Squat Depth: How Low Should I Go?
By Titled Sport and Exercise Physiotherapist, Michael Phipps
There's a lot of debate about squat depth in the fitness world, from dogmatic views that everyone should squat "ass to grass," to advocates of partial or shallow-range squats for strength and athletic performance. In this article, I'll break down the rationale behind these different approaches and look at some of the science that informs them.
Squat depth and biomechanics
From a biomechanics perspective, the amount of knee flexion (knee bend) you achieve during a squat influences two key variables: the length-tension relationship, and the external knee flexion moment arm.
Length-tension refers to the degree of stretch, or tension, placed on the quadriceps as the knee flexes. This mainly loads the vasti, the three quadriceps muscles that cross only the knee. The fourth quadriceps muscle, rectus femoris, crosses both the hip and the knee, so its overall length barely changes through a squat: hip flexion shortens it while knee flexion lengthens it, and the two roughly cancel out. That's why the vasti carry most of the length-tension load as squat depth increases. Greater knee flexion places the vasti under greater tension, and mechanical tension is one of the key stimuli for both muscle hypertrophy (an increase in muscle size) and strength gains.
However, hypertrophy isn't driven by mechanical tension alone. Metabolic fatigue also plays a meaningful role (Schoenfeld, 2010), and the two likely interact rather than act independently. More broadly, muscle growth and strength adaptation reflect overlapping biomechanical, neural and metabolic factors.
A similar effect happens at the hip: the gluteus maximus is placed in a lengthened position as the hip flexes, increasing mechanical tension and requiring greater force from the glutes to control the descent and drive hip extension. Another way to increase mechanical tension without changing depth is to increase the load used through the same range of motion.
The moment arm refers to the length of the lever around a joint's axis of rotation. At the knee during a squat, greater depth requires both greater ankle dorsiflexion (bending the ankle so the shin travels forward over the toes) and greater knee flexion, which lengthens the external knee flexion moment arm. A longer moment arm means greater external torque at the knee, which the quadriceps must resist to control the descent and drive the ascent, increasing muscle tension through a similar pathway to the one above.
In summary, squat depth influences the moment arms and length-tension relationships at both the knee and hip which can contribute to hypertrophy and strength development. But that's not the whole picture, as external load also plays a significant role. It's also worth remembering that not everyone is capable of squatting deep, for reasons I'll get into next.
Human variability
Not everyone can squat deep. There are several reasons for this, including muscle strength, anatomical variation, age, joint mobility, and limb-to-torso length ratios.
Take the hip joint, for example: there's enormous variability in socket (acetabular) orientation, depth, and ligamentous laxity (how much give there is in the ligaments holding a joint together). This variability accounts for everything from world-class Olympic weightlifters catching enormous loads overhead in a deep squat position, to dancers performing effortless high kicks and splits. Much of this is genetically determined and can't be changed through training.
Limb length is another factor. Shorter limb-to-torso ratios tend to favour deeper squats, largely because of the biomechanics discussed above. It's part of why elite weightlifters often have longer torsos relative to their limbs, while a very tall basketball player squatting deep with the same ease is a rare sight. For that population, selecting different exercises or limiting range of motion might deliver a better training return.
Injury and pain
Several conditions can limit how deep someone can comfortably squat. Hip conditions such as labral tears, hip impingement (femoroacetabular impingement syndrome, or FAIS) and hip osteoarthritis can restrict the hip's actual, or comfortable, range of motion. In this population, continuing to push into depth may exacerbate symptoms and impact on training outcomes.
At the knee, conditions such as patellofemoral pain (pain around or behind the kneecap), patellar tendinopathy (pain in the tendon below the kneecap), meniscal injuries and knee osteoarthritis can present similarly: greater squat depth can be associated with increased symptoms.
It's important to stress that squatting itself shouldn't be avoided: it's a fundamental activity of daily living, from standing up out of a chair to crouching down to weed the garden. Some people recovering from injury benefit from gradually working into a greater range of motion to build strength and functional mobility; others benefit from a short or longer-term reduction in squat depth to help manage symptoms.
Lower back pain is another situation that can impact squat depth. People often talk about the "butt wink," the rounding of the lumbar spine that can happen at the bottom of a deep squat. This is thought to happen either because someone's run out of available hip range of motion, or because they can't maintain hip flexion control through the deepest part of the squat. Honestly, it's often not worth fixating on. Most people's lower lumbar spine flexes to some degree at end-range squat depth, even with a perceived perfect technique (Howe & Lehman, 2021). Some people do get low back pain with squatting, particularly if they're sensitive to lumbar flexion, and a period of reduced depth can help symptoms settle while they keep training.
