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Here’s What You Need To Know…

1. The squat is one of the most important lifts known to mankind. Effectively training this essential human movement pattern leads to increased strength, hypertrophy, and performance.

2. Regardless of the variation, there are mandatory components seen in EVERY squat. This is to ensure maximal mechanical efficiency and reduce the risk of injury.

3. The multiple variations of the squat all involve different loading tools, bar positions, and depths. Each have their application. The variation of choice will depend on the individual’s goals and injury history.

4. Regardless of your preferred variation, progressive overload is KEY for long-term strength gains, hypertrophy development, and performance.

Considered the “king” of all lower body exercises, the squat represents one of the most fundamental human movement patterns known to man. If you stand up and sit down from a chair or toilet, you are squatting and should also be training this pattern as well! Regardless of the squat variation of choice, there are a few mandatory components present in EVERY squat in order to maximize mechanical leverage and reduce the risk of injury.

  • The lumbar spine must remain in a neutral position throughout the entire repetition. This promotes core stability and ensures a proper transfer of force.
  • The foot must remain firmly planted on the ground and stable throughout the entire rep. The heel cannot rise from the ground, and the foot cannot turn out during the rep.
  • When an external load is applied, the load must stay in a vertical line over the midfoot. This reduces unneeded additional moment arms and maximizes mechanical leverages.

With the feet and lumbar spine stabilized and the weight centered over the midfoot, joint angles will vary primarily due to where the load is placed, aka the rationale behind barbell squat variations.

Different Variations of the Squat

It’s time to take a look at the marquee differences between the major squat variations to determine which squat variation is the best fit for you and your clients based on your body, skill level, goals and of course, past medical, orthopedic and injury history. Lets jump into one of the most notorious squats in the fitness industry, the quarter squat.

The Quarter Squat

The quarter squat represents one of the most popular variations seen in many physical therapy clinics and even some gyms today. This variation is characterized by a relatively vertical torso, lack of hip abduction, and reduced hip and knee flexion.

quarter squat

The bar is still centered over the midfoot even during the quarter squat exercise.

While many physical therapists are now promoting full range of motion squats, those that intentionally limit depth often do so because “deep squats are BAD for the knees.” The rationale goes like this: Research shows that the highest retropatellar forces are seen at 90⁰ of knee flexion, so therapists for decades have been telling their patients to go no deeper than 90⁰ (1). To give you a frame of reference, knee flexion is usually between 120-130⁰ at the bottom of a properly performed full ROM back squat. What many fail to realize is these SAME compressive forces actually DECREASE at knee flexion angles greater than 90⁰.

At angles greater than 90⁰, a phenomenon known as the “wrapping effect” occurs where the increased surface between the quadriceps tendon and the intercondylar notch promotes increased load distribution AND enhanced force transfer (1). Additionally, increased soft tissue approximation between the distal hamstrings and proximal calf musculature also lead to greater force distribution (2).

While there will be times that squat depth NEEDS to be limited, intentionally limiting depth when the individual otherwise possesses the mobility is futile, as you miss out on potent strength, hypertrophy, and performance improvements.

The Box Squat

The box squat represents another common variation typically seen in the physical therapy and fitness realms. In this variation, a box is utilized so the trainee can sit down at the bottom of the movement. What is unique about the box squat is the trunk angle and ankle position. When the trainee sits down on the box and pauses, the trunk angle slightly changes, a feature not seen in the free-standing variations. Initially, the trunk is inclined forward during the descent, but as the trainee rests on the box, he/she rocks back slightly, thus achieving a more vertical torso position before the trunk is then inclined forward again to start the ascent (3). Additionally, due to the act of sitting back onto a box, very little ankle dorsiflexion is required in this variation as well.

the box squat

Notice the change in trunk angle as the trainee sits down on the box. Although the amount of “rock back” should be minimized, a more vertical trunk angle does occur at the transitional phase. 

