A Three-Dimensional Movement Analysis of the Spike in Fistball
Article A Three-Dimensional Movement Analysis of the Spike in Fistball
Andreas Bund 1,*, Saeed Ghorbani 2 and Franziska Rathjens 3 1 Institute of Applied Educational Sciences, University of Luxembourg, Esch-s.-Alzette L-4365, Luxembourg, Luxembourg 2 Department of Physical Education and Sport Science, Aliabad Katoul Branch, Islamic Azad University, Aliabad Katoul, Iran; [email protected] 3 Institute of Sport Science, University of Oldenburg, Oldenburg D-26129, Germany; [email protected] * Correspondence: [email protected]; Tel.: +352-46-66-44-9731
Academic Editor: Eling Douwe de Bruin Received: 16 July 2016; Accepted: 30 November 2016; Published: 2 December 2016
Abstract: Due to its relevancy to point scoring, the spike is considered as one of the most important skills in fistball. Biomechanical analyses of this sport are very rare. In the present study, we performed a three-dimensional kinematic analysis of the fistball spike, which helps to specify performance parameters on a descriptive level. Recorded by four synchronized cameras (120 Hz) and linked to the motion capture software Simi Motion® 5.0, three female fistball players of the second German league (24–26 years, 1.63–1.69 m) performed several spikes under standardized conditions. Results show that the segment velocities of the arm reached their maximum successively from proximal to distal, following the principle of temporal coordination of single impulses. The wrist shows maximum speed when the fist hits the ball. The elbow joint angle performs a rapid transition from a strong flexion to a (almost) full extension; however, the extension is completed after the moment of ball impact. In contrast, the shoulder joint angle increases almost linearly until the fistball contact and decreases afterward. The findings can be used to optimize the training of the spike.
Keywords: movement analysis; biomechanics; fistball
1. Introduction Fistball is a traditional ball game in which two teams with five players play against each other on a field separated by a net. Similar to volleyball, the idea of the game is to hit the ball with a part of the arm or the fist in such a way across the net that it is difficult or impossible for the other team to return it. Within the team, the ball can be played directly or indirectly by three different players, thus, the standard sequence consists of three elements: defense (trapping the ball), passing and offense (attacking shot/spike). Fistball is played mainly in Europe and South America, but is becoming more and more popular in Africa, Asia and North America too. At the World Games as well as at Continental Championships, national teams play against each other. The organization of these events is done by the International Fistball Association (IFA) [1], which was co-founded in 1960 by Germany, Brazil, Switzerland, Austria and Italy. In recent years, an increasing professionalization on the athletic and organizational levels can be observed. The field of sport science, however, has paid little attention to fistball so far and very few scientific papers on the topic are available. Besides older publications on methodological aspects (e.g., [2,3]), studies often deal with the risk of injury in fistball [4,5]. Runer et al. [5], for example, found over the course of 12 months an overall injury rate of 12.2 injuries/1000 h of exposure. The most common types of injury were abrasions and contusions. An exception is provided by Leser [6], who has developed and evaluated a computer-based observation system for fistball.
Sports 2016, 4, 55; doi:10.3390/sports4040055 www.mdpi.com/journal/sports Sports 2016, 4, 55 2 of 11
Of particular interest to the present work is a study of Soeser and Schwameder [7]. Focusing on the hitting side of the body, they performed a three-dimensional kinematic analysis of the fistball serve. The results can be summarized as follows: (1) The execution of the serve shows in many characteristics (e.g., ball drop, turning back the hitting side shoulder, and body extension in the moment of ball impact) a high degree of standardization, i.e., the execution is very similar across different players and performance levels; (2) A kinematic chain can be seen that typically occurs in throwing movements, i.e., hip, shoulder, elbow and wrist/fist successively reach their maximum speed and become slowed down in order to transfer and maximize the impulses from proximal to distal body segments. As expected, players from the national team reached significantly higher body segments and ball velocities then players from federal or regional leagues. Similar to the serve, the spike is a typical hitting movement whose main phase is performed above the head. It is therefore expected that the results of Soeser and Schwameder [7]—e.g., in terms of the kinematic chain and the temporal coordination of impulses—are also valid for the spike. However, it should be noted that the spike starts with a one-legged kick-off jump in the air and, thus, is performed without ground contact. Consequently, the biomechanical conditions of serve and spike differ significantly. In addition, the spike usually coordinates with the trajectory of the passed ball and therefore has to be available and executed under highly variable conditions. Generally speaking, a good technical execution of the spike requires that the player has the right distance to the ball and that he or she is able to accelerate strongly and temporally coordinate the segments of the hitting side of his or her body. At the moment of ball impact, speed and trajectory of the ball are determined by the velocity, rotation and inclination of the fist, the point of ball contact, and the movement direction of the hitting arm [7]. The lack of biomechanical and especially kinematic analyses of motor skills used in fistball was the reason to conduct this study. The following aims were determined:
(1) The description of the spike in fistball based on three-dimensional recorded kinematic parameters with high frequency. (2) The identification and weighting of performance-determining factors by a comparative analysis of kinematic parameters of different players.
