Old-school lifting advice decrees that allowing your knees to travel over your toes while squatting is a cardinal sin that will only ever lead to knee pain and injury. The argument is that, because the knees have to travel further forward, it places more stress on the joint. Thus, more potential for things to go wrong.
But joints are capable of adapting to greater loads, as a new study into the impact of squat depth on joint pain suggests. It's a reminder that if your anatomy forces your knees past your toes, or if you simply want to emphasise the stretch on your quads, your knees may actually become healthier.
The Study
The study, published in the European Journal of Sport Science, examined the effect different squat depths had on neuromuscular and functional adaptations as well as joint pain and stiffness. They were split into four separate groups: one group completed full range-of-motion squats, the second performed squats to parallel, the third half-squats, and the fourth group stopped training altogether (they functioned as a control group).
Each group was encouraged to squat according to their individual range of motion – for most people, letting their knees travel forward is natural, safe, and necessary to achieve proper depth and balance.
In the three squatting groups, everyone used the same relative load based on their one-rep max (1RM), with researchers periodising their training from 60% to 80% of that total over the study period. Throughout, the only difference was the depth of the squat trained.
Participants self-reported pain, stiffness and disability based on the WOMAC Index (Western Ontario and McMaster Universities Osteoarthritis Index) specifically designed for hip or knee osteoarthritis.
What to read next
Researchers evaluated neuromuscular adaptations through 1RM strength and mean propulsive velocity (MPV) – the average speed of a barbell when powering out the squat – at each squatting depth. A countermovement jump, 20-metre sprint, and Wingate test assessed functional performance.
The Results
Those performing half squats recorded almost three times as much pain and stiffness than the groups taking their squats to parallel or even full depth.
One possible explanation is that partial squats place relatively greater demands on the quads while involving the hips and glutes less than deeper squats, potentially increasing stress around the knee.
Strength and power gains generally increased with squat depth too – the group performing full-squats achieved the highest functional performance, and was the only group to increase their 1RM and MPV in all three of the depth tests.
What This Means For Us
Everyone's squat is unique – one person with shorter legs and a longer torso might be able to sit deeper in their squat, while someone else with longer legs might have to employ a forward lean that allows their knees to travel over their toes. Neither is inherently bad: it's just what works best for that body.
Refusing to allow your knees much movement isn't actually conducive when it comes to real life either. When you're standing up from a chair or walking down the stairs, your knees naturally track over your toes. In fact, restricting forward knee travel unnecessarily shifts more load to the hips and lower back, which can create issues as a result.
'We recommend using full squats or parallel squat exercises to improve strength and functional performance in well-trained athletes. In turn, the use of half squats is inadvisable due to the limited performance improvements and the increments in pain and discomfort after continued training,' researchers concluded.
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