve movin g with simulation #2. (The sequ ences of the simul ated Williams' point to th e diago nal line recomm ended for jump also happen to show more images of th e Vzro = 4.50 m/s. One poss ibl e option wo uld be to l09 combine the he ight that Williams had at the end of th e run-up in jump 82 (hm = 48%) with a much faster speed (vH 1 = 8.2 m/s). (See th e horizontal arrow in the graph shown on this page.) T his larger amoun t of fina l run-up speed should all ow Williams to generate more li ft during the takeoff phase, and thus to produce a larger he ight for his c.m. at the peak of the jump. (See Appendix 2 for exercises that w ill help to produce fast and low conditions at th e end of th e run up .) An alternative option would be to put th e c. m. in a lower position at the end of th e run-up, equivalent for in stance to about 46.5% of Williams' own standing height. This would be a fina l run-up height similar to th ose used by Littleton, Nieto and Shunk in 2007. With such a position at the end of th e run-up, a fina l horizontal speed of about 8.0 m/s would be sufficient to quali fy as optimal. (See the arrow pointing downward and toward the right in th e graph .) T liAR I (Standard caution when increasing the run-up speed and/or lowering the c.m. height at the end of the run-up: Th e use of a Jaster and/or lower run up will put a greater stress on the takeoff leg, and thus it may increase the risk of injury if th e leg is not strong enough. Th erefore, it is always important to use caution in th e adoption of a faster and/or lower run-up. If the desired change is very large, it would be advisable to make it gradually, over a period of time. In all cases, it may be wise to further strengthen the takeoff leg, so that it can 7.6 7.8 8.0 8.2 withstand the increased force of the impact produced when th e takeoff leg is planted.) require some prior streng thening of Williams' hip fl exor muscles (th e muscles that cross over the front The second most important perform ance-related ofthe hip) and a lso of his abdominal muscles. problem in Willi ams' technique was probably the med iocre effectiveness of his bar clearance. T his can The third most important performance-related be improved in various ways: (a) It wou ld be good if problem in Williams' technique was probably th e Williams rotated further toward th e left during the weakness of his free- limb actions during the takeoff takeoff phase, to a position about I 0° beyond the phase. Williams should swing his right arm and the verti cal (in the v iew from th e back) at th e end of th e knee of his left leg harder forward and up, to higher takeoff ph ase. This would a ll ow him to generate a positions by the end of the takeoff phase. T his w iII larger amount of lateral somersaulting angul ar help him to obtain more li ft from the groun d. momentum, and therefore a lso a larger tota l amount of somersaul ting ang ular momentum. The resu lt wil l be an improved rotation over the bar, and probably better effecti veness in the bar c learance. (b) Williams also has to be careful not to take off too far from the plane of the bar and the standards (a problem that he had in jump 82). (c) But most importantly for the effectiveness of his bar c learance, Williams needs to delay briefly the start of hi s un arch in g until after his hips have crossed over to th e oth er side of the bar. T hen he needs to un-arch very strong ly and suddenly, as shown in s imulati on #2 . It is possibl e that the implementation of"c" might 110 0 N 0 ..... 0 ..... 0 0 0 ..... ro ro N ro w u z "'r-- w~ "" ...:l u lE: ""I ~ z ..., :::>p:: J. WILLIAMS #82 062407 2.24 M CLEARANCE TAKEOFF PHASE 10.00 10 . 02 10 . 04 10.06 10.08 10.10 10 . 12 10 . 14 10 . 16 10 . 18 10.20 10 . 22 J. WILLIAMS #82 062407 2 . 24 M CLEARANCE BAR CLEARANCE fl~1\r 10 . 22 10 . 34 10 . 46 10 . 58 10 . 70 10 . 82 10 . 94 -N 60 C . M. HEIGHT VS TIME / ~~ / 50 "'~ 40 9.40 9 .6 0 9.80 10.00 J . WILL IAMS #82 062407 2.24 M CLEARANCE t.N 114 J. WILLIAMS #82 062407 2.24 M CLEARANCE 11 5 J. WILLIAMS #82 062407 2 . 24 M CLEARANCE J. WILLIAMS #82 062407 2 . 24 M CLEARANCE COMP UTER- SIMULATED JUMP S I MULATI ON # 1 G-- G- D .