Hammer Curl

Move · Resistance Training · Movement, Typed Supps

Turning the palms to face each other takes the biceps off its strongest grip and hands work to the muscles underneath and alongside it.

Stage by stage

Set-up (Neutral forearm position): Thumbs up and wrists straight puts the forearm midway between pronation and supination for the whole set.
During the set (Torque shared three ways): The biceps loses its best flexion configuration, so brachialis and brachioradialis take a larger share of the work.
Immediately after (Forearm fatigues first): Grip and brachioradialis often give out before the upper arm, which is characteristic of this grip rather than a fault.
Weeks later (Brachialis adds thickness): Growth beneath the biceps displaces it outward, adding arm width and measured girth alongside forearm thickness.

Muscles trained

Primary: biceps, forearms

Intensity

3.5 METs (Resistance (weight) training, multiple exercises, 8-15 repetitions at varied resistance).

Time to effect

Weeks: Grip and forearm endurance improve quickly, since the forearms often fatigue before the biceps do on this grip.
Months: Visible forearm thickness and overall arm width, distinct from bicep "peak", become noticeable with consistent loading.

Related supplements

Creatine Monohydrate

Common myth

"Hammer curls only work the forearms, not the biceps." In reality: The biceps brachii stays very active in a hammer curl - it just shares the load with the brachialis and brachioradialis instead of doing nearly all the work like it does with a palm-up grip. The neutral grip shifts emphasis, it does not switch the biceps off.