Unlike Soeser and Schwameder [7], both sides of the body were included in the analysis.
2. Method
2.1. Participants and Task Three female fistball players aged from 24 to 26 years old who play in clubs in Germany’s 2nd league on the attack position took part in this study. The players were right-handed, 1.63 to 1.69 m tall and weighed at the time of the study from 55 to 72 kg. The task was to perform from a short run-out a spike against a fist ball attached to a rope from the ceiling, just above the fistball net that was stretched to a height of 1.90 following the competition rules. The ball height varied slightly depending on the body size of the player and was previously determined in several trials. Table1 shows the anthropometric measures of the players as well as the individual ball heights. The procedure of the study was designed according to the guidelines of the Helsinki declaration. All players provided informed consent prior to the study.
Table 1. Anthropemetric measures of the participants and individual ball heights.
Participant Body Weight (kg) Body Height (m) Ball Height (m) Player 1 55 1.62 1.94 Player 2 63 1.64 1.96 Player 3 72 1.69 1.96 Sports 2016, 4, 55 3 of 11 Sports 2016, 4, 55 3 of 11
2.2. Data Recording The spikespike (including (including the run-out)the run-out) was recorded was recor by fourded synchronizedby four synchronized and mutually and perpendicular mutually positionedperpendicular cameras positioned on 1.65 cameras m high on tripods 1.65 m (Basler high tr Scout)ipods (Basler with a frameScout) ratewith of a 120frame Hz. rate Based of 120 on Hz. the Baseddimensions on the of dimensions a volleyball of court, a volleyball four cameras court, fo withur cameras an oblique with view an oblique filmed theview player, filmed two the cameras player, twofrom cameras the front from and the two front from and the two back. from the The back recorded. The recorded space was space calibrated was calibrated using using a cube a cube with with2 × 2 2× × 2.52 × m 2.5. Figure m. Figure1 shows 1 shows the exact the exact position position of the of cameras the cameras and the and distances the distances among among each other. each other.Recordings Recordings were madewere inmade the gymnasiumin the gymnasium of the Universityof the University of Oldenburg of Oldenburg (Germany). (Germany). Each player Each playercompleted completed 4 to 6 trials 4 to hitting6 trials thehitting ball inthe a dynamicball in a dynamic and fluent and movement. fluent movement. For the subsequent For the subsequent kinematic kinematicanalysis, a analysis, total of 7 a body total points of 7 body of the points players of the (foot, players ankle, (foot, knee, ankle, hip, elbow,knee, hip, shoulder, elbow, and shoulder, wrist) were and wrist)bilaterally were covered bilaterally with covered light-reflective with light-reflec markers.tive Five markers. of these markersFive of these were markers affixed directly were affixed to the directlyskin, only to the footskin, and only the the hip foot markers and the were hip marker placeds onwere the placed shoe and on the a tight-fitting shoe and a shirt,tight-fitting respectively. shirt, Therespectively. exact localization The exact of localization the markers of is the described markers in is Tabledescribed2. in Table 2.
Figure 1. Measurement setup.
Table 2. Body points included in the kinematic analysis. Body Point Body Side Localization Body Point Body Side Localization Foot bilaterally Basis Metatarsales V Ankle Footbilaterally bilaterally Basis Metatarsales Malleolus V lateralis Ankle bilaterally Malleolus lateralis Knee Kneebilaterally bilaterally EpicondylusEpicondylus lateralis lateralis femoris femoris Hip Hipbilaterally bilaterally Trochanter Trochanter major major Elbow Elbow bilaterally bilaterally Epicondylus Epicondylus lateralis lateralis humeri humeri Shoulder Shoulderbilaterally bilaterally Acromio-clavicular Acromio-clavicular join join Wrist bilaterally Os capitatum Wrist bilaterally Os capitatum
2.3. Data Processing The trajectories of the above-mentioned body points were automatically digitized using the motion capture software Simi Motion 5.0 (Simi Re Realityality Motion Systems, Unterschleißheim, Germany). The beginning of the third last step (ground contac contact)t) was defined defined as starting point of the movement; the seventh frame after the ball contact was considered as thethe endend point.point. In In order to compare the recordings of the various trials and players, they were standardized in the post-processing on each 100 frames exactly. Specifically,Specifically, thethe followingfollowing kinematickinematic parametersparameters werewere calculated: calculated: • Path velocities of the hip, shoulder, elbow and wrist (unilateral, for the hitting side of the body)
