The pitching experiment was undertaken in our indoor biomechanics laboratory. The pitcher's flat mound was built using 25-mm thick 1.5 × 2.5 m plywood boards firmly attached on the floor using strong dual-side adhesive tape, and rosin powder was lightly scattered on the surface of the plywood to increase friction. An official pitcher's rubber plate was screwed on top of the pitcher's mound. At the front side of the pitcher's mound, a self-built 15-mm thick force plate (0.45 × 0.75 m) covered by a rubber-non-slip sheet (1 × 1 m) was firmly attached to the floor. The vertical component ground reaction force could be measured from this force plate, which was used to detect the instant of stride foot contact. The position of the pitcher's rubber plate was adjusted for each subject so that his striding foot would land at around the center of the Force Plate. The electrical signal from the force plate was amplified using a strain gauge amplifier (model: DMP-612A, Kyowa Co., Japan). Electrical signals from the amplifiers of the force transducer and force plate were stored on a personal computer via a 12-bit A/D converter sampling at a frequency of 1 kHz for each channel. ...
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