(, ~ ( Dt\1r1rir* ~-t--t-Jt f-ir+---Wrtt~--\t- £fif1~~~~~i\v 10 . 22 110 . 28 1 10 . 34 1 1o.4o 1 10.46 1o . s2 1 10.~8 1o164 1p . 1o 110.16 1 1o . 82 1 1o.88- 0'\- J . WILLIAMS #82 062407 2 . 24 M CLEARANCE COMPUTER-SIMULATED JUMP SIMULATION #2 G- G- D " ~ ( Dt\T1riF -If~~-!P-_t_ f~+---.---e-----tt-t £fif1ft~~~~~ 10.22 110 . 28 10 . 34 1 1o.4o 10 . 46 1 1o.s2 1 10.~8 1of64 1p . 7o 11o.76 1 1o . 82 1 10.88- --..) 118 COMPUTER-SIMULATED JUMP SIMULATION #2 J. WILLIAMS # 82 062407 2.24 M CLEARANCE 119 COMPUTER-SIMULATED JUMP SIMULATION #2 J. WILLIAMS #82 062407 2.24 M CLEARANCE 120 REFERENCES 17. Dapena, J., M. Feltner and R. Bahamonde. Biomechani cal analysis of high jump, #5 (Men). I. Dapena, J. Mechani cs of translation in the Fosbu ry- Report for Scientific Services Project (USOC/TAC) . fl op. Med. Sci. Sports E.xerc. 12 :37-44, 1980a. U.S. Olympi c Training Center, Co lorado Springs, 200 2. Dapena, J. Mechani cs of rotation in th e Fosbu ry-flop. pp, 1986b. Med. Sci. Sports Exerc. 12 :45-53 , 1980b. 18 . Dapena, J. , M. Feltner, R. Bahamond e and C.S . 3. Dapena, J. Simulation of modified hum an airborn e Chung. 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Willmott. High jump, #22 (Men). Report for Scientific Services Project (USATF) . USA Track & Field, In dianapoli s, 128 pp, 200 I b. 37 . Dapena, J. and A.P. Will mott. High jump, #23 (Men). Report for Scientific Services Proj ect (USATF) . USA Track & Field, In dianapo lis, 85 pp, 2002a. 38. Dapena, J., A.P. Willmott and B.J . Go rdo n. High jump,# 18 (M en). Report for Scientific Services Project (USATF). USA Track & Field , Indianapoli s, 98 pp, 1998b. 39. Dapena, J., A.P . Willmott and B.J . Go rdon. Hi gh jump, #20 (Men). Report for Scientific Services Project (USA TF). USA Track & Field, Indi anapolis, 97 pp, 1999b. 40. Dapena, J., A.P. Willmott and B.J . Go rdon. Hi gh jump, #28 (Men). Report for Scientific Services Project (USA TF). USA Track & Field, Indianapoli s, I 05 pp, 2004b. 4 1. Dapena, J., A.P. Willmott and B. W. Meye r. High jump, #26 (M en) . Report for Scientific Services Proj ect (USATr). USA Track & Field, Indianapo lis, 11 7 pp, 2003b. 42. Dapena, J., A.P . Wi ll mott and B.W. Meye r. Hi gh jump, #30 (Men). Report f or Scientific Services Project (USATF). USA Track & Field, Indianapo lis, 122 pp, 2006b. 43. Dyatchkov , V.M. The high jump. Tra ck Technique 34 : I 059 -1 074, 1968. 44 . Krahl , H. and K.P. Knebel. Foot stress durin g th e flop takeo ff. Track Technique 75:2384-2386, 1979. 45 . Ozo lin, N. The highjump takeoff mechani sm. Track Technique 52 :1668 -1 67 1, 1973 . ACKNOWLEDGEMENTS This research proj ect was funded by a grant from USA Track & Field. 122 APPENDIX I and th en pushing the c. m . up again , so th at by the time that the right foot lost contact w ith th e ground at TECHNIQUES FOR LOWERING THE t = 9.93 s th e c.m . was movin g upward at 0.4 m/s. CENTER OF MASS IN THE LAST Then, during th e last nonsupport phase (t = 9.93 - STEPS OF THE RUN-UP I 0.00 s), the c. m . made anoth er short projectile path , in whi ch it reached a max imum he ight and th en The f irst steps of a high jump run-up are norma l started dropping again. The c.m. drops w ith more running steps. The c.m . is lowered only near the end, and more speed with every hundredth of a second and this is achieved mainly through the combinati on that passes by before th e takeoff leg is pl anted. That of a lateral lean toward th e center of the curve and th e is why it is recommended th at high jumpers plant fl ex ion of th e knee of th e supporting leg (see Figure th eir takeoff leg very soon, so th at th ey w ill not be A2. 