Internal Rotation

Internal rotation, also called medial rotation, is rotation toward the body.

In pitching, internal rotation refers to the medial rotation of the arm where the axis of rotation is the length of the humerus.  During a pitch, this usually looks like forward rotation of the forearm.

The deltoid, subscapularis, teres major, latissimus dorsi, pectoralis major, and biceps brachii are muscles used for active internal rotation.

Passive internal rotation occurs as an inertial reaction during the deceleration phase of the pitch.

See also: external rotation.