| 摘要 |
PURPOSE: A self-exercisable baseball is provided to allow beginners to recognize gripping techniques with respect to the surface of the baseball and to improve the convenience of exercise. CONSTITUTION: Various gripping positions(1, 2, 3, 4, 5) are drawn on the surface of a baseball. The brightness of the drawing is varied according to the color of the baseball and to the gripping force of a user. The user is allowed to exercise various pitching techniques based on the drawn gripping positions.
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