How to Do It
- Stand holding a dumbbell in each hand at your sides with palms facing your body (a neutral grip, thumbs forward).
- Keep your elbows pinned close to your torso and your upper arms still.
- Curl both dumbbells up toward your shoulders, keeping your wrists straight and the neutral grip throughout.
- Squeeze briefly at the top without letting the elbows drift forward.
- Lower under control back to the starting position, resisting the weight on the way down.
Common Mistakes
- Swinging the torso or using the shoulders to heave the weight up instead of curling with the arms alone.
- Letting the elbows drift forward or away from the body, which reduces bicep tension.
- Rushing the lowering phase instead of controlling the full eccentric range.
- Rotating the wrist mid-rep instead of keeping the neutral grip that defines the hammer curl.
The hammer curl’s neutral grip shifts more work onto the brachialis and forearms than a standard bicep curl, which is why it’s a staple for building forearm size and thickness alongside the biceps.
It’s also easier on the wrists and elbows for lifters who feel discomfort with a supinated (palms-up) curl grip, since the neutral position keeps the forearm in a more natural line.
Pair it with a rowing movement like the barbell bent-over row on a pull day, or run it alongside a standard curl in a dedicated arm day workout for complete bicep and forearm coverage.
Hammer Curl vs Bicep Curl
Both curls train the elbow flexors, but the grip changes which muscle does the most work. The standard dumbbell bicep curl uses a palms-up grip that puts the biceps brachii through its longest range of tension. The hammer curl’s neutral, palms-facing grip shifts emphasis onto the brachialis and brachioradialis, the muscles underneath and alongside the biceps that give the arm its overall thickness.
| Hammer Curl | Bicep Curl | |
|---|---|---|
| Grip | Neutral (palms facing in) | Supinated (palms facing up) |
| Primary emphasis | Brachialis, brachioradialis, forearms | Biceps brachii |
| Wrist and elbow comfort | Often more comfortable | Can bother sensitive wrists |
| Best for | Forearm and arm thickness | Peak bicep size |
Neither replaces the other. Most well-rounded arm programs include both curls in the same session or rotate them week to week for complete coverage.
Muscles Worked by the Hammer Curl
- Primary: brachialis, brachioradialis
- Secondary: biceps brachii
- Stabilizers: forearm flexors and the shoulder, which keeps the upper arm still through the rep[1][2]
The brachialis sits underneath the biceps and, when well developed, pushes the biceps up and out, which is why hammer curls are a common addition for lifters chasing overall arm size rather than biceps peak alone.
Hammer Curl Alternatives
- Dumbbell bicep curl: the supinated-grip counterpart, putting more direct tension on the biceps brachii.
- Reverse curl: an overhand, palms-down grip that shifts even more emphasis onto the brachioradialis and forearms than the hammer curl.
- Cross-body hammer curl: curls the dumbbell across the body toward the opposite shoulder, adding a slight rotational demand.
- Barbell bent-over row: not an isolation substitute, but a compound pull that trains the biceps and forearms indirectly alongside the back.
Brachioradialis vs Biceps: Why Grip Angle Changes the Load Vector
Elbow flexion is produced by three muscles pulling across the same joint, and forearm rotation changes how much of the flexion torque each one contributes. The biceps brachii’s tendon wraps around the radius; that wrap gives it the greatest mechanical advantage for flexion when the forearm is supinated (palms up), because the tendon’s line of pull sits furthest from the joint’s axis of rotation in that position. Rotate to neutral (palms facing in, as in the hammer curl) and the biceps’ effective moment arm shrinks, since the radial wrap partially unwinds and the tendon’s pull angle moves closer to the joint center.
The brachioradialis works in the opposite direction. Its moment arm for elbow flexion is largest in the neutral, mid-pronation position and smallest at full supination, so the hammer curl’s fixed neutral grip places it at its mechanically strongest point in the range for the entire set. The brachialis, which crosses only the elbow and inserts on the ulna rather than the radius, is largely indifferent to forearm rotation and contributes a similar flexion torque regardless of grip. This is why a neutral grip does not simply “add” forearm work on top of an unchanged biceps stimulus: it actively redistributes elbow-flexion torque away from the biceps’ peak-leverage position and toward the brachioradialis and brachialis, which is the direct mechanical reason hammer curls build forearm and mid-arm thickness that a supinated curl trains less directly.
Neutral Grip Kinematics and Elbow Torque
Because the neutral grip removes forearm rotation from the movement, the hammer curl isolates elbow flexion far more cleanly than a supinated curl, where lifters can unconsciously supinate further through the lift to recruit more biceps. With rotation fixed, the only joint action left is flexion and extension at the elbow, so total resistance torque at any point in the range is a direct function of the dumbbell’s weight and its horizontal distance from the elbow joint, which peaks when the forearm passes through roughly parallel to the floor. Keeping the upper arm vertical and the elbow pinned at the torso keeps that resistance arm consistent rep to rep; letting the elbow drift forward shortens the effective resistance arm and quietly reduces the torque the muscles have to overcome, which is why elbow drift lets lifters move more weight without actually working harder.