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Sports 2016, 4, 55 4 of 11 • Path velocities of the hip, shoulder, elbow and wrist (unilateral, for the hitting side of the body) • Joint angles of elbow, shoulder (unilateral, for the hitting side of the body), knee and hip • Joint angles of elbow, shoulder (unilateral, for the hitting side of the body), knee and hip (bilateral) (bilateral) • • HeightHeight ofof thethe hiphip andand shouldershoulder (bilateral)(bilateral) •• CenterCenter ofof gravitygravity (CoG)(CoG) TheThe temporaltemporal coordinationcoordination ofof pathpath velocitiesvelocities andand accelerationsaccelerations ofof thethe hip,hip, elbow,elbow, shouldershoulder andand wristwrist ofof thethe hittinghitting sideside ofof thethe bodybody isis pivotalpivotal toto thethe impulseimpulse transfertransfer fromfrom thethe wristwrist toto thethe ballball andand largelylargely determinedetermine itsits speed.speed. TheThe jointjoint anglesangles werewere calculatedcalculated inin thethe clockwiseclockwise directiondirection throughthrough thethe SimiSimi MotionMotion softwaresoftware byby applyingapplying EquationEquation (1)(1) onon eacheach singlesingle frame.frame. TheThe basisbasis waswas thethe xx-coordinates-coordinates ofof thethe bodybody points,points, thatthat is,is, thethe anglesangles werewere analyzedanalyzed inin thethe sagittalsagittal plane.plane. TheThe elbowelbow jointjoint angleangle waswas determineddetermined byby thethe elbowelbow asas apexapex andand thethe wristwrist andand shouldershoulder asas endend pointspoints ofof thethe correspondingcorresponding triangle-legs.triangle-legs. TheThe shouldershoulder jointjoint angleangle waswas defineddefined byby thethe shouldershoulder asas apexapex andand thethe elbowelbow andand hiphip asas endend points.points. TheThe hiphip angleangle waswas measuredmeasured withwith thethe hiphip asas apexapex andand thethe shouldershoulder andand kneeknee asas endend points.points. Finally,Finally, thethe kneeknee waswas usedused asas apexapexand andthe the ankle ankle and and hip hip as as end end points points to to determine determinethe the kneeknee jointjoint angle.angle. FigureFigure2 2 demonstrates demonstrates thethe jointjoint anglesangles and their corresponding vectors. vectors.
FigureFigure 2.2. JointJoint anglesangles calculatedcalculated inin thethe study.study.
jointjoint angle angle = = acos(scalar acos(scalar product(v1, product(v1, v2)/(norm(v1) v2)/(norm(v1)× × norm(v2))) (1) (1) TheThe hiphip andand shouldershoulder heightsheights werewere calculatedcalculated fromfrom thethe zz-coordinates,-coordinates, i.e.,i.e., inin thethe frontalfrontal plane,plane, andand indicateindicate thethe playersplayers postureposture duringduring run-up,run-up, take-offtake-off andand hittinghitting phases.phases. TheThe assessmentassessment ofof thethe CoGCoG waswas mademade byby thethe SimiSimi MotionMotion softwaresoftware accordingaccording toto thethe HanavanHanavan humanhuman bodybody model.model. TheThe CoGCoG parameterparameter was was used used to to determine determine the the run-up run-up velocity velocity (horizontal (horizontal CoG-velocity CoG-velocity before before the take-off)the take-off) and theand jump the jump height height (maximum (maximum CoG-height CoG-height in flight in phase—CoG-heightflight phase—CoG-height at last groundat last ground contact). contact). Finally, theFinally, initial the path initial velocity path ofvelocity the ball of wasthe ball calculated was calculated as a key parameteras a key parameter of the spike of the movement. spike movement.
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3. Results 3. Results
3.1.3.1. Kinematic Kinematic Description Description of of the the Spike Spike FigureFigure 33 showsshows asas anan exampleexample thethe kinegramkinegram ofof playerplayer 1.1. TheThe sequencesequence showsshows howhow thethe playerplayer performs the run-up,run-up, thethe take-off,take-off, the the backwards backwards torsion torsion of of shoulder shoulder and and arm arm on on the the hitting hitting side side of theof thebody, body, the subsequentthe subsequent acceleration acceleration of these of these body body segments segments in the in direction the direction of the ball,of the the ball, ball the impact ball impactwith simultaneous with simultaneous body extension body extension and the and preparation the preparation of the landing.of the landing. The run-up The run-up velocities velocities differ differonly minimally only minimally and range and forrange all for players all players from 3.31 from m/s 3.31 to m/s 3.49 to m/s. 3.49 The m/s. maximum The maximum jump heightjump height varies variesbetween between 0.32 m 0.32 and m 0.43 and m. 0.43 The m. time The intervals time interv betweenals between take-off, take-off, ball impact ball impact and landing and landing are again are againrelatively relatively stable; stable; they rangethey range from from 0.26 s0.26 to 0.16s to 0.16 s and s and 0.35 0.35 s to s 0.20 to 0.20 s, respectively. s, respectively. Thus, Thus, similar similar to tothe the fistball fistball serve serve [7 [7],], we we also also found found for for the the spike spike only only smallsmall inter-individualinter-individual variance regarding the kinematickinematic of movementmovement phases.phases. However,However, it it should should be be noted, noted, that that the the players players who who participated participated in this in thisstudy study had had a very a very similar similar level level of performance. of performance.
FigureFigure 3. 3. KinegramKinegram of of the the fistball fistball spike spike (player (player 1), 1), with with timeline timeline (s). (s). higher higher resolution resolution picture. picture. Comma Comma shouldshould be be changed changed into into dot. dot.
