Chances are your knees just went forward past your toes. So why can’t they when you’re in the gym? Exactly. “Knees aren’t exploding all over place because knees are going past toes in daily life,” says Tony Gentilcore, CSCS. “And they aren’t in the gym.”
Hence why the exercise guideline, “don’t let your knees move past your toes,” actually keeps exercisers from maxing out the benefits of squats and lunges. When your knees stay behind your toes, the moves do not mimic those daily habits and, thus, don’t strengthen your body for life outside of the gym.
An even bigger concern: Restricting the natural forward movement of your knee during a squat increases the stress placed on your hips by 1,000 percent, while also placing undue stress on the lower back, according to research out of the University of Memphis. “That force has to go somewhere,” Gentilcore says.
However, according to that same study, letting your knees creep just past your big toes (or your second toes, if you have finger toes) during a squat only increases the pressure placed on your knee joints by 28 percent.
It’s some, but not a lot. And for most people, not enough to wreck havoc on your joints. Now, if you your have “cranky knees” as Gentilcore calls them, you might want to keep your knee more or less behind your toes so that the bottom portion of your leg (your tibia) is vertical.
However, if your knees are in good shape, there’s no reason not to let movement of your knees past your toes. Now, you don’t want your knee moving forward anymore than it has to. After all, if you somehow managed to lunge in a way that brought your front knee close to the ground, you could do some serious damage.
So how do you move your knees past your toes without letting them go too far? Gentilcore recommends following another cue: keep your weight in your heels. It will make sure any movement of the knees is natural and that you aren’t throwing all of your bodyweight forward.
Bonus: It will ensure you max out your glutes and hamstrings for the biggest benefits.
Originally written for Details.com.