Here’s a simple mathematical problem: if you’re doing a one-legged squat (a.k.a pistol squat), versus a barbell squat with your own bodyweight loaded on the barbell, which one puts heavier pressure on your leg?
The brief answer is, your leg is up against the same amount of resistance in both. However, the pistol squat is way more challenging on a skeletomuscular level.
Let’s break down the numbers first. Let’s say you weigh 70 kg. According to this source, each leg makes up roughly 17% of your bodyweight, so around 12 kg per leg or 24 kg both.
In a regular squat (no weights), your legs are pressing your upper body up. So two legs are pressing 70 – 24 = 46 kg, or each leg presses 23 kg.
If you load 70 kg on a barbell, each leg will go against another 70 / 2 = 35 kg. That makes a total of 23 + 35 = 58 kg per leg.
In a pistol squat, you’re using one leg to press your entire upper body plus the other hovering leg. That’s the upper body (46 kg) + one leg (12 kg) = 58 kg of pressure on the sole working leg.
So in theory, a bodyweight barbell squat and a pistol squat both put 58 kg on each leg.
However, it’s worth pointing out that pistols are way more difficult due to 2 factors:
1/ The range of motion is larger. A proper pistol allows you to squat all the way down, so that your knees are higher than your nipples, almost touching your collarbone. That’s pretty deep.
With a barbell squat, by contrast, most people only go slightly over 90 degrees, or their knees are a bit higher than their bellybutton.
This exceeded range of motion adds another level of difficulty to the pistol squat. It’s the same reason why some guys can bang out 30 half-rep pull-ups but struggle to do 10 with strict form.
2/ More stabiliser muscles are involved.
Squatting is a very natural movement, so a squat feels extremely comfortable. Your legs are simply extending up and down in a straight plane of motion, your feet firmly and stably planted on the ground.
An one-legged squat though is an extremely odd movement. You have to constantly maintain balance so as not to fall sideways or backwards, which means a bunch of hips, knees, ankle, and core stabiliser muscles have to do extra work in conjunction.
The same principle applies as to why any exercises on a smith machine feel far more comfortable than their free weights counterparts.
All in all, don’t underestimate the pistol squat. I firmly believe it is one of the best exercises for overall body development. It utilises so many muscles that are severely weakened and neglected in our sedentary lives.
If you’ve conquered the pistol squat and are looking for more challenges, do it weighted. I occasionally do weighted pistols while holding a 20 kg kettlebell, and it really is the worst, most dreadful exercise I’ve ever done. I can barely do 10 reps before grimacing in pain and panting like an obese dog after a run.