MUSCLE FORCE-VELOCITY AND POWER-VELOCITY RELATIONSHIPS UNDER ISOKINETIC LOADING

Abstract

Various studies indicated that human muscles in vivo manifest a substantially similar, if not the identical force-velocity relationship established for isolated, maximally stimulated animal muscles. In the present study, 15 healthy males and females, 18-38 yr old and representing varied activity patterns from sedentary to athletic, performed maximal dynamic knee extensions on an isokinetic loading dynamometer. Maximal torque forces attained at a specific point in the range (30.degree. before full extension) and at 7 loading velocities from 0 (isometric) to 288.degree. /s were recorded. The maximum 30.degree. torques exhibited by the various subjects ranged from 29-245 N-m. Over the 4 lower test velocities (0, 48, 96 and 144.degree. /s), all subjects exhibited less than a 15% deviation from their respective maximum 30.degree. torque values, which occurred most often at the 96.degree. /s test velocity. Maximal instantaneous power output at the 30.degree. position ranged from 98-680 W. In all 15 subjects this was attained at and remained generally constant over the 3 highest test velocities (192-288.degree. /s). A neural mechanism that restricts a muscle''s maximal tension in vivo is postulated as being responsible for the marked difference between the force-velocity relationship in human muscles in vivo and that exhibited by isolated animal muscles.