3.2.3.2. Path Path Velocities Velocities Figures 4–6 show the path velocities of the shoulder, elbow and wrist joint on the hitting side of Figures4–6 show the path velocities of the shoulder, elbow and wrist joint on the hitting side of the body. Aside from inter-individual similarities, the data indicate various individual characteristics the body. Aside from inter-individual similarities, the data indicate various individual characteristics of the players’ movement. During run-up, the path velocity of the right shoulder rises and falls of the players’ movement. During run-up, the path velocity of the right shoulder rises and falls according to the individual running cadence of the player. The cycle varies considerably, and the according to the individual running cadence of the player. The cycle varies considerably, and the differences between the velocity minima and maxima are significant. Player 1 shows clear differences differences between the velocity minima and maxima are significant. Player 1 shows clear differences concerning these parameters. Common to all players is that they rapidly accelerate the shoulder just concerning these parameters. Common to all players is that they rapidly accelerate the shoulder just before the ball impact in order to reach maximum speed. After the impact, the shoulder is strongly before the ball impact in order to reach maximum speed. After the impact, the shoulder is strongly slowed down in a short time period. slowed down in a short time period. The path velocities of the elbow and the wrist joint can be described analogous in essential points. The path velocities of the elbow and the wrist joint can be described analogous in essential During the run-up phase, the path velocity of the elbow again shows a cyclical pattern. Overall, the points. During the run-up phase, the path velocity of the elbow again shows a cyclical pattern. cycles vary inter-individually less than in the shoulder; however, the minimum–maximum Overall, the cycles vary inter-individually less than in the shoulder; however, the minimum–maximum differences are significantly smaller for player 3 than for players 1 and 2. The very fast acceleration differences are significantly smaller for player 3 than for players 1 and 2. The very fast acceleration of the elbow joint as well as the deceleration after the ball contact are also very similar between the of the elbow joint as well as the deceleration after the ball contact are also very similar between the players. Just before the ball impact, the players reach an almost equal velocity maximum. In contrast players. Just before the ball impact, the players reach an almost equal velocity maximum. In contrast to this, the speed of the wrist reaches its maximum exactly when the fist hits the ball; before and after to this, the speed of the wrist reaches its maximum exactly when the fist hits the ball; before and after that moment a strong positive or negative acceleration can be observed. While running-up towards that moment a strong positive or negative acceleration can be observed. While running-up towards the the net, the path velocity of the wrist again oscillates according to the players’ individual rhythm. As net, the path velocity of the wrist again oscillates according to the players’ individual rhythm. As with with the elbow joint, these cycles occur “flatter” for player 3 than for players 1 and 2. Furthermore, the elbow joint, these cycles occur “flatter” for player 3 than for players 1 and 2. Furthermore, player 3 player 3 does not achieve such a high maximum speed as the other two players. does not achieve such a high maximum speed as the other two players.
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Figure 4. Inter-individual comparison of the path velocities of the right shoulder joint (100 frames; FigureFigure 4. Inter-individual 4. Inter-individual comparison comparison ofof thethe pathpath velocities of of th thee right right shoulder shoulder joint joint (100 (100 frames; frames; dotted line = ball impact). dotteddottedFigure line line4. = Inter-individual ball = ball impact). impact). comparison of the path velocities of the right shoulder joint (100 frames; dotted line = ball impact).
Figure 5. Inter-individual comparison of the path velocities of the right elbow joint (100 frames; dotted Figure 5. Inter-individual comparison of the path velocities of the right elbow joint (100 frames; dotted Figureline 5.= ballInter-individual impact). comparison of the path velocities of the right elbow joint (100 frames; dotted lineFigure = ball 5. Inter-individual impact). comparison of the path velocities of the right elbow joint (100 frames; dotted lineline = ball = ball impact). impact).
Figure 6. Inter-individual comparison of the path velocities of the right wrist joint (100 frames; dotted Figure 6. Inter-individual comparison of the path velocities of the right wrist joint (100 frames; dotted line = ball impact). FigurelineFigure 6.= ballInter-individual 6. Inter-individual impact). comparison comparison of of the the path path velocitiesvelocities of of the the right right wrist wrist joint joint (100 (100 frames; frames; dotted dotted line = ball impact). line = ball impact).
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Sports 2016, 4, 55 7 of 11 The velocity maxima of the captured body points and the resulting ball speed are shown in The velocity maxima of the captured body points and the resulting ball speed are shown in Table Table3. For all players, the velocity maxima continuously increase from proximal (hip) to distal (wrist) 3. For all players, the velocity maxima continuously increase from proximal (hip) to distal (wrist) body points. This data suggests that in this case a kinematic chain is operating, in which the speed body points. This data suggests that in this case a kinematic chain is operating, in which the speed maxima of the involved body segments are placed in sequence so that the (distal) end link of the chain maxima of the involved body segments are placed in sequence so that the (distal) end link of the experiences maximum acceleration. chain experiences maximum acceleration. Table 3. Maxima of path velocities and resulting speed of the ball (m/s). Table 3. Maxima of path velocities and resulting speed of the ball (m/s).
