Which muscle is primarily responsible for shoulder extension, adduction, and internal rotation during pulling movements?

• A. Pectoralis Major
• B. Latissimus Dorsi
• C. Biceps Brachii
• D. Rhomboids

Answer: (B)

Latissimus dorsi is the muscle most responsible for shoulder extension, adduction, and internal rotation during pulling movements. Its broad origin along the lower spine, thoracolumbar fascia, iliac crest, and lower ribs, with an insertion on the humerus, allows a pull that extends the shoulder from a flexed position, pulls the arm toward the body's midline, and rotates the arm inward. In pulling actions like rows or pull-downs, this muscle provides the primary force at the shoulder joint for these motions, while other muscles contribute in supporting roles. Pectoralis major can assist with adduction and internal rotation but isn’t the main extensor in pulling; biceps brachii mainly handles elbow flexion and forearm movements, with only a secondary role in shoulder actions; rhomboids stabilize and retract the scapula rather than driving the primary glenohumeral movements.