The Biomechanics and Motor Control of Tap Dancing

Priscila Rocha, M.Sc., Jodie McClelland, Ph.D., Tony Sparrow, Ph.D., and Meg E. Morris, Ph.D.

Abstract knees, and hips for the nerve beats and amplitude, and symmetry of the lower Although tap dancing is a popular dance heel ball walks. There was a mild degree of limbs is a key determinant of tap danc- genre, little is known about the biome- asymmetry at the hip for the brush brush ing proficiency. chanics and motor control of this complex stamp steps (symmetry index 90%). The Most studies on motor perfor- motor skill. We conducted a detailed 3D results showed that experienced dancers mance and control pertaining to kinematic analysis of movement timing, had very high levels of proficiency in amplitude, and symmetry in three expe- controlling movement amplitude, timing, dance have been conducted in relation to ballet, flamenco, and Irish danc- rienced female tap dancers. Kinematic and inter-limb coordination across the 1-11 analyzes of three basic tap dance steps ankles, knees, and hips. This resulted in ing. For example, motion analysis 3,5,12,13 (nerve beats, brush brush stamps, and heel skilled, fast, and well executed dance steps. studies of ballet and flamenco ball walks) were undertaken. A 10-camera dancing6,10 have shown that elite per- Vicon motion analysis system was used ap dancing is a highly com- formers are highly skilled at control- to collect the data. The results showed plex motor skill requiring an ling movement speed, amplitude, and the feet and knees to play a major role in inter-limb coordination throughout movement execution. Each step required advanced ability to control movementT timing, movement am- the entire body and especially the at least 10° of ankle motion (range: 10° plitude, and inter-limb coordina- feet. These studies have also demon- to 66.8°). Knee range of motion varied strated proficiency in adapting motor from 1.3° to 147.4°. For each of the tion. Despite taking many years to dance steps the hips showed the smallest master, it remains a popular dance performance to the task constraints amplitude of movement, which was not genre throughout the world. Little is imposed by the accompanying music greater than 21° in two out of the three known about the biomechanics and and the dance routine. Tap dancing dance steps. Analyzes of movement timing also appears to have several elements motor control of tap dancing; hence, 8,9 showed that each of the dance steps was we conducted an analysis of some in common with Irish dancing ; both fast, accurate, and well synchronized. The basic tap dance steps using three- genres place considerable emphasis on nerve beats took on average 0.50 seconds, movements of the feet and legs, while the brush brush stamps 1.36 seconds, and dimensional (3D) motion analysis. We were particularly interested in the upper body is a secondary focus the heel ball walks 4.03 seconds. A high of attention.14,15 Neverthless, scant 3D degree of symmetry in total movement understanding the extent to which skilled control of movement timing, data are available on the biomechanics amplitude was evident at the ankles, of tap dancing, and little is known about its requirements for movement Priscila Rocha, M.Sc., School Allied Health, Department of Physiotherapy, speed, amplitude, and timing. College Science, Health & Engineering, La Trobe University, Bundoora, Australia; Only one study has analyzed the and CAPES Foundation, Ministry of Education of Brazil, Brasília, Brazil. Jodie kinematics and kinetics of tap dance McClelland, Ph.D., and Tony Sparrow, Ph.D., School Allied Health, Department sequences.14 In that study four tech- of Physiotherapy, College Science, Health & Engineering, La Trobe University, nically demanding tap dance move- Bundoora, Australia. Meg E. Morris, Ph.D., School Allied Health, Department of Physiotherapy, College Science, Health & Engineering, La Trobe University; ments were evaluated in order to and Healthscope, Northpark Private Hospital, Bundoora, Australia. understand the factors predisposing to injuries in professional tap danc- Correspondence: Priscila Rocha, M.Sc., School Allied Health, Department ers. A comparatively low incidence of of Physiotherapy, La Trobe University, Bundoora, Melbourne, Victoria 3086, injuries was reported for tap dancers, Australia; [email protected]. and this was correlated with compara-

