Joint torque, power and EMGs during starting dash

Abstract

A study was performed to compare joint torque development with EMG actiVities ， and to inves − tigate the relationship between peak torque and power during different phases of leg movement at djf琵 rent sprint velocitEes from the stalt 三 ng dash to f山 str三 de． Cinematographic recordings of spr 加 t move 皿 ent together with ground reaction forces and EMGs from seven lewer limb muscles were ob ・ tained from four male spr 血 ters at the lst ， 3rd， 5th， 9th， 13th and 19th （ maximal velocity ） steps from the sprint start ． Joint torq耳e and power in the hip， lmee and ankle were computed from analysis of the film and ground reaction forces ． The resUltS can be summariZed as follows ： 1） The developmental pattems of jQint torque and power ， and ・ the ・ EMG ・ actiVities ・ were ・ similar from the 且rst step to the maximal velocity ． 2 ） The phases of torque development were para ］ lel to the related EMG aCtiVities ． 3） Stretch ・ shortening cycles of muscle were observed in the m ． Solells during the foot contact pedod and in tbe m ． Biceps femoris during tle latter half of the sWing period ． 4） There was no peak torque or power that showed a dec τ ease with increased sprint ve1 ity ． 5 ） Peak torque and power that increased with sprint velocity were （ a ）torque and positive pow − er of the hip flexors during the first half of the swi 皿g period， （ b ）torque of the hip extensors durhng the latter half of the sWing period ，（ c ）torque and negative power of the knee extensors during the first half and latter half of the sWing period ， （ d）torque of the ankle extensors during the middle of the foot contact periOd ， （ e ） negative power of the anlde extensors during the 血rst half of the foot contact pe 豆 od ， and （ f ）positive power during the latter haif of the foot contact period ． These results suggest that muscles in the hip and knee joints cooperate with the change in swing movement ， and that mus ・ cles in the anlde joint cooperate with the change in drive movement as sprint velocity increases・ 6） The peak torque and power that remained high independent of sprint velocity were （ a ）tor − que and positive power of the hip extensors from the middle of the swing period to the middle of the foot contact period ， （ b）torque of the ankle extensors during the foot contact period ， a皿 d （ c ）power of 廿Le ankle extensors during the latter half of the foot contact period ， These resultS indicate the impor − tance of the hip extensors and ankle extensors in sprinting ．