How do you count reps on the Alternating Dumbbell Bench Press?

Most programs count each lower-and-press with one arm as one rep for that side, so 10 reps means 10 with each arm. Writing it as reps per side keeps sets comparable from session to session.

Is the alternating version better than the regular dumbbell bench press?

Neither is better overall. The Dumbbell Bench Press lets you press more weight with both arms at once, while the alternating version adds a longer set, a still hold at the top and more work for the trunk to keep the body square, so many lifters use it as an accessory rather than their main press.

Should the top arm stay fully straight while the other arm presses?

Yes, keep it straight with the dumbbell directly over the shoulder, so the weight rests on a stacked arm instead of on bent elbows. If it starts to bend or drift, the weight is too heavy for the set.

How is this different from the Dumbbell Single-Arm Bench Press?

The Dumbbell Single-Arm Bench Press uses one dumbbell and finishes all of one side's reps before switching, with the other hand empty. Here both hands hold a dumbbell, the sides trade every rep and the waiting arm holds its dumbbell at the top.

Should I use less weight than on the regular dumbbell bench press?

Usually a little less, because the top arm has to hold its dumbbell still for the whole set and the set lasts about twice as long. Start lighter than your regular dumbbell press and add weight once both arms finish every rep without the top dumbbell drifting.

Alternating Dumbbell Bench Press

What Is the Alternating Dumbbell Bench Press?

Alternating Dumbbell Bench Press is a compound exercise that primarily targets the chest and also engages the front of the shoulders and the triceps. It is an intermediate-level movement performed lying on a flat bench, with both dumbbells pressed up over the shoulders to start. One arm lowers its dumbbell to the side of the chest and presses it back up while the other arm holds its dumbbell still at the top, then the arms swap roles. Because the waiting arm stays straight overhead instead of resting at the chest, both arms carry a load for the whole set.

The alternating pattern changes the press in two ways. Each lowering is done with one dumbbell at a time, so the body is loaded unevenly and the trunk, especially the obliques, has to keep the torso flat on the bench instead of letting it roll toward the working side, while the holding arm and its shoulder work to keep the top dumbbell steady. The set also lasts longer than a regular dumbbell press for the same number of reps per arm, which adds time under tension for the chest and shoulders, and it shows any difference in strength or control between the two sides, since each arm has to press on its own.

Dumbbells also ask more of the arms and shoulders to steady the weight than a barbell does. In a study of 12 resistance-trained men pressing both dumbbells together, the men lifted about 17% less with dumbbells than with a barbell, with similar chest and front-shoulder activity, lower triceps activity and higher biceps activity. The study did not test an alternating press, but it explains why dumbbell pressing calls for lighter loads than a barbell bench press.

It is an accessory lift rather than a competition or test lift. Lifters usually place it after their main pressing work, or use it in place of the Dumbbell Bench Press when they want more trunk control and longer sets at a moderate weight. It also differs from the Dumbbell Single-Arm Bench Press, where one dumbbell is pressed for all of one side's reps before switching, while here both hands hold a dumbbell and the sides trade every rep.

The movement suits lifters who already press a pair of dumbbells with steady control and want a harder stability challenge without adding much weight. Newer lifters should build a base with the Push-Up and the regular Dumbbell Bench Press first, until both dumbbells stay stacked over the shoulders at the top without drifting.

Muscles Worked

MuscleActivation

Pectoralis Major: Primary
Deltoid: High
Triceps Brachii (Lateral Head): Medium
Triceps Brachii (Medial Head): Medium
Biceps Brachii: Low
External Oblique: Low
Infraspinatus: Low
Serratus Anterior: Low
Triceps Brachii (Long Head): Low
Rectus Abdominis: Minimal

Instructions

Sit on the end of a flat bench with a dumbbell standing on each thigh, held with an overhand grip.
Lie back, using your knees to help bring the dumbbells to the sides of your chest, then press both up until your arms are straight and the dumbbells sit over your shoulders with your palms facing your feet.
Keep your head, upper back and hips on the bench and your feet flat on the floor with knees bent, and draw your shoulder blades back and down.
Keeping one arm straight with its dumbbell still over its shoulder, lower the other dumbbell under control to the side of your chest, with the elbow angled about 45 to 60 degrees from your torso and the forearm vertical.
Press that dumbbell back up until the arm is straight and both dumbbells are level at the top again.
Hold it there and lower the dumbbell in the other hand the same way, then press it back up.
Keep alternating sides, breathing in as you lower and out as you press, and keep your torso square on the bench without rolling toward the working arm.
To finish, lower both dumbbells to your chest together, bring them down to your thighs and sit up using your knees.

