Which muscle mass prevents shoulder flexion in the stay apparatus?

Which muscle mass prevents shoulder flexion in the stay apparatus?

• A. Triceps
• B. Biceps
• C. Pectoralis major
• D. Deltoid

Answer: (A)

In the stay apparatus, the goal is to keep the limb in an extended, weight-bearing position with minimal muscular effort. The muscle mass that best prevents shoulder flexion is the triceps brachii, especially its long head, which crosses the shoulder joint. When the elbow is fixed in extension to bear weight, the long head of the triceps remains taut and acts to extend the shoulder as well, resisting any tendency of the shoulder to flex. This helps lock the limb in a straight line for standing. The other muscles listed mainly influence shoulder movement in different ways (for example, the biceps brachii flexes the elbow and can assist shoulder flexion, while the deltoid and pectoralis major contribute to other shoulder actions) and do not serve the same stabilizing role in the stay mechanism.

In the stay apparatus, the goal is to keep the limb in an extended, weight-bearing position with minimal muscular effort. The muscle mass that best prevents shoulder flexion is the triceps brachii, especially its long head, which crosses the shoulder joint. When the elbow is fixed in extension to bear weight, the long head of the triceps remains taut and acts to extend the shoulder as well, resisting any tendency of the shoulder to flex. This helps lock the limb in a straight line for standing. The other muscles listed mainly influence shoulder movement in different ways (for example, the biceps brachii flexes the elbow and can assist shoulder flexion, while the deltoid and pectoralis major contribute to other shoulder actions) and do not serve the same stabilizing role in the stay mechanism.