Performing the Squat: Safety, Depth, and Foot Position

3 Feb

The squat is one of the most functional exercises anyone can perform.  The term functional is something that gets thrown around very loosely in the fitness community today.  The squat is functional because it mimics movements that individuals perform on a daily basis such as sitting in a chair or lifting heavy objects from the floor.  For many years, strength and conditioning programs use the back squat to improve athletic performance such as sprinting ability (McBride et al. 2009, Comfort et al. 2012).   Bodybuilders, professional and recreational, often perform the squat to stimulate large amounts of muscle mass in one movement.  Even with many people performing this exercise on a weekly basis, questions and concerns often arise regarding this technical lift.  In this article, I am going to the following questions:

Are loaded squats safe?  

What is the appropriate depth that I should squat?

How should I position my feet and how wide?

Before I dive into answering these questions, I want to briefly review the basic anatomical and biomechanical areas of focus during a squat.  A squat is a closed-chained, multijoint exercise that involves several major muscle groups (Clark et al. 2012).  Descending into a squat involves flexion of the hip, knee, and ankle joint.  While ascending back to the starting position involves hip and knee extension and plantar flexion of the ankle joint (Schoenfeld 2010).   The quadriceps, hamstrings, gluteus maximus, hip abductors, hip adductors, and other hip flexor/extensors are dynamically activated to perform this movement.  To provide stability, the large muscles of the back and core are isometrically contracted to safely protect the spine.  As you can see, by performing one movement, large amounts of musculature can be activated. 


In 1961, a study by Dr. Klein at the University of Texas, revealed that full squats increased the laxity in the collateral and anterior cruciate ligaments (Klein 1961).  Shortly thereafter, the American Medical Association (AMA) released a position stand stating that full squats can cause “potential for severe injury to the internal and supporting structures of the knee joint.”   Full squats were removed from many military and education-based physical fitness programs.  It wasn’t long before other follow up studies replicated Klein’s protocol, but found contradicting results.  The data showed no reduction in the stability of the collateral or anterior ligaments.  Current research has shown that the anterior cruciate ligament (ACL) is under the most shear force during the beginning of the squat at 15° to 30° of knee flexion.  The posterior cruciate ligament (PCL) experiences the most shear force as the knee reaches 90° of flexion, with diminishing force past this point (Comfort 2007, Schoenfeld 2010).  Almost no shear forces were observed below the parallel position, probably due to the fact that compressive forces are greatly increased as one moves deeper into the squat.  Compressive forces are caused by the compression of the menisci and other soft tissue structures from the posterior, upper tibia and the superior posterior femoral condyles (Li 2004, Schoenfeld 2010).  From the current body of evidence, loaded squats are considered a safe form of exercise when performed with proper technique.  Injury during the squat movement usually occurs when a lifter is using bad technique, too high of load, or has a pre-existing pathological condition that was not addressed.  Understanding proper mechanics can make the squat a safe and effective way to achieve many fitness goals.


Squats are often categorized into 3 distinct groups: partial squats, half squats, and deep squats.  Partial squats consist of a knee angle of 40°, while half squats range from 70° to 100°.  Anything greater than 100° would be classified as a deep squat (Schoenfeld 2010).  Determining the appropriate depth for a lifter is dependent on many factors such as anatomical structure, training goals, and training status.  Speaking from experience, I can say that not everyone will be able to perform a full squat.  Some individuals may have an anatomical condition that will not allow certain joints to move through a complete range of motion.  Always go through the range of motion that presents no joint discomfort.  To my knowledge, the sport of powerlifting is the only sport that requires an athlete to squat to a certain depth.  This sport requires athletes to squat to a depth where the hip joint descends below the top of the knee.  So depending on the circumstances, squat depth may be a pre-determined height.

The main interest in squat depth is usually in regards to muscle activation.  The quadriceps, hamstrings, and gluteus maximus are the most common muscles observed for muscle activity in the squat.  Quadriceps activation has been shown to peak at approximately 80° to 90° of flexion with the same values observed at greater degrees of flexion (Schoenfeld NSCA).  Other data also suggest that squatting deep would have no extra benefit on quadriceps activation (Caterisano et al 2002).  One main argument to these conclusions are that participants used the same load in the half squats and deep squats (Clark 2012).  In most conditions, individuals will be able to lift greater loads in the partial or half squat than they can a deep squat.  The greater load lifted during the squat, the greater the quadriceps activation (Paolli et al 2009).  Caterisano et al. also found that gluteus maximus activation was significantly higher in the deep squat compared to the partial and parallel squat (2002).  The gluteus maximus is a powerful hip extensor which helps to control eccentric lowering into the squat while also providing powerful force to extend the hips back to the starting position.  The hamstrings, another powerful hip extensor, are not quite as active during the squat as the gluteus maximus.  As a bi-articulate muscle group, the hamstrings shorten at the knee joint and lengthen at the hip joint so there is relatively no change in length-tension ratio.  Therefore, the current body of data suggests that squatting to parallel would be beneficial for training the quadriceps and to achieve better gluteus maximus development, one may add full squatting into their program.


It is a common belief in the fitness industry that foot width and placement will affect the activation of specific lower body musculature during the loaded squat.  A few studies have investigated the difference in muscle activation between narrow stance squats (less than shoulder width), normal stance squats (shoulder width), and wide stance squats (greater than shoulder width).  The gluteus maximus and adductor longus experience significantly greater activation with a wide stance compared to a narrow stance (Clark et al. 2012).  This is potentially due to the fact that most individuals push their hips back and knee track out over the toes during a wide stance squat.  By doing this, you would engage the hip musculature more during the squat movement.  The same studies have shown no significant changes in quadriceps activation during different stance widths.  Based on this data, doing close stance squats may not prove to activate the quadriceps more effectively than other widths.  Instead, one should strive to increase the load lifted to enhance quadriceps training.

Squatting is one of the most common exercises in strength and conditioning programs, and the current body of research claims it to be completely safe when performed with proper technique.  Squat depth should be chosen according to the anatomical structure and goals of the individual.  Feet width in the squat is recommended to be approximately shoulder width, however each individual should find a position that is most comfortable for them.  Remember that squatting, like any technical athletic movement, is often improved by practice and repetition.

Please list any comments or questions below.


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