The purpose of this study was to examine the validity of using movement trajectory in throwing motions to evaluate motor development among children. Forty-nine elementary school students participated in the study (15 first graders, 17 second graders and 17 third graders). The manner in which the subjects threw softballs were recorded and analyzed, then the subjects were grouped according to their throwing movement trajectory types. The movement trajectories were classified into 4 types：unimodal-circle, unimodal-elliptic, bimodal-circle, and bimodal-elliptic types. We did statistical comparisons in the throwing distance among the four groups. The correlation between the ellipse ratio and the throwing distance was also computed. It was found that throwing distance in the bimodal trajectory group was significantly longer than that of the unimodal trajectory group. There was a significant correlation between the ellipse ratio and throwing distance. Therefore, this evaluation that expected motor developmental stage from movement trajectory in throwing motion is suggested as new motor developmental evaluation. Its clinical utility was also discussed.
