How Grip Changes Which Arm Muscle Works Hardest
Why a curl's grip position shifts emphasis between the biceps and brachialis.
Before this: The Arms: An Overview
You will be able to
- Explain why a supinated grip emphasizes the biceps brachii.
- Explain why a neutral grip shifts emphasis toward the brachialis.
- Match the barbell curl, hammer curl, and triceps pushdown to the muscle each emphasizes.
Two flexors, one grip-sensitive
Both the biceps brachii and brachialis flex the elbow, but only the biceps also supinates the forearm. This means:
- A supinated (palm-up) grip, as in a standard barbell curl, lets the biceps contribute both its
flexion and supination strength — emphasizing it.
- A neutral grip (palms facing each other), as in a hammer curl, removes the supination component,
shifting relatively more demand onto the brachialis.
Extension is simpler
Elbow extension doesn't have this grip-sensitivity issue — the triceps brachii is the prime mover regardless of forearm rotation, which is why triceps exercises focus more on shoulder position (overhead vs. at the side) than grip to change emphasis between its three heads.
Sources for this lesson
“The biceps brachii's supination action makes its elbow-flexion contribution grip-dependent, unlike the brachialis.”
Anatomy and Physiology 2e — OpenStax, Rice University · Ch. 11.5 Muscles of the Pectoral Girdle and Upper Limbs
Peer-reviewed textbook · License: CC BY-NC-SA 4.0 · Last checked 2026-07-19
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