1 in Appendix 2). At th e instant that th e takeoff dropping w ith too much speed at th e start of th e foot is pl anted on th e ground to begin th e takeoff takeoff phase. T he c. m. of this athl ete was dropping phase, th e c. m . should be comparati vely low, and it at -0.3 m/s at the start of th e takeoff phase (vzm = should have a large hori zonta l velocity. -0.3 m/s). At th e in stant th at th e foot lands on th e ground in So in th e technique shown by athlete A, th e c.m . a norm al running step, the c. m. of th e athlete has a is already low two steps before th e start of th e takeoff large hori zonta l velocity and also some downward phase, and it may be lowered still a little bit more in verti cal velocity. But in th e last step of a high jump the last step. When th e takeoff foot fin ally makes run-up it is important th at th e downward vertical contact w ith the ground to start th e takeoff phase, the velocity be minimized, in order not to waste effort c.m . is more or less low but not dropping very fast (if brak in g this downward moti on during th e takeoff there is not a long de lay in the planting of th e takeoff phase. Consequently, the run-up of a high jumper foot; if th ere were a long delay, th e speed of dropping should id eally lead to th e fo ll owing conditions at the could be large). start of the takeoff phase: large hori zontal velocity, Figure A I .2 shows athlete B, with a very reasonably low c.m., and minima l downward vertical different technique. The c. m. was very hi gh two velocity. steps before the takeoff phase (after th e athlete Figures A I . I, A I .2 and A 1.3 show examples of pushed off into th e next-to-last step, th e c. m. reached three techniques used by high jumpers to lower the a he ight of about 59% of the standing height of th e c. m . In th ese three figures, th e hori zontals of th e athlete). Running with such a high c.m. is mu ch graphs show time (the shaded bars at the bottom more comfortable th an running like athlete A, but it indicate ground support phases; th e clear bars is not possible to start a norma l takeoff phase unless indicate nonsupport phases, in whi ch both feet are off the c. m. is lower th an th at. Therefore, athlete B, the ground; t = I 0.00 s was arbitrarily assigned to th e conscious ly or subconsciously, reali zed th at th e c.m . start of th e takeoff phase). The verticals of th e had to be lowered . For this, th e athlete simply did graphs show th e he ight of th e center of mass over th e not stop the drop complete ly during the period of ground, expressed as a percent of th e standing he ight support over th e right foot (t = 9.84-9.95 s). When of th e athl ete. th e ri ght foot left th e ground at t = 9.95 s, the athl ete T he graphs correspond to three fema le high was much lower th an in the previous step, but th e j umpers w ith similar persona l best marks. To c. m . was not goin g up at this tim e: It was still fac i Iit ate the expl anati on of th ese techniques, we w ill dropping. The speed of dropping became still larger assum e th at a ll three athletes took off from th e left in th e fo llowing nonsupport phase. Even though th e foot. The c. m. of athlete A, shown in Figure A 1.1, athlete planted th e takeoff foot very soon, by th en th e was gradu all y lowered in the late part of the run-up. c. m . was dropping at a very large speed (-0.7 m/s), At about t = 9.48 s (two steps before the takeoff and this is not good for th e takeoff phase of th e jump. phase started), the c. m. was a lready rather low . The advantage of th e technique used by jumper T hen, as th e athlete pushed with th e left leg into th e B is that it made it very easy for th e athlete to next-to-las t step, th e c.m. went up to start a short mainta in (and even in crease) a fast run-up speed in projectile path in th e air (t = 9.63 s). The c. m. th e last steps. Athl ete A was not abl e to ma intain reached th e peak of th e path at t = 9.66 s, and th en speed quite as well , because it is diffi cult to run fast started dropping again . By th e time th at th e ri ght foot over a deeply fl exed support leg. T he disadvantage was planted, at t = 9.75 s, th e c.m. was dropping at of th e technique of athlete B was th at th e c.m . was about -0.9 m/s. Then th e support of th e right leg dropping w ith a large speed at th e start of the takeoff reversed th e vertical moti on of th e c.m ., first stopping phase, while th e c.m . of athlete A was moving more the downward moti on at t = 9 .82 s (at a he ight fl at. somewhat lo wer than in th e previous support phase), The id eal would be to lower the hips early, as h (%) 60 peak of path is reached ballistic path starts rappin g peak of path is reached body starts going ~ ~· ='"I ~ > 50 """"I """" lowest point of path right foot in left leg support is planted right foot leaves gro t.dnd do~wardmo'tion is st pped by the support of the right leg Athlete A 40 N w 9.60 9.80 10.00 t (s) h (%) 6~ very hi g h path landin g of d ro ppi n g ri g ht f oot a t s t a rt t akeoff phase "rj ~· c ""! ~ >,_. 