Introduction

Squatting is a fundamental human movement pattern that involves nearly every muscle in the body. Squatting improves fitness, performance, and mobility for activities of daily living and other associated tasks.

Sports science has demonstrated that squats are excellent for building strength, power and mobility. Full squats can help counteract many of the chronic musculoskeletal (MSK) problems faced today, such as weak gluteals, hunched back, weak torso, etc. If a person can perform a full depth squat with their own bodyweight, they are probably a reasonably fit and healthy person.

The body weight squat, and its variations, is a core exercise in any fitness professional’s arsenal.

What is a Squat?

In strength training, the squat is a compound, full body exercise that trains primarily the muscles of the thighs, hips and buttocks (gluteals), quadriceps (vastus lateralus medialis and intermedius), hamstrings, as well as strengthening the bones, ligaments and insertion of the tendons throughout the lower body.

The Muscles behind the Movement

  • Primary Muscles: Gluteus Maximus (glutes), Quadriceps (quads), Hamstrings.
  • Secondary Muscles (Synergists/Stabilisers): Erector Spinae, Transverse Abdominus, Gluteus medius/minimus (Abductors), Adductors, Soleus, Gastrocnemius.

Why Squats?

Squats are considered a vital exercise for increasing the strength and size of the legs and buttocks, as well as developing core strength. Isometrically, the lower back, the upper back, the abdominals, the trunk muscles, the costal muscles, and the shoulders and arms are all essential to the exercise and thus are trained when squatting with proper form.

Variations

  • Bodyweight squat: performed with no weight or barbell, often at higher repetitions than other variants.
  • Overhead squat: a non-weight bearing variation of the squat exercise, with the hands facing each other overhead, biceps aligned with the ears, and feet hip-width apart. This exercise is a predictor of total-body flexibility, mobility, and possible lower body dysfunction.
  • Face the wall squat: performed with or without weights. It is primarily to strengthen the vertebrae tissues. In the Chinese variant weights are not used. Toes, knees and nose line up almost touching the wall. Advanced forms include shoeless, wrists crossed behind the back, and fists in front of forehead, all performed with toes and knees closed and touching the wall.
  • Hindu squat: performed without weight where the heels are raised and body weight is placed on the toes; the knees track far past the toes.
  • Jump squat: a plyometric exercise where the squatter engages in a rapid eccentric contraction and jumps forcefully off the floor at the top of the range of motion.
  • Pistol Squat (Single Leg Squat): a bodyweight squat done on one leg to full depth, while the other leg is extended off the floor. Sometimes dumbbells or kettlebells are added for resistance.

Practical Tips

There are a number of practical tips that can be used to enhance performance and reduce the risk of injury.

Balance Stability and Mobility

The prime movers in the squat are the muscles around the hips and knees, but all joints below the belly button (hip, knee, ankle, foot) and most of the spine need both stability and mobility to squat properly.

Keep the Hips Mobile

Muscles around the hips help stabilise the pelvis and knees during squats. If someone lacks hip mobility, they will often lean forward too much when squatting (stressing the spine). Or they will initiate the squat by “popping the butt” up too quickly.

Knees Follow the Toes

When squatting, keep knees stable, in line with the hips and feet. When the knees flare out or cave in (beyond a couple degrees), tendons and ligaments become vulnerable and work extra hard to resist awkward forces. This is probably why young athletes can “get away” with ugly squats (but this catches up with them as they age). Make sure knees follow the direction of the toes. If your toes point out while squatting (which is a normal variation, especially for women with wider pelvises), so should your knees. Do not panic if the knees go slightly over the toes, as this can help to ease the movement for the lower back. What’s most important is that your hips are back, behind your heels.

Keep Ankles Mobile and the Feet Planted Firmly

The ankles help with support and power generation during squats. Limited ankle mobility can lead to the heels coming off the floor, foot pronation (outside of the foot elevating) and the knees caving in. Exercisers should choose footwear that allows them to push through the mid-foot/heel.

