One-Arm Seated DB Extension

A muscular man seated on a bench performing a seated dumbbell tricep extension. The image shows a sequence from start to finish of the exercise, with the man raising a dumbbell overhead with one arm.

Exercise Description

The One-Arm Seated Dumbbell Triceps Extension is an isolation exercise that targets the triceps one arm at a time. Performing the exercise in a seated position reduces balance demands, allowing greater focus on triceps activation and proper technique. The overhead position places the long head of the triceps under a deep stretch, making this exercise highly effective for building upper-arm size, strength, and muscular symmetry.

Primary Muscles Worked

  • Triceps Brachii (Long Head, Lateral Head, and Medial Head)

Secondary Muscles Worked

  • Anconeus

  • Anterior Deltoids (Stabilization)

  • Rotator Cuff Muscles (Stabilizers)

  • Upper Trapezius

  • Core Muscles (Stabilization)

How to Perform Correctly

Setup

  1. Sit upright on a bench with your feet flat on the floor.

  2. Hold a dumbbell in one hand and press it overhead until your arm is fully extended.

  3. Keep your chest lifted and your spine neutral.

  4. Engage your core for stability.

  5. Position your elbow close to your head and pointing upward.

Movement

  1. Slowly lower the dumbbell behind your head by bending your elbow.

  2. Keep your upper arm stationary throughout the movement.

  3. Lower the weight until you feel a comfortable stretch in your triceps.

  4. Pause briefly at the bottom position.

  5. Extend your elbow and raise the dumbbell back to the starting position.

  6. Squeeze your triceps at the top of the movement.

  7. Complete all repetitions on one arm before switching sides, or alternate arms as desired.

Common Mistakes to Avoid

Allowing the Elbow to Flare Out

  • Keep the elbow close to your head to maximize triceps engagement and maintain proper alignment.

Using Excessive Weight

  • Heavy weights can compromise technique and increase stress on the shoulder and elbow joints.

Moving the Upper Arm

  • The upper arm should remain relatively stationary throughout the exercise.

Arching the Lower Back

  • Sit upright and engage your core to maintain proper spinal alignment.

Using Momentum

  • Avoid swinging the weight or using body movement to assist the lift.

Incomplete Range of Motion

  • Lower the dumbbell fully under control and extend the elbow completely at the top.

Lowering the Weight Too Quickly

  • Control the eccentric phase to maximize muscle activation and joint safety.

Arm Exercises