Abstract
We followed the records of the standing broad jump and the vertical jump continuously for 2 months (except Sunday) to the students (2 females and 3 males) who had studied physical education in the university, and found that the record of the standing broad jump enhanced but that of the vertical jump did not changed. Then they paused for 3 months and were checked again. But the records of the both jumps did not change. The electromyographes of M. rectus femoris, M. glutaeus maximus, M. biceps femoris and M. gastrocnemius were recorded at the same time and the decreasing tendency of the muscular contraction time in the both jumps was observed. Even in the same subject the activity order of the four muscles mentioned above varied considerably, and it was impossible to find that a definite pattern could be gotten by repeat of our measurement.
In the standing broad jump the record could not be changed by the adjustment of muscular coordination but generally by that of muscular strength. In the vertical jump activity order of the main muscular groups varied excessively when the jumping height was changed.
