| 摘要 |
PROBLEM TO BE SOLVED: To provide a ball which enables a user to make effective and original training by amplifying a characteristic load and applying this load to the fingers and arms when throwing a breaking pitch in addition to make training of the way of gripping the ball for throwing the breaking pitch. SOLUTION: Set points for the fingertips for throwing the breaking pitch are displayed on the surface of a sponge ball the core of which is formed of a metallic ball used as a weight.
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