What is the prime mover for Shoulder Horizontal Adduction?

What is the prime mover for Shoulder Horizontal Adduction?

• A. Pectoralis Major
• B. Pectoralis Minor
• C. Deltoid
• D. Latissimus Dorsi

Answer: (A)

Shoulder horizontal adduction means bringing the upper arm across the front of the body. The muscle that does this most effectively is the pectoralis major. Its fibers span the front of the chest and attach to the humerus, so when it contracts, it pulls the arm toward the midline across the chest, creating that across-the-body motion. Both heads contribute to this action, with the clavicular part more involved in flexion and the sternocostal part helping drive the arm inward as it moves from an abducted position. Other muscles in the region don’t move the upper arm in that cross-body path as the primary driver. Pectoralis minor mainly stabilizes the scapula rather than moving the arm. The deltoid can assist in shoulder movements, especially its anterior portion during flexion, but it is not the primary horizontal adductor. Latissimus dorsi acts more as a powerful extensor and internal rotator and adductor in different planes, so it’s not the prime mover for this specific action.

Shoulder horizontal adduction means bringing the upper arm across the front of the body. The muscle that does this most effectively is the pectoralis major. Its fibers span the front of the chest and attach to the humerus, so when it contracts, it pulls the arm toward the midline across the chest, creating that across-the-body motion. Both heads contribute to this action, with the clavicular part more involved in flexion and the sternocostal part helping drive the arm inward as it moves from an abducted position.

Other muscles in the region don’t move the upper arm in that cross-body path as the primary driver. Pectoralis minor mainly stabilizes the scapula rather than moving the arm. The deltoid can assist in shoulder movements, especially its anterior portion during flexion, but it is not the primary horizontal adductor. Latissimus dorsi acts more as a powerful extensor and internal rotator and adductor in different planes, so it’s not the prime mover for this specific action.