The triceps brachii muscle, often called the triceps, is the largest muscle on the back of the upper arm, making up approximately two-thirds of the total arm mass. Developing this muscle is necessary for increasing arm size and overall upper-body strength. Many people search for ways to train the “inner tricep,” a popular term highlighting the part of the muscle that contributes significantly to the arm’s full, horseshoe shape. This guide clarifies the anatomy behind this phrase and details the specific training mechanics and exercises required to fully develop this area.
Triceps Anatomy and the “Inner” Misconception
The triceps brachii is named for its three distinct heads: the long head, the lateral head, and the medial head. All three heads converge into a single tendon that attaches to the ulna bone at the elbow. Their collective primary function is to extend, or straighten, the elbow joint. The long head is the largest of the three and contributes the most to the overall mass of the triceps muscle.
The term “inner tricep” is not an anatomical phrase, but it refers to the long head. This head is positioned toward the torso (medial side) of the arm, giving it the appearance of being the “inner” part when viewed from the back. The long head is unique because it originates from the scapula (shoulder blade).
In contrast, the lateral and medial heads originate directly from the humerus (upper arm bone). Because the long head crosses both the elbow and the shoulder joints, its activation is sensitive to shoulder position. This dual-joint function is the fundamental difference that dictates specific training strategies for maximum growth.
Exercise Mechanics for Long Head Activation
Maximizing the growth of the long head relies on a specific mechanical principle related to its unique attachment point on the shoulder blade. Because the long head crosses the shoulder joint, moving the arm into a specific position can place the muscle under a greater stretch, which enhances its ability to contract forcefully. Research shows that muscles trained in a lengthened position often experience greater hypertrophy.
To achieve this maximal stretch and subsequent activation, the shoulder joint must be flexed, meaning the arm is positioned overhead. When the arm is raised above the head, the distance between the long head’s origin on the scapula and its insertion on the ulna is increased, effectively putting the muscle in a stretched state. This stretched position significantly increases the activation of the long head during the elbow extension movement.
Another effective position, though less common, is shoulder hyperextension, where the arm is pulled slightly back behind the body. Any exercise that moves the arm away from the side of the body will preferentially recruit the long head over the other two. Maintaining a full range of motion in these positions is necessary to take advantage of the muscle’s full length-tension relationship. Using a moderate weight that allows for a slow, controlled eccentric, or lowering, phase in the stretched position can further amplify the muscle-building stimulus.
Key Exercises to Develop the Long Head
To apply the mechanics of long head activation, the training program must prioritize movements that place the arm in an overhead or stretched position. The Overhead Dumbbell Extension is arguably the most effective single exercise for this purpose. Holding a single dumbbell with both hands, the elbows are pointed straight up toward the ceiling, keeping them close to the head to maintain shoulder flexion. Lowering the weight slowly behind the head creates a deep stretch in the long head, and the subsequent upward press fully contracts the muscle.
The Cable Rope Overhead Extension is another highly effective variation, offering consistent tension throughout the entire range of motion, a benefit over free weights. To perform this, face away from a high cable pulley and pull the rope overhead so the hands are behind the head, maintaining the elbows in a high, fixed position. Pressing the rope outward and upward ensures the long head is working under constant resistance, which is beneficial for maximizing time under tension.
The Lying Triceps Extension, often called a “Skull Crusher,” is also a powerful long head builder, especially when performed with a slight modification. Lying on a bench, the weight is lowered toward the crown of the head. Allowing the upper arms to drift slightly back behind the head at the bottom of the movement increases the long head stretch. This subtle change in shoulder angle transforms the exercise into a more long-head-focused movement.
For a compound movement, the Close-Grip Bench Press effectively recruits all three heads of the triceps. Its ability to handle heavier loads makes it a potent tool for overall mass. Using a grip slightly narrower than shoulder-width shifts more emphasis to the triceps compared to a standard bench press. Although it does not place the long head in the maximum stretch of an overhead movement, the heavier resistance ensures a strong mechanical tension is placed on the muscle.