It is of considerable interest to anyone who must describe exercise programs to know to what extent training is acquired under any one exercise speed in isokinetic training. Therefore, the present study was designed to investigate the effect of isokinetic training at both high and low velocities on strength gain of the quadriceps and hamstring muscles producing maximal isokinetic contractions. The 14 young male subjects were assigned randomly to one of 2 training groups using the Rehabilitation and Testing System (Model No. Cybex 340); groupⅠ, training at 60°/sec (n=7); group Ⅱ, training at 180°/sec (n=7).

The results are as follows;

1) In groupⅠ, the muscle strength of the right quadriceps showed significant increment at all test speeds and muscle strength increments at the training speed were significantly higher than those at high test speed. The right hamstring muscle showed a significant strength increment at test speeds 30°/sec and 60°/sec only. In the left knee, which was not trained, only the quadriceps showed significant muscle strength increment at test speeds less than 90°/sec.

2) In group Ⅱ, the quadriceps and hamstrings of the right knee showed significant muscle strength increments at all test speeds, and there were no significant difference among test speeds. At increments confined to the quadriceps at all the test speeds, with the exception of speeds at 60°/sec and 270°/sec.

3) At each test speed, angles of peak isokinetic torque at the knee joint showed no significant difference following pre and post training.

The optimal number of repetitions, sets, frequency and rest intreval necessary to obtain maximal effectiveness of isokinetic training has not yet been specifically established. This, therefore, together with the above mentioned results, requires further investigation before these results can be more suitably supported as a reliable and valid concept.