Torque development in isokinetic training.

Twenty men were randomized into three groups that performed maximal isokinetic knee extensions five days a week for 12 weeks; a fourth group was a control group. The training protocol was different for the opposite lower extremity of each subject, such that subjects in group I trained at 36 degrees/sec with 20 or 60 repetitions, group II did 20 repetitions at 36 degrees/sec with one limb and 60 repetitions at 108 degrees/sec contralaterally, and group III trained at 108 degrees/sec with 20 or 60 repetitions. Group IV did no training. Bilateral pretraining and posttraining vastus lateralis muscle biopsies were done, and maximal torque-velocity tests (0 degrees to 234 degrees/sec at 18 degrees/sec steps) were performed every two weeks. The muscle biopsies were examined for muscle-fiber area and enzyme activity. Statistical analysis of the torque-velocity curves showed that subjects who trained at 36 degrees/sec made significant overall gains in torque and significantly greater torque gains than those training at 108 degrees/sec. Torque gains were not made uniformly during the 12 weeks of training; they occurred primarily during the initial 4 to 8 weeks. There were no significant increases in muscle-fiber areas in response to training, but there were increases in glycolytic and mitochondrial enzyme activities. These findings suggest that the critical variable for developing strength (maximal torque), at least within the context of isokinetic training, is the amount of torque developed during training.