Which muscle group is primarily responsible for lifting the arm away from the body (abduction)?

• A. Pecs
• B. Traps
• C. Deltoid
• D. Abs

Answer: (C)

Abduction is the movement of lifting the arm out to the side away from the body at the shoulder joint. The deltoid muscle, especially its middle fibers, is the primary mover for this action, pulling the humerus outward to raise the arm. At the very start, the supraspinatus helps initiate abduction for the first about 15 degrees, then the deltoid takes over as the main driver as you lift higher. To allow the full range of motion, the scapula must rotate upward, a role supported by the trapezius and serratus anterior, which enables the arm to rise overhead. The pectoralis major would generally bring the arm toward the midline or across the chest, not away from the body, and the abdominal muscles don’t move the arm at the shoulder. So the deltoid is the best answer for lifting the arm away from the body.