Acceleration

Phase 4

Acceleration-This is the phase in which you bring your arm forward and release the ball at the target.

Shoulder Girdle
With your throwing shoulder, the scapula protracts using the serratus anterior muscle and pectoralis minor muscle.
The scapula of your glove hand retraction using your rhomboid muscles and the middle/lower fibers of the trapezius muscle.

Shoulder Joint
Throwing Hand- Diagonally adducts shoulder joint by concentrically contracting your pectoralis major, anterior deltoid, and coracobrachialis muscles.
Glove Hand- Shoulder joint stays in adduction by eccentrically contracting your latissimus dorsi, teres major, and lower pectoralis major muscles.

Elbow Joint
Your glove hand elbow by concentrically contracting both heads of the biceps brachii, brachialis, and brachioradialis muscles. Your throwing hand forearm also stays slightly supinated by concentrically contracting the biceps brachii, brachioradialis, and supinator muscles.

Hip Joint
Non throwing foot causes the hip to stay externally rotated by eccentrically contracting your piriformis, gemellus superior and inferior, obturator internus and externus, and quadratus femoris muscles.
Opposite side of your hip stays internally rotated by concentrically contracting your gracilis, semitendinosus, and semimembranosus muscles.

Knee Joint
Non throwing knee remains slightly flexed by concetrically contracting your biceps femoris, popliteus, semimembranosus and semitendinosus.
TThrowing knee remains internally rotated by isometrically contracting your popliteus, semimembranosus and semitendinosus muscles.