How often have you heard that statement in regards to exercise? When squatting, lunging or anything else that involves bending the knees “make sure not to let the knees go over the toes.” This is NONSENSE. Forget about it, because if that were true, we would not be able to climb stairs! Alwyn Cosgrove, a man who KNOWS his stuff, wrote this recently about the myth that won’t die:
Have you ever heard someone warn you, “Don’t let your knee pass your foot during lunges?” Well, as you might’ve guessed, it’s a load of crap. What about the other knee? In a lunge, it’s supposedly “too dangerous” for the knee of the front leg to extend past the toes. Meanwhile, the knee of the back leg is past the toes the whole time.
I’ve had people respond to that by saying there’s no load on the back leg during a lunge. Okay then… put 135 pounds on your back and go down to the bottom of a lunge. Now lift your back foot off the floor. I rest my case.
When we look at the science regarding the knees going forward, one study jumps out. Fry, Smith, and Schilling (2003) examined joint kinetics during back squats under two conditions.
The first condition placed a board in front of the participants’ shins, which restricted forward displacement of the knee. In the second condition, movement wasn’t restricted at all. They squatted normally and the knees were allowed to pass the toes.
The researchers found that restricting the forward excursion of the knees during the squat increased anterior lean of the trunk and promoted an increased “internal angle at the knees and ankles.”
The results showed a 22% decrease in knee torque and a 1070% increase in hip torque! That stress has to go somewhere. Keeping the knees behind the toes definitely reduces the forces on the knee, but those forces were transferred more than tenfold to the hips and lower back.
Obviously this study was in regard to squatting. However, the knee angle in a lunge is similar and we could expect similar findings. So, intentionally keeping your knees behind your toes during squats or lunges might be a little better for your knees, but it’s much, much worse for your lower back and hips.
– (Alwyn Cosgrove)
And with that….I rest my case.