Why your hammer grip feels different than a bicep curl
Forearm rotation and elbow angle differentially modulate biceps brachii and brachioradialis muscle stiffness and EMG activity during low-load isometric contractions: a cross-sectional study in healthy individuals
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Surprising Findings
Brachioradialis stiffness decreases steadily as you bend your elbow — no matter your grip.
Most assume muscles get stiffer when contracted, but this shows the brachioradialis behaves like a spring that loosens with flexion — contradicting assumptions about muscle-tendon behavior during movement.
Practical Takeaways
Use supinated curls (palms up) to maximize bicep growth at 60° elbow angle; use pronated curls (hammer grip) to target forearm strength at 90°–120°.
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Surprising Findings
Brachioradialis stiffness decreases steadily as you bend your elbow — no matter your grip.
Most assume muscles get stiffer when contracted, but this shows the brachioradialis behaves like a spring that loosens with flexion — contradicting assumptions about muscle-tendon behavior during movement.
Practical Takeaways
Use supinated curls (palms up) to maximize bicep growth at 60° elbow angle; use pronated curls (hammer grip) to target forearm strength at 90°–120°.
Publication
Journal
BMC Sports Science, Medicine and Rehabilitation
Year
2025
Authors
Yiming Chen, Shujuan Huang, Peifeng Shen, Yuanchao Li, Yanan He, Guotong Dong, Siqi Huang, Meixia Zou, Zhijie Zhang, Chunlong Liu
Related Content
Claims (10)
Your bicep gets stiffer as you bend your elbow — but only if your palm is up or sideways. If your palm is down, it gets looser the more you bend.
How stiff your bicep feels when you bend your elbow depends on both how bent your elbow is and which way your palm is facing — but how hard your brain tells your bicep to work doesn’t change as much with that combination.
Even when you're not trying to bend your elbow, the muscle on the outside of your forearm feels stiffer if your palm is facing up than if it's facing down or straight ahead.
When your palm is facing down and you bend your elbow with a light weight, the muscle on the outside of your forearm works harder than when your palm is up.
Your bicep works best at different elbow angles depending on whether your palm is up, down, or straight — it’s strongest at 45° if your palm is down, and 60° if it’s up.