The purpose of this study were to measure the peak torque, total work, average work of knee extensors by using the Cybex 6000 Testing & Rehabilitation system in the healthy twenties, and to compare control groups with experimental groups in order to investigate effects of facilitation in isometric exercise of kne extensor. Twelve subjects were tested, 6 men and 6 women, between the aged o f 2 0 and 25, mean values of the height of 166.7cm and of the body weight o f 63.4kg. results were as follows; 1) The mean peak torques of quadriceps at speed of 60°/sec were 128.8452.44 ft-lbs of pre-test and 129.5051.36ft-lbs of post-test in control groups. The experimental groups were 110.84÷35.22 ft-lbs o f pre-test and 109.0034.53 ft-lbs of post-test. The mean peak torque of quadriceps at speed of 180° /sec were 74.84$39.49 ft-Ibs of pre-test and 78.34÷33.01 ft-lbs o f post-test in control groups. The experimental groups were 64.0024.06 ft-lbs of pre-test and 151.50 192.26 ft-lbs of post-test. 2) The mean values of total work at speed of 60° /sec were 114.67$43.19 ft-lbs of pre-test and and 47.56 ft-lbs of post-test in control groups. The experimental groups were 97.84$34.59 ft-lbs of pre-test and 97.34+33.68 ft-lbs of post-test. The mean values of total work at speed of 180°/sec were 59.6737.09 ft-lbs of pre-test and 72.0031.75 ft-lbs of post-test in control groups. The experimental groups were 56.6122.11 ft-ibs of pre-test and 61.1722.64 ft-Ibs of post-test. 3) The average power at speed of 60°/sec were 109.1743.72 watts of pre-test and 108.50+46.86 watts in control groups. experimental groups were 90.84÷29.85 watts of pre-test and 95.34÷28.53 watts of post-test. The average power at speed of 180° /sec were 186.84 106.35 watts of pre-test and 186.17+86.01 watts of post-test in control groups. The experimental groups were 150.67+60.34 watts of pre-test and 161.17+59.71 watts of post-test. 4) The average ROM were 0.89+0.01° of pre-test and 0.90+0.01° of post-test in control group. The experimental groups were 0.89+0.01° of pre-test and 0.89+0.01° of post-test.