Throwing Biomechanics

Original Editor - Vinit Kothekar

Top Contributors - Vinit Kothekar, Vidya Acharya, Kim Jackson, Olajumoke Ogunleye, Naomi O'Reilly, Wanda van Niekerk, 127.0.0.1, Rachael Lowe, WikiSysop and Claire Knott

Introduction

Baseball pitching is one of the most intensely studying athletic motion. Although focus has been more on shoulder, entire body movement is required to perform a baseball pitching. Throwing is also considered one of the fastest human motions performed, and maximum humeral internal rotation velocity reaches about 7000 to 7500^o/second.

Phases of Pitching

Overhead baseball pitching has been divided into four, five or six phases depending on the investigator studying the motion. But most commonly five phases of overhead baseball pitching has been identified. (1) windup, (2) cocking, (3) acceleration, (4) deceleration and (5) follow through.

Windup

• The pitcher is facing the batter with the baseball concealed away from the batter and in the glove, and both the feet in contact of the ground. This is known as the windup stance.
• For a right handed pitcher, throwing arm is right arm, gloved hand is left, lead/stride leg is left lower extremity and pivot/stance leg is right.
• The phase of windup begins with the initiation of the stride leg and ends when the ball separates from the glove4 and the stride leg reaches highest point.
• The ipsilateral leg and trunk rotation approximately 90o and contralateral hip and knee flex.
• During windup phase the energy is transferred from stride leg to pivot leg and winding up of the stride leg occurs. It is an important phase which is responsible for imparting the velocity which is driven to the point of ball release. It is reported that about 50% of the velocity of the ball during overhead throw is generated from step and body rotation. The body’s overall center of gravity is raised and minimal stress is imparted on shoulder during this phase.
• The purpose of windup is threefold, (1) to establish a rhythm to achieve correct timing for subsequent movements, (2) to conceal the ball and distract the hitter and (3) to place the body in a position that may contribute to the propulsion of the ball.
  

Cocking

Cocking phase is further divided into (a) early cocking and (b) late cocking.

Early cocking phase

• It begins with end of windup phase or when the stride leg reaches its maximum height and it ends when the stride leg contacts the mound/ground.
• During an ideal pitch, at this point the throwing arm is in ‘semi-cocked’ position. With arm approximately in 90^o abduction, 30^o horizontal abduction, and 50^o external rotation.
• As the ball is removed from the glove, the center of gravity is lowered by flexing the knee of pivot leg and the stride leg gradually extends and move towards the batter.
• Its main function is to allow a linear and angular motion of the trunk, which lands directly in front of the pivot leg with toes pointing slightly in. Knee and hip of the pivot leg extend and initiate pelvic rotation and forward tilting followed by upper torso rotation.

Late Cocking phase

• This phase begins from the point stride leg contacts the ground to the point of maximum external rotation of throwing arm.
• During this phase, the trunk is perpendicular to the batter and upper extremity position is finalized. The pelvis reaches its maximum rotation and upper torso continues to rotate and tilt forward and laterally.
• Shoulder is abducted about 90^o, 10^o to 20^o horizontally adducted and laterally rotates to about 175^o. Wrist is in neutral and elbow is elevated about shoulder height and is 90^o flexed.
• During this phase, a varus torque of about 64 N-m is generated at the elbow and about 67 N-m internal rotation torque is generated at the shoulder. Scapula is elevated and upwardly rotated which provides adequate subacromial space to avoid impingement.