You need to squat deep!
Deep squats, full squats, below parallel squats, “ass-to-grass” squats, whatever you want to call them – This is probably the most talked about lift in strength training.
There are lots of opinions when it comes to squat depth. Some say that squatting as deep as possible is the only way to lift. Others think that it will screw up your knees. So, what does the science say?
Here’s what you need to know.
Deeper is better
The squat is a compound, full-body exercise that engages most muscles of the lower body. For that reason it’s widely considered to be fundamental strength movement, that much is clear. However, wide-ranging form in the gym has led to some confusion when it comes to safety.
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For example, a simple change in foot placement, barbell placement, or squat depth have huge consequences on training outcomes. A recent study found that shallow squats (about 60° knee angle) improved lower-body strength and vertical jump performance, but deep squats (below 90° knee angle) were MORE effective, promoting greater muscle mass and strength development (Reference 1).
That’s an important lesson for athletes to consider – You might be able to lift more right now by cutting your squat depth, but science suggests that you’ll be less muscular and strong overall.
What’s happening in your knee when you squat?
There are clear benefits to squatting deeper and making the lift harder, but, there’s also the ever-present safety question.
The knee joint accepts both shear and compressive forces when loaded during a squat. Ligaments (such as the ACL and PCL) stabilize the joint by regulating the shear or opposing forces. Cartilage absorbs the compressive force and stabilizes the interaction between your tibia and femur. These shear and compressive forces are typically inversely related and can be both helpful and harmful.
With knee flexion, shear forces decrease and the compressive forces increase. What this means is that stress to your ACL and PCL does not go up and you sink deeper in the squat. Increased compression around the back of the knee serves to stabilize the joint (Reference 2).
Damage to the knee only appears to occur when these compressive forces become excessive and surpass the normal capacity of the cartilage, which doesn’t appear to occur in injury free people (Reference 3).
What if you are injured?
While deep squats safe for most people, injuries require special consideration.
Sometimes it’s necessary to refrain from squatting deeper than about 60 degrees due to pain. That’s the point in the range of motion where forces on the front of your knee – around the patellofemoral joint – are at their highest.
You should also limit squat depth in the case of dysfunctional movement patterns or flexibility/mobility limitations. A great example is ankle mobility. Impaired motion at the ankle can lead to valgus, or caving knees. This is bad because it causes an uneven distribution of forces within the knee, increasing injury risk.
When in doubt, break out the squat box and only lower the height when position improves. Do that and you won’t have to worry about busting any knees.
Sore knees? Get on the box.
Take home points
Bottom line, here’s what you need to know:
- Deep squats result in greater activation of lower-body musculature compared to shallow squats.
Squatting past parallel does not result in greater shear forces, which means ACL and PCL stress does not increase past parallel.
- Deep squats increase compressive forces, which stresses the cartilage of the tibia and femur. However, recent data suggests that this cartilage is capable of enduring the magnitude of compressive forces (in injury free individuals).
- Deep squats are safe for individuals without any contraindications, assuming they are performed at a load and velocity consistent with their ability to maintain symmetry and position.
Under the supervision of a qualified professional, healthy athletes can squat deep without any concern over knee injury.
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20 Responses to “You need to squat deep!”
What are your thoughts on deep squats and having a “butt wink”, the point where your butt/lower back starts to curve?
Yeah, you have to address it. I would consider a wink to be like a knee injury. Better to work on position, and stop short of the wink during lifting. You don’t want loss of position under high load. Better to be patient.
Looked good for me until the part about limited range of ankle motion. Any suggestions to increase range of motion there? Especially for someone with a chronic Achilles problem…
Rob, do you have lifting shoes? That’s the first, quick thing. Bit of heel works wonders. You could also stand with your heel on a rubber mat. Helps with position. I would be careful with too much mobility work, I suppose. Is this problem stable?
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I have a question – I had 2 acl reconstructions and quite a bit of cartilage loss. I’ve been back at crossfit for awhile now so the injury isn’t really a pressing issue at this point and my strength is back. If I do deep squats, but there is no pain, am I in the clear? I typically have solid form and excellent range of motion but I’m not trying to win the crossfit games. I’d like to continue to get stronger but I don’t want to cause more damage. Should I avoid heavy deep squats or squat snatches altogether even if I don’t have any pain during or after? Or does lack of pain mean that I have enough cartilage left to support the movement? Thanks!!
