A pushup is a foundational bodyweight exercise that engages a large network of muscle groups in the upper body and core. The primary function of the movement is to push the body away from the floor, focusing biomechanically on the chest, shoulders, and the back of the arms. Pushups work the triceps much more than the biceps, which have a minimal role during standard execution.
The Triceps: Primary Movers for Elbow Extension
The triceps brachii is the large muscle on the back of the upper arm, composed of three heads: the long, lateral, and medial heads. This muscle group is the main force generator for the extension of the elbow joint, which is the defining action of the pushup. The triceps must work forcefully to straighten the arms and lift the body upward against gravity.
During the upward phase of the pushup, the triceps contract concentrically, shortening while generating force to push the body from the floor. When the body is lowered, the triceps work eccentrically, lengthening in a controlled manner to resist gravity. This eccentric action is important for building muscle size and strength. The medial head is often engaged across all movement speeds, while the lateral and long heads contribute more significantly as the load increases.
Why the Biceps Act Primarily as Stabilizers
The biceps brachii, located on the front of the upper arm, is designed to perform elbow flexion and forearm supination, the opposite action of the pushup. Since the pushup involves elbow extension, the biceps are not responsible for generating the pushing force. Instead, the biceps act mainly as dynamic stabilizers for the elbow and shoulder joints throughout the movement.
This stabilizing function is an isometric contraction, meaning the muscle is active and under tension but does not change length. The biceps help to counteract the forces produced by the triceps and other pushing muscles, ensuring the elbow joint remains stable. Any fatigue felt in the biceps during a standard pushup is usually an indication of this supportive stabilization work.
The Role of the Chest and Shoulders
While the triceps are the primary arm movers, the pushup is a compound exercise involving the entire upper body, with the chest and shoulders providing the largest contribution of force. The pectoralis major (chest muscle) is the main agonist, responsible for horizontal adduction—bringing the upper arms toward the center of the body. The sternal head of the pectoralis major is particularly active in a standard pushup position.
The anterior deltoids (front of the shoulders) act as a synergist, assisting the chest and initiating the push away from the ground. These muscles also help stabilize the shoulder joint throughout the full range of motion. The serratus anterior, located along the side of the rib cage, plays a supporting role by protracting the shoulder blades, ensuring proper shoulder positioning. The pushup is accurately described as a chest, triceps, and shoulder exercise.
Modifying Pushups to Maximize Triceps Activation
To specifically increase the workload on the triceps, the hand position must be narrowed to shift the mechanical advantage away from the chest. The diamond pushup, where the hands are placed close together to form a diamond or triangle shape beneath the chest, is the most effective modification for this purpose. This narrow placement forces a greater degree of elbow extension, placing a heavier load directly onto the triceps brachii.
Research using electromyography (EMG) has shown that the triceps experience significantly greater electrical activity during a diamond pushup compared to a standard pushup. The narrow hand position minimizes the leverage of the pectoralis major, requiring the triceps to take on a higher percentage of the total force needed to lift the body. For those seeking to build strength and size specifically in the back of the arm, incorporating close-grip variations is an effective way to target all three heads of the triceps.