One Arm Dumbbell Bench Press
The one arm dumbbell bench press is a unilateral version of the standard dumbbell bench press, pressing a single dumbbell straight up while your other arm and your core work to keep your torso from twisting. Beyond building the chest, shoulders, and triceps like any bench press, it adds a real anti-rotation core demand that the two-arm version doesn't ask for, since nothing balances the load on the opposite side.
Why it works
Pressing with both arms at once means the two sides of the load balance each other out, so your torso barely has to resist any rotation. Take one arm out of the equation and that balance disappears: the pressing arm creates a real turning force through your shoulders and ribcage, and your core, obliques, and the resting arm's position all have to work to keep you square on the bench. That extra stabilization demand is why this variation is often used to expose (and fix) side-to-side strength imbalances between arms, on top of the usual chest, shoulder, and triceps work a bench press provides.
Set up
- Sit on a flat bench holding one dumbbell in the working hand, resting it on your thigh.
- Lie back while bringing the dumbbell to your chest with the same motion you'd use for a two-arm press.
- Plant both feet flat on the floor and set your shoulder blades back and down against the bench.
- Rest your free hand lightly on your stomach, or hold the side of the bench if you need extra stability at first.
How to do it
- Press the dumbbell straight up over your chest, keeping your wrist stacked over your elbow.
- Actively resist the urge to let your torso rotate toward the working side as you press.
- Lock out at the top without letting your shoulder shrug up toward your ear.
- Lower the dumbbell back down under control, following the same straight path back to your chest.
- Keep your hips and shoulders square to the ceiling through the entire rep, on both the way up and down.
- Complete all reps on one side before switching the dumbbell to the other hand.
Form cues
- Brace your core hard before each rep to resist rotation.
- Keep both shoulders pinned to the bench, not just the pressing side.
- Press straight up, not out over your face or off to the side.
- Move the same speed up and down; don't let the weight drop fast.
Breathing: Take a breath and brace before you press, exhale as the dumbbell locks out at the top.
Common mistakes
Letting the torso twist and the opposite shoulder lift off the bench during the press.
Fix: Brace your core before you press and keep both shoulder blades pinned to the bench for the entire rep, using a lighter weight if that's what it takes.
Pressing the dumbbell out over the face or off to the side instead of straight up.
Fix: Keep your wrist stacked directly over your elbow and press in a straight vertical line over your chest.
Using a weight so heavy that only the working side stays under control while the rest of the body compensates.
Fix: Choose a weight where you can complete every rep with your hips and shoulders staying square, even if that means going lighter than your two-arm press.
Rushing through reps on the weaker side to match the stronger one.
Fix: Train each side to the same standard of control rather than the same number of fast reps, since the point of the exercise is partly to close that gap.
How to program it
- Because it's a loaded, single-limb compound press, one focused session a week per side is a sensible default unless you're pairing it with lighter accessory pressing later in the week.
- Start with 3 sets of 8 to 10 reps per side at a weight noticeably lighter than your two-arm dumbbell press, since the added stabilization demand limits how much load you can control.
- Use it earlier in a session while your core is fresh enough to resist rotation properly, rather than at the end when fatigue makes twisting more likely.
- If one side is noticeably weaker, train that side first while you're freshest, and match the stronger side to the same weight rather than letting it drift ahead.
Safety notes
- Start lighter than you'd expect based on your two-arm press, since the stabilization demand is the real limiting factor here, not raw pressing strength.
- Stop the set if you feel your torso twisting more than a small amount; that's a sign the weight is too heavy for controlled reps.
- Keep a spotter or use a lighter weight than your one-rep comfort zone when trying this variation for the first time.
Exercise profile
- Force
- Push
- Mechanics
- Compound
- Category
- Strength
Frequently asked questions
How much weight should I use for one arm dumbbell bench press?
Start noticeably lighter than your two-arm dumbbell press, often by 20 to 30 percent, since resisting the rotation is usually the limiting factor before your pressing strength is.
One arm vs two arm dumbbell bench press: what's the real difference?
The two-arm version balances the load evenly, so your torso barely has to resist rotation. The one-arm version removes that balance, adding a real core and anti-rotation demand on top of the same chest, shoulder, and triceps work.
Can I do one arm dumbbell bench press without a bench?
You can perform a similar unilateral press lying on the floor, though your range of motion will be shorter since your elbow will stop at the floor rather than dropping below bench height.
Why does my torso twist when I press with one arm?
Usually the weight is heavier than your core can currently control, or your feet and shoulder blades aren't set firmly against the bench and floor. Lighten the load and focus on bracing your core before every rep.