5~ I N Athlete B 4.0 -N ~ 9.60 9.80 HL£m t (s) h (%) 6~ very small downward rtical velocity zero) at takeoff brief phase ~ ~· c '"I I'D >.... 50 I w e upward the time ght foot ground low point of body in the middle of the support phase of the right foot Athlete C 40 N Vl 9.60 9.80 10.00 t (s) 126 athl ete A did, but avoiding any loss of hori zonta l speed. For this, athlete A would need special drills and exercises (see Appendix 2); athlete 8 would need to start lowering th e c.m. earlier, two or three steps before takeoff, and this athlete would also need to do the drills and exerc ises; oth erw ise, she would brake the hori zontal speed of th e run-up when she lowered the hips. Figure A 1.3 shows an interesting technique by a third athlete (athlete C) . In th e middle of th e las t support phase of th e approach run (t = 9. 85 s), th e c. m . of athlete C was lower th an th ose of athletes A and 8 , but in th e second ha lf of this support phase th e athl ete li fted th e c. m . consid erably, and by th e end of it (t = 9.95 s) th e c. m. had a rath er large upward vertical velocity (0.5 m/s). The a irborne phase th at fo ll owed was very brief. By th e beginn ing of th e takeoff phase (t= I 0.00 s), th e c. m . was at about th e same he ight as those of th e oth er two j umpers, but it was not dropping at all : The vertical velocity of athl ete Cat th e start of th e takeoff phase was 0.0 m/s. At this point, it is not possible to decide wheth er athl ete C would have been better off ma inta ining a lower path of th e c. m . in th e last step, at th e expense of a moderate negati ve vertical velocity at the start of th e takeoff phase (like athlete A), or with th e present technique, in whi ch she sacri ficed part of the previous lowering of th e c.m . in order to avo id having any negati ve verti cal velocity at th e start of the takeoff phase. In sum, based on th e in fo rmati on presently avail abl e, th e techniques used by athletes A and C to lower the c. m. appear to be equa ll y good, but th e technique used by athlete 8 seems to be worse, because it leads to a very large downward velocity at th e start of th e takeoff phase. 127 APPENDIX 2 ground, to stop th e forward moti on. After stopping momentarily in position e, th e takeoff leg makes a EXERCISES TO HELP THE LOWERING OF slight push forward on the g round, and by reacti on THE CENTER OF MASS I N THE LAST STEPS th e athlete goes backward again to position a. The OF THE RUN-UP exerc ise is repeated over and over until the non takeoff leg gets tired. Many high jumpers have difficulties in th e last Important po ints to cons ider: The whole moti on steps of the approach run: They are unable to run fast should be very slow. T he knee of th e non-takeoff leg while keeping th e ir hips low . This is a typica l should be kept very fl exed at about 90° throughout problem in high jumping technique. It takes some th e who le exercise. Fro m positions a to d th e athlete should feel as if he/she w ere goin g to kneel with th e FigureA2.1 non-takeoff leg, w ith the hip well fo rward . The most di ffic ult point of th e exerc ise is at position d . Between posit ions d and e, the non-takeoff leg should not be extended s ig nificantly. The id ea is to th rust th e hips forward (but without extending the knee of the non-takeoff leg) at th e last in stant, just before losing balance fo rward . Immediate ly afterward , th e foot of th e takeoff leg is planted ahead of th e body to stop th e forward moti on (position e). It would possibly be desirable, from th e point of view of motor learning, to have th e trunk acquire between positions d and e some backward lean, similar to th e one th at occurs in actua l jumping (see Figure A2 . I). However, this is difficult to do w ith th e we ights, and it is not cru c ia l fo r th e