In general, running shoes are not good squatting footwear; they are too ‘squishy’ and do not provide enough support. It may be more advisable to wear thin-soled shoes, hard-soled shoes or even go barefoot.

Keep the Spine Neutral and the Chest Proud

Remember the mobility-stability balance? For a good squat, you need lower back stability and upper back mobility. The angle of the torso should remain relatively constant during a squat (as upright as possible, limiting forward lean). This does not mean straight up-and-down, but rather keeping a natural arch in the spine, folding from the hips (rather than rounding or hunching), and keeping the chest proud. As the hips go back during the downward movement, the torso will naturally lean forward slightly to compensate.

With an un-weighted squat (i.e. bodyweight only), it is all right if the lower back slightly rounds in the bottom position. When you add resistance, especially with a barbell (which pushes the thoracic spine more into extension), you will naturally straighten out a little bit. Simply focus on keeping the spine neutral (i.e. a natural S-curve) with minimal rounding.

The lower back is often the weak link for weighted squats, especially in someone with longer legs and a shorter torso. If you are tall and/or have long legs (in relation to your torso), you may have trouble staying upright with standard barbell back squats. Try a wider stance and/or front squats.

The erector spinae muscles are critical during squats, as they help resist vertebral shear forces. They can be strengthened (along with other torso muscles) by doing more squats. Forces on the spine while squatting with heavy weights can be quite high, beyond what most biomechanics equations predict we are able to support. However, the spine adapts over time to increased loads.

Injury Controversy

Although the squat has long been a basic element of weight training, in recent years it has been the subject of considerable controversy. Some fitness professionals allege that squats are associated with injuries to the lumbar spine and knees, whilst others continue to advocate the squat as one of the best exercises for building muscle and strength. Also, some fitness professionals advocate that incomplete squats (i.e. those terminating above parallel) are both less effective and more likely to cause injury than a full squat (i.e. terminating with hips at or below knee level).

Remember, there is a low rate of knee injury in competitive weightlifters. These are the people who frequently perform deep squats for countless reps each week.

Shear versus Compressive Forces

One key reason that full squats do not hurt the knees has to do with the difference between compressive and shear forces.

  • Shear force is sideways force: In the case of the knee, shear force would be loads that go crosswise to the shinbone, such as leg extensions (in which the machine’s pad sits on the shins and presses perpendicular to them).
  • Compressive force is downwards force: In the case of the knee, compressive force would be loading along the length of the bone, such as in a squat.

Joints are better able to withstand compressive forces than shear forces. In addition, with squats many muscles fire at once, which also helps to protect the knee joint. During leg extensions there is only quad contraction and with leg curls there is only hamstring contraction. This can displace the tibia and stress the anterior & posterior cruciate ligaments (ACL & PCL).

However, during squats, both the quads and hamstrings contract. This helps to balance out the tibia in relation to the femur. This keeps the ACL and PCL happy and healthy, and can also help rehabilitate damaged ligaments. Along with loading, shear and compressive forces increase with:

  • Fatigue;
  • Poor technique;
  • Faster rep speed; and
  • More resistance.

What does this all mean?

  1. Full depth squats, done properly and carefully, at an appropriate speed, are safe.
  2. But you might want to quit doing those heavy leg extensions.

Learning to Squat

If you have stiff ankles, immobile hips, a weak torso, discomfort, and strange noises in your joints with squatting, then you are likely to have a faulty movement pattern that needs adjustment.

If squatting results in acute pain, or you lack the mobility/strength to do one properly, swallow your ego and modify the movement (see squat progressions below).

Full depth squats are often safer than shallow squats because it takes less external resistance (and less stress on the joints) to create the same stress on the muscles (thanks to lever arms). This makes full depth squats ideal for most people. However, exceptions to this include:

  • Knee rehab (which should progress to full squats, in most cases);
  • Extremely long legs in relation to torso; and/or
  • Exercisers who have specific partial-squat-related goals, such as athletes training jump squats.

