Monday 1 August 2016

The Bottom Line on Squat Depth

“Squats are the king of all exercises!” While classic muscle magazine cliché may be a bit of a stretch, squats can be a great exercise. However, to get the most out of them, you have to do them right. A big part of squat form is your depth. How low should you go? If you start asking around, you will get a different answer depending on who you ask. Powerlifter: “Thighs parallel!” Olympic-Style Weightlifter: “To the bottom.” Sport coach: “Half or quarter squats because that is as low as we go in our sport”. My answer: “It depends.” (Helpful, I know, but hang in there – I’ll elaborate). To make things more confusing, some of the latest research seems to contradict what we previously thought about squat depth. It’s time we get to the bottom of this issue of squat depth (I’m so proud of myself for that pun).

My Squat Story
I started my squat journey in our high school weight room. The PE teach unlocked the door and let us loose. Having no idea what we were doing, we wandered over to the squat rack, loaded up the barbell and started partial squatting. This followed by more weight on the bar and less distance covered. 

A few years later I took a course to become a certified trainer. The course (taught by an aerobics instructor) told us to only go down to 90 degrees. I complied and went out squatting high and teaching my clients to do the same. Over time, I ran into 2 problems with myself and my clients the first was knee pain. At one point, my knee pain was so bad that I even spend 100’s of dollars on patella tracking braces thinking that was the problem. 

The second problem was lack of results. Eventually, I worked up to doing over 500lbs for 10 reps in the partial squat. It was amazing to put 5 plates on each side of the bar, watch the look of awe on the faces of onlookers and see that steel bar bend under that heavy load as I un-racked and walked the bar out. However, while this was an amazing exercise for stroking my ego, I knew I was in trouble. My back hurt and my knee ached. My legs weren’t getting bigger nor did I find any change in my athletic performance. 

As I learned more and was influenced by successful coaches, I abandoned my partial squats and moved to full range of motion front squats, deadlifts and Olympic lifts. My knee problems went away, my back sent me a thank you note and my performance improved. As I implemented these changes for my athlete’s training programs, they also got great results. 

What Does the Research Say? 
If you are not into the science, you can stop reading hear and skip ahead to The Bigger Picture & My 2 Cents and the practical applications below (I won’t be offended).

Back in 2010, Brad Schoenfeld did an excellent literature review on the kinematics and kinetics of squatting. Here is a quick summary as it pertains to squatting depth: 
  • The hamstrings offset the forward sheer stress of squatting to take stress off the ACL
  • Greater knee flexion in the squat leads to greater knee compression. However, even in powerlifters squatting 2.5x body weight, the highest compression levels (8,000N at 130°) is still below the limit of the patella tendon (which is about 10,000-15,000N). Also, the quad tendon is even thicker and thus likely has an even higher limit
  • The maximum amount of shear on the knee occurs in the first 60° of knee flexion (i.e. the top part of the squat or partial squat)
  • The peck force on the ACL occurs between 15° and 30° of flexion and decreases significantly at 60°
  • The PCL (posterior cruciate ligament) shear shows up at about 30° of flexion, peaks at 90° and then decreases from 90° to 120°
  • Key point thus far: ACL and PCL stress is greater in partial squats than full squats
  • Deep squatting may stress meniscus and cartilage – consider individual’s knee health history
  • Quad activity peaks at 80° to 90° of flexion
  • Partial squats may work the vastus medialis more
  • Hip extensor force peaks at about 90°
  • Greater squatting depth equals greater gluteus maximus activation
  • Squatting depth does not seem to effect hamstring involvement
  • Half squatting with 0.8 to 1.6 times body weight (my note: this is not much weight for a half squat) puts 6-10x body weight compression force on the low back vertebrae. Many athletes routinely squat at or above the threshold for spinal failure (about 7,800N). 
  • Squatting with excessive lumbar extension (my note: this is common in back squats) increases disc pressure (2° increase in extension = 16% increase in compression).
  • Front squats place less stress compression stress on the knee and low back without changing muscle activation of the quads and hamstrings. Front squat may hit the quads even harder.

Previous research by Weiss et al. back in 2000 found that deep squats improved strength and vertical jump better than partial squats. This was again validated in 2012 when Hartman, et al. also found better vertical jump performance with full squats. Then in 2013, Bloomquist, et. al. found superior results for size and function with deep squats compared with partial squats. 

