This is a study on the nature of the extensor and flexor muscles by the leg extention and leg curl exercise. The strength of the static muscles were measured with the "Tremax system" and for the strength of the dynamic muscles the "ADR" was used. Measuring the strength of the extensor muscles at bar no.1 to 4 of the Tremax System，it comes to a maximum at bar no.2 (extention 60°) but it declines radically when approaching extention 0°. Compared to the extensor muscles, the flexor muscules showed relatively small differences between bar no.5 to 8. The maximum of the flexor muscles is at bar no.6 (flection 30°). These results are almost identical with the 30 RPM strength curve of the Cybex-Machine. Therefore it is possible to conclude that static training as well as resistance training for rehabilitation will be as effective as that of the Cybex-machine. I compared the data of leg curl exercise among individuals using six testees. The difference of the strength of the static muscule group measured with the Tremax System is large，while those of the dinamic muscle group measured with the ADR remain comperatively small.