Squats, does depth matter?

Image of barbell in Liverpool Street personal training studio

Short answer, yes.

I can see this post putting a few noses out of joint (it should do), so rather than just offering my opinion I’m going to direct you to an EMG study on the contribution of different hip and thigh muscles at varying depths of the back squat.

Electromyography, or EMG for short, is a technique used to measure the activation level and recruitment order of muscles.

Here’s why depth matters: when doing partial-reps the outer thigh (vastus lateralis) is doing 39% of the work, with only a 17% contribution from the glutes. The other major players are the hamstrings and VMO. If the emphasis is always on the vastus lateralis, the quadriceps will become structurally imbalanced, increasing susceptibility to chronic knee pain. To further compound knee issues, the highest stress on the kneecap occurs at 90° – so you’d be stopping and reversing the movement at the knee’s weakest point.

In over eight years, training hundreds of clients, I’ve never seen anyone with overactive glutes. Quite the contrary. Once you break parallel during the squat the glutes become the dominant muscle, with their contribution more than doubling from 17% to 35%!

Partial squats will only strengthen the muscles over a short range, leading to:

  • Muscle imbalances
  • Increased susceptibility to injury
  • Decreased flexibility
  • And decreased proprioception (body awareness)

Your trainer might argue that you’re “overloading the strength curve” with the half-reps they’re promoting, but I’d counter that by suggesting chains and bands would be better suited to serve that purpose.

For me, technique, tempo, joint angle and range of motion will (nearly) always take precedence over weight on the bar.


Caterisano, A., Moss, R.E., Pellinger, T.K., Woodruff, K., Lewis, V.C., Booth, W. and Khadra, T., 2002. The effect of back squat depth on the EMG activity of 4 superficial hip and thigh muscles. The Journal of Strength & Conditioning Research16(3), pp.428-432

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