Abstract
The purpose of this study was to examine the appearance of the bimodal force curve during a rapid voluntary movement. The subjects used in this study were five healthy males. A voluntary maximal elbow extension to visual stimulus was adopted as a rapid movement. The dynamic force required to extend the elbow was measured at the wrist with a tension transducer. The surface EMG was recorded from the triceps brachii muscle by means of small circular disc electrodes.
The mean value of occurrence of the bimodal force curve was 60% with a light load, and it had a decreasing tendency as the load increased. There was positive correlation coefficient between the rate of force drop and F'max of the bimodal force curve. It was found that the bimodal force curve was hardly affected by the change of elbow angle.
From these results, the appearance of the bimodal force curve was discussed with respect to the following;
1) The visco-elastic properties of muscle.
2) The synergy of elbow extensors.
3) The inhibitory phenomenon caused by spinal reflex.
