Hammer Curls: Benefits, Muscles Worked, and More

For lifters seeking larger, stronger arms, there are few exercises as effective as the hammer curl - a novice-friendly and rather simple exercise best known for its effectiveness at training the biceps muscles, among others.

However, before jumping the gun and throwing this classic arm exercise into your routine, it’s a good idea to better familiarize yourself with the benefits and salient points of performing hammer curls.

Hammer curls are a dumbbell-based compound exercise best known for inducing strength and hypertrophy developments in the forearms and biceps. 

While they are most often compared to bicep curls due to the similarity in technique, they are in fact distinctly different exercises with each holding their own respective roles within a workout.

What are Hammer Curls?

In more technical terms, hammer curls are a single joint compound exercise performed with dumbbells for the purposes of inducing light to moderate stimulus on the “pull” muscles of the arms.

They are often performed with a low amount of weight and moderate amount of repetition volume so as to allow for slower, more controlled repetitions. 

Many lifters consider hammer curls to be simply another bicep curl variation, despite the fact that hammer curls utilize an additional muscle group that most bicep curl variations do not.

Who Should Do Hammer Curls?

Hammer curls are an excellent movement for practically any type of lifter, though they are most often seen in bodybuilding programs due to their capacity to build the thickness of the upper arm via targeted brachialis recruitment.

Equipment Used

Hammer curls require a pair of dumbbells, though may be performed with other weighted fitness implements like kettlebells or specially-shaped hammer curl barbells.

How to Perform a Hammer Curl

To perform a hammer curl, the lifter will stand with the dumbbells held at their sides, core contracted and shoulders squared so as to avoid additional momentum being added to the exercise.

Then, squeezing the biceps and forearms, they will keep the palms facing each other as they draw the weights upwards, bending the elbow as the dumbbells approach the shoulders.

The wrists must remain in-line with the forearm, and the upper arms must remain stationary as they do this.

At the apex of the repetition, the lifter will squeeze the biceps for a moment before slowly returning the dumbbells to their original position at their sides.

What Muscles Do Hammer Curls Work?

The hammer curls primarily work two main muscle groups; the biceps brachii along the front of the upper arm, as well as the brachialis-brachioradialis chain that aids in elbow flexion.

Unlike other curl exercises, the inclusion of the brachialis and brachioradialis means that not only are the biceps targeted by the movement, but also the larger parts of the forearm, as well as a muscle group that is seldom recruited along the outer side of the upper arms.

With a muscular activation pattern spanning nearly the entire length of the outer arm, it can be quite obvious why the hammer curl is seen as an excellent arm-thickness builder.

What are the Benefits of Hammer Curls?

Not only are hammer curls known for being excellent arm builders, but they also present several other benefits that may come in quite useful if your goals aren’t constrained solely to achieving muscular hypertrophy.

Physical Development of Biceps and Forearms

Hammer curls are particularly useful as they are one of the few exercises that directly work the brachialis and brachioradialis, two muscles that greatly contribute to the grip strength of the forearm and the general appearance of width through the entire arm itself.

Whereas regular curl exercises will primarily work the short head of the bicep, the hammer curl targets the longer head of the bicep alongside the aforementioned muscle groups - thereby making it arguably more effective an arm builder than the conventional bicep curl.

Reinforcement of Elbow Flexion Mechanic

The biceps brachii, brachialis and brachioradialis are all known as “elbow flexor muscles” meaning that they directly contribute to the act of the forearm moving towards the upper arm, such as one would do while performing a curl exercise.

Though this movement sees limited use in regular day-to-day life, it is quite frequently utilized in athletic activities and weightlifting, meaning that the reinforcement of this biomechanic from hammer curls is absolutely essential for exercisers of all kinds.

Natural Movement Pattern

A common complaint among lifters that perform supinated grip exercises is pain along the forearm or wrists. Whether due to inflexibility of the tendons therein or issues in form, such pain is often an obstacle that many lifters have to overcome or otherwise avoid during training.

Fortunately, the hammer curl’s far more natural movement pattern negates this entirely.

The neutral grip form, positioning of the elbow in relation to the humerus and angle of resistance all create a movement that is unlikely to result in the safe sort of discomfort as exercises like the barbell bicep curl or chin-up.

Easy to Program, Easy to Perform

Due to the simplicity and relatively low amount of weight needed to perform hammer curls, it is both easy to fit into a weightlifting program as well as relatively easy to master. 

Not only does this greatly reduce the amount of calculation needed to work it into a training plan, but it also makes the hammer curl excellent for novices who are as of yet unfamiliar with the general principles of proper exercise mechanics.

How are Hammer Curls Programmed?

Hammer curls are comparatively easy to fit into a training program, as they are quite low impact and are not meant to be performed with a significant amount of weight.

Programming Weight and Volume

In terms of sets and reps, hammer curls are often performed for 2-4 sets of 8-12 repetitions, though individuals seeking even more volume may bump up the number of repetitions as high as 16.

