Dumbbell One-Arm Triceps Extension
One dumbbell, one arm, held straight overhead and lowered behind the head while the upper arm stays vertical. Because the shoulder is flexed, the long head of the triceps starts already lengthened — and the single-arm setup means your stronger side cannot quietly cover for the weaker one.
Own the movement
Set up first, then execute. Every cue below is something you can check on your next set.
Before the first rep
- Sit on an upright bench with a back pad, or stand with feet hip-width — either works, but a back pad stops you arching.
- Clean one dumbbell to your shoulder, then press it overhead to a straight arm beside your ear.
- Turn the palm to face forward so the little finger points at the ceiling. This keeps the elbow tracking cleanly.
- Support the working upper arm with your free hand, or grip the bench, so the elbow stops drifting outwards.
- Brace your abs and tuck the ribs down — an arched lower back is how people cheat this into a shoulder movement.
Every rep
Breathing & tempo — Inhale as the dumbbell travels behind your head, exhale as you extend. Three seconds down, one second up, and no pause at the top.
Before you load it
- Keep the free hand ready near the dumbbell. Failing behind your own head with a heavy bell is one of the few ways a small arm exercise causes a real injury.
- Sharp pain at the point of the elbow means stop — this position loads the triceps tendon at its longest, and it is the classic aggravator of existing elbow tendinopathy.
Sets, reps & load
Where to start, and what to change when it stops being hard.
Start with a 6-10 kg dumbbell — far lighter than lifters expect, because the arm is at a long lever and the long head is in a weak position. Add 2 kg only when you can hit 15 reps with the elbow held motionless. If you have to swing the torso, the dumbbell won that set.
What goes wrong
The errors that show up most often, and the cue that fixes each one.
Cup the working elbow with your free hand and physically hold it beside your ear. If it still wanders, the dumbbell is 4 kg too heavy — this movement rewards small loads.
Sit against a back pad, squeeze the glutes and pull the front ribs down. The load should be moving through elbow extension only, not through a lumbar hinge.
Lower until the forearm is well past parallel and you feel tension deep in the back of the arm. The stretched position is the entire reason for choosing an overhead variation.
Start every set with the weaker arm and cap the strong side at the same rep count. Otherwise the imbalance persists for years.
Why bother
The long head crosses the shoulder as well as the elbow, so it only reaches full stretch when the arm is overhead. Pushdowns and dips train the triceps with the elbow at your side and leave that head short; this position is the direct fix, and it is why an overhead extension belongs in most arm sessions.
Doing it one arm at a time costs time and buys honesty. Two-arm overhead work lets the dominant side take an extra 10-15% of the load without you noticing. Here each arm has to finish its own reps, and you will usually find one side gives out two reps early.
Where it fits
Second or third triceps movement of a push day, after a heavy press, in the 10-15 range. Pair it with a pushdown or a dip rather than another overhead variation — one stretched-position movement per session is enough, and the long head takes several days to recover from it.
If this one isn't it
No kit, too hard, or too easy — here's where to go instead.
Same job, different kit
Start here instead
Asked and answered
One arm at a time or both hands on one dumbbell?
Both-hands versions let you load heavier and are fine as a mass builder, but they hide side-to-side differences and the elbows tend to flare. Use the single-arm version when you want the imbalance visible and the elbow position controlled.
How heavy should this get?
Much lighter than your pushdown. A 12-16 kg dumbbell for sets of 12 is respectable; chasing 25 kg here almost always means the torso is doing the lifting. Judge the movement by elbow stillness, not by the number on the bell.
Seated or standing?
Seated with a back pad, for anything you intend to progress. Standing lets you drive the weight up with a lean and a lumbar arch, and that cheat arrives quietly — you will add 4 kg and think it was the triceps. Stand only when every bench is taken, and cut the load when you do.
My elbows ache the day after. What should I change?
Reduce the load and stop lowering into the deepest range for a few weeks, then rebuild depth gradually. Warming the elbows up with a set of 20 light pushdowns before the first working set helps more than anything else.