THE QUESTION
The question “How low should I squat” is one that wafts through the air of weight rooms and fitness centers almost as often as the unique malodorous scent of nitrogen rich sweat from protein supplementation. Everyone from your gym rats to physicians to your aunt Betty seem to have an opinion on the appropriate squatting depth, and many will deliver their opinion with the utmost conviction.
The answer to this question of course depends on what your goal is. I agree with Dr Stuart McGill who says “Exercises are tools to get specific jobs done. The way an exercise is performed depends on the rationale for choosing that exercise. First, list the objective and then decide on the best tool. Usually the best exercise is the one that creates the largest effect with the minimal risk to the joints. “
In what follows, I offer two categories of “goals” for squatting, and make recommendations about squatting depth for each.
TWO SQUATTING-RELATED GOALS & MY RECOMMENDATIONS FOR EACH
1. Squatting as competition
Some reasons you’d squat to compete:
- Powerlifting
- Crossfit competition
- Impressing your friends in the gym
Recommendation when squatting to compete:
Weigh value of the goal against the risks.
The rules of those competitions determine what your squatting depth will be (e.g., your friends at the gym will only count your squats if you get your thigh parallel to the ground). It is in your long-term best interest to squat to the depth prescribed by your competition with the safest technique possible. That being said, when you decide to enter those competitions, you agree to their rules and you assume the risk involved. You won’t get cut any slack at most powerlifting competitions if you tell the judge that you don’t squat to hip crease below the top of the knee because you are unable to do it safely. While there are people who squat unsafely their whole life and manage to get away with it, they are trying their luck. If you can’t do it safely, I recommend you don’t compete.
2. Squatting for fitness
Some reasons you’d incorporate squatting into training:
- Preventing injury
- Maintaining range of motion
- Joint health
- Building muscle (hypertrophy)
- Strongman competition
- Olympic weightlifting
- Crossfit for fitness
- Athletic performance besides weightlifting, this list is nearly endless: hockey, football, rugby, parnter acrobatics etc
Recommendation when squatting for fitness:
Prioritize Safety.
You may have looked at the goals list above and realized you have several goals. If you are like most people, one of these goals is preventing injury. It is with this in mind (i.e., through the lens of a physical therapist) that I base my recommendations for squatting depth.
In what follows I offer my top two rules for squatting safely as in the picture below.
Safe Squatting Rule 1: Set the depth as the lowest you can squat BEFORE your lumbar spine bends forward (i.e., lumbar flexion).
Risks of lumbar flexion
Of all the injuries you could sustain while squatting, the one which is most sudden and most debilitating is a back injury, particularly a disc herniation. Most other squatting injuries come on gradually with some warming, giving you time to modify the activity, change your technique, mobilize, stabilize etc but a disc injury often does not give you this warning. A slow unloaded deep squat in which the lumbar spine is allowed to flex can be used as a stretch for the paraspinal muscles. However, Lumbar flexion under load increases the risk of lumbar disc injury [1,2], and when increasing repetitions, duration, speed of movement and especially when adding weigh to the squat I recommend avoiding lumbar flexion.
Identifying lumbar flexion
Many people I have worked with have a very difficult time knowing when their lumbar spine begins to flex in a deep squat. Below is a list of ways to determine when your spine flexes:
1. Tape The Lumbar Spine
Arch your back slightly and have someone put a strip of tape from the base of your pelvis at the sacrum up to the bottom of your rib cage where the lumbar spine ends and the thoracic spine begins. When the tape is on and you flex the lumbar spine you should feel the tape tugging. Don’t overtighten the tape.
2. Have A Friend Film You
Have a friend record you squatting with your waist exposed using an app such as Coach’s Eye or Ubersense. Playback the video in slow motion and watch for the following clues of lumbar flexion. Its not quite as easy as you might think.
- Rounding Back. Look for a curling forward of the spine. Beware that in the people with well developed lower back muscles (erector spinae) the spine iteself will not be visitble and you may not see flxion.
- Butt Wink. An unforgettable term that refers to the moment when the pelvis tilts posterior usually during descent.
- Caving Chest. This often happens on the ascent when the hips rise up but the chest and bar do not.
Safe Squatting Rule 2: Set the depth as the lowest you can squat BEFORE valgus collapse.
Risks of dynamic valgus collapse
With regard to a slow and controlled double leg squat, the dynamic valgus mal-alignment poses some immediate threat to the menisci and medial collateral ligament of the knee. However, the primary concern is that over time the abnormal stress this pattern places on the knee cap can instigate patello-femoral pain syndrome. A dynamic valgus mal-alignment during explosive tasks such as jumping and landing as well as during single leg squats and single leg jumping poses the threat of ACL tear, meinscus injury, medial collateral ligament injury and patellar tendinopathy in addition to patello-femoral pain syndrome. For a discussion of the role of dynamic valgus in knee injury see Powers et al 2010.
Identifying dynamic valgus collapse
A dynamic valgus collapse is a well described pathological lower limb alignment that is identified by the presence of one or more of the following features:
- Arch of the foot collapses (pronation)
- Toes turn out (relative tibial external rotation)
- Knees caving towards each other (genu valgus)
- Thighs turn in (femoral internal rotation)
- Thighs come together (femoral adduction)
SO YOU KNOW THE DEPTH AT WHICH YOUR SQUAT BECOMES UNSAFE… NOW WHAT?
1. Learn to squat down to the safe depth. To do this I recommend setting up hurdle using a light theraband to touch with your pelvis at the bottom. Once you have learned this depth precisely you can take the hurdle away.
2. Identify what is limiting you from squatting deeper, and work on those limitations until you can squat deeper without lumbar flexion or dynamic valgus mal-alignment. A good place to start is increasing ankle dorsiflexion mobility but you may have other factors limiting your squat in which case assessment by a professional is warranted.
REFERENCES
Peer-Reviewed Journal-Published Scientific Research
Un-Reviewed Self-Published Opinions
1. A blog post by Joshua Nackenson which summarizes the review: Hartmann H1, 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. 2013 Oct;43(10):993-1008.
*The main thrust of this article and Joshua’s post is that there is no substantive research showing that squatting beyond a 90 degree knee angle (well above “knee parallel with hip crease”) is not dangerous. I agree. My only reservation is that the enthusiasm for deep squatting is not tempered by an explicit discussion of the role of loaded lumbar flexion in intervertebral disc injury and that the fact that without strict monitoring, most people will flex the spine when squatting below parallel.
2. This blog post on squatting depth also prioritizes a neutral lumbar spine in determining depth albiet in a somewhat less systematic and research based manner.
3. My blog posts on the importance of ankle range of motion and body proportions on squatting mechanics and depth.
Posture Movement Pain 
Always informative and practical read Brian! Thanks.