The triceps brachii muscle group comprises approximately two-thirds of the upper arm mass, making its development paramount for arm size. Achieving the highly-sought “horseshoe” shape requires specific training to emphasize the lateral head. This outer portion of the muscle contributes significantly to the width and definition seen from the side. By manipulating body position, grip, and exercise selection, it is possible to shift the mechanical load to maximize growth in this specific area.
Anatomy of the Triceps and the Lateral Head
The triceps brachii, which is Latin for “three-headed muscle of the arm,” is the sole muscle on the posterior of the upper arm. It is composed of the long head, the medial head, and the lateral head. All three heads converge to insert into the olecranon process of the ulna and are primarily responsible for extending the elbow joint.
The lateral head, often referred to as the “outer tricep,” originates only on the humerus. This means its function is limited exclusively to elbow extension, and its muscle length is not affected by shoulder position. The long head, in contrast, originates on the scapula, crossing the shoulder joint, so its tension is heavily influenced by arm elevation. By selecting exercises that minimize the long head’s involvement, the lateral head must take on a larger share of the workload.
The Role of Grip and Body Position in Targeting
Targeting the lateral head hinges on two main biomechanical principles: minimizing the long head’s contribution and optimizing the grip for stability and force transfer. When the arm is kept by the side of the torso, or in a position of minimal shoulder flexion, the long head is in a relatively shortened state and cannot generate maximal force. This technique effectively forces the medial and lateral heads to become the dominant movers in the exercise.
The most effective body position for lateral head emphasis involves keeping the upper arm perpendicular to the floor throughout the movement, typically accomplished with pushdown variations using a cable machine. The constant tension provided by the cable, in contrast to free weights, allows the muscle to be loaded consistently throughout the entire range of motion, which is beneficial for muscle growth.
The choice of grip also plays a role in shifting the emphasis toward the outer portion of the triceps. A pronated (overhand) grip or a neutral grip is generally preferred for lateral head work, as these grips often provide better stability and a more direct line of force. Avoiding the supinated (underhand) grip is advised, as this position can sometimes shift a greater focus to the medial head.
Specific Exercises for Outer Tricep Development
Cable Pushdowns using a V-Bar or Straight Bar are effective for placing tension on the lateral head. To perform this, use a pronated grip and keep the elbows tucked in close to the sides of the body. The goal is to isolate the elbow joint action, ensuring that the upper arm remains stationary and only the forearm moves.
A specific variation is the Rope Pushdown, which allows for a forced external rotation of the forearm at the bottom of the movement. By using a neutral grip on the rope and actively pulling the ends apart as the elbows fully extend, a strong peak contraction is achieved in the lateral head. This slight outward rotation at the end range of motion enhances the mechanical tension on the outer tricep fibers.
Dips performed with an upright torso are a mass builder that heavily recruits the lateral head. Unlike dips where the body leans forward to engage the chest, maintaining a vertical posture with the elbows kept close to the body ensures the triceps are the primary muscle group involved. The ability to progressively overload this movement with heavy weight makes it an effective stimulus for lateral head development.
Finally, the Single-Arm Cable Extension is an isolation exercise that allows for focus on one side at a time, addressing any potential strength or size imbalances. Stand facing the cable column, use a single handle with a neutral grip, and push the handle down and slightly across the body until the arm is fully extended. The neutral grip and the slight cross-body motion help to drive the contraction into the lateral head.