Thanks for the question Jen. I’m glad to hear that you have been back in the gym, pain free! I’ll try to answer your questions to the best of my knowledge (without knowing your full history). In short: No pain is a good sign and you can likely continue to do deep squats as long as you stay pain free. But, progress more slowly than you think. Your history puts you at a greater risk of injury, so make sure to pay attention to your body and back off if necessary.
Great stuff Jim!
What are your thoughts on feet position (toes pointed out/forward and stance width)?
You bring up good questions. In general, you should point your toes slightly outwards with your knees always tracking you toes (keeping proper alignment). But, the degree that you toes are pointed depends a lot on your stance width. With a wider stance, you can point your feet more forward (with your knees again, tracking your toes). Remember, these are general guidelines and the exact degree of your foot angle depends on mobility and strength. If you knees begin to cave in, you can try to point your feet ‘less outward’, bring your stance in closer, and/or decrease the weight. There is no perfect foot angle or stance width for everyone, this will be based a lot on personal preference, goals, and again, individual mobility and strength.
Great article. I really appreciate the refs provided — the more physiology the better.
A question about meniscus injury: I train with a few athletes who have torn their meniscus in the past. Some have pain; some do not. It is safe to assume that if the pain is gone then the injury is healed? These tissues get such poor blood-flow, are so weakly innervated, and heal so slowly that I worry.
….and then I read the comment from Jen… lesson learned!
Thanks, Jimmy! I always try to get other perspectives because crossfit “coaches” usually don’t really know what they’re talking about when it comes to those who have had serious injuries. I went to a Sixers team doc at Rothman and he told me that I can “squat heavy” and that was the FIRST time that any surgeon actually said that to me. My other surgeon told me not to squat below parallel and to buy a bike! However, he was impressed that I gained ALL of my strength back so quickly after surgery. I looked at him and just shrugged.
I did, however, learn to take it easy with squat cleans and squat snatches. or avoid them altogether. Something about those movements causes soreness. Do you have thoughts on rehbands? I have one for my “bad” knee – do you think they are worth it? I am looking at upgrading to the 7mm thick version.
It’s always nice to get a second opinion from a different physician if possible, like you did. I have not personally used rehbands. The use of knee sleeves (like rehbands or other brands) is really up to user preference. If it feels good, go for it! It probably won’t hurt anything. You might have to try out a couple of different brands/thicknesses to see what works best for you.
I have recently increased the volume of my squats and weightlifting, with that my ankles and knees frequently crack. I have taken fish oil and worked on the necessary mobility but going past a certain depth my knee will crack. Is there a cause or fix for this?
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I think intuitively the fact that older people and injured athletes feel pain when going deep is probably a sign to those pain free that depth causes stress within the knee that probably arent great to train through when young and/ or pain free. Same way that young people can perform with poor form and feel no consequences or pain until they are older, it didnt mean there was nothing wrong with their poor form when younger.
Hi Jim, I’m 44 years old and squat (usually building to 95% of 1RM) about 3x per week and CrossFit 5x per week. I never played sport and (therefore) never had any injuries. I squat very deep with my butt about 15cm from the floor at the bottom, so my mobility is good. I experience no pain at all. But, here is my concern : My knees make clicking and grinding sounds when I walk up stairs, deadlift and squat. Is this a problem? Is it an early sign of injury potential? Should I do something about this, or can I carry on as usual. ps – I’ve been doing CrossFit for about 3 years. My knees were actually sensitive / experienced light pain before I started CrossFit, but didn’t make these weird noises.
I’m 45 and only from my personal experience have the following observations.
My knees used to creak with no pain and I noticed that when I stopped running 5km routinely just for a change replacing it with rowing my creaky knees over some weeks nearly totally stopped creaking.
I also noticed that when I squat and deliberately keep knees out in a pronounced way as Kelly Starrett suggests I get no noise either when going past parallel on squats
Maybe it is to do with the tracking of the knee as it bends and running or narrow knees straight squats aren’t great for knee heAlth.
Not sure this post helps but just thought I’d share my experience given our age and similar experience.
I would also note that I deadlift and squat once a week 3 sets of heavy which for me is 2 and 1.5 times body weight for reps. It is enough easily to maintain strength and I deliverately don’t do more weight or more leg strength work as I think it’s unnecessary. Too much of the industry is about more weight and pushing the whole time but past a certain point me quite certain you pass a trade off point of health and longevity.
I have no joint issues and look men’s health cover model condition and just don’t see any upside in loading the joints more than enough to hold decent functional and aesthetic outcomes. More should be written on this by fitness professionals as the good news is maintenance of decent shape is relatively easy and I’m sure healthier than continually loading more strength.
All the best