Table 1 Participant Characteristics Experience Age Dancing Teaching Participants (years) (years) (years) Injuries Comorbidities Medication A 24 21 7 0 0 0 B 27 22 10 0 0 0 C 27 22 10 0 0 0 tively small ground reaction forces, perform different tap dance steps skeletal injuries, co-existing medical joints forces, and moments that are a and movement phases; and conditions, and pain in the previous hallmark of skilled performance.14 3. Examine symmetry in amplitude six months. They gave informed Given the paucity of existing and timing between the right and written consent in accordance with data, we investigated some basic tap left legs. La Trobe University Australia Ethics dance steps (nerve beats, brush brush Committee requirements. stamps, and heel ball walks) to provide Methods a 3D kinematic analysis of movement Participants Experimental Protocol timing, amplitude, and symmetry in Three experienced and highly skilled Each participant performed the three experienced tap dancers. The specific female tap dancers participated basic tap dance steps mentioned pre- aims were to: in this study (Table 1). This was a viously, chosen from the Australian 1. Quantify the typical range of mo- sample of convenience of young Tap Dance Syllabus17 levels 1 and 2, tion at the feet, knees, and hips adults aged 20 to 30 years, with executed in random order. These steps in experienced and highly skilled experience in dancing and teaching are frequently combined to create tap dancers; the Australian Tap Dance Syllabus.16 complex routines. All dance steps were 2. Determine the time taken to Participants were free of musculo- analyzed with respect to three move-

Table 2 Tap Dance Step Elements Steps Description Instruction Movement Phase Nerve Lift the moving leg forward without touching the floor. The ball of the Down phase: maximum peak Beats Keep the standing knee flexed. The ball of the foot of the foot strikes the of dorsiflexion to maximum moving leg strikes the floor 12 times. Only the ball of the floor 12 times, peak of plantar flexion foot touches the floor. Each nerve beat movement phase is completing 11 Up phase: maximum peak of composed of dorsiflexion, progressing to plantar flexion, nerve beats with plantar flexion to maximum and finishes with dorsiflexion. each leg peak of dorsiflexion Brush Keep the knee of the supporting leg flexed during the One movement Brush whole sequence. Brush forward: Lift the moving leg back- phase each leg Brush forward: first peak angle Stamps ward while flexing the knee. Swing the moving leg forward, of knee flexion to first peak hitting only the ball of the foot on the floor. Continue the angle of knee extension movement until the foot is off the floor and the moving Brush backward: first peak knee is extended. Brush backward: Swing the moving leg angle of knee extension to backward, hitting only the ball of the foot on the floor. the second peak angle of knee Continue the movement until the foot is off the floor and flexion the knee of the moving leg is flexed. Stamp: Return the Stamp: second peak angle of moving leg to the standing position, stamping a flat foot knee flexion to third peak angle down on the floor with both knees bent. Each brush brush of knee flexion stamp movement phase is composed of one brush forward, a brush backward, and a stamp. Heel Flex the knee of the supporting leg. Stance: Lift the mov- Two movement Stance: heel contact on the Ball ing leg forward, striking the back edge of the heel on the phases each leg, floor to heel lift and then toe Walks floor while keeping the toe lifted (maximum dorsiflexion). alternating the off Drop the ball of the foot to the floor transferring weight feet Swing: toe off to heel contact quickly, moving forward. Repeat the movements with the other leg. Swing: The moving leg is behind the supporting leg. Lift the toe off the floor and move the leg forward until the heel strikes the floor, initiating the stance phase again. Each movement phase is composed of one stance and a swing component. Journal of Dance Medicine & Science • Volume 21, Number 3, 2017 125 ment phases: preparation, movement, and right ankles, lateral aspect of head software was used to reconstruct the and recovery. The movement phase of of left and right fifth metatarsals, over position-time coordinates for each of each step was also subdivided, as will the left and right second metatarsal the marker and segment orientations. be explained in detail for each dance heads, and the left and right calcaneus step below. Table 2 summarizes the bones. During the tap dance routines Data Analysis elements of each step. the raw position-time coordinates for Data points of interest were extracted The dancers were instructed to the lower-limb markers were sampled from each individual trial for each begin each step with the right foot continuously at 100 Hz, using a dancer. These individual data were followed