The squat is a moderately complex compound exercise with a variety of mechanics and form cues native to its performance that both ensure the safety of the individual performing it and any training stimulus they wish to achieve by doing so.
One among these exercise mechanics is that of the squat depth; a major portion of squatting technique that is responsible for factors such as muscle group activation intensity, risk of lower back injury and even the difficulty of the exercise in general.
For the most part, the term squat depth refers to how deep the exerciser lowers themselves during the eccentric portion of each repetition of the squat movement - what is otherwise known as the descending phase or “the hole” in powerlifting slang.
In technical terms, squat depth refers to the exercise mechanic native to the squat movement wherein the exerciser’s knees firstly enter a state of flexion as the hips are lowered to parallel or below parallel to the patella prior to the knees then entering a state of extension as the exerciser returns to an upright position.
The degree of squat depth is a vitally important aspect of the squat exercise and similar movements due to the fact that certain muscle groups of the posterior chain are only recruited to the fullest possible extent within a certain range of motion, thereby dictating the effectiveness of the squat exercise itself.
It is quite difficult for an exerciser to assess their own squat depth solely from their own point of view, as doing so will generally require a side or profile view of the legs and torso so as to ensure correct form and that the depth of the squat is indeed below a parallel level.
As such, if assessing one’s own squat depth or that of another individual, it is far better to do so as they face away from the observer.
Squat depth is considered among one of the most important aspects of the squat exercise due to the fact that it acts both as a safety mechanism and a characteristic that dictates the effectiveness and muscle group activation pattern of the movement itself.
Performing squats with an improper and insufficient depth such as within the ranges of 60-90 degrees of knee flexion will generally result in excessive pressure being placed on the knees as they bear more shear force as the exerciser arrests their momentum alongside constantly supporting the exerciser’s bodyweight.
In addition to this, the quadriceps femoris are extended to a greater length and thus receive greater muscle fiber recruitment in lower depths of knee flexion. This is in addition to gluteus muscle group recruitment that is otherwise greatly reduced in squats that do not utilize a full range of motion and depth.
With these two factors encompassing practically the entire function of a squat exercise, one can surmise that there is very little reason for an uninjured exerciser to perform a squat without the correct squat depth; as doing so would defeat the purpose of the squat.
As was previously mentioned, improper squat depth is capable of resulting in excessive knee joint stress that may result in chronic or acute injury over time, an altogether avoidable risk that may spell the end of a lifter’s fitness career if not treated properly.
However, other risks associated with improper squat depth are also a factor; with such matters like the development of muscular imbalances among the many muscle groups of the legs, “butt wink” wherein the pelvis tilts as the exerciser arrests their momentum, and even internally rotating knees or knee valgus due to the excess stress placed on the joints.
While all these factors are not always immediately caused by incorrect squat depth, they nonetheless pose a serious risk that can otherwise develop into a life-long nagging injury, especially if improper squat depth is combined with other factors relating to risk of injury, such as other errors in form, excessive usage of weight or a lack of preparatory work.
In healthy exercisers wishing to maximize the effectiveness and safety of the squat - yes, correct squat depth is the surest way to ensure that the squat acts in such a manner.
However, this is not always the case, as individuals with certain training goals or conditions may find that performing a shorter range of motion such as a half squat or partial squat may in fact be safer or more comfortable in their particular situation.
Specifically, exercisers of advanced age, individuals with a history of injury that limit their comfortable range of motion or athletes wishing to train a particular sticking point in their squat form are all in a unique position that allows them to benefit from the performance of lesser squat depth repetitions.
Contrary to unsubstantiated claims often circulated through many fitness-related communities, proper squat depth is in fact not dangerous to the knees or any other joint involved in the squat exercise, so long as the exerciser is of sound health and adequate mobility.
While squatting to a depth that the exerciser is unfamiliar or uncomfortable with may negatively affect their form adherence - this is not usually a direct result of correct squat depth itself and more of the exerciser’s improper preparatory work or insufficient proprioception.
As such, apart from the aforementioned individuals that may benefit from squatting with a shorter range of motion, utilizing the correct knee flexion beyond that of parallel or 90 degrees is rather safe for the most part.
Utilizing correct squat depth during a squat involves more than simply lowering the hips and glutes to the correct angle of knee flexion, as there are still other form cues to fulfill and bodily mechanics to account for that make achieving proper squat depth somewhat complicated.
Certain degrees of knee flexion are known to result in greater amounts of pressure and force being applied to the patellar joint and its surrounding tissues, while conversely other angles are capable of maximizing muscle group recruitment during the exercise.
Generally, healthy exercisers with adequate mobility are advised to perform the squat to parallel or somewhat beyond parallel with no hard number being cited as many individuals possess different lengths of femurs.
However, an angle anywhere between 90 and 130 degrees is considered to induce the greatest and most wide-reaching muscular activation during the exercise, maximizing gluteus, hamstring, hip flexor and quadricep muscle group recruitment.
Utilizing an incorrect spinal angle can greatly alter the safety and effectiveness of correct squat depth, as improper lumbar and thoracic curvature can force the pelvis to move within a more limited range of motion and bend the torso forward, resulting in greater knee pressure.
This, over time, can cause tendonitis, the ever infamous patello-femoral pain syndrome, various connective tissue strains and sprains or even total patellar dislocation in the most extreme of situations.
With this in mind, the exerciser must ensure that their squat depth is not only of an appropriate angle for knee safety, but also of the positioning of their lower back and pelvis in relation to this knee flexion angle so as to prevent any untoward injuries from occurring.
The positioning of the barbell atop the exerciser’s back (if the exercise is a barbell squat) can also alter the ease at which the exerciser can achieve proper squat depth, as low and high bar squats place a different angle of resistance on the exerciser’s torso and thus alter the mechanics of the exercise.
In the case of the low bar squat, the barbell rests atop the upper back instead of the trapezius “shelf” that makes up the shoulders, forcing the torso to bend at a more forward angle and thereby pushing the pelvis backwards, allowing greater knee flexion to occur as the hips have to travel less distance.
For the high bar squat, however, the barbell is laid atop the exerciser’s shoulders and as such places the torso in a nearly upright position, with the pelvis following suit and thus increasing the range of motion of the movement incrementally as well as increasing the distance the pelvis must move to achieve greater squat depth.
While both high bar and low bar versions of the barbell squat are relatively safe and equally allow for correct squat depth, it is the low bar squat that is most conducive to safe and stable knee flexion, and as such individuals having trouble achieving proper depth with the high bar squat may benefit from switching the position of the barbell on their back.
1. Hartmann, H., Wirth, K. & Klusemann, M. Analysis of the Load on the Knee Joint and Vertebral Column with Changes in Squatting Depth and Weight Load. Sports Med 43, 993–1008 (2013). https://doi.org/10.1007/s40279-013-0073-6
2. Murawa M, Fryzowicz A, Kabacinski J, Jurga J, Gorwa J, Galli M, Zago M. Muscle activation varies between high-bar and low-bar back squat. PeerJ. 2020 Jun 8;8:e9256. doi: 10.7717/peerj.9256. PMID: 32551198; PMCID: PMC7289144.
3. da Silva JJ, Schoenfeld BJ, Marchetti PN, Pecoraro SL, Greve JMD, Marchetti PH. Muscle Activation Differs Between Partial and Full Back Squat Exercise With External Load Equated. J Strength Cond Res. 2017 Jun;31(6):1688-1693. doi: 10.1519/JSC.0000000000001713. PMID: 28538321.