Your biceps get the credit, but the brachialis does most of the actual work of bending your elbow, especially when your palm faces down or in. Plenty of articles promise to help you "isolate" this muscle with special brachialis exercises. That promise doesn't survive contact with basic anatomy.

The muscles involved in elbow flexion are the biceps brachii and brachioradialis on the surface, as well as the deeper brachialis. All three work together every time you bend your arm, and you can't switch two of them off to isolate the third.

What you can do is shift more of the workload onto the brachialis. Pronating your grip changes the mechanics: when pronated, the brachioradialis is more active during elbow flexion since the biceps brachii is in a mechanical disadvantage. That's a more useful goal than chasing true isolation, since the brachialis produces the majority of force during elbow flexion and isn't affected by pronation or supination of the forearm. Pronating your grip doesn't turn the brachialis on. It turns the biceps down, so the brachialis and brachioradialis end up doing relatively more of the work.

This article ranks the best exercises for doing exactly that, based on the actual mechanics of pronation and grip angle rather than gym folklore. You'll also get a four-week program that builds the mind-muscle connection first, then loads it properly once your form catches up.

Can You Actually Isolate the Brachialis? The Biomechanical Truth

Every muscle in your arm shares real estate with its neighbors, and the brachialis is no exception. It lies beneath the biceps brachii and originates from the anterior aspect of the distal humerus, inserting onto the tuberosity of the ulna. Every time you bend your elbow, you recruit several muscles at once. You can't flip a switch and work the brachialis by itself. Anyone selling you "pure isolation" brachialis exercises is stretching the truth.

Why the Biceps Always Crashes the Party

Jeff Cavaliere of ATHLEAN-X has explained this mechanism in his training content: the biceps brachii is one of the primary bi-articular muscles crossing the shoulder and elbow, playing a role in multiple motions of the upper extremity. Because it crosses both joints, it activates during almost any pulling or curling motion, regardless of how you position your arm. Try to cut the biceps out of a curl, and it will fight for the job anyway. That's how the joint is wired.

Isolation vs. Maximal Activation: What You're Actually Training For

Your goal isn't isolation. It's shifting the workload so the brachialis muscle does more of the heavy lifting while the biceps gets pushed into a supporting role. Grip position, wrist angle, and elbow path all change which muscle takes the lead. That distinction is the foundation for every movement in this program.

What Is the Brachialis Muscle? A Quick Definition

The brachialis is the muscle underneath your biceps that bends your elbow, running from the lower half of your humerus down to your ulna. It doesn't rotate your forearm the way the biceps does, so brachialis exercises work the same whether your palm faces up, down, or sideways. This single-purpose design—pure elbow flexion—is exactly why isolating it pays off.

Where the Brachialis Sits (and Why It Adds Arm Width)

Picture your upper arm from the side. The biceps sits on top, closer to the skin. The brachialis lives underneath it, separated from the triceps by a band of connective tissue on the back side of the arm.

A well-developed brachialis pushes your biceps upward and outward. Viewed from the front, that translates to a wider arm and a more pronounced gap between biceps and triceps, the look most lifters chase when they talk about arm "peak."

Why This Muscle Matters Beyond Looks: Strength and Joint Health

The brachialis is the only pure flexor of the elbow joint, producing the majority of force during elbow flexion no matter how you grip the bar.

A strong brachialis also protects your elbow joint under load. Building this underarm muscle supports both your grip strength and your joint longevity over time during heavy pulling work.

Grip Science: How Pronation Angle Determines Which Muscle Does the Work

Your wrist position changes which elbow flexor does the heaviest lifting. Rotate your forearm and you change the angle of pull for each muscle crossing the elbow, which shifts how much tension each one has to generate. That's basic joint mechanics.

Coratella and colleagues used EMG to measure how biceps brachii, brachioradialis, and anterior deltoid excitation shift during bilateral biceps curls performed with different handgrips, testing bodybuilders in supinated, pronated, and neutral positions. Their results showed clear, measurable differences in muscle recruitment based on grip alone: biceps brachii and brachioradialis activation were highest with the supinated grip during the ascending phase, while the anterior deltoid showed greater activation with pronated and neutral grips. The elbow doesn't care what you call the exercise. It cares what angle your hand is at when you load it.

