With the patientís shoulder relaxed, place your fingers on the muscle on the anterior upper chest near the clavicle. Ask the patient to flex and horizontally adduct the shoulder. With unclear muscle activity in the clavicular portion of the pectoralis major, ask the patient hold against a gradually increasing attempt to produce a push on the arm in the direction of shoulder extension and horizontal abduction to resist shoulder flexor and horizontal adductor effort. Clavicular and sternal portions of the pectoralis major can be activated by alternately resisting shoulder flexion to activate the clavicular portion and then resisting extension at or greater than 90 degree of shoulder flexion to activate the sternal portion.