exercise. The exercise should effort to correct this problem, but th e improvements first be done with onl y a I 0 Kg bar w ithout weights. that the correcti on produces are definitely worth the Then, when th e ath Jete has learn ed the exerc ise, very effo rt. li ght we ights can be added . As the athlete gets The greatest difficulty is to be able to pass over stronger, the we ights should gradually be in creased. th e deeply-flexed non-takeoff leg in th e next-to-last step, and have th e non-takeoff leg support the whole body with no sign of coll apse or of braking. This is Figure A2.3 demonstrated very well by the athlete in Figure A2 . I. Figure A2.2 shows an exerc ise with weights that can help the high jumper to acquire th e necessary support strength in th e non-takeoff leg. (This exerc ise was dev ised by Arturo Oliver.) The start of the exerc ise is in a static pos ition (a) . Then, th e Figm·e A2.2 A second exerc ise is shown in Figure A2.3. It was also devised by Arturo 0 li ver, and it consists of 30 to 50-meter runs at about 50%m of ax imum speed, with the hips he ld low (as low as in the last steps of a hi gh jump approach run), and carry in g a 20-25 Kg barbell on the shoulders (IMPORTANT: Wrap a a b c d c towel around th e bar). The main id ea is to force th e athlete to run w ith low, fl at, non-boun cy steps; if the athlete makes bouncy steps, th e barbe ll w ill bounce ath Jete pushes off gently with th e back leg (th e on the shoulders, th e ath Jete w i II notice it, and make takeoff leg), to place th e weight of th e body over th e adjustm ents in th e running to prevent th e excessive non-takeoff leg. The body th en s lowly passes over bouncing. Make sure that no one is in your way th e non-takeoff leg (pos itions b-d), and finally, at the when you do this exercise! last instant, the takeoff leg is placed ahead on th e When th e athlete is able to do th ese exercises 128 fai rl y well (say, after one month of practi ce), it w ill be time to start introducing th e new moti ons into actual jumping. It may be good to start w ith low intensity "pop-ups" using a short run-up (four or six steps) at a slow speed. The emphasis should be on lowering the hips in the last two or three steps without losing any speed. Then, the length and speed of the run-up fo r these pop-ups should be in creased graduall y, and after a few days (or weeks -- it depends on how quickly the athlete assimilates the new movements), th e athlete w ill be practi cing with a full hi gh jump run-up and a bar. When j umping us in g the full speed of a normal high jump, it will be more difficult to avoid braking while the athlete passes over th e deepl y-fl exed non-takeoff leg in th e last support of th e run-up. To avoid bra king, the a thlete will have to co ncentrate intensely on trying to pull backward with the non-ta keoff foot w hen it la nds on the g round. 129 APPENDIX 3 from th e back, it causes th e path of the c.m. of th e athl ete to deviate a little bit to th e left during the PRODUCTION OF LATERAL takeoff phase, making ang le p0 be generally SOMERSAULTING ANGULAR MOMENTUM somewhat sma ll er th an ang le p 1 (see Figure 2 and Table 2 in th e main text of the report). This is T he ma in text of this report explain s th at high interesting for us, because it implies that by jumpers need a combinati on of fo rward comparing th e s izes of these two angles we can check somersaulting angul ar momentum (HF) and lateral whether an athlete pushed away from the center of somersaulting angul ar momentum (HL) to be able to th e curve during th e takeoff phase or not. achi eve a norma l rotati on over the bar (see "Angul ar The technique described above is used by most momentum"). In this secti on of th e report we w ill athl etes. However, some jumpers push directly deal in greater depth w ith HL and how it is produced. down, or even toward th e center of th e curve, during The three images in the upper left part of Figure the takeoff phase (in these j umpers, ang le p0 is equa l A3. 