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

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.