by the left foot, and to 10-camera Vicon motion analysis used to investigate consistency be- perform the sequence as required by system (Vicon, Oxford Metrics Ltd., tween repetitions. When a specific the rhythm of the selected music, Oxford, UK). movement was repeated more than “Black Cabaret,” with 118 bpm (0.51 Additional reflective markers were once, these data were combined seconds between each beat). Each cemented to rigid thermoplastic shells to derive an average value for each movement sequence was performed to construct rigid-body marker clus- dancer. Descriptive statistical analyses and analyzed separately. Although ters that were firmly attached to the also included the range of motion of familiar with the dance steps, dancers thighs and shanks using Velcro straps. each joint and medians and ranges were instructed to practice each of the A standing trial was initially captured in general. steps twice before testing. to identify and calculate the joints’ The total amplitude of movements centers. The medial condyle and at the ankles, knees, and hips was Data Capture medial malleolus markers were then analyzed for each movement phase of Thirty-six retro-reflective markers, removed and were not used during the each dance step. The total amplitude placed by a trained and experienced movement trials to avoid interference of movement for each of the joints evaluator, were used to identify lower with the performance. was determined by calculating the limb and pelvic movement patterns in difference between the peak angle of the three planes of motion. The mark- Data Processing flexion and the peak angle of exten- ers were attached to the following Raw position-time signals were first sion for each movement phase. The anatomical landmarks: left and right interpolated to compensate for oc- time taken to complete each of the anterior superior iliac spines, left and cluded markers using a window of up movement phases for each limb for right posterior superior iliac spines, to 10 frames, followed by a 4th order each dance step was also measured. left and right mid-superior aspect of zero-lag Butterworth Filter with a The symmetry in performance the left iliac crests, lateral and medial cut-off frequency of 6 Hz. Following between left and right limbs was cal- condyle of the left and right knees, data sampling, VISUAL3D (c-motion culated for both amplitude and tim- lateral and medial malleolus of the left Inc., Germantown, Maryland, USA) ing using the Gait Asymmetry Index

Table 3 Movement Amplitude for Different Tap Dancing Steps Brush Brush Stamps Heel Ball Walks Brush Brush Nerve Beats Forward Backward Stamp Stance Swing Hip range of Right 0.4 12.0 6.1 11.2 29.4 68.7 motion (degrees) (0.2-2.5) (6.3-17.5) (5.2-13.4) (6.4-19.8) (26.4-34.3) (52.4-69.9) Left 1.4 13.5 12.7 14.3 36.7 68.6 (degrees) (0.1-3.3) (10.1-21.2) (9.3-14.9) (13.3-15.8) (20.7-40.5) (61.4-71.5) GA (%) 92 80 67 86 90 96 Knee range Right 2.8 126.8 145.3 90.2 47.6 125.6 of motion (degrees) (1.3-15.3) (109.2-129.8) (126.9-147.4) (88.9-99.5) (46.3-48.9) (123.5-129.7) Left 2.7 121.0 143.9 95.9 49.1 130.5 (degrees) (2.6-16.4) (120.5-143.1) (138.3-145.3) (86.5-103.4) (48.3-49.9) (113.0-145.9) GA (%) 99 95 98 98 96 99 Ankle range Right 45.0 29.2 33.2 14.7 39.5 62.2 of motion (degrees) (44.3-50.8) (28.2-35.4) (32.8-42.3) (10.0-27.7) (25.8-59.0) (61.3-66.8) Left 50.7 31.3 34.6 14.0 37.3 64.9 (degrees) (41.2-57.1) (29.6-34.4) (28.8-38.8) (11.0-29.8) (34.2-41.5) (58.6-65.7) GA (%) 97 97 94 97 97 100 Median (range); GA = Gait Asymmetry Index. 126 Volume 21, Number 3, 2017 • Journal of Dance Medicine & Science

(GA)18,19 according to the following formula: GA = (Xr / X1) x 100%. This formula assumes that Xr is the variable recorded for the right limb and Xl for the left limb. The first and last nerve beats were excluded from the analysis to avoid interference from the preparation and recovery phases. Therefore, nine nerve beats were evaluated. To explore the time to completion of the nerve beats the movement phase of the nerve beat step was sub-divided into two sub-phases: the upward phase and the downward phase (Table 2). Variation in the timing between these phases was analyzed by calculating the consistency in timing across each sub-phase of the nine nerve beats. The movement phase for the brush brush stamps was analyzed for the three different sub-phases: brush forward, brush backward, and stamp (Table 2). Heel ball walks were divided into first stance-first swing, and second stance-second swing phases (Table 2). Results Movement Amplitudes for the Feet, Knees, and Hips The amplitude of movement varied across movement phases and