Clavicular Head Of Pectoralis Major

The clavicular head of the pectoralis major, or upper chest, contributes significantly to upward pressing movements. In traditional push-ups, it activates to about 30% of its maximum capacity, helping initiate upward force.

While its activation is similar to the one-arm push-up, the clavicular head also plays a stabilizing role. It helps keep the body aligned and balanced as you press up with one arm. This stabilization is vital as the asymmetrical load shifts more demand onto the upper chest.

Strengthening the clavicular head offers the benefits of push-ups, like improved upper body power and enhanced performance in incline presses.

Sternal Head Of Pectoralis Major

The sternal head, or middle chest, is the largest part of the pectoralis major. It’s highly engaged during one-arm push-ups. This muscle generates the force needed to push your body back up by bringing your arm toward the body’s midline.

As you lower down, the sternal head stabilizes your torso and prevents rotation from the uneven load. It keeps your chest and shoulders engaged throughout the movement. Strengthening the sternal head improves your control during challenging push-up variations and boosts overall upper-body endurance.

Abdominal Head Of Pectoralis Major

The abdominal head of the pectoralis major, or lower chest, plays a key role in the one-arm push-up. It provides extra strength during the final push phase of the movement.

As your body drives upward, this muscle activates to help complete the movement. It's especially active when pushing from the bottom position, closer to the ground. Additionally, the abdominal head aids in stabilizing your arm as it moves inward, maintaining control throughout the movement.

Beyond push-ups, the abdominal head improves chest power and supports exercises targeting the lower chest, like dips or decline presses.

Anterior Deltoid

The anterior deltoid, at the front of the shoulder, stabilizes the shoulder joint during the one-arm push-up. Unlike other shoulder muscles, it primarily controls forward arm movements while helping keep the shoulder steady as you push up.

Due to the uneven load on one arm, it engages more heavily, making it crucial for preventing shoulder strain. This muscle is also essential for maintaining both control and power throughout the exercise.

Triceps Long Heads

The triceps long head is the largest part of the triceps and runs along the back of the upper arm. It extends the elbow and helps stabilize the shoulder joint during the one-arm push-up.

Unlike the other triceps heads, the long head also helps move your shoulder. This makes it essential to handle the added demand of this unilateral movement. Its strength is key for controlled arm movement and keeping the shoulder steady.

Triceps Medial Heads

Though smaller than the long head, the triceps medial head plays a crucial role in elbow extension during the push-up. Located deeper in the arm, it helps sustain the endurance needed for repeated movements.

While the long head focuses on larger, forceful motions, the medial head ensures smooth, controlled arm movement. It becomes especially active as you fully extend your arm, helping you complete each push-up with precision.

Triceps Lateral Heads

The triceps lateral head on the outer upper arm plays a key role in elbow extension during the one-arm push-up. Narrow hand placements in compound tricep exercises typically activate this head more. However, the one-arm variation still demands significant involvement.

The lateral head helps stabilize the arm and control movement against the uneven load. It’s especially active when extending the elbow, ensuring you can complete each push-up with proper form and power.

Quadriceps

Surprisingly, the quadriceps, the powerful muscles at the front of your thighs, play a crucial role in the one-arm push-up. While it's often seen as an upper-body move, your quads work hard to keep your legs straight and body stable.

As you push up, your quads engage to prevent your hips from sagging or your legs from wobbling. This lower body activation helps maintain perfect form, ensuring balance and control from head to toe throughout the entire movement.

Upper Rectus Abdominis

The upper rectus abdominis, or upper abs, is in the front of your torso, just below your chest. During the one-arm push-up, this muscle works overtime to keep your body stable and prevent hips from sagging or twisting.

Because only one arm supports your weight, this push-up variation demands more core activation than a standard push-up. The upper abs stay engaged to maintain alignment and control, ensuring balance and preventing unwanted movement.

Lower Rectus Abdominis

The lower rectus abdominis, below your belly button, plays a role in controlling your lower body during the one-arm push-up. This muscle stabilizes your hips and prevents them from sagging or shifting as you perform the movement.

This variation requires more balance, so the lower abs engage to keep your hips aligned with your upper body. Their activation is critical for maintaining proper form and avoiding unwanted lower body movement.

Obliques

The obliques, along the sides of your torso, prevent your torso from rotating during the one-arm push-up. Due to uneven weight distribution, the obliques work hard to resist twisting and keep your body in a straight line.

These muscles stabilize your spine and play a crucial role in maintaining core integrity throughout the movement. Their activation helps balance the body, making it easier to perform this challenging exercise with proper form.

Serratus Anterior

The serratus anterior, located along the sides of your ribcage, helps control shoulder movement during the one-arm push-up. Its main job is to stabilize your scapula (shoulder blade) as you push your body up.

This prevents shoulder instability and ensures a smooth pressing motion. In standard push-ups, it activates at around 24-50% of its maximum potential.

During one-arm push-ups, the serratus anterior has to work harder to keep your shoulder blades properly positioned. This is essential for preventing shoulder strain and maintaining upper body strength.