Effect of ball size and weight on throwing distance and initial release conditions for long throws by fifth-grade elementary school students

In this study, fifth-grade elementary school students were asked to throw a softball size 1 (Soft), a handball size 0 (Hand), and a handball size 0 of similar weight to the softball (Red), and the effects of using these three different combinations of ball size and weight on throwing distance and release conditions were examined.Participants were 63 fifthgrade elementary school students (29 boys and 34 girls), who threw the three different types of balls two times each.The throwing motion was recorded at 120 fps using two digital cameras, and the ball's landing point was measured.Variables such as initial velocity, release angle, and release height were calculated for each throw, and the theoretical throwing distance without the effect of air was calculated, as were the imparted velocity, stroke distance and time, ball momentum, and force applied to the ball from grounding of the foot on the throwing side to ball release.The analysis results showed that the effect of air after release was small for all three types of balls, and that the initial velocity was largely reflected in the throwing distance.The effect of the different balls on release height was negligible, while that the release angle may have been affected by the difference in ball weight, which affects the vertical component of the initial velocity vector.Furthermore, the imparted velocity increased in the order of Soft, Red, and Hand, but the momentum and force applied to the ball were greater for Soft than for Red, and greater for Hand than for Soft and Red.The smaller imparted velocity for Red than for Soft may be due to the smaller force applied to the ball, while the considerably larger momentum and force applied to Hand than to Soft and Red may be due to the greater weight of Hand compared with the other balls.Comparing the long throws of Soft to those of Hand and Red for each subject, the throwing distance decreased for both Hand and Red compared to Soft.However, when the large and heavy Hand was used, the main factor was the lower initial velocity, and when the large-sized Red was used, not only the lower initial velocity but also the release angle was considered to affect the throwing distance.In the long throw by these students, the degree of each variable's influence at release, which contributes to the throwing distance, appears to differ depending on the size and weight of the ball used.