The pursuit of a wider, thicker upper arm requires a focused approach that moves beyond standard bicep curls. Maximizing the visual width of the arm involves specifically targeting two muscle groups: the short head of the biceps brachii and the brachialis. By understanding the unique functions of these muscles and selecting exercises that prioritize them, you can develop a fuller arm aesthetic that appears broad from the front. This specialized training strategy is the most effective way to achieve a significant increase in arm girth.
Understanding Arm Width Anatomy
Arm thickness is determined by the size of the three main elbow flexors, not just the visible bicep peak. The biceps brachii is a two-headed muscle, consisting of the long head and the short head. The long head, which attaches higher on the shoulder blade, primarily contributes to the “peak” of the bicep.
The short head, located on the inner side of the arm, is the primary contributor to the overall width and fullness when viewed from the front. The third muscle is the brachialis, a powerful elbow flexor that lies deep beneath the biceps brachii.
As the brachialis grows, it physically pushes the biceps brachii upward, enhancing the arm’s height and girth. This muscle functions as the workhorse of the elbow, generating substantial force, especially when the forearm is in a neutral or pronated (palm-down) position. Training the short head and the brachialis is the direct pathway to achieving a wider arm appearance.
Exercise Selection for Outer Biceps and Brachialis
Targeting the short head requires exercises that position the elbow in front of the body, which places the long head in a relaxed position. Preacher curls are effective because the pad forces the elbows forward, increasing the load on the short head. Using a wide grip on a barbell or EZ-bar during preacher curls further emphasizes this activation.
Concentration curls also isolate the short head by bracing the upper arm against the inner thigh, minimizing momentum and keeping the elbow forward. The short head is preferentially activated during the latter half of the curling motion, making exercises that maintain tension at the top beneficial. Spider curls, performed chest-down on an incline bench, are another movement that locks the arms forward, strongly targeting the short head.
The brachialis is best recruited using a neutral or pronated grip, as these hand positions mechanically disadvantage the biceps brachii. Hammer curls, where the palms face each other, are effective for the brachialis and the forearm muscle, the brachioradialis. Reverse curls, using an overhand (pronated) grip with a straight bar or dumbbells, also shift the focus onto the brachialis. For increased difficulty, a narrow-grip pull-up or inverted row with an overhand grip can load the brachialis with significant bodyweight resistance.
Optimizing Technique and Grip
To maximize the growth of the short head, manipulating your grip width is effective. A grip significantly wider than shoulder-width during a standard or preacher curl preferentially recruits the short head. Maintaining a fully supinated grip, where the palms face up, throughout the entire range of motion increases short head activation. You can enhance this by actively trying to twist the pinky finger toward the ceiling at the top of the curl.
For the brachialis, a neutral grip (palms facing each other) or a pronated grip (palms facing down) is necessary, as this removes the mechanical advantage of the biceps. Focusing on a slow eccentric (lowering) phase is beneficial for the brachialis. This controlled lowering motion, which can last three to four seconds, increases the time under tension and promotes growth.
Controlling the tempo and minimizing momentum is crucial across all width-focused exercises. When performing preacher or concentration curls, the elbow should remain firmly against the support to prevent the shoulder from assisting. For standing exercises, avoid swinging the torso or hips; the movement should be driven solely by the elbow joint flexion. Focus on squeezing the muscle, rather than just moving the weight, to result in greater muscle growth.
Training Frequency and Volume for Growth
To stimulate consistent hypertrophy in the arm muscles, training frequency should be high. Train the biceps two to three times per week, ensuring about 48 hours of recovery between sessions. This frequent stimulus, coupled with adequate recovery, is more effective for muscle growth than a single, high-volume session.
The optimal training volume for the biceps, including the short head and brachialis, falls within a range of eight to twenty sets per week. Beginning with twelve to sixteen total weekly sets dedicated to these muscles is a practical starting point. This volume can be distributed across two or three weekly sessions, using three to four sets per exercise.
For hypertrophy, the ideal repetition range is eight to twelve repetitions per set, with the intensity high enough that you are close to muscular failure. Progressive overload is the fundamental principle for growth, meaning you must continually increase the demand placed on the muscles. This can be achieved by gradually increasing the weight, performing more repetitions, or improving the quality of the movement through better technique and a slower tempo.