Unsung Advantages of Unilateral Strength Training

 As a competitive powerlifter, Samantha Rothberg used to pick up barbells that weighed two times as much as she did. Now, she often opts for much lighter dumbbells or kettlebells to perform unilateral exercises — movements where one limb moves independently — that she believes power her through triathlon after triathlon.

Meanwhile, Mike Boyle, former strength coach for the Boston Red Sox and Boston Bruins and partner at Mike Boyle Strength & Conditioning, rarely, if ever, has clients in his gym using barbells. “Nobody barbell bench presses, nobody barbell squats, nobody barbell deadlifts,” he said. “But we will do all those patterns with dumbbells and that allows people to be much more adaptive.”

That’s one of the benefits of unilateral training: Because you have one weight in each hand, or one leg under resistance, the exercise doesn’t force you into a certain position the way a barbell (or certain machines) can. In that way, they’re more forgiving and can be better for joint health.

Even though unilateral exercises are somewhat new to her own repertoire, “as a trainer, I would always program unilaterally for my clients,” said Rothberg, a certified strength and conditioning specialist and triathlon coach, primarily because everyone moves unilaterally through life. Think about it: When you walk, run, or climb stairs, you’re rarely standing on two feet at a time.

Boyle agrees that this is the number-one benefit of unilateral training: “I always say life is a game that’s played on one foot.”

The Benefits of Unilateral Training

Rothberg selfishly sees these types of exercises as a route to faster triathlon finishing times — but they can help anyone who runs. “When you’re running, you are trying to mitigate the lateral (side-to-side) forces even though you’re moving forward,” she said, “so you have to be able to balance, to make sure that your hips, knees, and ankles are in alignment when each foot hits the ground, and to be able to generate force off the ground with each foot strike.” Unilateral moves help her accomplish all of these things.

For example, she does step-ups onto a box or even an uneven surface like a BOSU ball, which simulates running on uneven terrain. This helps improve her proprioception, or awareness of where her body is in space — which can prevent the likelihood of twisting an ankle on an exposed tree root. She often does these moves with just her bodyweight or light dumbbells. “I’m not going to load myself up and put a barbell on my back and do a step-up onto a BOSU,” she said. “That’s a circus act.”

But, again, even if you’re never planning to see the starting line of an endurance event, unilateral exercises still have a place in your routine.

“We do it with just about everybody,” Boyle reiterated. “It’s more of a norm for us than it is the exception.” One key reason: to build balance. “I look at unilateral training and think you’ve got a built-in fall prevention program that you’re implementing in a group of people whose maybe highest risk is actually falling,” Boyle said of his older clients.

Indeed, falls are the leading cause of injury for adults aged 65 years or older, and 1 in 4 older adults report falling every year, according to CDC data. Rothberg first has her clients in this demographic get comfortable standing on one foot, then she’ll work in hinging movements similar to single-leg deadlifts but with a table or other surface in front of them so they have something to grab on to if they need it.

Especially with lower-body unilateral moves, balance is inherent. “Sometimes people will say, ‘I don’t like unilateral exercises because I have bad balance,’ and I kind of turn that around to them and say you want to be doing unilateral exercises because you have bad balance,” Boyle said.

Where Unilateral Beats Bilateral

This type of training can help correct muscular imbalances (think: One quad is more dominant than the other). “Just by nature of the exercise, you can’t favor one side when you’re doing one side at a time,” Boyle said. That said, you wouldn’t want to load one side more than the other in order to correct an imbalance — simply working both sides equally should naturally have that effect.

Rothberg added that some unilateral exercises, like a single-arm chest press, engage your core more than their bilateral counterparts. A small study of college students published in Medicine and Science in Sports and Exercise, found that unilateral training may lead to better core stability compared to bilateral training (with both forms of training improving strength and power).

Here’s where things get really interesting: Think about doing a bilateral bicep curl with both arms using a mini barbell — let’s say you could curl a 20-lb bar. Now, if you were to do a curl with just one arm, you’d likely be able to lift a little heavier — say, a 12.5-lb dumbbell.

“That is called the bilateral deficit,” said Lee Brown, EdD, CSCS*D, professor emeritus in kinesiology at Cal State Fullerton. “So one benefit of doing unilateral exercises is that you can lift more weight, and if you lift more weight, then of course you get a greater benefit to your muscle, which means you can get greater hypertrophy,” he said.

This effect can also help improve power, or how forcefully you can move a weight. In one small study of 15 people, published in The Journal of Strength & Conditioning Research, conducted by Brown and colleagues, those who did unilateral plyometric exercises saw bigger gains in both single and double-leg jumping performance as well as isometric leg press maximal force compared with those who did bilateral training.

Unilateral training can be particularly useful in rehab settings, say, if you had surgery on your right knee, said Brown, citing the idea of cross education. “What that means is that if I do a bicep curl with my right arm, then of course my right arm will get stronger over time. But there’s also some carry over to my left arm,” he said. So if you’re rehabbing your right knee, you can continue to exercise your left leg and see some benefit to the recovering side. The reason this works, he said, is that the body is constantly seeking homeostasis and equality on both sides.

Not for nothing, unilateral training is also safer, Boyle said. “We always emphasize the idea that we want training to be safe and we want training to be smart,” he said. “I think it’s smart because you’re training in the way that you’re going to move in life and it’s safer because you’re not requiring people to necessarily manage as much load. You don’t need hundreds of lb to do unilateral exercise.”

How to Get Started With Unilateral Training

The experts agree the key is to start slowly — and with just your bodyweight before adding dumbbells or any other implement (the single-grip cable machine and/or kettlebells can also be useful for unilateral training.)

Rothberg said to begin by seeing how long you can stand on one foot without holding on to something. (Yes, that’s unilateral training.) “You might find out you don’t even have enough strength to hold the knee up, so stand by a wall and practice that,” she said. Once you’ve mastered that on both sides, try closing your eyes, which makes the task more difficult.

From there, try a split squat where you stagger your feet one in front of the other as if they’re on railroad tracks and then squat down, lowering both knees toward the ground. (Boyle also likes the split squat as a standard issue exercise.)

Eventually, you can sprinkle in other unilateral moves, like side lunges, single-leg glute bridges, Romanian deadlifts, and kickstand deadlifts (one leg back so the toes are brushing the ground for balance and the front leg takes all the stress of the lift), all of which you can do with bodyweight or dumbbells.

As far as sets and reps, Boyle said he uses similar rep schemes to what he’d use for any other bilateral move — three sets of 8-12 reps on each side. For that reason, the only real downside to unilateral training? It will likely take longer. But the experts agree you don’t have to, nor should you, exclusively do unilateral exercises. “For the average person who just wants to get stronger, you can make a case for both,” Brown said.

Boyle, Rothberg, and Brown declared having no conflicts. Disclosure information for the study authors is available in the original study publication.

https://www.medscape.com/viewarticle/unsung-advantages-unilateral-strength-training-2026a1000hrs