The one-arm tricep extension is an isolation movement designed to strengthen the triceps muscle on the back of the upper arm. The triceps brachii muscle has three heads—the long, lateral, and medial heads—all of which are responsible for extending the elbow joint. By positioning the arm overhead, this exercise places a significant stretch on the long head of the triceps, which is the only head that crosses the shoulder joint, potentially leading to greater muscle growth in this area. This overhead position maximizes the stretch on the muscle fibers, which can be an effective stimulus for hypertrophy.
Setting Up the Exercise
The preparation for this lift begins with selecting the appropriate equipment, which is typically a single dumbbell. Choose a weight that allows you to complete your desired number of repetitions with strict form, as using a weight that is too heavy often compromises technique. You must safely move the dumbbell into the overhead starting position, using the non-working hand to assist in lifting the weight until the working arm is fully extended.
Establish a stable base, whether seated or standing, with the feet roughly shoulder-width apart to ensure balance. The grip on the dumbbell should be firm, with the palm facing inward or slightly forward. The upper arm should be positioned vertically, close to the head, with the elbow pointing straight forward. Maintaining this fixed upper arm position is paramount for isolating the triceps and minimizing strain on the shoulder joint.
Performing the Lift Step-by-Step
The movement begins with the eccentric, or lowering, phase, which should be executed slowly and under complete control. Inhale as you bend the elbow, allowing the dumbbell to descend in a controlled arc behind your head. The goal is to lower the weight until the forearm is approximately parallel to the floor, or until you feel a deep stretch in the triceps muscle. This deep stretch at the bottom of the movement is theorized to be a powerful stimulus for muscle development.
Throughout the lowering phase, the upper arm must remain completely stationary and vertical, acting as a fixed pivot point. Only the forearm should move, rotating around the elbow joint. Once the full stretch is achieved, immediately begin the concentric, or lifting, phase, forcefully contracting the triceps to extend the elbow. Exhale as you press the dumbbell back up to the starting position, maintaining the same smooth, controlled tempo.
Ensure the arm is fully extended at the top of the movement to achieve a maximal contraction of the triceps. Stop just shy of “locking out” the elbow joint completely to keep tension on the muscle. Avoid jerky motions or using momentum to lift the weight. The deliberate, slow lowering phase is just as important as the upward press for maximizing muscle fiber engagement and time under tension.
Form Cues and Avoiding Injury
To maximize the effectiveness of the exercise and ensure safety, several form cues should be strictly followed. A common error is allowing the elbow to flare out to the side during the movement, which shifts the tension away from the triceps and onto the shoulder joint. Keep the elbow tucked in close to the head and pointing forward throughout the entire set. Engaging the core muscles by bracing the abdominals is also necessary to prevent the lower back from arching excessively, especially when standing.
Selecting an appropriate weight is a safety measure, as attempting to lift a load that is too heavy can force the use of momentum, which greatly increases the risk of injury. The movement should be slow and deliberate, allowing for a strong mind-muscle connection with the triceps. If you notice any pain or significant discomfort in the shoulder, consider reducing the range of motion or the weight. The overhead position can be stressful on the shoulder capsule for individuals with limited mobility. The non-working hand can be used to lightly support the working upper arm, providing tactile feedback to help maintain the fixed, vertical position.
Seated Versus Standing Variations
The one-arm tricep extension can be performed equally effectively in both seated and standing positions, with the choice depending on individual goals and preferences. The standing variation requires greater overall body stability and engagement of the core musculature to maintain balance and an upright posture. This added requirement makes the standing version slightly more functional, as it integrates stabilizing muscles alongside the primary movers. However, the need to stabilize the torso can sometimes limit the amount of weight that can be lifted.
The seated variation, particularly when performed on a bench with back support, minimizes the role of the core and lower body in stabilization. By providing this external support, the seated position allows for a higher degree of isolation on the triceps muscle. This environment is conducive to lifting heavier loads or focusing intensely on the targeted muscle without the distraction of maintaining balance. Beginners or those aiming for maximal triceps hypertrophy may prefer the seated position for its added stability and focus, while more advanced lifters may opt for the standing version to incorporate a balance challenge.