Supinated Grip: Biceps' Home Turf

Palm-up curls put the biceps brachii in its strongest mechanical position. Biceps brachii is a supinator, while brachioradialis keeps the forearm in an intermediate position between supination and pronation, which is part of why a standard barbell curl feels biceps-heavy from the first rep. The brachialis still contributes, but it plays a supporting role here.

Neutral Grip: Brachioradialis Takes Over

Turn your palm to face your torso and the brachioradialis, the long forearm muscle running from the upper arm to the wrist, gets more involved. Bagchi and Raizada (2019) compared eight curl variations and found that hammer curls produced the greatest brachioradialis activation of any grip tested. That's the mechanism behind why hammer curls feel different in the forearm. Worth noting: newer EMG work from Coratella's group found brachioradialis activation peaked in the supinated position instead, so the research isn't fully settled on this point.

Pronated Grip: Where the Brachialis Gets Its Chance

Flip your palm downward and you strip away the biceps' rotational advantage. With supination taken out of the equation, the brachialis and brachioradialis pick up a larger share of the elbow flexion work.

The 45° Sweet Spot

Full pronation isn't always practical or comfortable under load. Until that claim can be confirmed, treat 45 degrees as a comfort-based starting point rather than a research-backed target, and adjust based on wrist strain. That's the range worth building your brachialis exercises around, and it's where the ranked list below starts.

Best Brachialis Exercises Ranked by Grip Science

Not every brachialis exercise pulls its weight equally. Some earn their spot through mechanical advantage, others through load capacity. A couple make the list because they train the muscle in a way that carries over to real strength. Here's the order that matters, based on grip mechanics rather than gym folklore.

1. Cross-Body Hammer Curl (Pronated Variation): The Gold Standard

This exercise tops the list because it pairs a pronated grip with a bar path that keeps tension on the brachialis through the full range of motion. For hammer curls, Cavaliere recommends switching out your neutral grip for a fully pronated forearm position and performing a cross-body variation, which will place more pressure on the brachialis.

ATHLEAN-X founder Jeff Cavaliere calls this the best dumbbell exercise for arm muscle isolation and brachialis training.

Hold a dumbbell in each hand with palms facing your torso. Curl one dumbbell across your body toward the opposite shoulder, keeping your elbow pinned to your side. Lower slowly, then repeat on the other arm. Do 3 sets of 10-12 reps per arm.

2. 45° Angled Cable Curl: Dialing In the Optimal Pronation Angle

A cable setup lets you fix the resistance angle in a way free weights can't. A patent for a multi-angle cable attachment sets the pronation angle at approximately 45 degrees specifically to optimize activation of the brachialis muscle. That angle sits between a fully neutral and fully supinated grip, which is the sweet spot this exercise targets.

Set the cable pulley at chest height with a rotating handle attachment. Rotate your wrist to a 45-degree angle between neutral and pronated, then curl with your elbow fixed at your side. Run 3 sets of 12 reps.

3. Reverse-Grip EZ Bar Curl: Heavy Load, Pronated Emphasis

Once you need to add real weight, this move takes over. The pronated grip shifts mechanical advantage away from the biceps and onto the brachialis and brachioradialis, letting you load heavier than you can with dumbbells alone.

Grip the EZ bar with palms facing down, hands just outside shoulder width. Curl with strict form, resisting the urge to swing the bar up with momentum. Keep the reps controlled, since this variation stresses the wrist more than others. Aim for 3 sets of 8-10 reps.

4. Rope Cable Hammer Curl: Constant Tension Neutral Grip

Cables solve the biggest limitation of dumbbell hammer curls, the dead spot at the top where gravity stops doing any work. A rope attachment keeps constant tension on the underarm muscles from the bottom of the curl to the top.

Attach a rope to a low pulley and grip each end with a neutral hand position. Curl straight up, keeping elbows locked at your sides, and squeeze at the top before lowering under control. 3 sets of 12-15 reps works well here, since the tension allows for higher rep ranges without losing intensity.

5. Neutral-Grip Chin-Up/Pull-Up: Functional Carryover for Pulling Strength

This is the only compound lift on the list, and it earns its place because meaningful brachialis and brachioradialis recruitment occurs during neutral-grip pulling movements. Isolation work builds the muscle. This builds the strength to use it.

Grip parallel handles or a neutral-grip bar with palms facing each other. Pull your chin over the bar without kipping, then lower with control. If bodyweight reps are easy, add a weight belt. 3-4 sets to near failure.

