Begins after the windup as your hands spread apart to form a T shape with your body. Simultaneously, your lead foot starts its motion towards the target you are throwing to.
Both scapulas upward rotate using using your serratus anterior muscle and middle/lower fibers of your trapezius muscle.
Abduction of both shoulder joints by concentrically contracting your supraspinatus, deltoid, and upper pectoralis major muscles.
Extension of about 170
Lead leg cause the hip to extend and abduct. Your hip extends concentrically by using your semitendinosus, semimembranosus, biceps femoris, and gluteus maximus muscles. This causes a posterior pelvic tilt. It also abducts by eccentrically contracting your gluteus medius and minimus, along with your tensor fasciae latae muscle. This causes a left lateral rotation pelvic tilt.
Lead knee starts to extend by concentrically contracting your rectus femoris, vastus intermedius, vastus lateralis, and vastus medalis. The opposite knee remains externally rotated by isometrically contracting your biceps femoris muscle.