1 show a back view sequence of th e takeoff phase to p 1 or larger than p 1, respecti vely). This leads to of a hi gh jumper and the fo rce th at th e athlete makes problems. If the athlete placed th e takeofffoot on the ground during the takeoff phase (actu all y, this directl y ahead of th e c.m ., th e athlete would not get force w ill change from one part of th e takeoff phase any latera l somersaulting rotati on the result could to anoth er, bu t fo r s implicity th e average force has even be a counterc lockw ise latera l somersaulting been drawn here in a ll three im ages). T he three rotatio n. T herefore, some of th ese athletes pl ace th e images in the upper ri ght part of Figure A3. 1 show takeofffoot ahead of th e c.m . but s li ghtly to the left the same sequence, but th e force shown here is th e (see athlete 2, in the middle row ofF igure A3 . I). equal and opposite fo rce th at th e ground makes on This a ll ows th ese athletes to obtain some lateral the athlete in reaction to the fo rce th at the athlete somersaulting angul ar momentum, but not much, makes on the ground. because during the takeoff phase the force exerted by T he athlete shown in th e s ix im ages in th e top th e ground on th e athlete passes only s li ghtly to th e row of Figure A3 .1 had a standard technique: At th e left of th e c. m. start of the takeoff phase, th e athlete was leaning Oth er athletes th at push toward the center of th e toward th e center of the curve (i n this case, to th e curve during th e takeoff phase want more angul ar left). T he takeoff foot was planted pretty much momentum th an th at, and th erefore they pl ace the directly ahead of the c.m ., and th erefore in this back takeoff foot on the ground ahead of the c.m. and very view the foot appears a lm ost directly undern eath th e markedly to th e left (see athlete 3, in the bottom row c. m . (th e sma ll c irc le in side th e body). During th e of Figure A3 .I). In th ese athletes the fo rce exerted takeoff ph ase, the athl ete exerted a fo rce on th e by th e ground on th e athlete passes c learl y to the left groun d, and by reaction the ground exerted a fo rce on of th e c. m., and therefore th ey get a good amount of th e athlete. The force exerted by th e ground on th e lateral somersaulting angul ar mo mentum. However, athl ete made the athlete start rotating c lockw ise in they pay a price for this: Because the foot is placed this back view. By th e end of th e takeoff phase, th e so fa r to th e left, th e c. m . is always to the right of th e athl ete was rotating c lockw ise, and the body had foot in a v iew from th e back, and therefore th e body reached a pretty much vertical position. has a marked lean toward th e ri ght by the end of the A key element fo r the producti on of the takeoff phase. clockwise rotati on of th e athlete is the fo rce exerted Most high j umpers push away from th e center of by th e ground on th e athlete. This force must pass th e curve during th e takeoff phase w ithout needing to clearly to the left of the c.m. If th e force passes too think about it. Therefore, it generally is not close to th e c. m ., th ere w ill be very little rotati on, and necessary to te ll athletes th at they have to do this. if it passes d irectly through the c.m . th ere w ill be no However, a j umper w ith th e problems demonstrated rotation at a ll . So the fo rce must be po in ting up and by athletes 2 and 3 of Fig ure A3. 1 w ill need to be sli ghtly to th e left, and this is what th e three images to ld to push w ith th e takeoff leg away from th e center in th e upper ri ght part of Figure A3. 1 show. To of the curve, and the coach should make up drills to obta in these fo rces, the athlete must push on the help to teach th e athl ete how to do this if the problem groun d down and s li ghtly to th e right, as the three occurs. im ages in the upper left part of Figure A3. 