Analysis Version
v1
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assertion
Analysis v1
Supported

To make your forearm muscle bigger, you need to curl with your palm facing inward, not up.

34
Pro
26
Against

Evidence from Studies

Supporting (1)

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Community contributions welcome

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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

Cross-Sectional Study
Human
2025 Jul 2

When you lift something with your palm facing sideways (neutral grip), your brachioradialis muscle works harder than when your palm is facing up (supinated grip), and this study proved it by measuring muscle activity.

Contradicting (2)

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Community contributions welcome

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The function of brachioradialis.

Cross-Sectional Study
Human
2008 Dec

The study found that the brachioradialis muscle works just as hard whether your palm is up, down, or sideways during elbow bending — so it doesn’t prefer the hammer grip like the claim says.

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Muscular coordination of biceps brachii and brachioradialis in elbow flexion with respect to hand position

Cross-Sectional Study
Human
2015

The study found that when you hold your hand like you're holding a hammer (neutral), your forearm muscle doesn't work harder than when your palm is facing up — in fact, it works the most when your palm is facing down.

Similar Assertions

No matter how you turn your hand while bending your elbow, the brachioradialis muscle works about the same amount.

26
0
90%

When your palm faces down and you bend your elbow, your forearm muscle (brachioradialis) works harder than when your palm faces up or straight ahead — but your bicep works the same no matter how your hand is turned.

26
0
87%

When your palm is facing down and you bend your elbow slightly, your forearm muscle (brachioradialis) works harder than when your palm is up — it’s like your body uses this muscle more to help when your hand is in a 'handshake' position.

34
0
84%

When you bend your elbow by lifting something, the brachioradialis muscle works much harder pushing up than it does lowering the weight slowly.

26
0
84%

When you bend your elbow and twist your forearm at the same time, your biceps work harder, but the muscles on the side of your arm work less — your body doesn’t just turn muscles on or off the same way every time.

21
0
83%

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