Title Hip Title HipShoulder Shoulder Elbow Elbow Wrist Wrist Ball Ball Player 1 4.41Player 1 4.415.23 5.238.98 8.98 11.7911.79 12.45 12.45 Player 2 4.22Player 2 4.224.65 4.658.28 8.28 11.4311.43 12.19 12.19 Player 3 3.82 4.95 8.37 8.65 10.89 Player 3 3.82 4.95 8.37 8.65 10.89
OfOf course, course, the the existence existence of of a a kinematic kinematic chain chain become becomess clearer clearer if if the the path path velocities velocities of of the the relevant relevant bodybody points areare presented presented together. together. This This is doneis done in Figure in Figure7 using 7 theusing example the example of player of 1, player who achieved 1, who achievedthe highest the ball highest speed ball with speed 12.45 with m/s. 12.45 m/s.
FigureFigure 7. 7. PathPath velocities velocities of of the the body body points points on on the the hi hittingtting side side of of the the body body of of player player 1 1 (100 (100 frames; frames; dotteddotted line line = = ball ball impact). impact).
3.3.3.3. Joint Joint Angles Angles ComparedCompared to to the the velocity velocity data, data, the the course course of of shou shoulderlder and and elbow elbow angles angles (Figures (Figures 8 andand9 9)) clearlyclearly revealsreveals greater inter-individual differences.differences. This This concerns concerns in in particular particular the the players’ players’ run-up run-up and and take-off take- offphases. phases. Player Player 2, for 2, example,for example, keeps keeps her playing her playing (“hitting”) (“hitting”) arm during arm during the run-up the run-up close to close the body to the so bodythat the so shoulderthat the shoulder angle slightly angle opensslightly and opens closes an accordingd closes according to the running to the cadence.running cadence. During and During after andtake-off, after atake-off, very fast a very extension fast extension of the shoulder of the shoulder joint to anjoint angle to an of angle ca. 130 of ◦ca.takes 130° place, takes whichplace, which just as justquickly as quickly evolves evolves into astrong into a flexionstrong flexion at the moment at the moment of ball contact. of ball contact. For player For 1 player and especially 1 and especially player 3, playerthe angle 3, the course angle is basicallycourse is similar,basically however, similar, the however, extension the and extension flexion and of the flexion shoulder of the angle shoulder occurs anglein a smaller occurs rangein a smaller and less range abruptly. and less Concerning abruptly. player Concerning 3, Figure player7 illustrates 3, Figure that 7 theillustrates playing that arm the is playingstretched arm far is out stretched when she far is out moving when towardshe is moving the net (shouldertoward the angle net (shoulder about 40◦ angle). That about might 40°). be partly That mightresponsible be partly for theresponsible low jump for height the low of 0.34 jump cm, height because of 0.34 in this cm, position because the in armthis canposition hardly the be arm used can as hardlyan additional be used swinging as an additional element. Inswinging contrast toelement. the other In players,contrastthere to the is noother significant players, flexion there ofis theno significantshoulder angle flexion when of the she hitsshoulder the ball. angle Instead, when the she hip hits angle the decreasesball. Instead, considerably the hip angle at this decreases moment, considerablythus, player 3at is this using moment, the entire thus, upper player body 3 tois performusing the the entire hitting upper phase body of the to spike.perform the hitting phaseIn of respect the spike. to the elbow angle, even greater differences occur between the players, only during andIn after respect the ball to the impact elbow do angle, the profiles even greater tend to differences match each occur other. between Previously, the players, the arm only posture during was andvery after specific the toball the impact individual do the and profiles notably tend had to no match consistent each relationother. Previously, to the run-up the and arm take-off posture action. was very specific to the individual and notably had no consistent relation to the run-up and take-off action. Player 1 successively reduces the elbow angle during the run-up phase; only the take-off leads to a
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Sports 2016, 4, 55 8 of 11 SportsPlayer 2016 1, successively4, 55 reduces the elbow angle during the run-up phase; only the take-off leads8 of 11 to temporarya temporary extension. extension. Concerning Concerning the the countermovem countermovementent of of the the playing playing arm, arm, the the elbow elbow angle first first temporary extension. Concerning the countermovement of the playing arm, the elbow angle first oscillates slightly followed by an explosive stretching until ball contact; however, the ball contact is oscillates slightly followed by an explosive stretching until ball contact; however, the ball contact is made shortly before the maximum extension of the arm is reached. In contrast to this, player 2 starts made shortly before the maximum extension of the arm is reached. In contrast to this, player 2 starts with an extended elbow angle (<120(<120°),◦), which which is is then then gradually gradually flexed flexed on on after after the the take-off take-off and and finally finally with an extended elbow angle (<120°), which is then gradually flexed on after the take-off and finally opened again to hit the ball. Striking (and (and certainly certainly unusual) unusual) in in this this case is the short-term (slight) opened again to hit the ball. Striking (and certainly unusual) in this case is the short-term (slight) “intermediate”“intermediate” extensionextension during the jumping phase (about frame 75). Finally, player 3 shows a third “intermediate” extension during the jumping phase (about frame 75). Finally, player 3 shows a third variant: During run-up and take-off the elbow is bent more and more. The extension of the arm takes variant: During run-up and take-off the elbow is bent more and more. The extension of the arm takes place only before and after the ball impact andand isis aa bitbit lessless pronouncedpronounced thanthan forfor thethe playersplayers 11 andand 2.2. place only before and after the ball impact and is a bit less pronounced than for the players 1 and 2.