dance steps. Nevertheless, for each of the three tap dance steps the total movement amplitude was found to be greater at the ankle and knee than at the hip (Table 3, Fig. 1). During performance of the nerve beat steps, the ankle joints showed greater movement amplitude (range: 41.2° to 57.1°) than the hips (range: 0.1° to 3.3°) and knees (range: 1.3° to 16.4°). For the brush brush stamps, the knee joints had the highest movement Figure 1 Movement amplitude for different tap dance steps. GA: Gait Asymmetry amplitude in all movement phases. Index. The greatest motion at all lower limb joints occurred during the brush ankles was also important, presumably Movement Timing backward phase of these movements. in an effort to create the well-known All tap dancing steps were performed During this particular phase the range tap sound. very quickly by these elite performers of knee motion was between 126.9° For the heel ball walks, the great- (Table 4, Fig. 2). Tap steps were fast, and 147.4°, the range of ankle motion est range of motion for all lower limb accurate, and well synchronized with was between 28.8° and 42.3°, while joints occurred during the swing respect to the different movement the range of hip motion was between phase. During this phase the knee phases. The nerve beats were com- 5.2° and 14.9°. Although the control joints contributed more to movement pleted quickly by all dancers, taking of knee flexion and extension was the amplitude (range: 113.0° to 145.9°) only 0.49 to 0.50 seconds, which key determinant of control for the than the ankles (range: 58.6° to 66.8°) corresponds to one beat per second of brush brush stamps, motion at the and hips (range: 52.4° to 71.5°). the accompanying music. The brush Journal of Dance Medicine & Science • Volume 21, Number 3, 2017 127 brush stamps were completed within 1.25 to 1.70 seconds, and the heel ball walks took 4.02 to 4.08 seconds to be performed. For the nerve beats, the time taken to perform the upward movement phase (range: 0.33 to 0.37 seconds) was approximately twice as long as the time taken to execute the downward movement phases (0.13 to 0.16 seconds). There was only 0.03 seconds variation between the nine downward phases for the nerve beats, and less than 0.17 seconds difference between the upward phases, showing how consistent the movements were across the sequences. The time to complete the forward phases and the backward phases of the brush brush stamps steps was comparable. However, for this step the time taken to complete the stamp phase was quicker on the left side (Table 5, Fig. 2). Stance phase (1.29 seconds [1.21 to 1.37 seconds]) of heel ball walks was longer than the swing phase (0.74 seconds [0.66 to 0.81 seconds]), (Table 5 and Fig. 2). In interpreting these timing results the concurrent amplitude regulation needs to be taken into account. For the nerve beats, the ankle joint moved the most, with approximately 50° of total movement amplitude for each phase. For the brush brush stamps, the knee joint moved the most, with approximately 140° total amplitude for each movement phase (Tables 4 and 5 and Fig. 2) Amplitude and Timing Symmetry A high degree of symmetry (> 97%) in total movement amplitude for the nerve beats and heel ball walks was found between the left and right sides for the ankles and knees, and slightly Figure 2 Time to complete movement phases.

Table 4 Time to Complete Movement Phase of Nerve Beats Right Left GA (%) Downward Upward Downward Upward Phase Phase Phase Phase Downward Upward (seconds) (seconds) (seconds) (seconds) Phase Phase Time to complete movement phase 0.15 0.35 0.15 0.34 97 100 (0.14-0.16) (0.33-0.36) (0.13-0.16) (0.34-0.37)

Time variation across nerve beats 0.03 0.06 0.03 0.07 89 60 (0.02-0.04) (0.04-0.08) (0.02-0.03) (0.06-0.17)

Median (range); GA = Gait Asymmetry Index. 128 Volume 21, Number 3, 2017 • Journal of Dance Medicine & Science

Table 5 Time to Complete Movement Phase of Brush Brush Stamps and Heel Ball Walks Timing to Complete Movement Phase (seconds) Right Left GA (%) Brush Brush Stamps Brush Brush Stamps 1.33 (1.32-1.70) 1.39 (1.25-1.40) 93 Brush Forward 0.47 (0.37-0.51) 0.55 (0.35-0.57) 92 Brush Backward 0.43 (0.40-0.53) 0.37 (0.35-0.67) 98 Stamp 0.46 (0.42-0.76) 0.38 (0.33-0.47) 72 Heel Ball Walks Heel Ball Walks 4.03 (4.02-4.08) 4.04 (4.02-4.13) 99 Stance 1.27 (1.26-1.33) 1.35 (1.21-1.37) 98 Swing 0.77 (0.68-0.81) 0.71 (0.66-0.79) 96 Median (range); GA = Gait Asymmetry Index. less for the hips (between 90% and tap dancers there were exceptional of a step and the music beat influence 96%; Table 3). For the brush brush levels of skill in regulating lower limb the range