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Sachi Ikudome, Kou Kou, Kisho Ogasa, Shiro Mori and Hiroki Nakamoto

This study examines whether the positive effect of choice on motor learning in a dart-throwing task varies by intrinsic motivation. Participants were allocated to a highly motivated or less-motivated group based on measured task motivation and randomly to a Choice or No Choice group. In Experiment 1, participants in the Choice group chose their dart color. In Experiment 2, they chose when to observe a model demonstration. Results showed that the effect of choice on motor learning differed between highly and less-motivated participants in Experiment 1 (i.e., interaction between motivation and choice) but not Experiment 2 (i.e., main effects of motivation and choice). Specifically, motor learning was enhanced in less-motivated but not highly motivated participants when choosing dart color, while it was enhanced regardless of initial intrinsic motivation when choosing model-demonstration time. Therefore, external provision of choice in a motor-learning situation may not be equally effective across learners.

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Toshimasa Yanai, Akifumi Matsuo, Akira Maeda, Hiroki Nakamoto, Mirai Mizutani, Hiroaki Kanehisa and Tetsuo Fukunaga

We developed a force measurement system in a soil-filled mound for measuring ground reaction forces (GRFs) acting on baseball pitchers and examined the reliability and validity of kinetic and kinematic parameters determined from the GRFs. Three soil-filled trays of dimensions that satisfied the official baseball rules were fixed onto 3 force platforms. Eight collegiate pitchers wearing baseball shoes with metal cleats were asked to throw 5 fastballs with maximum effort from the mound toward a catcher. The reliability of each parameter was determined for each subject as the coefficient of variation across the 5 pitches. The validity of the measurements was tested by comparing the outcomes either with the true values or the corresponding values computed from a motion capture system. The coefficients of variation in the repeated measurements of the peak forces ranged from 0.00 to 0.17, and were smaller for the pivot foot than the stride foot. The mean absolute errors in the impulses determined over the entire duration of pitching motion were 5.3 N˙s, 1.9 N˙s, and 8.2 N˙s for the X-, Y-, and Z-directions, respectively. These results suggest that the present method is reliable and valid for determining selected kinetic and kinematic parameters for analyzing pitching performance.