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The windup phase begins when the pitcher stepped back with his front foot
and positions his back foot against the rubber. The windup phase ends
when the front leg is at its maximum height and the two hands begin to
separate. During the stride phase, a pitcher moves his front foot toward
home plate as the two arms swing down and apart from each other. The stride
phase ends when the front foot touches the mound. During the arm cocking
phase, the pelvis and then upper trunk rotate to face home plate as the
throwing arm externally rotates at the shoulder. The arm cocking phase
ends when the shoulder reaches its maximum external rotation. The arm
acceleration phase was from the instant of maximum shoulder external rotation
until ball release. From ball release until the arm stops internally rotating
is defined as the arm deceleration. Follow-through begins with maximum
shoulder internal rotation and ends when the pitcher regains a balanced
position. The greatest kinetic and kinematic values occurred during the
arm cocking, acceleration, and deceleration phases, implying that these
are the phases where overuse injuries are likely to happen.
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