1 show. Most athletes are not aware th at during the takeoff phase th ey push w ith th eir takeoff foot s li ghtly away from the center of the curve, but th ey do. As th e fo rce exerted by the ground on th e athlete usually points upward and to th e left in this v iew 130 Figure A3-1 force made by the athlete force made by the ground on the ground on the athlete athlete 1 athlete 2 athlete 3 13 1 APPENDIX 4 athlete in the Specific Recommendati ons secti on). Jumpers not included in this report should first DRAWING THE PATH OF A HIGH JUMP assume that their id eal p1 ang le is 40°. Then, if th e RUN-UP run-up curve drawn based on that ang le does not fee l comfortable, they should experiment with oth er p1 The curved run-up used in the Fosbury-flop style valu es until th ey find an ang le th at fee ls good. For of hi gh jumping makes th e athlete lean toward th e most athletes the optimum value ofp 1 w ill be center of the curve. This he lps th e jumper to lower somewhere between 35° and 45°. th e c. m. in th e last steps of th e run-up. It also a llows the athlete to rotate during the takeoff phase from an Deciding the radius of curvature of the run-up ini tial position in which th e body is tilted toward th e path (distance r) center of the curve to a fin a l position in whi ch th e The run-up curve needs to have an optimum body is essentially vertical; th erefore, it a ll ows th e radius of curvature. If the radius is too small, th e athlete to generate rotation (latera l somersaulting curve w ill be too tight, and the athlete will have angul ar momentum) without hav ing to lean difficulty running; if th e radius is too large, the curve excessively toward the bar at th e end of the takeoff. will be too straight, and th e athlete w ill not lean A curved run-up has c lear benefits over a straight enough toward th e center of th e curve. The optimum one, and th erefore all high jumpers should use a radius w ill depend on th e speed of the jumper: The curved run-up. However, a curved run-up is a lso faster the run-up, th e longer the radius should be. We more complex. T herefore, it is more diffi cult to can make a rough estimate of th e optimum value of learn , and requires more attention from th e athlete the radius of curvature for an individua l high jumper 2 and the coach. using th e equation r = v2 I 6.8 (men) orr = v I 4 .8 T he curved run-up can also be a source of (women), where r is th e approxim ate value of th e in consistency: There are many different possible radius of curvature ( in meters), and v is the fin al path s that the jumper can fo ll ow between th e start of speed of the run-up (in meters/second). Jumpers who th e run-up and th e takeoff point. If the athlete does know their fin al run-up speed (such as th e jumpers not a lways fo ll ow the same path, th e distance analyzed in this report) can make a rough initi al between th e takeoff point and the bar w ill vary fr om estimate fo r the ir optimum radius of curvature by one j ump to anoth er. T hi s inconsistency w ill make it substituting into th e appropriate equation the ir own diffi cu It fo r th e athlete to reach th e peak of the jump vH 1 valu e from Table 3 (or a di fferent va lu e ofvH1 directly over the bar. proposed fo r that ath Jete in the Specific To make it eas ier for a high jumper to fo ll ow a Recommendations section). For jumpers not given run-up path cons istently, it can be useful to analyzed in this report, it is more difficult to select a mark th e desired path on the ground for practice good initia l estimate for th e radius of curvature, but sess ions (Dapena, 1995a; Dapena et at. , !997a) . But the fo ll owing rough guidelines can be foll owed for before drawing th e run-up path , it will first be olympic-level high jumpers: 6.5-ll m for men ; necessary to choose valu es for the two ma in factors 7.5-1 3 m for women. In a ll cases (even for the th at determine th e path : (a) th e final directi on of th e jumpers analyzed in this report), th e optimum valu e run-up and (b) th e radius of curvature. of th e radius of curvature for each in dividual athlete will ultimate ly have to be fo und through fin e-tuning, Deciding the final direction of the run-up path usin g tria l and error. (angle PI) The fina l di recti on of the run-up can be defin ed Actual drawing of the run-up as the angle between th e bar and th e directi on of Materi als needed: a measuring tape (at least 15 moti on of the c.m . in th e las t a irborne phase of the meters long), a piece of cha lk , and white adhes ive run-up immediately before the takeoff