Performance outcomes
Partial range-of-motion squats are popular in some strength and power sport circles. The idea is that many sporting movements only use a short range of hip and knee extension. Sprinting and jumping are good examples: the hip only extends through a small range under load.
The evidence on this doesn't line up neatly, partly because the studies look at different people with different goals. In already well-trained lifters, adding partial squats on top of full-range training gave a small, not statistically significant, boost to strength and power in the seven weeks before competition (Bazyler et al., 2014). For typical trainees building general strength and muscle, the picture leans the other way: deeper squats built more quad muscle and improved jump performance more than shallow squats in one study (Bloomquist et al., 2013), and full squats built more glute and adductor muscle than half squats in another, with quad growth about the same either way (Kubo et al., 2019). Some of this comes down to specificity: training at a certain depth mostly makes you stronger and more capable at that depth, so the "right" answer depends a lot on what you're training for.
Zooming out, the 2026 ACSM position stand pooled evidence across many studies and found that training through a full range of motion (across all muscle groups) is linked to better strength gains, though it noted the evidence for range of motion's effect on muscle growth specifically isn't strong enough yet for a firm conclusion (Currier et al., 2026). Put simply: for most people, training with a fuller range of motion is likely to pay off more, and partial squats are best kept as a specific tool for advanced athletes at certain points in their training, not a default for everyone else.
My recommendation
If you're already squatting "ass to grass" and have no issues, keep doing what you're doing. There's no single right or wrong depth here, and squatting deep can be a great way to build strength in your quads and glutes.
If you've got a new or existing injury limiting your comfortable range of motion, you may need to reduce your squat depth or use an alternative exercise. The leg press, for example, lets you adjust load, range of motion and volume independently, and can be a useful strategy for managing pain or injury. Single-leg variations or seated knee extensions are other options and can provide a useful stimulus if you've got a one-sided (unilateral) weakness or pain limiting your progress.
If you're an older adult concerned about your mobility getting out of a chair, or looking to preserve functional independence, squatting to or beyond 90 degrees (roughly chair height) is a valuable training strategy, provided pain or injury isn't limiting your comfortable range of motion.
Plain language summary
How deep you squat is really up to you.
There's no single "correct" depth: it depends on your body, your goals, and whether you're managing any pain or injury.
Deeper squats generally work your muscles harder, but everyone's hips and legs are built differently, so what's comfortable for one person might not be for another.
For older adults, squatting to at least a chair height is important for functional independence
If you've got hip or knee pain, adjusting how deep you squat, rather than avoiding squats altogether, is often a good way to keep training while things settle down.
If you're not sure what's right for you, see a physiotherapist
This article contains general information only and isn't a substitute for individual assessment or advice from a qualified health professional.
References
Bazyler CD, Sato K, Wassinger CA, Lamont HS, Stone MH. The efficacy of incorporating partial squats in maximal strength training. J Strength Cond Res. 2014. doi:10.1519/JSC.0000000000000465
Bloomquist K, Langberg H, Karlsen S, Madsgaard S, Boesen M, Raastad T. Effect of range of motion in heavy load squatting on muscle and tendon adaptations. Eur J Appl Physiol. 2013.
Currier BS, D'Souza AC, Fiatarone Singh MA, Lowisz CV, Rawson ES, Schoenfeld BJ, et al. American College of Sports Medicine Position Stand. Resistance Training Prescription for Muscle Function, Hypertrophy, and Physical Performance in Healthy Adults: An Overview of Reviews. Med Sci Sports Exerc. 2026;58(4):851-872. doi:10.1249/MSS.0000000000003897
Howe L, Lehman G. Getting out of neutral: the risks and rewards of lumbar spine flexion during lifting exercises. Strength and Conditioning. 2021.
Kubo K, Ikebukuro T, Yata H. Effects of squat training with different depths on lower limb muscle volumes. Eur J Appl Physiol. 2019. doi:10.1007/s00421-019-04181-y
Schoenfeld BJ. The mechanisms of muscle hypertrophy and their application to resistance training. J Strength Cond Res. 2010. doi:10.1519/JSC.0b013e3181e840f3