When programming for weight, lifters will often use slightly more than their conventional bicep curl working weight, or otherwise enough to leave “one in the tank” despite the high number of repetitions per set.

Placement in Exercise Order

Hammer curls, like other low-weight curl exercises, are best performed near the end of a workout after heavier compound exercises have already been completed.

This is simply to avoid prematurely fatiguing the smaller muscle groups of the arms, of which could lead to injury or poor performance if the exercise is placed prior to a major lift.

Common Hammer Curl Mistakes

Despite the simplicity of the hammer curl, there are several common mistakes that are best avoided so as to maximize the efficiency of the exercise.

Swinging the Torso or Moving the Upper Arms

Regardless of whether it is with the hammer curl or any other curl exercise, swinging the upper body, moving the upper arms or otherwise “cheating” the movement by making use of additional momentum is a very common mistake.

Not only does adding momentum to the exercise increase the lifter’s risk of injury, but it will also reduce the actual involvement of the biceps and forearms, defeating the entire purpose of the exercise.

Detaching Elbows From the Sides

While some amount of movement of the elbows is needed in order to raise the dumbbell, entirely detaching the elbows from the sides of the torso and allowing them to float freely can place unneeded activation on other muscles of the body, taking the focus away from the biceps and forearms.

As much as possible, it is best to keep the elbows against the sides of the upper body, and to ensure that they never pass beyond the abdomen.

Rotating the Wrists into a Bicep Curl

Whether subconsciously or not, lifters performing the hammer curl with excessive weight may accidentally rotate the wrists out of a neutral rotation, turning the exercise into a bicep curl instead.

Not only does this place excessive torque and force on the wrists, but it will also eliminate the brachioradialis from the exercise, meaning that this particular mistake should be avoided.

Rushing the Movement

Like many other exercises, performing the hammer curl in too rapid a fashion can lead to a greater risk of injury, as well as reduce the time in which the muscles are placed under tension - the latter being considered quite important for muscular hypertrophy.

For the best results from regular hammer curl performance, every repetition should be performed slowly and in a controlled manner.

Insufficient Range of Motion

Often a sign of poor mobility or excessive weight being used, being unable to complete the full range of motion of the hammer curl is another common mistake that should be avoided as much as possible.

The dumbbell should move from its resting point next to the thighs all the way up to near shoulder-elevation, otherwise nearly the full range of motion of the elbow joint in most healthy individuals.

If the lifter is having trouble achieving this, the inclusion of an arm-focused mobility drill and a reduction in the weight of the dumbbells should easily fix the issue.

Hammer Curl Variations

In case you’ve already tried out hammer curls and want something new, here are a few variations that are based on the conventional hammer curl’s movement pattern.

1. Incline Hammer Curls

For lifters seeking a larger range of motion than what a standing hammer curl can allow, performing the exercise while lying on an incline exercise bench can allow for a vertically wider movement to occur - targeting the biceps to a greater degree and also eliminating the risk of upper body swinging.

2. Cross-Body Hammer Curls

In case the conventional hammer curl’s recruitment of the brachioradialis and brachialis is insufficient, performing cross-body hammer curls where the dumbbell is drawn towards the midline of the body may be of help.

Not only does this exercise improve activation of these often-forgotten muscle groups, but it also forces the lifter to perform the movement in an alternating fashion, creating more quality repetitions and a longer time under tension.

3. Alternating Hammer Curls

Alternating hammer curls are simply a hammer curl variation that alters the tempo of the exercise, with the lifter performing the movement with one arm at a time so as to improve their focus on each individual muscle group.

This can effectively lengthen the time under tension for both arms, improving muscular hypertrophy and reinforcing the mind-muscle connection to the biceps and forearms.

4. Machine or Resistance Band Hammer Curls

For lifters who wish to maintain a constant time under tension throughout each repetition, performing hammer curls with the use of a cable machine or resistance band is the ideal choice.

Not only will doing so improve the hypertrophic response of the biceps and forearms, but it will also reduce involvement of stabilizer muscle groups - creating a more isolated training stimulus that is perfect for fitting into more intense workout programs.

In Conclusion

Keep in mind that - though the hammer curl is appropriate for most exercisers - it may be incompatible with individuals who have a history of elbow, forearm or wrist injuries, or those who already perform neutral-grip pull-ups at high volume.

Otherwise, try out 2-3 sets of 8 repetitions each to get a feel of this highly popular arm building exercise.

References

1. Marcolin G, Panizzolo FA, Petrone N, et al. Differences in electromyographic activity of biceps brachii and brachioradialis while performing three variants of curl. PeerJ. 2018;6:e5165. doi:10.7717/peerj.5165.

2. Oliveira LF, Matta TT, Alves DS, Garcia MA, Vieira TM. Effect of the shoulder position on the biceps brachii emg in different dumbbell curls. J Sports Sci Med. 2009 Mar 1;8(1):24-9. PMID: 24150552; PMCID: PMC3737788.