Turns out, training one leg at a time can be just as effective and provide an alternate path to stronger, more athletic legs. Just last year, a study in the International Journal of Exercise Science compared muscle activity in the back squat, split squat (both legs on the floor and a split stance), and Bulgarian split squat (rear foot elevated). There was no significant difference in the amount of muscle activated by the three exercises, except that the Bulgarian split squat worked more of the hamstrings—meaning, Bulgarian split squats can be a useful alternative to barbell squatting.
When squatting sucks
The classic back squat is, admittedly, tough to beat as an overall muscle- and strength-builder. It targets the quads, glutes, hamstrings, and lower back, but also requires work from the core, upper back, and shoulders to stabilize the bar. Because it’s designed to let you lift heavy loads, it encourages bone growth and the release of muscle-supporting hormones such as testosterone and growth hormone.
The trouble is, most people simply can’t execute it properly.
“A well-performed back squat in a commercial gym is like the Sasquatch,” says Ben Bruno, a Los Angeles trainer to celebrities and athletes. “Everybody talks about it, but nobody sees it.” Most lifters don’t have the hip mobility to squat without their tailbone tucking under, which puts the lower back at risk for injury. They’ll also fall forward on the descent, or fail to push their hips back far enough, so their knees travel well in front of their toes, which can cause knee injury. Despite these problems, most trainers still push back squats on their clients.
“Strength and conditioning pros abide by, ‘This is how we’ve always done it, so you have to do it this way,’” says Bruno, who offers a dissenting opinion. He never has clients perform back squats, opting instead to form the bulk of their lower-body training with front squats, trap-bar deadlifts, Romanian deadlifts, and various single-leg exercises.
A leg to stand on
Working one leg at a time, as with the split squat, the lunge, or stepup exercises, is generally considered an adjunct to barbell-squat training, never the core of the legs workout itself.
It’s time to change that. Single-leg exercises offer similar benefits to traditional squatting, yet reduce the risk for injury. “They allow you to get a training effect for your legs with much less load,” Bruno says. “If you can back-squat 225lbs for five, but do Bulgarian split squats (take a staggered stance and raise your back foot on a bench) with 75-lb dumbbells, which is 150lbs total, your legs will get a lot more load without subjecting your spine to 225lbs.” You can put more than 100lbs directly on one leg (studies show the back leg takes up about 15% of the load)—which is more than the back squat can load on each leg, given how the weight is distributed (your back and shoulders take on much of the burden). In other words, split-squatting offers a more direct leg hit.
It’s also easier to keep your shins vertical (so the knee doesn’t move past the toe) when performing a squat on one leg, so you avoid putting shear forces on the patella. “A lot of knee pain is caused by weak glutes,” Bruno says, “and single-leg exercises force you to stabilize in three planes of movement, which works the glutes hard.”
Finally, because single-leg training must be done lighter, it doesn’t cause the same nervous-system fatigue that heavy squats or deadlifts do, so it can be done three or four times a week without fear of overtraining, Bruno says. For instance, you could do Bulgarian split squats on Monday, lunges on Wednesday, and stepups Friday. More frequent training means more stimulus for growth.
Interestingly, the same doesn’t go for training one arm at a time, Bruno says. “There’s no less load on your joints when doing single-arm presses instead of double-arm.”