The purpose of this study is to analyze the torque curves obtained through Cybex Machine while performing isokinetic exercises in knee extension and flexion. Subjects were five male (aged from 18 to 23) and five female (aged from 18 to 19) athletes. Loaded turn speeds of Cybex Machine were set at 0, 3, 6, 9, 12, 15, 20, 25 and 30 r. p. m. Subjects performed exercises sitting upright with arms crossed in front. The results obtained from the exercises were as follows: 1)The peak value of muscule torque at each turn speed tended to decrease with the increase speed in both extension and flexion for both sexes. The value disparity between extension and flexion at the same speed respectively was 1.2〜1.7 : 1. 2)The angle in which the maximum strength was reached at each loaded turn speed was decreased with the increase of turn speed in extension for both sexes. In flexion, however, the angle became greatest at the medium speed. 3)The work calculated from torque curves at each turn speed decreased with the increase of speed in both extension and flexion. 4)The power calculated from torque curves at each loaded turn speed described a parabola, reaching the maximal value at 25 r. p. m. The power value at lower speed did not show any differences both in extension and flexion. But the value of extension was greater than that of flexion at higher speed, and besides, the disparity became greater with the increase of turn speed.