Squat Progressions

Most adults in Western cultures (where people sit instead of squat) do not squat well when they start. Exercisers have typically lost their natural childhood ability to drop down easily on their haunches. Therefore, many exercisers will have to re-learn how to squat properly.

Basic Overview of the Squat Movement

  1. Start in a standing position, with good posture. Feet can be anywhere from close together, with toes pointed forwards, to wide, with toes pointed out. Experiment and find which foot placement works best for you.
  2. Take a deep breath, lifting the ribcage.
  3. Keeping this ‘proud chest’, push the butt back first and then sit down (imagine sitting down in a chair that is not there, or sitting down on the toilet).
  4. Let the torso tip forward naturally from the hips as the butt shifts back.
  5. Keep the heels down.
  6. Go down until your hamstrings touch your calves (beginners go down as far down as you can go).
  7. Drive through the heels, keeping the chest ‘proud’ and head up and ascend.

Squat Variations

The squat is not a single exercise, it is an exercise concept. By mixing up the loading (overhead, front, back, dumbbells held at the sides, etc.), form (1 or 2 legs), speed, foot placement, etc. you can have a hundred (or more) variations on the basic idea. Some of these variations include:

  • Plate squats: Plate squats encourage upright posture and appropriate load distribution. Hold the plate parallel to the ground. If the plate tilts downwards, you are probably rounding your back. To increase difficulty, try balancing a ball on top of the plate (use a light plate as you are not doing this movement to show off).
  • Back squats: In the classic back squat, the barbell sits on the trapezius/upper back, not on the neck.
  • Jump squats: If you want a powerful leg contraction, jump. Adding resistance to jumps can increase power output and jump height. When it comes to optimal jump squat form, the thighs do not usually go below parallel. To load the jump, weighted vests are ideal. You can also hold dumbbells, though it is somewhat more awkward. Barbell and Smith machine jump squats tend to be the most dangerous, because of the loading on the spine.
  • Front squats: In the front squat, the weight sits at the top of the front of the shoulders, in the ‘groove’ between deltoids and collarbone. Because the torso stays more upright in front squats, this style of squatting minimises compressive forces on the spine and knee joints. If the barbell begins rolling forward from the shoulders, there is a lack of mobility and/or torso strength. Many people think wrist range of motion is the limiting factor here, but it is usually tight internal shoulder rotators (pectoral major, latissimus dorsi, teres major, subscapularis). Work on keeping elbows high throughout the movement.
  • 1-leg squats: When you have mastered two legs, try one. Working one side at a time can increase demands from supporting hip muscles.
  • Bulgarian split squat: Place one foot behind you on a bench or step. Use this non-working leg for balance only, drive through the front leg.

Troubleshooting the Squat

When you are working on learning to master the squat, try snapping photos or videotaping yourself. This can provide invaluable feedback.

Trouble Getting a Comfortable Squat Pattern

  • Try a wider stance, with your toes pointed out a little (remember knees follow toes);
  • Use natural foot positioning (similar to other athletic movements), with toes slightly out;
  • Keep heels on the ground. If need be, put small plates under your heels until you develop better mobility in hip and ankle joints;
  • Control squat speed, using a 2-3 second descent (unless your sport/activity demands another style);
  • Maintain a neutral spine posture;
  • Take breaks, fatigue can result in poor mechanics;
  • Keep your hands close to your body;
  • Look forward and keep your head up;
  • Work on mobility drills for ankles, hips and the thoracic spine;
  • Use squatting progressions (see above); and/or
  • Consider the services of fitness professional.

Trouble Keeping the Weight on Your Heels

  • Build hip mobility;
  • Build core stability;
  • Build ankle mobility;
  • Build thoracic spine mobility;
  • Take off your shoes or get a thin soled shoe; and/or
  • Keep your chest proud and core tight.

Trouble Squatting Deep

  • Get your body warmed up;
  • Widen your stance and rotate your toes out;
  • Think about squatting between your legs;
  • Build ankle, thoracic spine, and hip mobility;
  • Build core stability;
  • Start the squat by sitting your hips back;
  • Try box squat progressions (high to low box); and/or
  • Decrease the resistance you are using.