Common Mistakes

Letting the top dumbbell drift
The holding arm bends or lets its dumbbell wander toward the face or out to the side instead of keeping it still over the shoulder.
Rolling toward the working arm
The torso and hips twist as one dumbbell lowers, which turns the trunk's job of resisting rotation into a rocking motion and takes load off the chest.
Flaring the elbows
Lowering with the upper arm out at 90 degrees to the torso puts more stress on the front of the shoulder than an elbow angle of about 45 to 60 degrees.
Dropping the dumbbell too fast
Letting the working dumbbell fall to the chest and bouncing it back up loses control at the bottom, where the shoulder is most exposed.
Going too heavy
Using the weight from a regular dumbbell press often means the holding arm gives out before the working arm finishes its reps.
Lifting the hips
Pushing the hips off the bench to drive the press arches the lower back and makes the torso harder to keep square.

Injuries

Alternating Dumbbell Bench Press is a medium risk exercise when performed with proper technique. The front of the shoulder and the chest take the most strain at the bottom of each rep, especially when the elbow flares out to 90 degrees or the dumbbell sinks below the level of the chest. The holding arm adds a risk of its own: as it tires, its dumbbell can drift toward the face or out to the side, and the wrist can bend back under the load.

Choose a weight you can hold still at the top for the whole set, not just one you can press. Keep the elbows angled about 45 to 60 degrees from the torso, lower only to the side of the chest, and keep each wrist stacked over its elbow. End the set as soon as the top arm starts to shake or bend, lower both dumbbells to the chest together before you sit up, and have a spotter stand by for heavier sets.

If keeping the torso square or the top arm steady is hard, go back to the Dumbbell Bench Press, pressing both dumbbells together, or try the Dumbbell Floor Press, where the floor limits how deep the elbows can go. To progress, add load gradually or pause briefly at the bottom of each rep.

Stop if you feel sharp or pinching pain in the front of the shoulder, pain deep in the chest or near the armpit, or numbness or tingling down the arm, and see a qualified clinician if it persists.

Overview

Primary Focus: Chest
Equipment: Dumbbell and bench
Modality: Strength
Difficulty: Intermediate

Alternative Exercises

Frequently Asked Questions

Q: How do you count reps on the Alternating Dumbbell Bench Press?: Most programs count each lower-and-press with one arm as one rep for that side, so 10 reps means 10 with each arm. Writing it as reps per side keeps sets comparable from session to session.
Q: Is the alternating version better than the regular dumbbell bench press?: Neither is better overall. The Dumbbell Bench Press lets you press more weight with both arms at once, while the alternating version adds a longer set, a still hold at the top and more work for the trunk to keep the body square, so many lifters use it as an accessory rather than their main press.
Q: Should the top arm stay fully straight while the other arm presses?: Yes, keep it straight with the dumbbell directly over the shoulder, so the weight rests on a stacked arm instead of on bent elbows. If it starts to bend or drift, the weight is too heavy for the set.
Q: How is this different from the Dumbbell Single-Arm Bench Press?: The Dumbbell Single-Arm Bench Press uses one dumbbell and finishes all of one side's reps before switching, with the other hand empty. Here both hands hold a dumbbell, the sides trade every rep and the waiting arm holds its dumbbell at the top.
Q: Should I use less weight than on the regular dumbbell bench press?: Usually a little less, because the top arm has to hold its dumbbell still for the whole set and the set lasts about twice as long. Start lighter than your regular dumbbell press and add weight once both arms finish every rep without the top dumbbell drifting.