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Pectoralis MajorOVERVIEW
EXAMINATION Insertion Fixed: May assist in elevating the thorax, as in forced inspiration. PECTORALIS MAJOR (CLAVICULAR PORTION) Strength Testing of Upper Fibers: Position ““ the subject in supine with shoulder in 90º flexion, slight medial rotation, and elbow flexed. Stabilize ““ against the opposite shoulder. Resist ““ against horizontal adduction of the humerus towards the opposite shoulder (in the direction of horizontal abduction). Possible Substitutions of Upper Fibers: Sternocostal fibers of pectoralis major, coracobrachialis, anterior deltoid, biceps brachii, or general trunk movement. PECTORALIS MAJOR (STERNOCOSTAL PORTION) Strength Testing of Lower Fibers: Position ““ the subject in supine with shoulder in approximately 45º flexion, slight medial rotation, and elbow flexed. Stabilize ““ against the opposite hip. Resist ““ against adduction of the arm obliquely toward the opposite iliac crest in a lateral and cranial direction. If the subject”™s abdominal muscles are weak, the trunk may need to be stabilized. Possible Substitutions of Lower Fibers: Clavicular portion of the pectoralis major, pectoralis minor, or latissimus dorsi. Relevant Anatomy:
Origin of Upper Fibers (Clavicular): Anterior surface of sternal ½ of clavicle. Insertion of Upper Fibers (Clavicular): Crest of greater tubercle of humerus. Insertions of upper fibers are more anterior and caudal on the crest than the insertion of lower fibers. Origin of Lower Fibers (Sternocostal): Anterior surface of sternum, cartilages of superior six or seven ribs, and aponeurosis of external oblique. Insertion of Lower Fibers (Sternocostal): Crest of greater tubercle of humerus. Insertions of lower fibers are more posterior and cranial than the insertion of lower fibers. |