2000 年 15 巻 p. 97-105
During human walking, the body accelerates during the second half of the phase in which the foot touches the ground, before it decelerates. Recently developed real-time ultrasound imaging makes it possible to observe the behavior of the muscle-tendon complex during walking. Muscle fiber (MF) of the m. gastrocnemius medialis (MG), which acts as one of the main agonist muscles, contracted isometrically during the body acceleration phase, whereas the MG tendinous tissue (TT) was lengthened. Before toe clearance, both the MF and TT shortened drastically without MG activation. No mechanical power exerted by the MF contraction was observed while the foot was on the ground, but the TT provided mechanical power in lengthening (negative) following the shortening (positive) during the body acceleration phase. It was observed that during walking the MG fiber contracts isometrically whereas the tendinous tissue is stretched, causing the storage of elastic energy in tendinous tissue. Before toe clearance, the abrupt shortening of tendinous tissue and total muscle-tendon complex is caused by release of the elastic energy stored in tendinous tissue.