Figure 8. Inter-individual comparison of the joint angles of the right shoulder joint (100 frames; dotted Figure 8. 8. Inter-individualInter-individual comparison comparison of of the the joint joint angles angles of of the the right right shoulder shoulder joint joint (100 (100 frames; frames; dotted dotted line = ball impact). lineline = = ball ball impact). impact).
Figure 9. Inter-individual comparison of the joint angles of the right elbow joint (100 frames; dotted Figure 9. Inter-individual comparison of the joint angles of the right elbow joint (100 frames; dotted lineFigure = ball 9. Inter-individual impact). comparison of the joint angles of the right elbow joint (100 frames; dotted lineline = = ball ball impact). impact). Are joint angles and path velocities systematically linked with each other, e.g., at the time of ball Are joint angles and path velocities systematically linked with each other, e.g., at the time of ball contact?Are Higher joint angles degrees and of path extens velocitiesion and, systematically thus, greater linkedbody angles with each should other, result e.g., in at higher the time path of contact? Higher degrees of extension and, thus, greater body angles should result in higher path velocitiesball contact? of the Higher distal degreespoints of of the extension body. Of and, course, thus, the greater question body cannot angles be shouldanswered result reliably in higher with velocities of the distal points of the body. Of course, the question cannot be answered reliably with paththe very velocities small sample of the distal used pointsin this ofstudy; the body.however, Of course, the available the question data supports cannot bethis answered assumption: reliably For the very small sample used in this study; however, the available data supports this assumption: For withexample, the very player small 1 hits sample the ball used with in this an study;elbow however,angle of 129° the availableachieving data a maximum supports wrist this assumption: velocity of example, player 1 hits the ball with an elbow angle of 129° achieving a maximum wrist velocity of 11.79For example, m/s, while player player 1 hits 3 stretches the ball the with elbow an elbow only angleto 115°, of which 129◦ achieving leads to a awrist maximum velocity wrist of only velocity 8.37 11.79 m/s, while player 3 stretches the elbow only to 115°, which leads to a wrist velocity of only 8.37 m/s.of 11.79 m/s, while player 3 stretches the elbow only to 115◦, which leads to a wrist velocity of m/s. only 8.37 m/s.
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Sports 2016, 4, 55 9 of 11 3.4. Height of Hip, Shoulder and CoG 3.4. Height of Hip, Shoulder and CoG Overall, the bilateral measurement of the height profiles of hip and shoulder shows only small Overall, the bilateral measurement of the height profiles of hip and shoulder shows only small inter-individual variance: During run-up, hip and shoulder move on both sides at the same level. inter-individual variance: During run-up, hip and shoulder move on both sides at the same level. During the take-off of the player, both pivot points are raised; however, on the (right) hitting side of During the take-off of the player, both pivot points are raised; however, on the (right) hitting side of thethe body body they they are are raised raised higher higher than than on on thethe leftleft side due due to to the the increasing increasing extension extension of of this this part part of ofthe the body.body. At At the the moment moment of of ball ball contact, contact, thethe rightright hip an andd shoulder shoulder reach reach the the highest highest point point in inall allplayers. players. However,However, the the difference difference between between the the heightheight onon the right side side and and the the left left side side of of the the body body vary vary from from playerplayer to to player. player. In In relation relation to to the the hip, hip, forfor playerplayer 1 this was ca. ca. 9 9 cm, cm, for for player player 2, 2,ca. ca. 16 16 cm cm and and for for playerplayer 3, 3, only only ca. ca. 5 5 cm. cm. In In other other words,words, playerplayer 2 is clearly more more tilted tilted during during the the hitting hitting phase phase than than thethe other other two two players. players. The The height height differencedifference between the the right right and and left left shoulder shoulder is isabout about 16 16to 18 to 18cm. cm. FigureFigure 10 10 illustrates illustrates as as an an example example the the heightheight profileprofile ofof the left and and right right shoulder shoulder of of player player 1. 1.
FigureFigure 10. Height 10. Height profies profies of right of right and leftand shoulder left shoulder of player of player 1 (100 1 (100 frames; frames; dotted dotted line line =ball = ball impact). impact).
