A woman doing a squat with a barbell on her back using a power rack in a gym

Squat depth: how deep should you squat to build muscle?

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The ‘ass to grass’ squatting technique is heralded as the best by some trainers. Getting as low as possible, and definitely past the point where your thighs are parallel with the ground, is seen as the only way to squat.

How do you really get the most from your squat? Well, the research is quite contrary. 

Are deep squats good for the glutes?

A 2002 study from the Journal of Strength and Conditioning found that activation of the glutes increased with the increase in squat depth. Essentially, the lower you go, the more your glutes will work. In a partial squat, the muscles took 17% of the load, 28% in a parallel squat, and at full-depth, the glutes were loaded with 35% of the weight. That means that lower squats can build bigger and stronger glutes, compared to other muscles. 

Yet, some researchers have disputed the science behind this study based on the well-established fact that knee flexion increases quad activation. In a squat, the lower you go the more your knees flex. Therefore, your quads will activate more, and the squat mainly becomes a quad-building exercise. 

More recent research, such as a 2016 study from the Journal of Sports Medicine, suggests that squatting to parallel actually produces the most muscle activation in the quads, while the glutes were most active in either shallow or deep squats (when knees were bent at 20° and 140°). That would suggest bending a little or a lot is the best way to engage your glutes. 

What’s the best squat depth?

Clearly, it’s confusing. It comes down to your goals and the muscle growth you want to encourage. But generally, it seems that 90° might be the best place to squat. The 2016 paper concluded that overall, parallel squats encouraged the most muscle activation through each muscle in the leg. In a 1996 paper from Medicine & Science in Sports & Exercise researchers concluded that in people who are already well-trained there’s no difference between parallel and full squats. The researchers from a 2007 paper from the Strength and Conditioning Journal also pointed out that squatting to full depth is only more effective if you can maintain the correct form through your spine. 

What’s more important than squat depth?

Some people have biomechanics or mobility issues that make squatting ‘ass to grass’ impossible. While the good news is that parallel is probably just as good, there’s more to a squat than just how deep you go. A 2009 paper from the Journal of Strength and Conditioning focused on the act of ‘sitting back’ into your squat for optimal muscle and strength gains. They pointed out that sitting back allows for hip extension which allows the glutes to “immediately become a part of the lift, particularly increasing activation in a deeper squat. For those with knee pain, this can make an immediate difference in their ability to perform the lift. For athletes without current knee issues, it can be a way to avoid future problems because of overloading.”

Most importantly, the best way to squat is however you feel safe. If you feel the glute burn when you’re down low, you’re probably going to be engaging them. Similarly, if you feel comfortable and your muscles feel engaged when you’re at parallel, stick there. 

Want to improve your squat form? Sign up to the Strong Women Training Club for two new workouts every week. 

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Chloe Gray

Chloe Gray is the senior writer for stylist.co.uk's fitness brand Strong Women. When she's not writing or lifting weights, she's most likely found practicing handstands, sipping a gin and tonic or eating peanut butter straight out of the jar (not all at the same time).