foot is planted tape. on th e ground. This ang le is call ed p1 in thi s report, Te ll the athlete to make a few jumps at a and its valu es are g iven in Table 2. (The ang le of the chall eng in g height, using his/her present run-up. fin al run-up directi on should not be confused with the Us in g adhesiv e tape, make a cross on the ground to angle between th e bar and the lin e jo ining the last mark the position of th e takeoff point (point A in two foo tprints. T hi s latter angle is ca ll ed t1, and it is Figure A4. !). genera ll y l 0-1 5 degrees small er th an th e angle of th e Put one end of th e measuring tape at point A, fi nal run-up directi on, p1.) Jumpers analyzed in this and measure a distance j para ll el to the bar. The report should use th e value of p 1 given in Table 2 (or valu e of j depends on th e fin al di recti on desired fo r in some cases a d ifferent value proposed fo r the th e run-up (p 1): 132 P I To find the center of the curve (po int D), put one end of the tape at po int A , and make the tape pass 25 ° 1.75 m over po int C. The center of the curve will be ali gned 30 ° 2.70 m w ith po ints A and C, and it will be at a distance r 35 ° 3 .65 m from po int A . (Genera l guide lines fo r the optimum 40 ° 4.65 m valu e of r were g iven previously in thi s Appendix.) 45 ° 5.75 m Mark po int D w ith cha lk . With center in point D and rad iu s r, draw an arc 50° 7 .00 m fro m po int A to po int E. (Po int E has to be at the same di stance from the plane of the bar and the (General guid elines for th e optimum va lue ofp 1 standard s as po int D.) The arc from A to E is th e were g iven previously in thi s Appendix. If you want run-up curve. Mark it with strips of adhesive tape. to try a P1 ang le intermediate between the ones g iven Put a transverse piece of tape at point E to mark th e in this table, you should use a valu e of j interm ediate start of the curve. between the ones g iven in the table.) Starting at po int E, draw a straight lin e Mark th e new po int (B) w ith cha lk. Put one end perpendicular to th e bar (E-F), and mark it w ith strips of the tape at po int B, and measure a distance k = I 0 of adhesive tape. Set the bar at a chall eng in g he ight, meters in th e direction perpendicular to the bar. and have the jumper take a few jumps. By trial and Mark the new po int (C) with cha lk. The line j o ining error, find the optimum position fo r the start of th e point A and po int C indicates th e direction of th e run-up (po int G), and mark it w ith a transverse piece center of the curve relati ve to the takeoff po int. of adhes ive tape. Figure A4.1 The run-up is now ready . The set-up just described can be left in place for tra ining, and it w ill contribute to dri II into the athlete the pattern th at the run-up should fo ll ow . Things to remember: Qf------0 • Po int E indicates the pl ace where the curve A should start, but the athlete does not necessarily have -7 ._ to step on this po int. • Some jumpers may find it d ifficult to fo ll ow E exactly th e path marked by the adhes ive tape in th e 0 ' _ , trans ition fro m the straight to the curved part of th e II I run-up. This should not be a problem : It is acceptabl e to deviate somewhat from the path marked T by the adhesive tape in the area around point E, as ·c long as the athlete deviates consistently in the same way in every jump. • It is important to fo ll ow the tape very precisely in the middle and fin al parts ofthe curve. CC 11LCr or the c u n C The set-up described above can be left in pl ace for tra ining. However, one or two marks w ill have to suffice fo r competitions. Distances a, b, c and d should be measured in the training set-up (see Figure A4.2). In the competition, distance a w ill be used to reconstruct the position of po int H. Distances b and c will then be used to reconstruct the triang le fo rmed by the standard and po ints G and H. This will a ll ow th e athlete to locate the start of the run-up (po int G). sturt or the run-up - '*" G Distance d can be used to find the positi on of po int E if the rules of the competition a ll ow for a mark to be placed at th at po int. OF 133 Figure A4.2 b G