of motion, faster steps, such stamps, there was a high degree of movement size, movement timing, as nerve beats, were associated with symmetry (> 94%) between the left and inter-limb coordination. One a smaller movement amplitude than and right knees and ankle total am- of the key aims of this study was to brush brush stamps and heel ball plitudes. In contrast, the total hip am- understand what proportion of joint walks, as described above. The timing plitude was moderately asymmetrical motion occurs at the ankles compared for heel ball walks had some similari- between sides (67% and 86%). Sym- with knees and hips for each of the ties to normal gait. During this dance metry was less for the brush backward three core steps in tap dancing. The step the stance phase was twice as long phase (Table 3). results showed that for the perfor- as the swing phase, which was similar The time taken to complete the mance of nerve beats, ankle range of to straight line walking during which upward and downward movement motion was on average approximately 60% of the cycle duration is in the phases of the nerve beats was con- 50°, which was three times that of stance phase.20 sistent between sides, with a timing the knees (average maximum of 15°) In most cases, movements were symmetry close to 100% in both and almost 50 times that of the hips highly symmetrical in these elite per- phases. The time variations across the (on average 1.3°). In contrast, brush- formers. Despite the small degree of nine nerve beats were more marked brush-stamps movements emphasized irregularity in hip movement ampli- between sides, especially in relation knee range of motion (maximum of tude for the brush brush stamps, the to the upward movement phase, with 130° on average), being three times dancers were able to maintain high only 60% timing symmetry (Table 4). that of the ankles (maximum of 35° levels of hip symmetry for the other A high degree of symmetry (> on average) and 10 times that of the dance steps. High levels of symmetry, 92%) between sides could be seen for hips (average 12°). Heel ball walks close inter-limb coordination, and the time taken to complete the brush presented the most even distribu- efficient muscle activation are charac- forward and brush backward phases tion of motion down the lower limb teristics that distinguish highly skilled of the brush brush stamps (Table 5). joint chain, with approximately equal dancers from novices.1,21,22 However, the stamp phase showed range at ankles and hips (around 50° Each person is unique and finds lesser symmetry, as the time to com- on average), being half the range of his or her own biomechanical solu- plete this phase was faster on the left motion at the knees (around 100°). tions to performing a skilled dance side than on the right side (symmetry Thus, a notable finding was that suc- movement.23 In this study, even index = 72%). cessful motor performance relied on highly skilled dancers did not show For the heel ball walks, high levels a high degree of amplitude control, exactly the same performance for each of symmetry (> 96%) between sides especially at the ankles and knees. movement sequence. There were small were observed with respect to the time The role of the hip for some of the differences within and between limbs taken to complete each movement steps may well be to provide stability, and across performers. The dance phase of the sequence, with timing allowing the ankles and knees to move steps were generally executed using a symmetry ranging from 96% to 98% fast with high amplitude, creating the similar approach by the three danc- (Table 5). tap dance sound. ers, although individuals had subtle Tap dancing movements were characteristics that were a signature Discussion performed very quickly. The timing of their individuality. The capacity for Tap dancing is a popular yet demand- to complete each tap dancing step variability in performance rather than ing dance genre from a technical point was closely associated with the total adherence to a stereotyped mode is a of view. Our study showed that in elite movement amplitude. As the timing characteristic of highly accomplished Journal of Dance Medicine & Science • Volume 21, Number 3, 2017 129 and skilled dancers.1,21,22 Such subtle of biomechanics in understanding Gdos S, Ribeiro LP, Loss JF. Kine- differences in motor execution are best dance movement: a review. J Dance matic evaluation of the classical ballet identified using the 3D biomechan- Med Sci. 2008 Sep;12(3):109-16. step “plié.” J Dance Med Sci. 2015 ics analysis, which allows for precise 3. Gorwa J, Dworak LB, Michnik R, Jun;19(2):70-6. measurement of skilled performance. Jurkojć J. Kinematic analysis of mod- 14. Mayers L, Bronner S, Agraharasa- ern dance movement “stag jump” makulam S, Ojofeitimi S. Lower A limitation of this study was the within the context of impact loads, extremity kinetics in tap dance. J small sample size and restriction of injury to the locomotor system and Dance Med Sci. 2010 Mar;14(1):3- data collection to experienced and its prevention. Med Sci Monit. 