The triceps brachii is a significant muscle group located on the back of the upper arm, responsible for the majority of the arm’s size and contributing substantially to overall upper body strength. Unlike the biceps, the triceps muscle is composed of three distinct sections that all work together to extend the elbow joint. Understanding the different origins and functions of these three heads allows for strategic exercise selection to ensure complete development of the arm. Subtle adjustments to arm and body positioning during exercises can shift the primary emphasis among the three heads, leading to more comprehensive muscle growth.
The Three Heads of the Triceps Muscle
The triceps brachii is named for its three origins: the long, lateral, and medial heads. All three heads converge into a common tendon that inserts onto the olecranon process of the ulna (the prominent bone at the back of the elbow), making elbow extension their shared mechanical action. The primary difference lies in their starting points on the upper arm and shoulder structure.
The long head is unique because it originates on the infraglenoid tubercle of the scapula (the shoulder blade). This attachment point means the long head crosses two joints—the shoulder and the elbow—making it a biarticular muscle. Its activation is highly influenced by the arm’s position relative to the torso, assisting in shoulder extension and adduction.
In contrast, the lateral and medial heads originate directly on the humerus, the main upper arm bone. The lateral head arises from the posterior surface of the humerus, superior to the radial groove, positioning it on the outer side of the arm. The medial head originates inferior to the radial groove, placing it deeper and beneath the other two heads. Since these two heads do not cross the shoulder joint, their function is limited strictly to elbow extension.
Activating the Long Head
Targeting the long head requires specific mechanical consideration due to its attachment to the shoulder blade. To generate the greatest stretch and activation, the arm must be placed into shoulder flexion (moved overhead). This position stretches the long head at the shoulder joint, making it more active during elbow extension.
Overhead dumbbell extensions are a prime example of a movement that emphasizes this position. Holding the weight directly above the head with the elbows pointing upward places the long head under maximum stretch, forcing it to contribute significantly to the lifting phase. Cable overhead triceps extensions, performed by facing away from the machine, achieve the same mechanical advantage with consistent tension.
Another effective exercise is the lying triceps extension, sometimes called the skull crusher. Instead of keeping the upper arms strictly perpendicular to the floor, allowing the arms to drift slightly backward toward the head increases the stretch on the long head. This slight shoulder flexion ensures the long head is elongated, promoting greater muscle activation and hypertrophy.
Isolating the Lateral Head
The lateral head contributes to the visible “horseshoe” shape and is best activated when the arm is kept close to the torso. Exercises performed with the shoulder in a neutral or adducted position (arm stabilized alongside the body) shift the emphasis toward the lateral and medial heads. This positioning removes the stretch from the long head, allowing the other two heads to bear the majority of the load.
Cable pushdowns are a foundational exercise for targeting the lateral head effectively. Using a straight bar or a V-bar attachment with a pronated (overhand) grip, while keeping the elbows tightly pinned to the sides, concentrates the tension on the outer triceps. The constant tension provided by the cable machine is highly beneficial for maximizing motor unit recruitment in the lateral head.
Compound movements like the close-grip bench press are also highly effective, especially for strength and size development, as they allow for the use of heavier resistance. By using a shoulder-width or slightly narrower grip, the elbows are naturally tucked closer to the body, which minimizes chest involvement and places a greater workload on the triceps, particularly the lateral head. Furthermore, triceps kickbacks, when performed with the upper arm parallel to the floor, are an isolation exercise that focuses a strong contraction on the lateral head at the point of full elbow extension.
Understanding the Medial Head
The medial head is often referred to as the workhorse of the triceps because it is actively involved in virtually all elbow extension movements. Due to its smaller size and deeper location, it is not as visually prominent as the long or lateral heads, but it provides foundational strength. Research indicates that the medial head is highly active even at low resistance levels and during the initial phase of elbow extension.
It is generally unnecessary to search for specific isolation exercises for the medial head, as it is automatically recruited during any exercise that involves straightening the arm. When performing movements designed to target the long or lateral heads, the medial head is always contributing to the effort. Its function is to provide stable force, especially for lower-force, precise movements.
Therefore, the best approach for developing the medial head is simply to ensure consistent, quality training across a full range of motion. Exercises that focus on the final degree of elbow extension, such as pushdowns or kickbacks, naturally involve the medial head’s contribution to the lockout. Maintaining proper form and achieving complete extension in all triceps exercises is the most reliable way to guarantee that this foundational head is sufficiently stimulated.
Overhead dumbbell extensions are a prime example of a movement that emphasizes this position. Holding the weight directly above the head with the elbows pointing upward places the long head under maximum stretch, forcing it to contribute significantly to the lifting phase. Similarly, cable overhead triceps extensions, performed by facing away from the machine and pushing the cable forward, achieve the same mechanical advantage with consistent tension.
Another effective exercise is the lying triceps extension, sometimes called the skull crusher, when performed with a slight adjustment to the arm angle. Instead of keeping the upper arms strictly perpendicular to the floor, allowing the arms to drift slightly backward toward the head increases the stretch on the long head. This slight shoulder flexion ensures the long head is elongated, which research suggests promotes greater muscle activation and hypertrophy.
Isolating the Lateral Head
The lateral head, which contributes to the visible “horseshoe” shape on the outside of the arm, is best activated when the arm is kept close to the torso. Exercises performed with the shoulder in a neutral or adducted position, meaning the arm is stabilized alongside the body, tend to shift the emphasis toward the lateral and medial heads. This positioning removes the stretch from the long head, allowing the other two heads to bear the majority of the load.
Cable pushdowns are a foundational exercise for targeting the lateral head effectively. Using a straight bar or a V-bar attachment with a pronated (overhand) grip, while keeping the elbows tightly pinned to the sides, concentrates the tension on the outer triceps. The constant tension provided by the cable machine is highly beneficial for maximizing motor unit recruitment in the lateral head.
Compound movements like the close-grip bench press are also highly effective, especially for strength and size development, as they allow for the use of heavier resistance. By using a shoulder-width or slightly narrower grip, the elbows are naturally tucked closer to the body, which minimizes chest involvement and places a greater workload on the triceps, particularly the lateral head. Furthermore, triceps kickbacks, when performed with the upper arm parallel to the floor, are an isolation exercise that focuses a strong contraction on the lateral head at the point of full elbow extension.
Understanding the Medial Head
The medial head is often referred to as the workhorse of the triceps because it is actively involved in virtually all elbow extension movements. Due to its smaller size and deeper location, it is not as visually prominent as the long or lateral heads, but it provides foundational strength. Research indicates that the medial head is highly active even at low resistance levels and during the initial phase of elbow extension.
It is generally unnecessary to search for specific isolation exercises for the medial head, as it is automatically recruited during any exercise that involves straightening the arm. When performing movements designed to target the long or lateral heads, the medial head is always contributing to the effort. Its function is to provide stable force, especially for lower-force, precise movements.
Therefore, the best approach for developing the medial head is simply to ensure consistent, quality training across a full range of motion. Exercises that focus on the final degree of elbow extension, such as pushdowns or kickbacks, naturally involve the medial head’s contribution to the lockout. Maintaining proper form and achieving complete extension in all triceps exercises is the most reliable way to guarantee that this foundational head is sufficiently stimulated.