Biomechanics of Throwing

The Shoulder is most prone to get injured whilst throwing. For better understanding the throwing process, we will divide the motion into five phases:

  1. Wind-up
  2. Cocking
  3. Acceleration
  4. Release and Deceleration
  5. Follow-through

Phases of Throwing


Wind-up Phase

This phase always precedes cocking when throwing any object, but the effect on injuries is insignificant. Proper execution of the wind-up, however, is essential to an efficient throwing performance.


Cocking Phase

This phase does not contribute significantly to injuries either. But correct cocking positions the body for maximum throwing performance. In this phase, maximum tension is applied to all the muscles used in acceleration. The cocking motion should be a smooth, well-controlled process of advancing the Shoulder and chest.


Acceleration Phase

Most throwing-related injuries occur in acceleration and deceleration. Correct execution of these phases and proper development of the arm muscles involved improve performance and lessen the chance of injury.  In acceleration, the body is brought forward, followed by the arm in a “whipping” motion.  The Shoulder is subjected to tremendous forces and stress, which must be offset by the muscles responsible for decelerating movement.  If these muscles are weak or fatigued, the Shoulder Joint becomes unstable which can cause damage.

Release and Deceleration:

Release and Deceleration Throwing

At the moment the ball is released, it has been accelerated to maximum velocity. The shoulder muscles responsible for stabilizing the joint are placed under tremendous stress. The elbow also is at risk in this phase.


Follow-through Phase

This phase allows the body to make a smooth recovery from the severe deceleration forces, reducing forces on the shoulder and tension on the rotator cuff. Understanding of these throwing phases should help a ball player apply his or her knowledge to lessen the chance of injury and improve the performance.