Which muscle is the prime mover for scapular protraction, with assistance from pectoralis minor?

Which muscle is the prime mover for scapular protraction, with assistance from pectoralis minor?

• A. Deltoid
• B. Pectoralis minor
• C. Middle trapezius
• D. Serratus anterior

Answer: (D)

Scapular protraction is produced most effectively by the serratus anterior. Its fibers run from the ribs to the anterior surface of the medial border of the scapula, so when it contracts it pulls the scapula forward along the rib cage, pushing the medial border away from the spine. This is exactly the movement called protraction and is essential during pushing actions. Pectoralis minor can assist by pulling the scapula forward and downward, but its line of pull is less favorable for creating full protraction, so it acts as a stabilizing helper rather than the main driver. The deltoid mainly moves the arm, and the middle trapezius retracts the scapula, which is the opposite direction of protraction. Hence, serratus anterior is the primary muscle for scapular protraction, with assistance from pectoralis minor.

Scapular protraction is produced most effectively by the serratus anterior. Its fibers run from the ribs to the anterior surface of the medial border of the scapula, so when it contracts it pulls the scapula forward along the rib cage, pushing the medial border away from the spine. This is exactly the movement called protraction and is essential during pushing actions.

Pectoralis minor can assist by pulling the scapula forward and downward, but its line of pull is less favorable for creating full protraction, so it acts as a stabilizing helper rather than the main driver. The deltoid mainly moves the arm, and the middle trapezius retracts the scapula, which is the opposite direction of protraction. Hence, serratus anterior is the primary muscle for scapular protraction, with assistance from pectoralis minor.