Why Standard Bicep Curls Might Be Leaving Your Forearm Gains Behind
By Maya Lin-Takahashi
The brachioradialis is the thick muscular band sitting on the top lateral side of your forearm. It gives the lower arm its athletic, dense appearance from the front. Crucially, the brachioradialis does not cross the wrist joint; it originates on the lateral supracondylar ridge of the humerus and inserts into the distal radius. Its sole job is flexing the elbow.
When you supinate your wrist, the radius and ulna lie parallel, giving the biceps brachii supreme mechanical advantage and diminishing the workload of the brachioradialis. When you shift your hands into a neutral grip dumbbell curl, palms facing each other, the radius crosses over the ulna. This subtle twist puts the biceps at a severe mechanical disadvantage, neutralizing its ability to supinate.
The nervous system compensates by recruiting the brachioradialis and the underlying brachialis muscle growth to complete elbow flexion. In a debate between hammer curls vs supinated curls, hammer curls generate dramatically higher electromyographic (EMG) activity across the brachioradialis. If lower-arm development lags, running underhand curls set after set simply repeats the wrong movement pattern.
Maya is a hardware enthusiast who tests and reviews smart home devices, smartphones, wearables, and audio gear. She focuses on practical consumer value and build quality.
