What is the primary action of the brachioradialis?

• A. Elbow extension
• B. Forearm pronation
• C. Elbow flexion with the forearm in neutral
• D. Wrist flexion

Answer: (C)

The brachioradialis functions mainly as an elbow flexor, and it is most effective when the forearm is in a neutral position (neither fully pronated nor fully supinated). Its path crosses the elbow in a way that, with the forearm neutral, its line of pull best aligns with the elbow’s bending action, giving its largest moment arm and strongest flexion torque. When the forearm is pronated, or especially when it’s supinated, other elbow flexors (like brachialis and biceps depending on the rotation) take on more of the work, so brachioradialis isn’t the primary contributor in those positions. It does not cause forearm pronation and it isn’t primarily a wrist flexor, so its main action remains elbow flexion with the forearm neutral.