LEG EXTENSION POWER AND MUSCLE-FIBER COMPOSITION

Abstract

Muscle fiber composition was related to the isokinetic measure of peak torque production through a range of leg extension velocities. Males (21) were biopsied from the vastus lateralis muscle to determine their percent distribution of slow twitch (% ST) and fast twitch (% FT) muscle fibers as identified through myofibrillar ATPase activity. All subjects showed a decline in peak torque with increasing velocities. Subjects with predominantly FT fibers were able to generate 11, 16, 23 and 47% greater relative peak torque than could predominantly ST subjects at lever arm velocities of 115, 200, 287 and 400.degree./s, respectively. Likewise the correlations between relative torque production and % FT were significant (P < 0.05) and increased from r [correlation coefficient] = 0.44 to r = 0.75 as velocity increased from 115-400.degree./s, respectively. Muscle fiber composition apparently becomes increasingly more related to power performance as the velocity of movement increases.