The primary goal in the windup phase is to set a rhythm that correlates the timing of body parts and to prepare/build kinetic energy (1). The windup phase begins with the initiation of leg movement. At the beginning of the windup phase, the throwing hand and the glove hand are together and in proximity to the body's midline, anywhere from the waist to the head while taking a step back using the leg on the non-glove side. This leg is also used as the stride leg and the contrary leg is used as the support leg. When the weight is transferred, the body rotates 90 degrees while the stride leg tightens at the hip and knee so that the pelvis rotates towards the throwing arm (11). The body winds up so that all components of the body, from the leg to the arms, are able to contribute to the ball's driving force. Energy expenditure, force generated, and speed are a relatively at low levels. Even though the windup phase doesn't contribute to the balls driving force, it is important so that each phase following is achieved. A bad windup can contribute to poor balance at maximum lead knee height secondary to reduced lower extremity strength and trunk control, premature forward movement towards home plate before reaching the balance point, tilting the center of gravity posteriorly, and a high hand placement with shoulder in greater than 900 of abduction (5). .
The transition to the cocking phase begins when the hands separate and ends when abduction and maximum lateral rotation of the shoulder is reached (3). The cocking phase is divided into two phases, early cocking and late cocking. These two phases come into affect depending on the time at which the forward foot makes contact with the ground. In the early cocking phase, the scapula is pulled back and the humerus is abducted, laterally rotated, and horizontally extended (5). The stride leg then starts to extend the knee, abduct, medially rotate, and extend the hip.
