How is serratus anterior strength tested via MMT?

• A. Retract scapula against resistance; palpate along lateral border
• B. Depress scapula against resistance; palpate spine
• C. Protract scapula against resistance with thorax stabilization; palpate along medial border
• D. Elevate scapula against resistance; palpate acromion

Answer: (C)

Serratus anterior strength is tested by provoking scapular protraction while isolating the muscle from other movers. The best way to do this is to have the patient push the scapula forward (protraction) against resistance, while you stabilize the thorax to prevent the shoulder girdle from compensating with other muscles. Palpation along the medial border of the scapula is ideal because the serratus anterior runs along that border and its contraction pulls the scapula forward and hugs the medial border to the rib cage. If the muscle is functioning well, you’ll feel a distinct serratus contraction as the medial border tightens and the scapula protracts. Substitutions from other muscles (like the trapezius or pectoralis minor) are minimized by thorax stabilization, which keeps the movement focused on protraction. Options that involve retracting, depressing, or elevating the scapula don’t test the serratus anterior’s primary action, which is protraction.