Which of the following actions is not performed concentrically by the trapezius muscle?

• A. Retraction of the scapula
• B. Protraction of the scapula
• C. Depression of the scapula
• D. Elevation of the scapula

Answer: (B)

Verified step by step guidance

1. Understand the function of the trapezius muscle: The trapezius is a large, triangular muscle located in the upper back. It is responsible for moving, rotating, and stabilizing the scapula (shoulder blade) and extending the neck.
2. Identify the actions performed by the trapezius muscle: The trapezius muscle can perform several actions, including elevation (lifting the scapula), retraction (pulling the scapula towards the spine), and depression (lowering the scapula).
3. Recognize the term 'concentrically': In muscle physiology, a concentric contraction occurs when a muscle shortens as it exerts force. This is typically the action performed when a muscle is actively moving a part of the body.
4. Evaluate the given actions: Retraction, depression, and elevation of the scapula are actions that the trapezius muscle can perform concentrically. Protraction, however, involves moving the scapula away from the spine, which is not a function of the trapezius.
5. Conclude which action is not performed concentrically by the trapezius: Since protraction of the scapula is not an action that the trapezius muscle performs, it is the correct answer to the question.