Dumbbell One Arm Triceps Extension (on bench)

Target muscle: Triceps Brachii
Equipment: Dumbbell
Body part: Upper Arms
Type: Strength

The dumbbell one arm triceps extension (on bench) is a single-arm isolation exercise that targets the triceps brachii of the upper arm. Performed seated on a bench with one dumbbell pressed overhead, it lets you train each arm independently to even out strength imbalances and build the back of the upper arm.

How to do the Dumbbell One Arm Triceps Extension (on bench)

1Sit upright on the bench with your feet flat on the floor and your core braced.
2Hold a single dumbbell in one hand and press it straight overhead until your arm is fully extended, palm facing forward or inward.
3Keep your upper arm vertical and close to your head, with your elbow pointing toward the ceiling.
4Lower the dumbbell behind your head under control by bending only at the elbow, until your forearm passes roughly parallel to the floor.
5Feel the stretch in the triceps at the bottom, keeping your upper arm still throughout.
6Extend your elbow to press the dumbbell back up until your arm is fully straight, squeezing the triceps at the top.
7Complete your reps on one arm, then switch the dumbbell to the other hand and repeat.

Form tips

Keep your upper arm fixed and vertical so the movement happens only at the elbow, isolating the triceps.
Lower the weight slowly and under control to protect the elbow and keep tension on the muscle.
Brace your core and keep your torso upright instead of leaning to one side to help lift the weight.
Use your free hand to lightly support the working upper arm if you need extra stability.

Common mistakes

Letting the elbow drift forward or flare out, which shifts work off the triceps and stresses the joint.
Using a weight so heavy that your torso twists or leans to swing the dumbbell up, which cheats the rep.
Stopping short at the top and not fully extending the elbow, which reduces triceps activation.
Bouncing out of the bottom instead of controlling the stretch, raising the risk of elbow strain.

Frequently asked questions

What muscles does the dumbbell one arm triceps extension work?

It isolates the triceps brachii, the muscle on the back of your upper arm responsible for straightening the elbow.

Why train triceps one arm at a time?

Working one arm at a time lets you fix side-to-side strength imbalances and focus fully on the working triceps with a longer range of motion.

How many sets and reps should I do?

For building the triceps, 3 to 4 sets of 10 to 15 reps per arm with a controlled tempo works well. Pick a weight you can move without your torso twisting.

Is this exercise good for beginners?

Yes. Start with a light dumbbell to learn the movement, keep your upper arm still, and add weight only once your form is solid.