The isokinetic machine generally allows a relatively safe application of maximal loading to a specific muscle group as well as an accurate and objective evaluation of muscle strength and endurance. However, still there is not enough scientific background in establishing the optimal number of repetitions of each set, optimal number of sets per day, and frequency and rest interval between each set of exercises for most effective isokinetic training. The purpose of this study is to determine the optimal number of repetitions for ideal isokinetic training to improve muscle strength.

Twenty three male volunteers were randomly assigned to three training groups. All groups were trained for isokinetic knee flexors and extensors using the Cybex 340 isokinetic dynamometer three times a week for 6 weeks at 1800/sec. 5 repetitions for group 1, 10 repetitions for group 2 and 15 repetitions for group 3 were used for training and all subjects were tested before and after training at 60, 120, 180, 240, 3000/sec for peak torque improvement of quadriceps.

All three groups showed improvements in peak torque after training. However, 10 and 15 repetition groups showed higher incremental ratio of peak torque than the 5 repetition group. The incremental ratio between 10 and 15 repetition groups was not significant. It was concluded that isokinetic training is repetition-specific in peak torque improvement and 10 repetition is the optimal number of repetitions for isokinetic training according to this study.