Wrist and elbow alignment
Set the dumbbell handle across the palm with the thumb pointing up and keep the wrist stacked rather than bent back. Start with the upper arm hanging beside the torso. As you curl, let the elbow remain close without forcing it behind the body. A small amount of elbow movement at the end of the range is less important than avoiding a swing or a shoulder-driven start. If the wrist rotates into a palms-up grip, you have changed the exercise into a different curl; that can be useful, but record it separately.
Use a slow lowering phase as your main rep-quality check. The dumbbell should travel through the same comfortable range on every repetition, with the forearm approaching the upper arm without the shoulder rolling forward. If the final repetitions shorten dramatically, reduce the load or use alternating arms so you can keep the torso still. Cross-body hammer curls and rope cable curls are valid variations, but their path and load should not be compared directly with a standard two-dumbbell set.
Select the variation by the limiter
| Limiter or goal | Useful choice | Trade-off |
|---|---|---|
| Strict neutral-grip practice | Standard dumbbell hammer curl | The load may be limited by grip |
| One side lags | Alternating or single-arm curl | The session takes longer |
| Shoulder movement appears | Seated curl with back support | Less whole-body feedback |
| No dumbbells | Rope cable curl | Stack numbers are machine-specific |
| A different arm path | Cross-body hammer curl | Not the same movement target |
Sets, reps, and load progression
Start with two to four sets of eight to fifteen repetitions and keep one to three technically good repetitions in reserve. Record the grip, variation, load, reps, and whether the last repetition used the same range as the first. Add reps before load. When every set reaches the top of the range without torso swing, elbow drift, or wrist collapse, make a small increase and return to the lower end. If one arm stalls, match the stronger arm to the weaker arm instead of allowing the stronger side to accumulate extra repetitions. The biceps exercises hub can help place this work alongside rows and supinated curls.
Stop for sharp or worsening elbow, wrist, or shoulder symptoms and seek individual guidance from a qualified professional if they persist.
References
- Anaerobic and Muscle Endurance Development: Lifting Guidelines. National Strength and Conditioning Association (2017)Back to claim
- American College of Sports Medicine Position Stand. Resistance Training Prescription for Muscle Function, Hypertrophy, and Physical Performance in Healthy Adults: An Overview of Reviews. Medicine & Science in Sports & Exercise (2026)Back to claim
- Updating ACSM's Recommendations for Exercise Preparticipation Health Screening. Medicine & Science in Sports & Exercise (2015)
See our exercise methodology for how this evidence is applied and its limits.
Frequently Asked Questions
- What muscle do hammer curls work on?
- Hammer curls primarily work the brachialis and brachioradialis, the forearm muscles that sit underneath and alongside the biceps, along with the biceps themselves. The neutral, palms-facing grip shifts more emphasis onto these muscles than a standard curl, which is why hammer curls are a staple for building forearm size and thickness.
- Is hammer curl really effective?
- Yes, the hammer curl is effective for building forearm and brachialis size, muscles a standard bicep curl trains less directly. It is also easier on the wrists and elbows for lifters who feel discomfort with a palms-up curl grip, since the neutral position keeps the forearm in a more natural line throughout the movement.
- Is hammer curl better than bicep curl?
- Neither is better outright, they train overlapping but different muscles. The standard bicep curl puts more direct tension on the biceps through a palms-up grip, while the hammer curl shifts emphasis onto the brachialis and forearms with a neutral grip. Most well-rounded arm programs include both rather than choosing one over the other.
- How do I know if I'm doing hammer curls correctly?
- You are doing hammer curls correctly if your elbows stay pinned close to your torso throughout, your wrists stay straight in a neutral, palms-facing grip, and you lower the weight under control instead of dropping it. If your torso swings or your elbows drift forward, the weight is too heavy for strict form.
- Is a 50 lb hammer curl good?
- Curling a 50 lb dumbbell per arm with strict form is an advanced level of strength that most recreational lifters take years of consistent training to reach, well above what most intermediate lifters use. For most people, a controlled 15 to 30 lb hammer curl with good form is a solid, realistic working weight.
- Should beginners do hammer curls?
- Yes, hammer curls are beginner friendly, since the neutral grip is easier on the wrists than a standard curl and the movement has a low skill floor. Beginners should start with light dumbbells and focus on keeping the elbows pinned to the torso before adding weight, since forearm and elbow tendons adapt more slowly than the biceps themselves.
- What is a common mistake people make when doing hammer curls?
- The most common hammer curl mistake is swinging the torso or heaving with the shoulders to move the weight instead of curling with the arms alone, usually a sign the load is too heavy. Letting the elbows drift forward mid-rep is a close second, since it shifts tension off the target muscles and turns the movement into a shoulder exercise.
- Are hammer curls for shoulders?
- No, hammer curls are primarily an arm exercise, targeting the brachialis, brachioradialis and biceps rather than the shoulders. The shoulders play a minor stabilizing role in keeping the upper arm still through the rep, but they are not the muscles the movement is built to train or grow.