One Arm Supinated Dumbbell Triceps Extension
A lying single-arm extension performed with the palm turned back toward your own face. The underhand grip is the weakest position your forearm can hold a dumbbell in overhead, so this is deliberately light, high-control work — and the reversed grip is a balance problem long before it is a triceps problem.
Own the movement
Set up first, then execute. Every cue below is something you can check on your next set.
Before the first rep
- Choose a dumbbell around half what you use for a neutral-grip single-arm extension, and expect to go lighter still on the first session.
- Lie flat with feet planted, rotate the palm to face you while the dumbbell is still at your chest, then press it up already supinated.
- Let the wrist stay straight and stacked under the handle rather than bending back under the load.
- Grip the working bicep with the free hand to pin the upper arm in place.
- Angle the working upper arm about 10-15 degrees back from vertical so there is still tension at the top.
Every rep
Breathing & tempo — Inhale down, exhale up, and do not hold your breath — the loads are too light to need bracing and holding it only tightens the wrist. Three seconds down, one-second squeeze, two seconds up.
Sets, reps & load
Where to start, and what to change when it stops being hard.
Start at 3-4 kg per hand — genuinely. Twelve slow reps per arm with 8 kg, wrist straight and palm fully supinated the whole way, is about as far as this variation usefully goes. Progress by adding reps and slowing the eccentric rather than by loading; when 8 kg feels easy, switch to a neutral or pronated grip and load that instead.
What goes wrong
The errors that show up most often, and the cue that fixes each one.
Keep the knuckles stacked over the forearm and drop 2 kg. A collapsing wrist here is the load being higher than your grip position can carry, not a weak triceps.
Cap the weight and chase reps and control instead. Do your heavy triceps work on an EZ bar or a machine and let this stay a light finisher.
Set the grip at your chest where your shoulder has leverage, then press. Rotating a load overhead on one wrist is the part of this movement most likely to tweak something, and it buys you nothing.
Hold the bicep with the free hand and fix a point on the ceiling the elbow must stay under. If the elbow travels, end the set there.
Why bother
Supinating the forearm rotates the dumbbell so its weight sits behind your line of grip rather than balanced over it. Holding that at arms length demands constant wrist and forearm control, which is why the same person who extends 14 kg neutral will struggle honestly with 6 kg here.
Popular lore says the underhand grip carves out the medial head. Treat that with suspicion: all three heads share one tendon into the ulna and all three extend the elbow together. What the grip genuinely does is change where you feel the effort and force you to move slowly, and both of those have value at the end of a session.
Where it fits
A finisher, 2 sets per arm, after the heavy triceps work is already done. It is not a movement to build a program around — nobody adds meaningful load to a supinated single-arm extension. Use it as a change of stimulus for a block, or when your elbows want a break from pronated bar work.
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
Why can I barely handle any weight on this?
Because a supinated grip puts the dumbbell's mass behind your palm at the top of the rep, so your wrist and forearm are fighting a rotational load the entire set. That limit is the grip position, not your triceps. Going lighter is the correct response, not a sign of weakness.
Does the underhand grip target the medial head?
Not in any way you can rely on. The three heads insert through a shared tendon and fire together to extend the elbow. Grip changes shift comfort, leverage and where you feel the burn, but you cannot pick a head off a menu. Use variety for its own sake and stop there.
Should I do this instead of pushdowns?
No — alongside, at most. A pushdown or a machine extension lets you load the muscle properly and take a set to failure safely. This variation caps out at a weight most people could curl for twenty reps, so it belongs at the end of the session, not at the start.
My wrist aches afterwards. Is that normal?
Mild forearm fatigue is expected; an aching wrist joint is a signal to change something. Lower the weight, keep the knuckles stacked over the forearm rather than letting the hand fall back, and if it persists switch to a neutral grip where the wrist sits in a far more natural position.