Increased Bicep Size
The hammer curl has you curl with a neutral wrist, which is a sturdier position since it aligns with your elbow more naturally. This slight angle change increases activation of muscles like the brachialis, brachioradialis, and short head of the biceps brachii, further enhancing grip performance and muscle building potential of the arms. (2)
The gains in arm size come from the multiple muscle groups involved: brachialis, brachioradialis, and biceps brachii (most notably the short head). All three muscles span across the lower and upper arm and act as strong elbow flexor muscles, helping bring the arm from a resting extended position to fully flexed at the elbow. (2)(3)(4) When performed properly, hammer curls add bulk to the forearms and help add inches onto your biceps — making it a top pick for bodybuilders wanting to round out their physiques on stage.
Improved Grip Strength
Most people think of hammer curls as a biceps exercise — because it mainly is — but it can help you create crushing grip strength, too. The neutral-grip position that you hold the dumbbell in recruits more of the elbow flexor muscles in your forearms along with muscles like the flexor carpi radialis and extensor carpi ulnaris. Because you’re generally stronger in a neutral-grip position, you can also use heavier weight, overloading the forearms and biceps more than using exercises like concentration curls.
Wrist Stability
The hammer curl is done with the wrist in a neutral position (palms facing each other), rather than being supinated (palms facing your face) and/or pronated (palms facing the floor). Neutral-grip movements may increase the stability and strength of the muscles surrounding the wrist, enhancing overall injury resilience of the wrist joint and surrounding tissues.