TheThe measurement measurement of of the the CoG CoG providesprovides informationinformation on on the the horizontal horizontal velocity velocity while while running-up running-up andand on on the the jumping jumping height height of of the the players. players. TheThe run-up ve velocitieslocities just just before before the the take-off take-off are are at at3.43 3.43 m/s, m/s, 3.493.49 m/s m/s and and 3.31 3.31 m/s m/s and and thus thus very very little. little. Compared Compared with with this, this, the the differences differences in in the the jump jump heights heights are greater:are greater: 0.43 m, 0.43 0.32 m, m 0.32 and m 0.34 and m. 0.34 Due m. to theDue sample to the size,sample it issize, not possibleit is not possible to determine to determine a correlation a betweencorrelation run-up between velocity run-up and velocity jump height. and jump In addition,height. In theaddition, CoG heightthe CoG profile height is profile very similar is very for allsimilar players. for all players.
4. Discussion4. Discussion BasedBased on on the the fact fact that that only only very very little little sport sport science scienc researche research on on fistball fistball is is available available to to date, date, the the aim ofaim the presentof the present study wasstudy to was carry to out, carry on out, a descriptive on a descriptive level, a level, three-dimensional a three-dimensional kinematic kinematic analysis ofanalysis the spike of in the fistball. spike in Using fistball. camera-based Using camera-based motion capture motion softwarecapture software (Simi Motion (Simi 5.0),Motion kinematic 5.0), parameterskinematic suchparameters as velocity, such as angle velocity, and trajectoryangle and oftraj differentectory of bodydifferent points body were points bilaterally were bilaterally recorded, digitizedrecorded, and digitized finally evaluated. and finally Based evaluated. on the Based comparison on the comparison of several players, of several we identifiedplayers, we and identified weighted parametersand weighted that significantlyparameters affectthat significantly the spike performance. affect the spike The results performance. can be summarized The results ascan follows: be summarizedThe kinematic as follows: pattern of movement phases shows only a small range of inter-individual variance. Run-upThe velocity kinematic and temporalpattern of sequence movement of run-up,phases take-offshows only and landinga small arerange relatively of inter-individual similar across thevariance. players. Run-up velocity and temporal sequence of run-up, take-off and landing are relatively similar across the players. 1. The analysis of the path velocities of several body points demonstrates individual styles in the 1. The analysis of the path velocities of several body points demonstrates individual styles in the execution of the fistball spike; they concern, in particular, timing and range of velocity changes. execution of the fistball spike; they concern, in particular, timing and range of velocity changes. 2. In terms of a kinematic chain, the hip, shoulder, elbow and wrist joint reach their maximum 2. In terms of a kinematic chain, the hip, shoulder, elbow and wrist joint reach their maximum speedspeed successively successively and and temporarilytemporarily coordinated. Th Thee deceleration deceleration of of each each more more proximal proximal joint joint causes the impulse to be (partly) transferred to the next joint or limb, so that the wrist, as the end of the chain, receives the highest speed. Sports 2016, 4, 55 10 of 11
3. The courses of the joint angles, especially of that of the hitting arm, differ considerably from player to player. As expected, extended elbow angles tend to be associated with greater speed of distal body points. 4. The height profile of hip, shoulder and CoG is basically similar for all players. Due to the extension during the hitting phase, the points on the hitting side of the body are higher than the corresponding points on the opposite side. The hip axis is clearly more inclined than the shoulder axis.
Overall, our results are in line with those of Soeser and Schwameder [7] on the fistball serve, taking into account that the latter of course found higher values for joint and ball speed due to the gender (male) and level (semi-professional) of their participants (e.g., ball speed: 24.69–28.01 m/s compared to 12.19–12.69 m/s in our study). The impulse transfer within a kinematic chain was clearly demonstrated in both studies. It occurs typically in such throwing movements. As expected, fistball is, in this regard, comparable to other sports in which an object has to be maximally accelerated by a strike (short contact) or a throw (long contact): the biomechanical principle of optimal coordination of impulses applies [8]. Specifically, this is also documented for the spike in volleyball [9], the goal shot in handball [10–12], and the tennis serve [13]. Another commonality between the present study and that of [7] is the relatively strong lateral inclination of the upper body during the hitting phase, which is reflected in significant height differences between left and right hips and shoulders. In connection with the coordination of impulses, positive relationships between certain parameters are to be expected, firstly between path velocities and resulting ball speed, and secondly, between joint angles and path velocities. In both cases, our findings indicate such a positive relationship; however, it is not supported by statistical evidence because of the small sample size. This reflects a serious weakness of the present study: The comparative analysis had to remain on the descriptive level; an inferential statistical analysis was not possible. A larger sample consisting of players of different performance levels, as used by Soeser and Schwameder [7], would have been desirable in order to get statistical evidence about the relationship of various kinematic parameters and their influence on the fistball spike performance. Another problem comes from the limited number of body points that were included in the analysis. Although we have measured the trajectories of the main joint angles on both sides of the body, some important aspects of the spike movement were not considered. For example, the prono-supination of the hitting arm—i.e., the internal-external rotation of the arm during the execution of the spike—was not taken into account. Neither was the angle between the player’s body and the hall floor as a measure for the body inclination before and during the ball contact determined. Our analysis is therefore not complete and in terms of reliability the results should be seen as an approximation.
