Unilateral exercises: what one side at a time does, and what it doesn't

A unilateral exercise trains one arm or one leg at a time: a split squat, a step-up, a one-arm row. A bilateral exercise uses both together: a squat, a deadlift, a bench press. Most programs mix the two, and the useful question is what the one-sided version adds.

This page covers what the training studies show for muscle and strength, the bilateral deficit, what is and isn't known about muscle imbalances, the main exercises for the legs, glutes, back, chest and arms, and how to program them beside the two-limb lifts.

What unilateral training does for muscle and strength

• Muscle: no clear difference. A 2025 meta-analysis of nine studies found no significant difference in muscle growth between one-limb and two-limb training, though the authors call the evidence limited.¹
• Strength: whichever you train. In the same analysis, two-limb training raised two-limb strength more and one-limb training raised one-limb strength more; the authors' reading is that strength gains follow the principle of specificity.¹ A 2026 analysis of 24 randomized trials with 588 people, 17 of the trials in athletes and many on jump or combined programs rather than lifting alone, found the same split, an edge for one-sided training on one-leg jumps, and no difference for sprints or changes of direction.²
• Strong on both lifts. In a five-week trial, 18 academy rugby players trained twice a week with either the back squat or the rear-foot-elevated split squat; both groups got stronger on both lifts, with no significant difference between them.³
• Also the other side. Training one limb also raises strength in the untrained one, an effect called cross-education: the American College of Sports Medicine's 2026 position stand found strength improved in the untrained, opposite limb.⁴

So the studies show no clear edge for one side at a time over two, in either direction. It's a way to train the same muscles with lighter equipment, to get stronger at one-sided tasks, and to make each side do its own share of the work.

The bilateral deficit

When both limbs push at once, each one can produce less force than it does on its own. That's the bilateral deficit: a drop in the force from a single limb during an all-out effort with both. A 2016 review calls it an inconsistent phenomenon. Its size varies, it doesn't always appear, and the reverse, a two-limb boost, has been measured too.⁵ A 2026 review counted it in 50 of 63 studies of dynamic movements and found that training shifts it: two-limb training shrank it, and one-limb training enlarged it. The same review describes the research on whether it matters for athletic performance as contradictory.⁶

In practice, it's one reason one-leg and two-leg strength don't line up neatly: what you lift on two legs may not be twice what one leg can do. It isn't a reason to drop the squat. The training studies above found no clear difference in muscle growth either way.

Unilateral exercises for muscle imbalance: what is and isn't shown

"Muscle imbalance" usually means one side stronger than the other. Researchers call it inter-limb asymmetry, and they have studied it mostly in athletes:

• Linked with performance, not shown to cause anything. A 2018 systematic review of 18 studies found that strength differences between the legs may be detrimental to jumping, kicking and cycling. Every one of those results came from associations: no randomized trial was included.⁷
• Training can shrink it. A 2026 review of 11 studies of leg training covering 297 athletes aged 12 to 30 found that asymmetries shrank more consistently with one-sided training than with two-sided training, and that giving the weaker limb the extra attention, starting each exercise with it or adding volume for it, looked more effective still. The authors add that differences between the studies limit how far the findings generalize.⁸

What isn't shown: that a small difference between your sides is a problem for someone who lifts recreationally, that two-limb lifts create one, or that one-sided work has to be added to fix one. If one side is clearly and consistently behind on the same exercise, the review's two strategies are starting with the weaker side and adding volume for it. This page's cautious version: start with the weaker side, match its reps on the stronger one, and give it an extra set only if the gap holds over several weeks.

The main unilateral exercises

Three studies show what the one-sided versions ask of the rest of the body. In 15 training-experienced men, the single-leg deadlift worked the gluteus medius and the biceps femoris, one of the hamstrings, harder than the conventional deadlift.⁹ In 15 resistance-trained men, one-arm rows worked the obliques more than two-arm rows, while two-arm rows generally worked the muscles along the spine more.¹⁰ In 11 adults, six men and five women, one-arm chest presses produced more activity in the trunk's stabilizing muscles than two-arm presses, and one-arm shoulder presses more in the back's.¹¹ All three measured activity during a set, not growth over weeks.

For the glutes, the glute workout builds a session around two of the leg exercises above.

How to program them beside bilateral lifts

• After the main lift. Squat or deadlift first, then one single-leg exercise; bench press or row first, then a one-arm version if you want one. The two-limb lift carries the most load, so it goes where you're freshest.
• Two or three sets a side. The ACSM's 2026 stand advises at least two sets per exercise.⁴ A set on each side counts as one set for those muscles.
• Weaker side first, then match its reps on the stronger side, so both sides do the same work.
• As the main lift at home. When the dumbbells are light, one leg at a time is how they keep up with your legs; the dumbbell version of the leg day leans on it.
• Plan the time. Every set happens twice, so a one-sided exercise takes about twice as long as its two-sided version. One or two per session is usually plenty.
• Balance first, load second. If balance gives out before the muscle does, hold a rack or a wall with your free hand, or move to a split squat with the back foot on the floor.

Common mistakes

• Always starting with the strong side. The weaker side sets the reps; the stronger one matches them.
• Letting the other side help. Pushing off the back foot on a split squat or step-up, or twisting the trunk to heave a one-arm row.
• Loading ahead of your balance. If you wobble, go lighter or hold something with the free hand.
• Replacing every two-limb lift. Muscle growth showed no clear difference either way, but two-limb strength follows two-limb training.
• Training through something that hurts. Sore muscles the next day are normal; anything sharp or lasting isn't. Stop, and see a doctor or a physical therapist.

If you'd rather not plan it alone

Choosing a single-leg exercise is easy; deciding which two-limb lift it follows, how many sets your week already has, and whether one side needs more is the part a page can't do. Coaching is the version where your workouts are built around the days you actually have, and a weekly call looks at the week you just had and rebuilds the next one. Coaching to build muscle explains how that works, and here's how to apply. Otherwise: add one single-leg exercise after your next squat, weaker side first.