1) Subjects were healthy 16 adult men in this experiment. The relationship between amplitude and contraction time, and the relationship between force amplitude and EMG dwell time during ballistic force exertion by thumb adduction ware examined. The target force levels were defined at three levels, which were 10%, 30% and 50% of MVC. 2) Mean values of MVC derived from all subjects before taining weren\u27t larger than those after training. 3)The contraction time and EMG dwell time increased with force increment. These two relationships, force-contiraction time and force-EMG dwell time expressed as linear equations (regression equatio). Contraction time and EMG dwell time decreased remarkably after training under conditions of 30% and 50% of MVC. Therefore, Slopes of linear equations decreased, but y-intercepts remained the same 4) It is suggested that at a given ballistic force amplitude, the duration of neuronal output can be shortened by training. However, a certain essential unit time might be necessary to neuronal progrms of ballistic contraction, because the y-intercept of the regression equation did not changeafter training
