The SCIENCE behind DEEP SQUATS
Emily R Pappas, M.S.
Female athletes who want to be faster, more explosive, and more resilient often wonder if deep squats are dangerous for their knees.
While various research studies have found that deep squats can be highly effective for improving lower body strength, we still find that athletes, parents, and coaches question the significance of even the most fundamental human movements.
In this article we discuss the current research on DEEP squats (ie going below parallel), how they help female athletes develop lower body strength and power, and assist in reducing the chance of lower body related injuries.
Squat Strength & Athletic Movements
Squat strength has been linked to improvements in a variety of athletic movements such as sprint speed, vertical jump height, and lower body power production.
When considering this strength, evidence (1) suggests that deep squats promote greater muscle mass and strength development compared to partial squats (above parallel).
Athletes who are able to squat below parallel show a greater activation of their glutes, the biggest contributor in the production of speed and jump height.
While partial squats will help athletes improve their lower body strength and allow for greater force production as they sprint or jump, deep squats will show even greater improvement (1).
In other words, if you want to get the most out of your squats, depth is key!
Squat Strength & “Knee Health”
The confusion around deep squats is often associated with the amount of “stress” they place on the knee joint.
This stems from an article published way back in 1992 that argues that squatting depth directly affects knee joint health (2).
However, over the past 25+ years, we’ve learned a lot more about knee health and squats.
Researchers have been able to produce more detailed evidence, for both male and female athletes, against this argument.
In the initial study, the concern over deep squats related to the amount of stress placed on the anterior and posterior cruciate ligaments (ACL and PCL) with an increased flexion angle at the knee (3).
Over the years, more studies have concluded that deep squatting actually results in LESS movement between the tibia and femur.
Less shear movement (where forces act in parallel) and rotational movement between these two bones means there is LESS stress on the ACL and PCL than previously thought. (Most ACL and PCL injuries result from excessive shear force.)
And that’s not all. Although squats at parallel show no difference in the activation of the hamstrings and quadriceps compared to deep squats, they do show a significant difference in glute activation.
Higher glute activation in deep squats allows athletes to not only increase lower body strength, but also improve their ability to stabilize their knee joint. Larger glute activation and concurrent activation of the hamstrings and quads results in a decrease in the shear force applied to the ACL and PCL ligaments (1).
Ever perform a leg press or hamstring curl on a machine? Interestingly enough, these actually place MORE stress on the ACL and PCL compared to deep squats since they isolate quad vs. hamstring contraction. This type of isolated contraction can displace the tibia and stress the ACL and PCL ligaments.
Simply put, greater muscle activation from deep squats means less shear force applied to the ligament. This is KEY when improving your ACL and PCL health, as well as in the rehabilitation process from previous injuries (4).
Of course, if a muscle is not strong enough to absorb these forces, they may transfer to the tendon and ligament.
By strengthening the muscle (through movements like deep squats) we are able to decrease the chance that higher forces apparent in sprinting and jumping will be placed on our athlete’s ligaments and tendons.
“But don’t heavy squats already expose the body to high forces?”
Yes, but studies suggest that running actually causes GREATER stress on the knee joint than max intensity squats (5)!
Remember, stress is NECESSARY to allow your body to ADAPT and improve strength. Athletes who perform full-depth squats are imposing a NECESSARY stress to promote improved strength and better prepare their bodies to produce high forces.
RUNNING and JUMPING are HIGH FORCE activities. Athletes who perform DEEP SQUATS better prepare their bodies to both PRODUCE high forces and ABSORB them.
This means faster sprints and higher jumps AND decreased chances for force to be transmitted to tendons and ligaments (6).
Positioning Matters!
Before we even start thinking about depth, though, we must focus on joint position.
The positioning of an athlete’s hips, knees, ankles, and torso DIRECTLY influence the loading patterns of these joints and the angles they assume throughout the movement.
Although different variations of squats allow a greater emphasis on certain muscle groups (e.g. front squats allow for greater quadricep activation, while a low bar powerlifting style squat allows for greater posterior chain activation), the fundamental characteristics of body control and stabilization must be prioritized first.
