The brachialis muscle is a powerful, yet often overlooked, contributor to arm size and strength, playing a unique role separate from the more visible biceps brachii. When specifically targeted, it grows beneath the biceps, pushing the biceps muscle upward and outward. This creates the appearance of a higher peak and increases the circumference and thickness of the upper arm. Incorporating movements that isolate the brachialis is necessary for complete arm development.
Understanding the Brachialis Muscle
The brachialis is a thick, spindle-shaped muscle situated deep beneath the biceps brachii on the front of the upper arm. It originates on the lower half of the humerus and inserts directly onto the ulna, one of the forearm bones. This anatomical attachment makes the brachialis the primary and strongest flexor of the elbow joint.
Unlike the biceps, which crosses both the elbow and shoulder joints and is responsible for supinating the forearm, the brachialis acts purely to bend the elbow. Because it is a simple, single-joint flexor, its activation remains high regardless of wrist or forearm position. To truly isolate it, however, the biceps must be mechanically disadvantaged, forcing the brachialis to handle the majority of the load.
Primary Exercises for Brachialis Isolation
The most effective way to shift the workload away from the biceps and onto the brachialis is by altering the grip position during elbow flexion exercises. Since the biceps’ leverage is maximized when the palm faces up, exercises using a neutral or pronated grip reduce the biceps’ mechanical advantage. This maximizes brachialis and brachioradialis engagement.
Dumbbell Hammer Curl
The Dumbbell Hammer Curl is the most popular isolation exercise, performed with a neutral grip where the palms face each other. This grip neutralizes the biceps’ supination function, making the brachialis and brachioradialis the primary movers. The cross-body hammer curl variation involves curling the weight up and slightly across the body toward the opposite shoulder.
Reverse Curl
The Reverse Curl uses a pronated, or palms-down, grip. This places the biceps in its weakest position for elbow flexion, forcing the brachialis to compensate significantly. Reverse curls are typically performed with a straight or EZ-bar. They also heavily recruit the brachioradialis, adding density to the forearm and elbow region.
Zottman Curl
The Zottman Curl uniquely targets the brachialis by combining both supinated and pronated grips within a single repetition. The lifter curls the weight up with a supinated grip and then rotates the wrists at the top. The weight is lowered with a pronated grip. This eccentric phase under a pronated grip is potent for stimulating growth in the brachialis.
Optimizing Technique for Peak Engagement
Achieving maximum brachialis development relies heavily on strict execution, as even slight momentum quickly involves the stronger biceps. To ensure the brachialis is doing the work, the form must be controlled, avoiding any swinging or jerking motions with the torso. The elbows should remain fixed by the sides throughout the set, isolating the movement to the elbow joint.
Controlling the negative portion of the lift, known as the eccentric phase, is a powerful technique for maximizing muscle fiber recruitment. When lowering the weight, aim for a slow, deliberate tempo, such as a three-to-five second count. This extended time under tension stimulates a robust hypertrophic response. Use a full range of motion, ensuring the arm is completely straight at the bottom to achieve a maximal stretch.
Integrating Brachialis Work into Your Routine
For optimal growth, the brachialis should be trained with appropriate volume and frequency, similar to other smaller arm muscle groups. A general recommendation for direct elbow flexor work is between 12 and 20 total working sets per week. This weekly volume should be distributed across at least two, and ideally three, training sessions to allow for high-quality work without excessive fatigue.
The rep range for brachialis work should lean toward the moderate-to-high end, typically 10 to 15 repetitions per set. This rep scheme aligns with the strict form required and the goal of maximizing time under tension. Placing isolation movements at the beginning of an arm or upper body workout, when muscles are fresh, ensures maximal effort. Alternatively, integrating them on a back training day, after heavy pulling movements, serves as effective accessory work.