Ass to the ground, half way, and parallel are all choices for squat depth. This debate has been around longer than the one between democrats and republicans. I’m sure during the Stone Age, some caveman said to another caveman, “butt to ground…good”. Unfortunately, in recent articles and online forums, the debate has continued in the same fashion. With the hundreds of published research articles on knee and hip kinematics and kinetics, there should be little room for debate.
During a discussion on the depth of the squat, one has to establish the circumstances and reasons why they are squatting. There are two categories for why someone would perform a squat. One either squats for performance or for vanity. Simply put, you either squat for better looking legs or for some type of event in the future (sports, power lifting, return to function, etc.) Knowing the reason establishes a framework to discuss how low to go. Here I will explain the two reasons and how to use SCIENCE to decide how low to go.
Many people lift for vanity reasons. They want bigger, tighter, leaner, more vascular, toned, and slimmer body parts. If the reason you squat is related to one of these reasons, then you squat for vanity. Under these conditions, you should look in the research and decide how to squat effectively AND with the least amount of joint degeneration risk. I’ve lectured across the country teaching trainers about the necessity of approaching this topic with a “why do you squat perspective”.
Before you decide on how low to squat, there are a few key factors to consider.
- How flexible are your hamstrings?
- If you can’t lie on your back and lift one leg so it is perpendicular to the floor with the contralateral (other) leg straight against the floor, you have tight hamstrings.
- If your hamstrings are tight, it will pull your pelvis into a posterior tilt. This leads to rounding of the lower back.
- Have someone watch you squat from the Left side. Have them tell you when your pelvis rotates clockwise. You essentially, should not squat below whatever that knee angle that posterior pelvic tilt occurs. We have become a society of sitters. This has caused a majority of people to have tight hamstrings and an excessive POSTERIOR pelvic tilt. Of the 2500 patients for physical therapy that have passed through the clinic and the thousands of people lifting I have observed while lecturing across the country, I have witnessed the majority of people with excessive Thoracic kyphosis and posterior tilt.
- Where to turn your feet (out / in / straight)
- Start walking and look down. Observe the degree in which your feet turn out if any. Assuming you do not have hip rotation tightness (you can Google this info), you should squat with the same feet position as you walk. For example, if your feet are perfectly straight forward when you walk, then squat with them forward. If they turn out 20 degrees, then squat with them turned out 20 degrees. Do not read some article by someone who can squat 1000 pounds or is a “Certified Trainer” and have them tell you differently. Assuming you have no tightness, your feet placement is dictated by the amount of Femoral retroversion/antiversion. If you turn your feet out, when you are not built that way, you cause a detrimental chain reaction. Your arch drops, your feet pronate, your Tibia rotates medially, and your patella tracks excessively medially.
Now, once you have decided you do not have problems with the above, you can now decide how low to go. To avoid excessive compressive forces in the Patellofemoral (knee cap joint) and Tibiofemoral (actual knee with femur on top of tibia) joint, you have to consider what forces are acting upon those joints when squatting. According to Wallace et al (J Orthop Sports Phys Ther. 2002 Apr;32(4):141-8) Patellofemoral joint forces are greatest at 90 degrees during the squat. As the knee flexion angle increases, the compressive forces on the knee cap increases. A study by Wilk et al (Am J Sports Med. 1996 Jul-Aug;24(4):518-27) looked at Tibiofemoral joint compression forces with the squat. They found the highest forces at 91 degrees of knee flexion. If you consider the results of both studies, you will realize that high compressive forces exist at 90 degrees of knee flexion (AKA squatting to parallel). Upon detailed reading of the articles, you will also find that forces tend to increase dramatically after 60 degrees of knee flexion.
So what do you do with all that science? Well, if you are squatting for looks, I would recommend squatting only to 60 degrees. You compromise the decreased activation of more Glut Max and Hamstrings with less knee degeneration. The decision is for you to make. Read the articles and make informed decisions about your own joint health.
If you are squatting for performance, then the option of compromise may not exist. You may have to follow rules of the event (i.e. power lifting or testing for football). You should analyze the kinematic and kinetic needs of the knees. No pun intended. If your sport activity involves deep knee bending during the sport activity, then you need to squat low. Activation of the muscles in a firing pattern that most closely resembles the sport is more beneficial than textbook form. My only recommendation is to stock up on your high quality Glucosamine, MSM, and Chondroitin.
If your knees already hurt, I would recommend seeking the counsel of a qualified orthopedic doctor or physical therapist.