6. Single-Arm Zottman Curl: The Eccentric Finisher

The pronated lowering phase shifts stress onto muscles that a standard curl skips over. Save this for the end of your workout, when fatigue makes the eccentric emphasis count.

Curl a dumbbell with an underhand grip, then rotate your wrist to pronated at the top before lowering slowly, over 3-4 seconds, with palm facing down. Rotate back to underhand at the bottom and repeat. 3 sets of 10 reps per arm, focused entirely on the slow negative.

Rank matters less than consistency. Pick two or three from this list for your first week rather than trying to run all six on day one.

The 4-Week Brachialis Activation Program

Knowing which brachialis exercises work best doesn't help if you never program them. This block gives you four weeks of structured work, built to progress in order: connection first, then load.

Week 1-2: Building the Mind-Muscle Connection

For the first two weeks, your job isn't to lift heavy. Most lifters have never consciously felt the brachialis muscle fire on its own, so the goal here is learning what that feels like.

Train it twice a week, on non-consecutive days, using lighter loads and slower reps.

Rest 60–90 seconds between sets. Slow the eccentric phase down to a 3-second count on every rep. That tempo change does more for muscle awareness at this stage than adding weight ever will.

Week 3-4: Progressive Overload and Volume Increase

Once the movement pattern is locked in, it's time to load it. Weeks 3 and 4 bump frequency slightly and shift the rep ranges lower. The brachialis responds well to heavier, denser work under load.

Add weight only when you can complete every rep with clean form. If your wrist starts flaring or your shoulder joins the movement, drop the load back down.

How to Fit This Into Your Existing Bicep Training

You don't need to bolt this on as a separate workout. Slot these movements into your current bicep training as the first exercise on arm day, while your grip and joints are fresh. Training the brachialis before curls also means you're not fatigued from bicep-dominant lifts when you need the most focus.

If you already train arms twice a week, this program fits directly into those sessions without adding gym time. Swap one of your usual bicep curl variations for a movement from the hierarchy, and keep your total set volume for the arm about the same.

Brachialis Training FAQ

What Is the Brachialis Muscle?

The brachialis is a deep elbow flexor that sits underneath the biceps and directly pushes it upward when developed. Unlike the biceps, it has no role in forearm rotation, so it activates most when the forearm is pronated (palm-down) or neutral. Building the brachialis adds visible arm width that biceps training alone cannot produce.

Can You Isolate the Brachialis Muscle?

You can't isolate it completely, since it always fires alongside the biceps and brachioradialis during elbow flexion. What you can do is bias it heavily through grip and angle. A pronated (palm-down) grip during curling movements shifts the workload toward the brachialis because it strips away the biceps' ability to supinate the forearm, one of its main jobs.

Do Hammer Curls Work the Brachialis?

Yes. Hammer curls activate the brachialis, especially when you use a pronated grip or close the angle into your chest. The Crossbody Hammer Curl—performed with a pronated forearm and the dumbbell moving toward your torso—emphasizes brachialis engagement while minimizing biceps involvement.

How Often Should You Train the Brachialis?

Two to three times a week works for most lifters, especially if you're running a dedicated activation block. The muscle is small and recovers fast. It also gets hit indirectly on back and bicep days, so you're rarely starting from zero.

Why Is the Brachialis Important for Arm Size?

Because it sits underneath the biceps and pushes it upward, a developed brachialis adds width to your upper arm that biceps work alone won't produce. Research on elbow flexor mechanics confirms that a pronated grip increases brachialis activation, while a neutral grip increases brachioradialis activation. Train both angles and you're building arm size from two different directions.

Check the exercise breakdown below to see which grip actually wins, with real numbers behind it.

The Bottom Line

You can't isolate the brachialis muscle. It shares the elbow-flexion job with the biceps and brachioradialis on every rep. What you can control is which muscle picks up more of that load, and that comes down to wrist position. Turn your palm down, or angle it to 45 degrees, and you shift more of the mechanical demand onto the brachialis than a flat-palm curl ever will. Grip choice, not isolation, drives the activation shift.

Start the 4-week program from week one. Treat the first two weeks as skill work, not strength work. Don't scrap your existing biceps routine. Stack this program alongside it. The two complement each other instead of competing for space in your training week.

Stick with pronated and angled grip variations as your priority. Over several weeks, that choice compounds: a thicker-looking arm from underneath the biceps, and a grip strong enough to hold up when everything else in your training gets heavier.