Phases of Throwing There are 5 main phases of throwing wind up (see below) cocking acceleration deceleration follow-through Biomechanics scapula must work in concert with humerus to maintain glenohumeral stability the entire throwing motion takes approximately 2 seconds with wind up and acceleration phases taking approximately 75% of time (1.5 seconds) 1. Wind Up Description minimal force on the shoulder during first stage Muscle activity rotator cuff muscles are inactive during this phase 2. Cocking Sometimes described as 2 sub-phases early cocking peak muscle activation deltoid late cocking high torque phase with maximal shoulder external rotation most likely to cause internal shoulder impingement elbow valgus stress is greatest in late cocking phase peak muscle activation supraspinatus infraspinatus teres minor FDS and FCU muscles provide local dynamic stability of the elbow during late cocking protective against injury to UCL Associated pathology Medial ulnar collateral ligament elbow injury internal Impingement GIRD (glenohumeral internal rotation defect) SLAP tears ("Peel-back" mechanism during late cocking) 3. Acceleration Description rotates ball to release point Muscle activity early muscle activation triceps late muscle activation pectoralis major latissimus dorsi serratus anterior 4. Deceleration Description center of gravity moves over plantar foot Muscle activity eccentric contraction of all muscles is required to slow down arm motion highest torque phase Associated pathology recognized as the most harmful phase of throwing associated injuries superior labrum (SLAP lesion) biceps tendon injury brachialis injury teres minor injury 5. Follow-through Description phase where body rebalances and stops forward motion Muscle activity muscle activity returns to resting levels