Which statement best describes the actions of the biceps brachii?

Which statement best describes the actions of the biceps brachii?

• A. Flexes forearm (strongest with forearm at 90º and supinated)
• B. Flexes arm (weak)
• C. Supinates forearm (strongest supinator with forearm at 90º)
• D. All of the above

Answer: (D)

The biceps brachii crosses both the shoulder and elbow joints, so it can influence elbow flexion, shoulder flexion, and forearm supination. Its elbow-flexion action is strongest when the forearm is supinated and the elbow is around 90 degrees, because the moment arm and line of pull are optimal in that position. It also assists in shoulder flexion, but this is a weak contribution compared with primary shoulder flexors. It is also a powerful supinator of the forearm, especially when the elbow is flexed near 90 degrees, where its torque is greatest due to favorable alignment of its attachments. So all of these statements describe true actions of the biceps brachii.

The biceps brachii crosses both the shoulder and elbow joints, so it can influence elbow flexion, shoulder flexion, and forearm supination. Its elbow-flexion action is strongest when the forearm is supinated and the elbow is around 90 degrees, because the moment arm and line of pull are optimal in that position. It also assists in shoulder flexion, but this is a weak contribution compared with primary shoulder flexors. It is also a powerful supinator of the forearm, especially when the elbow is flexed near 90 degrees, where its torque is greatest due to favorable alignment of its attachments. So all of these statements describe true actions of the biceps brachii.