Why the Single Arm DB Bench Press is Actually Better Than the Standard Version

You’re probably used to seeing people hogging the flat bench with a massive barbell or a pair of heavy dumbbells, grunting through sets of ten. It’s the standard. It's what we do. But honestly? Most of those people are leaving a lot of gains on the table because they refuse to work one side at a time. The single arm db bench—or the unilateral dumbbell floor/bench press if you want to be fancy—is one of those moves that looks easy until you actually try to stay on the bench without sliding off. It's a humbling experience.

Most gym-goers view unilateral training as a "finisher" or something you do only when you're injured. That’s a mistake. When you press a single weight with one hand, your body isn't just worried about your chest. It's panicking. Your entire contralateral (opposite) side has to fire like crazy just to keep you from rotating onto the floor. This turns a basic chest move into a high-stakes core stability drill.

The Science of Why One Arm Beats Two

It’s called the bilateral deficit.

Research, like the studies published in the European Journal of Applied Physiology, suggests that the sum of force produced by each limb individually is often greater than the force produced by both limbs working together. Basically, your nervous system can focus its "battery power" better on one arm than trying to split it between two. When you do a single arm db bench, you’re often able to recruit more motor units in that specific pec and shoulder than you would during a standard press.

Then there's the core.

Dr. Stuart McGill, basically the godfather of spine biomechanics, has talked extensively about "the shimmy." When you have a load on only one side of the axis (your spine), your internal and external obliques have to work overtime to provide anti-rotation. You aren't just building a chest; you're building a trunk that can handle uneven loads in the real world, like carrying a heavy suitcase or wrestling a dog.

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It's functional. I know that word is overused, but here, it actually fits.

How to Do This Without Falling Off the Bench

Setup is everything. If you just lay down and start pushing, you'll fail.

First, sit on the edge of the bench with one dumbbell resting on your thigh. Kick it back as you lie down, but here is the secret: keep your non-working hand tight. Some people reach it toward the ceiling; others clench their fist against their chest. Whatever you do, don't let it just dangle. A dangling arm is a recipe for a loss of tension.

Your feet need to be wider than usual. This is your tripod. If your feet are tucked under your butt like a powerlifter, you're going to tip. Spread them out. Dig your heels in.

As you lower the weight, think about pulling the dumbbell down with your lat. Don't just let gravity take it. Stop when your elbow is slightly below the bench height—or when your upper arm hits the floor if you’re doing the floor press variation—and then drive it back up. You’ll feel a weird "tugging" sensation across your midsection. That’s your core doing its job. Don't fight it; embrace it.

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Common Mistakes That Kill Your Progress

People get greedy. They see their 80-pound dumbbell press for reps and think they can do the same with the single arm db bench.

You can't. Not at first.

If you go too heavy too soon, you’ll start "cheating" by tilting your hips. If your butt cheeks aren't both glued to the bench, the set doesn't count. You’re compensating. Another big one is the "death grip." While you want a firm grip, squeezing the life out of the handle can sometimes lead to elbow tendonitis if your forearm flexors are already fried.

Also, watch your shoulder blade. It needs to stay "packed." If your shoulder starts rounding forward at the top of the movement, you're putting the small rotator cuff muscles at risk. Keep that blade tucked into your back pocket.

Variations Worth Your Time

1. The Single Arm DB Floor Press: This is actually my favorite version. By lying on the floor, you limit the range of motion, which protects the shoulder joint. It's a godsend for people with "creaky" shoulders or those who tend to over-stretch at the bottom of a bench press. Plus, it forces you to generate force from a dead stop.
2. The Incline Version: Shift the bench to a 30-degree angle. Now, you’re hitting the upper pecs and the anterior deltoid. The stability requirement stays high, but the line of pull changes.
3. The Alternating Press: This is the middle ground. You hold two dumbbells up, lower one, press it back, then lower the other. It's technically unilateral work, but you have the counterweight of the "resting" dumbbell to help stabilize you. It's a good "bridge" exercise.

Why This Belongs in Your Program Right Now

If you have a strength imbalance—and let’s be real, we all do—the single arm db bench is the fastest way to fix it. Your dominant side loves to take over during a barbell press. It’s a bully. By isolating the sides, you force the "lazy" pec to do the work. Over time, this leads to better symmetry and, surprisingly, a bigger barbell bench press because your weak links are gone.

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It’s also incredibly taxing on the nervous system. You’ll find that a set of 8 reps with one arm feels way more exhausting than a set of 8 with both. That's the "neural drive" in action. You're teaching your brain how to coordinate movement under lopsided stress.

Practical Programming Steps

Don't overcomplicate it. You don't need a whole new "one-arm day."

• As a Primary Move: If you’re coming back from a shoulder tweak, make this your main lift. 4 sets of 6–8 reps. Focus on the tempo: 3 seconds down, 1 second pause, explosive on the way up.
• As an Accessory: After your heavy barbell work, throw these in for 3 sets of 10–12. It’ll flush the muscle with blood and challenge your stability when you're already tired.
• The "Core" Finisher: Try doing these on a stability ball if you’re feeling brave. It’s significantly harder and requires much lighter weight, but the abdominal recruitment is off the charts. Just... be careful.

Start with your weaker side first. If your left arm can only do 9 reps, your right arm only does 9 reps. No matter how much more the right side has in the tank, you stop. This is how you achieve true muscular balance.

Stop thinking of the bench press as just a "chest day" staple. When you switch to the single-arm variation, it becomes a full-body stability challenge that builds a bulletproof torso and a more powerful, symmetrical upper body. Grab a dumbbell, keep your feet wide, and stop letting your dominant side do all the heavy lifting.

Actionable Next Steps

1. Identify your weak side by performing a set to near-failure with a moderate weight on each arm separately.
2. Swap your secondary chest exercise (like machine flyes or incline DB press) for the single arm db bench for the next four weeks.
3. Record your sets from a side profile to ensure your hips and shoulders remain parallel to the floor throughout the entire movement.
4. Increase weight only when you can perform all reps without any hip shifting or "shimmering" on the bench.