The relationship between myoelectric signal and force was investigated. 16 healthy male volunteers performed isometric contraction of elbow flexor and extensor at 90 angle from the horizontal plane. The contracting force was measured at 20% maximal voluntary contraction(MVC), 40%MVC, 60%MVC, 80%MVC and 100%MVC. The myoelectric signal was detected from elbow flexor and extensor using monopolar surface electrodes at each force level. The recorded myoelectric amplitude, turns/mean amplitude, root mean square voltage and power. The relationship between contraction force and myoelectric signal parameters was analysed.

1) The frequency sensitive parameters, zero crossings and turns were increased abruptly with force form 0 to 20%MVC and increased gradually with force from 20 to 60%MVC, but decreased slightly with force from 60 to 100%MVC.

2) The amplitude sensitive parameters, mean amplitude and root mean square voltage were increased linearly with force from 0 to 100%MVC, and power value was increased curvilinearly with force from 0 to 100%MVC.

On the basis of this study, mean amplitude and root mean square voltage were superior to other parameters when used as descripters of contracting force in elbow flexor and extensor, and can be used as an indirect parameter of measuring force in the future.