5. Conclusions Nevertheless, we believe that from the kinematic description done in this study valuable insights for training and competition arise, especially as the analysis—apart from the ball passing—was carried out under typical game conditions. It has become clear, for example, how important it is to temporally coordinate the single impulses during the hitting phase in order to maximize the terminal speed of wrist and ball. Therefore, during practice, special attention should be taken that elbow, shoulder and wrist are accelerated in quick sequence, one after the other. Since the first impulse for the spike is produced in the torso, it seems reasonable to consider strengthening exercises for the core muscles as a regular part of the training regime. Vigorous torso and shoulder muscles can also help to prevent muscle injuries, which are quite common in fistball due to the partially strong inclinations and torsions of the upper body [4] (as demonstrated in this study.) Electromyography methods would provide further insight in this case. As the run-up is usually very short, the run-up velocity is believed to play only a minor part in the jump height. The jump height is mainly the result of the explosive strength of the legs and the coordinative quality of the jumping motion (e.g., fluent connection of up and downward movement, use of initial force, and arm movement). In addition, the run-up in fistball Sports 2016, 4, 55 11 of 11 is performed less in the up-front direction than, for example, in Handball. Of course, dynamometric measurements using force plates would be interesting in this context; combined with our findings, they would lead to a better understanding of the biomechanical structure of the fistball spike. The progressive professionalization in fistball and the increasing popularity of this sport in many countries should be reflected in the future by a stronger interest from sport science. This study as well as the work of [4–7] are a starting point.
Author Contributions: Andreas Bund and Saeed Ghorbani conceived and designed the experiment; Saeed Ghorbani and Franziska Rathjens performed the experiment; Andreas Bund analyzed the data; Andreas Bund and Saeed Ghorbani wrote the paper. Conflicts of Interest: The authors declare no conflict of interest.
References
1. IFV. Faustball. In IFA—50 Years Young/50 Jahre Jung; Meuter-Druck: Düsseldorf, Germany, 2010. 2. Keil, B. Fistball (Faustball); Sport-Verlag: Berlin, Germany, 1983. (In German) 3. Holzheuer, M. Fistball—The unknown sport (Faustball—Die unbekannte Sportart). Sportpraxis 1986, 6, 13–14. (In German) 4. Schmitz, A. Sports Injuries and Sports Damages in Fistball with a Special Focus on Shoulder Injuries of Offense Players (Sportverletzungen und Sportschäden beim Faustball unter Besonderer Berücksichtigung von Schulterverletzungen bei Angriffsspielern). Ph.D. Thesis, University of Münster, Münster, Germany, 2002. (In German) 5. Runer, A.; Runer, F.; Neunhäuserer, D.; Ring-Dimitriou, S.; Resch, H.; Moroder, P. A 1-year prospective analysis of injuries in amateur and elite fistball. Scand. J. Med. Sci. Sports 2014, 24, 188–194. [CrossRef] [PubMed] 6. Leser, R. On the use of a computer-based game observation system in competitive fistball (Zum Einsatz eines computergestützten Spielbeobachtungssystems im Leistungs-Faustball. In Sporttechnologie Zwischen Theorie und Praxis IV; Witte, K., Edelmann-Nusser, J., Sabo, A., Moritz, E.F., Eds.; Shaker: Aachen, Germany, 2006; pp. 209–214. (In German) 7. Soeser, K.; Schwameder, H. A three-dimensional kinematic analysis of the stand- and jump serve in fistball. In Proceedings of the XXIII International Symposium on Biomechanics in Sports, Beijing, China, 22–27 August 2005; China Institute of Sport Science: Beijing, China, 2005; pp. 160–163. 8. Wank, V.; Menzel, H.J.; Wagner, H. Throwing and putting (Werfen und Stoßen). In Handbuch Sportbiomechnik; Gollhofer, A., Müller, E., Eds.; Hofmann: Schorndorf, Germany, 2009; pp. 282–316. (In German) 9. Kuhlmann, C.H. Identification of Performance-Related Criteria for the Biomechanical Performance Diagnosis by the Example of the Volleball Spike (Identifizierung Leistungsrelevanter Parameter für die Biomechanische Leistungsdiagnostik am Beispiel des Angriffsschlages im Volleyball). Ph.D. Thesis, Technical University of Chemnitz, Chemnitz, Germany, 2010. (In German) 10. Van den Tillaar, R.; Ettema, G. A three-dimensional analysis of overarm throwing in experienced handball players. J. Appl. Biomech. 2007, 23, 12–19. [CrossRef][PubMed] 11. Wagner, H.; Pfusterschmied, J.; von Duvillard, S.P.; Mueller, E. Performance and kinematics of various throwing techniques in team-handball. J. Sports Sci. Med. 2011, 10, 73–80. [PubMed] 12. Wagner, H.; Pfusterschmied, J.; Klous, M.; von Duvillard, S.P.; Mueller, E. Movement variability and skill level of various throwing techniques. Hum. Mov. Sci. 2012, 31, 78–90. [CrossRef][PubMed] 13. Subijana, C.L.; Navarro, E. Kinetic energy transfers during the tennis serve. Biol. Sport 2010, 27, 279–287. [CrossRef]
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