Ah! The one question that most trainers dread to hear from their clients; however, it comes with the territory. Fortunately for our clients, we are not only here to kick their butts, but educate them the best we can on topics related to health and fitness that they may hear via social media or from family and friends. Of those many topics is the debate on whether or not your knees should go past your toes during a squatting movement.
Originally, it was suggested that if you allow your knees to go past your toes, knee injury would ultimately occur. As a result, many fitness and allied health professionals have recommended only squatting to a depth of parallel (this is where your thigh is parallel to the ground), which will help prevent your knees moving too far forward. However, some research actually suggests that this notion may be misdirected and not completely factual. So, first let me briefly present some research that dismisses this myth then I will touch upon why performing deeper squats can be beneficial.
A previous study1 investigated the joint kinematics and kinetics (joint angles and forces, respectively) during a restricted and unrestricted squat. A restricted squat consisted of placing a wooden board in front of the subjects’ toes, which would not allow the knees to travel past the toes during the movement. On the other hand, an unrestricted squat allowed the knees to travel past the toes. After conducting the experiment, the researchers concluded greater knee forces and a more upright posture with the unrestricted squat, but greater hip forces and more forward lean during the restricted squat. Interestingly, although the unrestricted squat placed about 30 more units of force on the knee than the restricted squat, the restricted squat placed about 10x more units of force on the hips than the unrestricted squat. Ultimately, this force would be transferred to the spine (not good). The researchers conclude that preventing movement at one joint may lead to adverse effects on other joints.
*Notice how forward he is forced to lean when his knees are restricted from passing the toes. I hope he has a good chiropractor!
Other researchers2,3 note that squatting below parallel (i.e. deep squats) should not be detrimental to the knee joint as previously thought, unless a current knee injury exists. These researchers performed literature reviews of the joint biomechanics during the squat exercise and report that although knee compressive and shear forces do increase with greater knee flexion angles, this should not be harmful to the healthy knee. You should also keep in mind that compressive forces are not necessarily a bad thing. They actually help to stabilize the knee joint throughout the range of motion and aid in minimizing shear forces as well2,3.
But what about the ACL and PCL (these are important ligaments that help stabilize the knee joint)?
Well, the researchers also reviewed the forces placed on these ligaments during the squat and report that peak ACL and PCL forces occur with lower knee flexion angles (15-30 degrees and 90 degrees, respectively)2,3. Thereafter, they begin to decrease and then level off with increasing squat depth.
Another interesting point is that Olympic Weightlifters, who typically perform deep squats on a regular basis (see photo below), experience small injury rates and when they do occur it appears to be a result of overuse4–6. Remember that these athletes start with low resistances and learn the movement first. Overtime, weight is progressively increased as strength and coordination improves (the key here is progressive overload). Having said that, the next time you head to the gym to squat do not just start performing deep squats with the same load you have been using with higher depth squats. First, you need to see if you can correctly obtain the range of motion. Start with a body weight squat and see if everything checks out. If you have no problem reaching a greater depth, I would recommend initially sticking with lower resistances in order for your muscles and joints to get accustomed to the essentially new movement and loading throughout a greater range of motion. However, if you cannot safely obtain this range, you may need to include additional strengthening and flexibility exercises, which overtime, can result in an improved range of motion. Moreover, if you experience any pain when squatting lower, then it may be best to stick with a higher squatting depth for the time being.
Ok, Ok, so now you may be thinking, “I’ve heard why it may not be bad for me, but does it offer any additional benefits?” You bet your butt it does (the pun here will be relevant in a second)! It can help maintain/improve hip mobility, which if limited, may lead to lower back pain7,8. Oh, and I should probably mention that squatting lower has been shown to increased gluteus maximus activation9. Yes, the infamous butt muscles work harder when performing deeper squats. More importantly, people who have greater gluteal strength seem to not experience lower back pain7,10. Also, your gluteal muscles help to stabilize your knee during movement2.
Next time you’re at the gym remove some plates from the bar (at least initially) and try squatting a little lower. You may like the results…
About the Author
Mark DiSanto received his Masters in Exercise Science and Nutrition from Sacred Heart University in Fairfield, CT. He holds certifications through the NSCA and USAW. Mark is a competitive weightlifter and a strength & conditioning coach at Old Greenwich Sports and Wellness Center in Old Greenwich, CT.
1. Fry AC, Smith JC, Schilling BK. Effect of knee position on hip and knee torques during the barbell squat. J Strength Cond Res. 2003;17(4):629–633.
2. Schoenfeld BJ. Squatting kinematics and kinetics and their application to exercise performance. J Strength Cond Res. 2010;24(12):3497–3506.
3. Escamilla RF, others. Knee biomechanics of the dynamic squat exercise. Med Sci Sports Exerc. 2001;33(1):127–141.
4. Calhoon G, Fry AC. Injury rates and profiles of elite competitive weightlifters. J Athl Train. 1999;34(3):232.
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6. Drechsler A. USA Weightlifting and Sports Performance Coach Course. 2003.
7. McGill S. Low Back Disorders: Evidence-Based Prevention and Rehabilitation. Human Kinetics Publishers; 2007.
8. Mellin G. Correlations of hip mobility with degree of back pain and lumbar spinal mobility in chronic low-back pain patients. Spine. 1988;13(6):668–670.
9. Caterisano A, Moss RF, Pellinger TK, et al. The effect of back squat depth on the EMG activity of 4 superficial hip and thigh muscles. J Strength Cond Res. 2002;16(3):428–432.
10. Kankaanpää M, Taimela S, Laaksonen D, Hänninen O, Airaksinen O. Back and hip extensor fatigability in chronic low back pain patients and controls. Arch Phys Med Rehabil. 1998;79(4):412–417.