We’ve been squatting – perfectly at that – since we were babies, yet somewhere along the way in our weight lifting education we were taught not to let our toes go over our knees and, as a result, we have lost the art of the perfect squat. At risk isn’t just the “perfect squat,” at risk is the integrity and health of our spine and back.
If you go to any gym and observe people squatting you will observe, for the most part, a significant forward lean of the torso as one attempts to maintain one's center of gravity within his or her base of support. This occurs because it is widely taught that one's knees should not bend past the toes when squatting.
The claim to this myth is from a Duke University study from 1978 that revealed a reduction in shearing potential of the knee occurred when the knee did not go past the toes in the squatting movement. By keeping the lower leg as vertical as possible, researchers believed such a movement was preserving the integrity of the knee. This theory – the idea that allowing the knees to move past the toes causes undue stress upon the patella and the ligaments of the knee – has been wildly maintained and still taught in many personal training certification courses. It continues being demonstrated in gyms across the country.
Squatting in this manner, however, may actually increase the risk of knee injuries and certainly places the spine in a position where it is very vulnerable to being injured. If you watch a toddler squat you will see a very different motion pattern. Toddlers will maintain a wide base of support, an erect spinal position, and their knees will be bent forward past their toes.
In actuality, limitation of knee movement during a squat can cause more damage and potential injury than any chance of knee stress incurred by the knee pressing out over the toes. According to a 2003 study by the University of Memphis, the forward movement of the knees over the toes increases pressure on the knee by 28%. Conversely, restriction of the knees’ mobility and a forward leaning of the torso was found to have a 1000% increase on hip stress. Conclusively, since 28% is significantly less than 1000%, the more important focus for squat form should be that of the movement of the spine. In short, do not squat with your spine bent forward!
Squatting without allowing your toes to move over your knees in this manner may actually increase our risk for knee injuries and over time can wear out the spine. A careful review of knee and spinal anatomy will help you understand why:
Modern humans retain a spinal structure that has anatomical features associated with a time in our evolution when we were chimp-like. As a result, our anterior longitudinal ligament is wider and thicker than the posterior longitudinal. This design helped support a spine that was under tension anteriorly because of the gravitational forces associated with quadrupedal motion. Ultimately, this structure does not provide enough protection posteriorly for the delicate nervous tissue originating from disc pathology as we evolved to modern day bipeds. The center part of the disc called the nucleus is positioned more centered/posteriorly to compensate for the forces in the disc that would attempt to move the nucleus anterior when we were quadruped. In modern times an increased anterior compression in the disc causes posterior nuclear migration, meaning that if we sit too much or lift with our spines we run the risk of a herniated nucleus pulposes.
The movable spine is made of twenty-four separate segments, giving it great mobility. This mobility was required when our spine tied our limbs together during quadrapedal motion. The associated muscle structure evolved to facilitate this motion. As we transitioned to a bipedal species, we required more stability of our spines to counter the side-to-side forces of bipedal gait. And while the stability strength of the spine is extremely important to modern human function, it is clear that the muscle structure of the spine is not designed to lift heavy loads when squatting. Ultimately, that job is left to the hamstrings, adductors and gluteals, and the spine should be held in a straight and stable position when squatting. Excessive spinal motion is caused by lower extremity muscle weakness and poor lower extremity joint control associated with modern human culture. As a result, this muscle weakness and poor joint control make it much easier to bend the spine forward in an attempt to lower the center of gravity within the base of support rather than to bend the hips and knees appropriately. The tiny joints and muscles associated with the spinal column are not designed for this purpose and thus are placed at risk for injury when we “hip hinge” to squat.
Our spines are simply not designed to accept load, especially in flexion, which is the exact thing we demand of it when we squat with our spine bent forward (or when we squat without the knees shearing over the toes). The discs and structure of the spine are highly vulnerable, which is why we are designed to use our hamstrings, quadriceps and gluteus muscles in order to maintain gravity as our basis of support. In order to properly engage these muscles, it is essential that the spine and torso remain erect throughout the squatting movement.
To further counter the “no knees past your toes” myth, it is important to look at the
biomechanical design of the patella itself. We are evolutionarily designed for this movement – that is, the movement of the knees going past the toes – because of the patella. The patella is a bone on the anterior surface of the knee that functions as a pulley allowing the quadriceps to straighten the knee joint even if the knee is bent past the toes. Otherwise, in this position the quadriceps would become a knee flexor. We have a patella so we can use the knee in a way that protects the spine when squatting.
Additionally, without an appropriate knee bend during a squat movement there is a great deal of stress on the spine and its associated musculature as one lowers their center of gravity within their base of support. This can lead to internal ligament weakness, making us more susceptible to injury when we use our knees during sporting activities, which often require frequent knee bending past the toes. Our knees went past our toes as toddlers when we first learned to squat and stand (again, thanks to the role of the patella), and should continue to do so now. Nothing has changed.
We propose that instead of focusing on the knees during a squat, that the focus be shifted to the spine. Since 80% of the human population will experience back pain during their life, the preservation of spinal integrity is of the utmost importance for everyone – no matter their age, health or place in life. A few facts about spinal health to be cogitated in considering the squat:
The spine is designed to be held stable and not bent forward.
The spine is not designed to accept excessive amounts of load, especially in flexion.
The spine needs to be held straight and erect when we squat, so, as a direct result, the knee simply must go past the toe.
To squat properly, shear your knees forward at about a 45-degree angle. As your knees pass your toes, drop your pelvis until you feel like your heels are going to come off the floor. As you want to keep your heels on the floor, use the heel-leverage simply as a way to assess how deep you should squat. With knees sheering forward, and pelvis dropping, your spine should remain upright, with your eyes looking forward and head erect. Imagine a yardstick being held behind your spine as you squat and try to keep that measuring stick perpendicular to the ground.
An even simpler way to make sure you are squatting properly is to focus more on the position of your upper body instead of the position of your knees. By keeping your spine erect and upright, you will experience a reduction of stress on your back and hips, sending the load of the squat to the muscles – the quads, the hams and the glutes – that are intended to support excessive loads.
Let your knees be free. Start squatting again like you did when you were a baby and you will experience more power in your squat and, more importantly, you will protect the integrity of your spinal health.
Visit our lower extremity exercise page to learn how to squat properly.