The difference between the dominant hand and the non-dominant hand in overarm throwing motions and ball-throwing distances were studied in student women. The subjects were divided into a trained group and an untrained group. A switch thrower, categorized in the training group, was also examined. The throwing time, moving distance and mean velocity of the ball in the overall throwing phase, back-swing phase and acceleration phase were determined by a high-speed video analysis system. Seven empirical parameters estimated from the overall throwing motion were also introduced. These physical quantities and parameters were compared between the dominant and non-dominant hands. The ball-throwing distances in the trained and untrained groups were 2.58 and 1.73 times higher for the dominant hand than for the non-dominant hand, respectively. The difference in these values for both the hands of the switch thrower, however, were very small. The throwing time, moving time, and mean ball velocity in the back-swing phase in the trained group were 1.16, 1.65 and 1.35 times higher for the dominant hand than for the non-dominant hand, respectively. These phenomena were not observed in the untrained group and the switch thrower. The mean ball velocities in the acceleration phase for the trained and untrained groups were 2.0 and 1.5 times higher for the dominant hand than for the non-dominant hand, respectively. These values were more highly correlated with the ball-throwing distance in the trained group than in the untrained group. Significant correlations between seven parameters and ball-throwing distance were all observed for the dominant hand. However, only three of these parameters showed significant correlations for the non-dominant hand. These results show that the relationship between ball-throwing distance and throwing motion is closer for the dominant hand than for the non-dominant hand. In the present paper, possible roles of the dominant and non-dominant hands in the relationship between throwing motion and ball-throwing distance are also discussed.

The change in R-R interval (RRI) induced by rapid postural change from a squat posture to standing was analyzed in 8 healthy male students (20.3±1.2 years of age) before and immediately after maximal running exercise. We instructed subjects to stand up as quickly as possible, and to repeat the standing-up movement three times at intervals of 2 min. Heart rate responses and heart rate variability were analyzed by the change in RRI induced by standing up. Heart rate (HR) increased quickly at the onset of standing up. The time (T) until the maximal HR (Hmax) was reached 9.79±1.44 s after standing up, and then the HR after Hmax decreased rapidly with time. The maximal HR was 1.20 times higher while standing up than in the squat position. Maximal running exercise significantly delayed the time taken to reach Hmax after standing up, and significantly diminished the increased HR to 1.15 times. The Hmax/Hmin ratio, which expressed the magnitude of autonomic activity during standing up, was significantly lower following maximal exercise, indicating that the cardiac sympathetic nervous system seems to be in a state of hyperfunction immediately after maximal running exercise. These findings suggest that disturbance in the postural adjustment of the cardiovascular system immediately after intense exercise may be induced by the delayed response and decreased amplitude of the HR.