TENDON ACTION OF 2-JOINT MUSCLES DURING H UMAN LOCOMOTION - MECHANICAL ENERGY-TRANSFER BETWEEN LINKS IN SHOCK-ABSORBING AND PUSH-OFF PHASES

We hate evaluated experimentally the amounts of the mechanical energy transferred by the two-joint muscles between the links of legs during squat vertical jumps and landings after jumping down from a height of 0,5. The experiments have been conducted on file healthy subjects in t he course of locomotions. The coordinates of markers attached to the s ubjects' bodies and the ground reaction forces have been registered. T he energy transferred by the two-joint muscles from and to the links f orming each joint has been determined by integration of the difference between the power developed in the joint by the control moment and th e total power of the muscles serving the given joint. It has been show n, that at squat vertical jump (the push-off phase) the two-joint musc les transfer mechanical energy from the proximal links of the leg to t he distal ones: from pelvis to shank (by the rectus femoris m.), and f rom thight to fool (by the gastrocnemius m.). At landing (the shock-ab sorbing phase) the two-joint muscles transfer energy from the distal t o proximal links: from foot to thight (by the gastrocnemius m.), and f rom shank to pelvis (by the rectus femoris m.). Thus the one-joint mus cles of the proximal links compensate for the deficiency in the force developed by the one-joint muscles of the distal links due to the <<te ndon action>> of the two-joint muscles. During push-off, the muscles o f the proximal links contribute to increase in the energy of the dista l links, and in the shock-absorbing phase, to its dissipation.