The New Study
Then, this year a new study by Rhea et al. came out in the journal of Human Movement. This study took a group of college athletes and had them follow a similar athletic training program consisting of squats, power cleans, lunges, reverse hamstring curls and step-ups. However, for the squats, one group did full squats, one did half squats and one did quarter squats. Researchers compared the effects of different squat depth on squat strength, vertical jump and sprinting speed. The results showed that full squats were the best at improving full squat strength. The ¼ squats showed the best improvement in speed and vertical jump. 

I must confess that because of personal and professional bias about squat depth, I wanted to find a major methodological hole in this study. However, I was actually quite impressed with the study design. There were two particular things that I liked about this study: they used more advanced athletes and the program lasted for 16 weeks. (The Weiss study I mentioned above only lasted for 9 weeks and used untrained subjects. The Bloomquist study lasted 10 weeks and had Physical education university students, not highly trained athletes). The authors mentioned that they did a mid-point test at 8 weeks and found no real difference. This makes sense as it would take longer to get used to the heavy loads that quarter squat allows you to handle.

The Bigger Picture & My 2 Cents
Remember that research does not “prove” anything. It simply provides evidence for theories and adds to our body of knowledge on a subject. Just because one study found something different to what other studies have found does not mean we should abandon fuller range of motion squats. 

Just because you can make a squat a “special strength exercise” (i.e. something very specific to a task such as jumping) doesn’t mean you should. As a strength coach, I still believe squats are better used as a general preparation (i.e. get you strong, athletic, functional, balanced and ready for special strength exercises) exercise than a special strength exercise. I believe that jump squats, Olympic lifts (e.g. power clean, power snatch, jerk), push press, trap bar jumps, body weight jump squats, sprinting and sled sprints are far better and safer special strength exercises than partial squats. Full squats build a solid foundation for these exercises. 

Sport coach puts in tens of thousands of hours coaching on the court/track/field/ice, watching video and playing the sport. This is what makes them true experts in their sports. Strength coaches put tens of thousands of hours coaching in the weight room, studying strength and performance training and being under the bar. This is what makes us experts in our area. We have to look beyond just joint angle specificity or statistical significance. I know the squat and I know the problems you can run into with partial squats. Just because we have a new study found that partial squats helped with vertical jump and sprinting speed, does not mean that these potential performance benefits are not without significant disadvantages that need to be considered.

Disadvantages of Partial Squats
  • At the top part of the squat you are in a very mechanically efficient position. This makes it very difficult to get enough weight on your back to challenge your legs.
  • Increases in weight in the partial squat are really about your shoulders, core and most importantly your mind getting used to having all that weight on your back. 
  • The extra weight needed in partial squats placed directly on the spine places a huge amount of stress and compression on the spine. 
  • There is a lot of shear forces on the knee in the top part of the range of motion. Trying to stop and reverse the squat at this point is very stressful on the knee.
  • It is easy to forget that a competitive athlete is already doing a ton of sport-specific stuff – playing and practicing their sport. This sport specialization creates dysfunction and overuse injuries. If all we do in the weight room is more of the exact same thing that happens all week in the sport, we are asking for trouble. 
  • Your body is subconsciously always looking for an easier way to survive training session. It will quickly figure out that the deeper you go, the harder it is. Unless one is being very careful to monitor depth, partial squats inevitably regress in depth over time. An athlete or lifter may start at 90degs but over the course of several workouts find that while they are using 100lbs more, they are now only doing to 45 degrees. This gradual regression of depth with a progression of weight is what I like to call false gains. You end up moving big weight, but get no real benefit from it.
  • Partial squats allow you to hide problems. You can be an orthopedic mess and full of mobility, stability and motor control dysfunctions, yet still be able to quarter squat. This provides you with the perfect opportunity to as Grey Cook would say, “build strength on top of dysfunction.” This is great way to set yourself up for a big injury in the future. 
  • You can be weak and still move what seems like “big weight” giving you the illusion of strength. 
While partial squats may have some benefits, you don’t want to throw out fuller range of motion squats.

