Some muscles of the chest assist with breathing while others assist with shoulder movements. Which of the following groups best represents muscles that assist with shoulder movements?

• A. Internal Oblique, Teres, Pectoral
• B. Intercostal, Serratus
• C. Serratus, Pectoral, Teres
• D. Serratus, Pectoral

Answer: (C)

The idea being tested is which chest-region muscles contribute to moving the shoulder, not just breathing. Serratus anterior, pectoralis major, and teres (major) all play direct roles in shoulder movement. Serratus anterior helps stabilize and protract the scapula, enabling the arm to reach outward. Pectoralis major powers movements of the upper arm such as flexion, adduction, and internal rotation. Teres major assists with shoulder adduction, internal rotation, and extension of the arm. Together, these three muscles coordinate movements of the shoulder joint and upper arm.

Other options mix in muscles whose primary job isn’t moving the shoulder. Intercostal muscles are mainly for breathing, and the internal oblique is a trunk/core muscle, not a shoulder mover. A group with only serratus and pectoral omits a key shoulder mover, and a group including an intercostal pairs breathing with shoulder work but doesn’t consistently represent muscles that move the shoulder. So the trio that includes serratus, pectoral, and teres best represents muscles that assist with shoulder movements.