Behavior of fascicles and tendonous structures of human gastrocnemius during
vertical jumping.
Kurokawa, Sadao, Tetsuo Fukunaga, and Senshi Fukashiro.
Department of Life Sciences (Sports Sciences), The University of Tokyo, Meguro,
Tokyo 153-8902, Japan
APStracts 8:0002A, 2001.
Behavior of fascicles and tendonous structures of human gastrocnemius medialis (MG)
was determined by use of ultrasonography in vivo during jumping. Eight male subjects
jumped vertically without countermovement (SQJ). Simultaneously, kinematics, kinetics,
and electromyography from lower leg muscles were recorded during SQJ. During phase I
(«minus»350 to «minus»100 ms before toe-off), muscle-tendon complex (MTC) length
was almost constant. Fascicles, however, shortened by 26%, and tendonous structures
were stretched by 6%, storing elastic energy of 4.9 J during phase I. During phase II
(«minus»100 ms to toe-off), whereas fascicles generate force quasi-isometrically, MTC
shortened rapidly by 5.3%, releasing prestored elastic energy with a higher peak positive
power than that of fascicles. Also, the compliance of tendonous structures in vivo was
somewhat higher than that of external tendon used in the simulation studies. The results
demonstrate that the compliance of tendonous structures, together with no yielding of
muscle fibers, allow MTC to effectively generate relatively large power at a high joint
angular velocity region during the last part of push-off.
Received 23 October 2000; accepted in final form 3 November 2000
APS Manuscript Number A206-0.
Article publication pending J Appl Physiol
ISSN 1080-4757 Copyright 2001 The American Physiological Society.
Published in APStracts on 29 January 2001