BODY CONTROL
One of our favorite sayings at Relentless is, “You have an entire foot, so you need to learn how to use it!” This means you need to feel your ENTIRE foot throughout the movement of the squat.
By maintaining an even distribution of weight across the foot (big toe, little toe, and heel all in contact with the floor), an athlete has more points of contact with the floor to push against and produce force.
This is the FUNDAMENTAL characteristic of any squat style. When an athlete’s heels or toes elevate off the floor during a squat, it means they have fewer points of contact to produce force against (1).
Even more, when an athlete lacks the body control to maintain balance in the foot, it leads to higher stresses put on certain joints (such as in the knees). When we squat, we want to maintain balance in our weight so that the muscles activated are also balanced.
Keeping your weight balanced THROUGHOUT the movement means both better force production (more points of contact) and greater joint stability.
CORE STABILITY
Beyond weight distribution, core stability is another FUNDAMENTAL component when considering joint positions in squat movements.
At Relentless, we like to teach our athletes that their CORE is the root of their strength. A strong core allows your body to move as a unit. Think of the core as the link to your limbs.
In a squat, without a stable core, the legs and hips are less able to transmit force as a unit up into the bar. Muscles that act in COORDINATION are able to produce and absorb HIGHER FORCES than if acting segmentally (3).
By prioritizing stability at the core, athletes are better able to maintain position and coordinate multiple muscle groups to help produce MORE force throughout a joint’s range of motion.
When In Doubt, DEEP SQUAT!
Instead of being influenced by all the noise and misinformation about fitness—which there is plenty of—it’s best to simply turn to science to help us understand WHY certain movement matters.
Scientists have been studying the efficacy of deep squats (below parallel) for decades. Current evidence shows that deep squats result in greater activation of lower body musculature compared to shallow squats, resulting in faster sprint performance and higher vertical jumps.
Even more, deep squats do NOT result in greater shear forces on your ACL and PCL. Instead, they show greater stabilization of the knee joint.
When prioritizing movement fundamentals of body control and core stabilization, females that squat deep are not only able to improve their strength, speed, and jump height, but also help reduce their risk of future knee injury.
In other words, go deep or go home!
References
1 Ciccone, T., Davis, K., Bagley, J., Galpin, A. (2016). Deep Squats and Knee Health: A Scientific Review. Center for Sport Performance, California State University, Fullerton.
2 Chandler TJ and Stone MH. (1992). The squat exercise in athletic conditioning: A position statement and review of the literature. Chiropractic Sports Medicine 6: 105-105,
3 Cotter, J. A., Chaudhari, A. M., Jamison, S. T., & Devor, S. T. (2013). Knee joint kinetics in relation to commonly prescribed squat loads and depths. Journal of strength and conditioning research, 27(7), 1765-74.
4 Andrews, R. (2005) https://www.precisionnutrition.com/all-about-the-squat
5 Escamilla RF. (2001). Knee biomechanics of the dynamic squat exercise. Medicine and Science in Sports and Exercise 33: 127-141.
6 Salem, G., Power, C. (2001). Patellofemoral joint kinetics during squatting in collegiate women athletes. Clinical Biomechanics 16: 424-430
About the Author
Emily holds a M.S. in Exercise Physiology from Temple University and a B.S. in Biological Sciences from Drexel University. Through this education, Emily values her ability to coach athletes with a perspective that is grounded in biomechanics and human physiology. Outside of the classroom, Emily has experience coaching and programming at the Division I Collegiate Level working as an assistant strength coach for an internship with Temple University’s Women’s Rugby team.
In addition, Emily holds her USAW Sport Performance certification and values her ability to coach athletes using “Olympic” Weightlifting. Emily is extremely passionate about the sport of Weightlifting, not only for the competitive nature of the sport, but also for the application of the lifts as a tool in the strength field. Through these lifts, Emily has been able to develop athletes that range from grade school athletes to nationally ranked athletes in sports such as lacrosse, field hockey, and weightlifting.
Emily is also an adjunct at Temple University, instructing a course on the development of female athletes.