The Front Squat

During the front squat, the weight is placed anterior to the trunk. For our purposes, we will also include goblet squats in this category, as the kinematics are very similar. In order to ensure that a front loaded barbell, dumbbell, or kettlebell stays over the midfoot, the client must maintain an upright torso and allow for significant forward knee migration and ankle dorsiflexion. Trying to “sit back” too far with an anteriorly loaded squat is pointless, as the weight will be forced to drift forward of the midfoot, creating an unneeded moment arm. Because a lighter weight is needed to stimulate a training effect, research shows us that front squats are “technically” less stressful on the knee and lower back compared to a back squat (4). We will see later, however, that this does not always transfer to “in the trench” experience.

the front squat

Trying to “sit back” too far with an anteriorly loaded squat is pointless, as the weight will be forced to drift forward of the midfoot.

The High-Bar Back Squat

The high-bar back squat is one of the most common barbell variations seen in gyms. In order to perform, the bar is placed on a muscular shelf created by the upper trapezius. Compared to a front loaded squat, the high-bar back squat will require more forward torso lean, more hip flexion, less forward knee migration, and less dorsiflexion. Because increased loads are needed to stimulate a training effect, studies do show that high-bar bar squats (despite LESS forward knee migration) produce increased joint stress on both the knee and lower back compared to the front-squat (4).

The High Bar Back Squat

In order to keep the bar centered over the midfoot, the high-bar squat requires more forward torso lean than the front squat.

The Low-Bar Back Squat

The low-bar back squat is one of the more uncommon variations seen in both the general fitness populations and clinical settings. Used frequently by the powerlifting population, the low-bar back squat is characterized by placing the barbell further down the back on a muscular shelf created by the rear deltoids.

the low bar back squat

Notice the increased relative torso angle on the low bar barbell back squat as compared to the high bar and front squat variations.

This will promote even more forward trunk lean and increased hip flexion than the high-bar back squat, but decreased knee flexion and ankle dorsiflexion. Additionally, for someone who has longer femurs, even more forward lean is required in order to center the bar over the midfoot. Due to the significant amount of forward trunk lean, the low-bar back squat is very posterior chain dominant, heavily recruiting the glutes, hamstrings, and adductors while minimizing knee extension torque (2).

Which Squat Variation is Optional for YOU?

Now that we have defined the key differences in the kinematics and biomechanics of each of these major squat patterns, it’s time to make intelligent recommendations as to which squat variant would be ideal for each type of athlete.

Post Operation Squatting

For someone who is recovering from a lower extremity surgery, whether it be a total hip/knee replacement, hip labral repair, or knee minescetomy, the quarter squat HAS to be used initially, as the affected joint will not possess the range of motion needed for a full depth squat. This is one of the only cases where I DO purposely limit range of motion…because you HAVE to. Additionally, there is no reason why one should wait until full range of motion is regained in the joint before he/she starts implementing a very basic mini-squat pattern. It is ADAMENT, however, that as the joint range gradually increases, squat depth is ALSO increased to reap the benefits of increased strength, hypertrophy, and performance (5,6).

Post-Op Winner: The Quarter Squat

Athlete Presenting with Hip Pain

Hip pain during squats is one of my favorite topics, as I have struggled with this on and off for nearly three years. Those who typically squat with a wider-stance and low-bar position often complain of deep anterior hip pain during squatting. Due to the exaggerated amount of forward lean and the necessity to keep a neutral lumbar spine, more hip flexion is needed to perform this lift, and often times it can aggravate the hip.

If you are someone who routinely low-bar squats, try altering stance width, degree of knee out, and amount of toe out first to see if that helps. If not, it may be time to temporarily take a break from low-bar squatting and switch to a variation that promotes a more vertical torso and decreased hip angle. Use the front squat and even high-bar squat variations while you figure out the true cause of your hip pain (which may not be biomechanical at all!)

Hip Pain Winner: Front Squat/High-Bar Squat

Athlete Presenting with Knee Pain

Knee pain during the squat is also a very common occurrence. I find that those who routinely train the Olympic lifts and front squat in high volume/frequency scenarios often complain of this issue. This is most likely due to the significant amount of forward knee migration used in these variations. Although there is nothing inherently wrong or dangerous with forward knee migration, (it’s actually NECESSARY for the Olympic lifts) for those that do acquire knee pain, the program may need to be adjusted. For this population, training a more hip-dominant pattern such as the low-bar squat for a while can be advantageous to allow those knees to calm down.