2014 10. highly proficient performers. Future Jun 27;20:1082-9. 15. Mayers L, Judelson D, Bronner S. studies should evaluate the kinematics 4. Krasnow D, Wilmerding V, Stecyk The prevalence of injury among tap and kinetics of a range of tap dance S, et al. Biomechanical research in dancers. J Dance Med Sci. 2003 steps in novices, community dancers, dance: a literature review. Med Probl Dec;7(4):121-5. and elite performers. The current re- Perform Art. 2011 Mar;26(1):3-23. 16. Australian Tap Dance Syllabus - Aus- sults do not generalize to older adults, 5. Wilson M, Lim B-O, Kwon Y-H. A tralasian Dance Association, 2016 children, or those with disabilities. In three-dimensional kinematic analy- Available from www.adatheatre.com. addition, all of the analyses were per- sis of grand rond de jambe en l’air au. skilled versus novice ballet dancers. J 17. Technical Rules International Dance formed with the dancers wearing tap Dance Med Sci. 2004 Dec;8(4):108- Federation Discipline: Tap Dance. In- dancing shoes. Because the weight of 15. ternational Dance Federation, 2012, the shoes and the sound produced by 6. Bejjani F, Halpern N, Pio A, et pp. 1-26. Available from: http:// the metal taps influence performance, al. Musculoskeletal demands on www.idfdance.com/files/firma.idf- future trials could compare perfor- flamenco dancers: a clinical and dance/upload/files/Rules/IDF%20 mance with and without footwear. biomechanical study. Foot Ankle Int. TECHNICAL%20RULES%20 1988 Apr;8(5):254-63. TAP%20DANCE%202012-2015. Conclusion 7. Bennell K, Khan KM, Matthews B, pdf. Tap dancing is an advanced motor et al. Hip and ankle range of motion 18. Plotnik M, Giladi N, Hausdorff skill that requires high levels of control and hip muscle strength in young fe- JM. A new measure for quantifying of movement amplitude, timing, and male ballet dancers and controls. Br J the bilateral coordination of human Sports Med. 1999 Oct;33(5):340-6. gait: effects of aging and Parkin- inter-limb coordination to generate 8. McGuinness D, Doody C. The in- son’s disease. Exp Brain Res. 2007 symmetrical and highly reproduc- juries of competitive Irish dancers. Aug;181(4):561-70. ible steps. The findings of this study J Dance Med Sci. 2006 Mar;10(1- 19. Błażkiewicz M, Wiszomirska I, emphasis the need for control of large 2):35-9. Wit A. Comparison of four meth- amplitudes of movement, particularly 9. Shippen JM, May B. Calculation ods of calculating the symmetry of the ankles and knees, within short of muscle loading and joint contact of spatial-temporal parameters of time periods. The hip appears to be forces during the rock step in Irish gait. Acta Bioeng Biomech. 2014 used predominantly in a supporting dance. J Dance Med Sci. 2010 Apr;16(1):29-35. or stabilizing role during these tap Mar;14(1):11-8. 20. Apkarian J, Naumann S, Cairns B. dancing steps. The high degree of 10. Voloshin AS, Bejjani FJ, Halpern A three-dimensional kinematic and side-to-side movement symmetry in M, Frankel VH. Dynamic loading dynamic model of the lower limb. J on flamenco dancers: a biome- Biomech. 1989 Jan;22(2):143-55. these participants is likely to be a com- chanical study. Hum Mov Sci. 1989 21. Bläsing B, Calvo-Merino B, Cross mon feature of professional dancers; Oct;8(5):503-13. ES, et al. Neurocognitive control however, future studies could compare 11. Lin C-F, Su F-C, Wu H-W. Ankle in dance perception and perfor- the performance of elite dancers with biomechanics of ballet dancers in mance. Acta Psychol (Amst). 2012 novices, across the age span, in health relevé en pointé dance. Res Sports Feb;139(2):300-8. and disease. Med. 2005 Jan-Mar;13(1):23-35. 22. Koutedakis Y. Biomechanics in dance. 12. Imura A, Iino Y, Kojima T. Biome- J Dance Med Sci. 2007;12(3):73-4. References chanics of the continuity and speed 23. Kiefer AW, Riley MA, Shockley K, et 1. Koutedakis Y, Jamurtas A. The danc- change during one revolution of the al. Multi-segmental postural coordi- er as a performing athlete. Sports Fouette turn. Hum Mov Sci. 2008 nation in professional ballet dancers. Med. 2004 Aug;34(10):651-61. Dec;27(6):903-13. Gait Posture. 2011 May;34(1):76- 2. Wilson M, Kwon Y-H. The role 13. Gontijo KNS, Candotti CT, Feijó 80.