Repeated isokinetic plantar flexions at different angular velocities.

Peak torque (PT), contraction work (CW) and mean power (CP) were measured for each of 200 repetitive isokinetic (maximum effort) plantar flexions. Simultaneous recording of integrated electromyograms (iEMG) were obtained from the three parts of the triceps surae muscle. Four tests at different angular velocities (30, 60, 120 and 180 degrees s-1 (degrees X s-1] were performed with at least 2 weeks between each test. The subjects were eight clinically healthy females (24-36 years). At all four angular velocities CW, CP and PT decreased steeply during the first approximately 70 contractions, followed by a steady-state level with no further significant decreases. The relative decreases of PT and CP were significantly smaller than for CW at all velocities. The relative CW decline increased with angular velocity; the relative PT and CP decreases were not velocity dependent. Also iEMG activity decreased in two phases during the 200 contractions and were on a significantly lower relative level at 180 degrees X s-1. However the reduction of range of motion was significantly greater at 180 degrees X s-1 and when the iEMG activity was compensated for this decrease the relative decreases in electromyographic activity were similar at the four angular velocities. The results indicated that CW was more sensitive to fatigue than PT and CP and that CW fatigue was dependent on angular velocity.