You’re probably used to the standard barbell bench press. It’s the king of the gym, right? Or at least that's what everyone says until their shoulders start clicking like a bag of marbles or they realize one pec is noticeably beefier than the other. Honestly, the single arm chest press is the correction most people didn't know they needed. It’s not just a "lighter" version of a regular press. It’s a completely different animal that forces your core to scream while fixing the imbalances your heavy barbell has been hiding for years.
Most people treat unilateral work—lifting with one side at a time—as an afterthought. They'll tack on some light dumbbell curls at the end of a session. But if you take the single arm chest press seriously, you'll find it’s one of the most demanding horizontal pushing movements you can do.
The Science of Why One Arm is Better Than Two
There’s this thing called the bilateral deficit. Basically, research suggests that the sum of force you can produce with each arm individually often exceeds what you can produce with both arms simultaneously. When you lock into a barbell, your dominant side usually takes over. You might not even feel it happening. Your right pec does 55% of the work, your left does 45%, and over five years of training, that gap becomes a physical "lean" in your physique and a potential injury risk in your rotator cuff.
By switching to a single arm chest press, you're forcing isolation. There is nowhere for the weak side to hide.
But the real magic isn't even in the chest. It's in the contralateral core stability. When you hold a heavy dumbbell in your right hand and lie on a bench, that weight wants to pull your entire torso off the right side of the pad. Your left obliques and deep transverse abdominis have to fire like crazy just to keep you from flipping over. Dr. Stuart McGill, a world-renowned spine biomechanics expert, often talks about the "anti-rotation" benefit of unilateral loading. You’re essentially getting a world-class core workout while you build a bigger chest. It’s efficient. It's smart.
How to Actually Do It (Without Falling Off the Bench)
Don't just grab a weight and start pumping. That’s a fast track to a bruised floor and a bruised ego.
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First, get your setup right. Sit on the edge of the bench with the dumbbell resting on your thigh. As you lie back, kick the weight up with your knee. This protects your shoulder. Once you’re flat, your feet should be planted wide. Like, wider than usual. This gives you a broader base of support so you don’t roll.
Now, here is the secret: keep your non-working hand tight. Some people reach for the sky with it, others grip the side of the bench. I prefer making a tight fist with the free hand and holding it over my ribcage or out to the side for counter-balance. This creates "irradiation"—a nervous system trick where tension in one part of the body increases strength in another.
Lower the weight slowly. Feel the stretch. Your elbow shouldn't be flared out at 90 degrees; that’s a recipe for impingement. Keep it tucked at about 45 degrees relative to your torso. Press up explosively, but keep your shoulder blade pinned back into the bench. If your shoulder starts rounding forward at the top, you've lost the tension on the pec and put it all on the delicate front delt. Not good.
Common Mistakes That Kill Your Gains
Stop ego lifting. Seriously.
If you usually bench 100lb dumbbells, don't expect to just grab a 50lb and have it feel easy. The rotational force makes it feel way heavier. Most guys try to go too heavy too fast, and their form turns into a weird, squirming mess. If your hips are lifting off the bench or your opposite shoulder is rising to meet the weight, you’re failing.
- The "Half-Rep" Habit: People get scared of the bottom of the movement because that's where the balance is hardest. Go for the full range of motion.
- The Loose Lower Body: If your feet are dancing around, your chest won't grow. Drive your heels into the turf.
- Holding Your Breath: Bracing is key, but don't pass out. Use the Valsalva maneuver—inhale and brace at the top, hold through the descent, and exhale as you finish the press.
Variations That Actually Matter
You don't just have to use a flat bench. In fact, a single arm chest press on an incline is arguably better for upper pec development and hits the serratus anterior—that "thumbprint" muscle on your ribs—even harder.
Then there’s the floor press version. If you have history with shoulder pain, the floor acts as a natural "stop" for your elbow. This prevents you from overstretching the joint capsule while still letting you load up the triceps and chest. It's a favorite for powerlifters like Louie Simmons of Westside Barbell fame, who used floor presses to blast through sticking points.
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Cable variations are also killer. Standing single arm cable presses turn the move into a full-body stability test. Because the resistance is coming from behind and slightly to the side, your legs and glutes have to engage just to keep you upright. It’s less about raw chest size and more about "functional" strength—the kind that actually helps you move a couch or tackle someone on a field.
Why This Belongs in Your Program
Look, the barbell bench is great for moving the most weight possible. No one is saying stop doing it. But the single arm chest press fixes the "blind spots" that the barbell creates.
Think about athletes. A quarterback doesn't throw a ball with two hands from his chest. A boxer doesn't punch with both hands at the same time. Life happens one side at a time. Training the single arm chest press builds that "cross-body" power where force transfers from your left foot through your core and out your right arm.
It also gives your joints a break. The fixed path of a barbell can be unforgiving. Dumbbells allow your wrist and elbow to find their own natural path of least resistance. If you’ve been feeling a nagging ache in your bicep tendon or the front of your shoulder, switching to unilateral work for 4-6 weeks can often let the inflammation settle while you still maintain your muscle mass.
Real-World Implementation
If you’re wondering where to put this in your workout, try using it as your second "big" move. Do your heavy bilateral work first—maybe a weighted dip or a standard bench—then move into 3 sets of 8-12 reps of the single arm press.
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Focus on the "tempo." Go 3 seconds down, a 1-second pause at the bottom to kill momentum, and then drive up. You will be shocked at how much harder a 40lb dumbbell feels when you can't use your other arm to steady the ship.
You might even find that your "weak" side isn't actually weaker in the muscle, but just "quieter" in the brain. The mind-muscle connection is real. Focusing on one pec at a time forces your brain to map those motor units more effectively. When you eventually go back to the barbell, you'll likely find you have better control and a more even "drive" off the chest.
Actionable Steps for Your Next Chest Day
To get the most out of the single arm chest press, follow this progression over the next month:
- Week 1: Find Your Baseline. Start with a weight about 40% of what you'd use for a standard 10-rep dumbbell press. Focus entirely on keeping your hips flat and your torso still. Perform 3 sets of 10 reps per side.
- Week 2: Increase Tension. Stick with the same weight but add a 2-second pause at the bottom of every rep. This eliminates the "bounce" and forces your core to stabilize the weight at its most unstable point.
- Week 3: Load the Movement. Increase the weight by 5-10lbs. You’ll notice the rotational pull is much stronger now. Fight the urge to grab the bench with your free hand; keep that hand balled in a fist on your chest.
- Week 4: The "Off-Set" Challenge. Slide your body slightly to the side of the bench so the working shoulder is actually hanging just an inch or two off the edge. This increases the demand on your core exponentially. Only do this if you are confident in your stability.
By the end of this cycle, your pressing mechanics will be smoother, your core will be noticeably tighter during heavy lifts, and those nagging shoulder imbalances will start to fade. The single arm chest press isn't a "soft" exercise—it’s a precision tool for building a bulletproof upper body. Stop ignoring the asymmetry and start pressing one arm at a time.