The Advantages of Full Squats
Full range of motion squats offer the following benefits: 
  • Build muscle
  • Improve sport and real-life performance 
  • Help maintain lower body mobility
  • Improve core and lower body stability and motor control
  • All you to work the muscles harder with less weight because of the mechanical difficulty of the lower position
  • Help maintain a natural, functional human movement pattern
  • Catch movement dysfunctions 
  • If someone can do a good-looking, full range of motion squat with a respectable weight, it tells me as a coach a lot about that person. 
Note: Full depth generally refers to breaking parallel. However, depending on the individual, it may be a little more or less. When training, do not get depth by relaxing at the bottom of the squat and bouncing off your ligaments. This puts a ton of stress on your knees and creates a prying effect as your hamstrings and calves push into each other. Also do not get depth by relaxing your core and hip flexors and tail tucking at the bottom. Remember that there is a difference between the natural human movement of squatting (the kind that kids do and many people around the world in non-developed countries still do) and squatting with a heavy load on you, In the former squat, it is okay to relax and tail tuck at the bottom (my kids do this all the time). In the latter squat (i.e. the heavy loaded one) it is not.

Genetics and Squat Depth 
It is also important to understand that your genetics impact your squatting ability. Your skeletal structure has a huge impact on how deep you can safely squat. For more information, check out this short, but excellent video by Dr. Stuart McGill:

Superior Alternatives to Partial Squats
The trap bar deadlift is better, safer alternative to a half squat. Holding the weight in your hands instead of sitting on your spine places less direct compression on the spine. Also, because it is slightly more hip-dominant, you get more hamstring activation which helps stabilize the knee joint and take stress off the ACL. Also, just as you are about to get into that vulnerable knee position at the bottom, the weight is on the ground and the stress is off your knees. Because you are coming to the floor each rep, it is easy to maintain the same range of motion each rep and prevent false gains. In addition, trap bar deadlifts allow you to use more muscles. I love trap bar deadlifts for athletes. (Note: the downside of trap bar is they don't work your glutes and hamstrings as much - this has to be accounted for in programming. If I use them with athletes, I add more direct glute and hamstring work as accessory).

Partial Squats                        Trap Bar Deadlift

Another fantastic alternative to traditional partial squats is to do you squats from the bottom pins in the power rack. This ensures that your depth stays consistent and saves the knees from that stressful reversal. To make these even safer, consider using a front squat grip or, if you have one a safety squat bar. Both these variations move the weight from directly on the spine to in front which decrease spinal compression.

Partial Front Squat from Pins

Partial Safety Squat Bar Squat from Pins

Squatting with bands or chains provides accommodating resistance. This causes less resistance at the bottom of the squat (where you are mechanically weaker) and more resistance at the top when you move into mechanically favorable positions. 

Practical Application: You and Your Squat Depth
  • Your goal should dictate not only what exercises you do, but also how you do them. 
  • If you compete in Powerlifting or Weightlifting, the decision has been made for you. However, both sports could benefit from certain aspects of the other. 
  • See the big picture. Every exercise and way of doing an exercise has pros and cons to it. You need to understand all these pros and cons and weight them carefully when making your training decisions
  • Whatever depth you decide to go, look for a way to ensure that you maintain this depth consistently. One great option for this is a touch n’ go box squat
  • If you choose to add some partial squats, consider some of the safer, superior alternatives such as trap bar deadlifts, Front/Safety bar squats from pins. Also, see partial squats as a supplement to, not a replacement of full squats. 

Want more on squats? Check out these squat posts: 

How about you? I welcome you to share your thoughts, comments or questions below or on my Facebook Page

Bloomquist, K, et al. Effect of range of motion in heavy load squatting on muscle and tendon adaptations. European Journal of Applied Physiology: August 2013, Volume 113, Issue 8, pp 2133–2142

Hartman, et al. (2012). Influence of squatting depth on jumping performance. Journal of Strength and Conditioning Research: 26(12): 3243–3261, 2012.

Rhea, MR, et al. Joint-angle specific strength adaptations influence improvements in power in highly trained athletes. Human Movement: 17(1), 2016

Schoenfeld, BJ. Squatting kinematics and kinetics and their application to exercise performance. Journal of Strength and Conditioning Research: 24(12): 3497-3506, 2010.

Weiss, et al. Comparative effects of deep versus shallow squat and leg-press training on vertical jumping ability and related factors. Journal of Strength and Conditioning Research: 14(3), 2000.

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