Do Your Knees Cave in During Squats

  • Place a light band around knees as a guide;
  • Strengthen the hip abductors/gluteals;
  • Focus on keeping the knees out and ‘spreading the floor; and/or
  • Decrease the resistance you are using.

Rehabilitation

The squat has been shown to be effective during the rehabilitation process of cruciate ligaments and/or patellofemoral injuries, with the most effective range of motion between 0 and 50 degrees of knee flexion (the vastus medialus oblique (VMO) tends to be activated more during partial squats).

The ultimate tensile strength of the patellar tendon is about 10,000 to 15,000 N. The highest recorded compressive forces were obtained in a study of power lifters lifting 2.5 times their bodyweight, approximately 8,000 N at full squat depth.

The greatest risk of injury with full depth squats is probably to the menisci and articular surfaces of the knee rather than the ACL/PCL. Strong hamstrings can help to increase knee stability during the squat.

Stress on the knee ligaments can be decreased by keeping the heels on the ground. Peak quad involvement during squats is from the upright position down to 90 degrees knee flexion. Beyond that, the hamstrings and gluteals contribute most. Foot placement (toes in, out, straight) does not seem to influence muscle activation. Only a very wide stance incorporates more of the adductors.

Further Reading

Chandler, J., McMillan, J., Kibler, B. & Richards, D. (0000) ACSM Current Comment: The Safety of the Squat Exercise. Available from World Wide Web: <http://www.acsm.org/docs/current-comments/safetysquat.pdf> [Accessed: 22 March, 2013]. ACSM is short for the American College of Sports Medicine.

Peak Performance. (2013) Squat Research Review. Available from World Wide Web: <http://www.pponline.co.uk/encyc/squat.html> [Accessed: 22 March, 2013].

Schuna, J.M. & Christensen, B.K. (2010) The Jump Squat: Free Weight Barbell, Smith Machine, or Dumbbells? Strength and Conditioning Journal. 32, pp.38-41.

Chiu, L.Z. & Burkhardt, E. (2011) A Teaching Progression for Squatting Exercises. Strength and Conditioning Journal. 33, pp.46-54.

Salem, G.J. & Powers, C.M. (2001) Patellofemoral Joint Kinetics during Squatting in Collegiate Women Athletes. Clinical Biomechanics. 16, pp.424-430.

Kritz, M., Cronin, J. & Hume, P. (2009) The Bodyweight Squat: A Movement Screen for the Squat Pattern. Strength and Conditioning Journal. 31, pp.76-85.

McBride, J.M. (2009) Relationship between Maximal Squat Strength and Five, Ten, and Forty Yard Sprint Times. Journal of Strength and Conditioning Research. 23, pp.1633-1636.

Gullett, J.C. (2009) A Biomechanical Comparison of Back and Front Squats in Healthy Trained Individuals. Journal of Strength and Conditioning Research. 23, pp.284-292.

Escamilla, R.F. (2001) Knee Biomechanics of the Dynamic Squat Exercise. Medicine and Science in Sports and Exercise. 33, pp.127-141.

Comfort, P. & Kasim, P. (2007) Optimizing Squat Technique. Strength and Conditioning Journal. 29, pp.10-13.

Escamilla, R.F. (2001) Effects of Technique Variations on Knee Biomechanics during the Squat and Leg Press. Medicine and Science in Sports and Exercise. 33, pp.1552-1566.

Fleming, B.C. (2005) Open- or Closed-kinetic Chain Exercises after Anterior Cruciate Ligament Reconstruction? Exercise and Sport Science Review. 33, pp.134-140.

Schoenfeld, B.J. (2010) Squatting Kinematics and Kinetics and their Application to Exercise Performance. Journal of Strength and Conditioning Research. 24, pp.3497-3506.

Waller, M. & Townsend, R. (2007) The Front Squat and its Variations. Strength and Conditioning Journal. 29, pp.14-19.

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