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Unformatted text preview: 9/30/09 Biomechanics Overhand Throwing Patter Write-up 1. The majority of people were more comfortable throwing the tennis ball because it was the lightest object, but still heavy enough that the kinetic link principal applied. Therefore, I will compare the other throws to that of the tennis ball. Tennis Ball : Preparation: The ball was held in the hand as opposed to fingertips. As the throwing arm brought the ball back there was rotation and flexion of the shoulder muscles in the sagittal plane and about the frontal axis, and the elbow was extended or bent at about 45 degrees. The forearm was protonated and the wrist rotated laterally. There was also hip and trunk rotation laterally. Simultaneously, there was a step backwards with the leg of the same side as the throwing arm, shifting weight backwards (which in turn will generate more force in the vertical motion forward during execution). Execution: As the motion began, a step forward with the opposite foot to the throwing arm elongates the arc of the ball’s trajectory; therefore there is more time for an optimum release point. As there was a step forward, weight transfers to this foot, shifting the center of gravity forward. There is hip rotation medially toward the target followed by quick medial rotation of the trunk. During rotation the shoulder muscles are stretched, allowing for the stretch reflex to generate more velocity at the release. Toward the end of the trunk rotation, the throwing arm begins to move forward by turning about its long axis; the shoulder does this action by inwardly rotating the humerus. At this point the elbow is bent at about a 45 degree angle, making the lever shorter and allowing for a quicker and more forceful extension of the elbow. As the arm comes forward, the elbow joint is extended. The final link is the wrist, which is extended at the point of release. These sequential actions of the kinetic link principle allow for maximum force to be transferred to the hand (will is transferred to the ball) and therefore maximum velocity to be generated at the point of release. The point of release is about the top of the arc of the ball’s trajectory, just as the arm is moving downward. This allows for an optimal vertical component of the ball’s path. Follow through: The throwing arm continued its motion through the arc generating angular force. The opposite arm swung laterally, creating more torque, and therefore more momentum in the ball’s release. There was flexion of the hips forward causing the center of gravity to be shifted forward....
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This note was uploaded on 10/19/2009 for the course IB 125 taught by Professor Scottt during the Spring '08 term at Berkeley.
- Spring '08