Research by Gullet et al, on the other hand, tells us a different story (4):

In this study, the authors reported DECREASED knee compressive forces in the front-squat compared to the back squat and ADVISE the use of front squat in people with knee pain for this very reason. What gives? It turns out that those who performed the back squat used significantly more weight than those who performed the front squat, so OF COURSE the exercise that used more weight will report increased knee joint stress. If the weight was kept constant, I surmise that the front squat WOULD show increased compressive force at the knee compared to the back squat, but this wasn’t studied. Additionally, what many people fail to realize is the fact that “increased compressive forces” does NOT always mean “increased risk for pain and injury.” This increased compression may be beneficial because MORE MUSCLE MASS IS BEING RECRUITED to stabilize the knee joint. More muscle mass sounds like a good thing to me!

Here’s the truth. Even though back squats DO show increased compressive forces at the knee compared to the front squat, they are generally tolerated BETTER by those with knee pain because forward knee migration and knee extension torque are reduced and the posterior chain is heavily activated. This is why our choice for knee pain during squats should be a variation that is heavily posterior-chain dominant, and the low-bar squat takes the prize (2,7)!

Knee Pain Winner: Low-Bar Back Squat

Athletes Presenting with Lower Back Pain

Though lower back pain is another entirely dense topic, I highly recommend reading Dr. John Rusin’s article, The Lifter’s Guide To Training Through Lower Back Pain, which gives lifters the tools to train through pain in the lower back while recovering in the process.

The “Tough” Beginner

On the initial coaching encounter, some people just won’t understand how to squat. While I truly believe that a good strength coach can teach the majority of clients how to perform a proper, full-depth squat in under 10 minutes, there will inevitably be some outliers. Some people, despite all of the verbal cues in the world just won’t understand how to properly engage the hip musculature and “sit back” into the squat. This is where the box enters the equation. For this population, having the box, set at the level of correct depth, may be needed initially to serve as a tactile cue of what to do. After progressively loading on a box, you can then remove it and progress these clients to free-standing.

The “Tough” Beginner Winner: Box Squat

Maximal Strength

If maximal strength is the goal, then the back squat is a MUST. That leaves us with the high-bar and low-bar squat as options. In general, many can lift about 10% more with a low-bar position compared to high-bar; this is why the majority of powerlifters utilize a low-bar position. With that being said, there are a TON of successful Olympic athletes and weight lifters safely squatting massive weights with the high-bar position as well.

Here’s the truth: the high-bar squat is a great exercise. If you like it and are good at it, keep doing it and you’ll make solid strength gains. In fact, there’s really not much difference in performance from 20-90% 1RM between the two options anyways. HOWEVER, if you are TRULY training for maximal strength, the low-bar squat may be the way to go (7)!

Maximal Strength Winner: Low-Bar Back Squat

The Bottom Line About Squat Variation

Regardless of your squat of choice, progressive overload is key. After surgery, the quarter squat represents an excellent choice to promote early loading. As joint ROM improves, one can then progress to full depth. Injury history also plays a major role in squat selection.

If one is currently dealing with knee pain, despite some contradictory research, the hip-dominant low-bar variation would be my go-to choice for this population. On the other hand, if hip pain is the issue, a more vertical torso option such as the front squat would be applicable.

For someone who just can’t understand the idea of “sitting-back,” the tactile cue of a box can work wonders. Finally, when it comes to maximal strength, the low-bar squat prevails, as it optimizes mechanical leverage and preferentially targets the large and powerful posterior chain musculature. Now that you know what variation is right for YOU, go out there and SQUAT.

About The Author

dr michael mash

Dr. Michael Mash, DPT, CSCS, FMS is a recently graduated physical therapist and certified strength coach located in Pittsburgh, PA. He started his company, Barbell Rehab, with the mission to incorporate more strength & conditioning principles into the world of physical therapy. His vision includes implementing the barbell lifts into clinical practice to both increase athletic performance and quality of life for all ages.

For more about Dr. Mash, visit his website: www.BarbellRehab.com


  1. Hartmann H, Wirth K, Klusemann M. Analysis of the load on the knee joint and vertebral column with changes in squatting depth and weight load. Sports Med. 2013;43(10):993-1008.
  2. Schoenfeld BJ. Squatting kinematics and kinetics and their application to exercise performance. J Strength Cond Res. 2010;24(12):3497-506.
  3. Swinton PA, Lloyd R, Keogh JW, Agouris I, Stewart AD. A biomechanical comparison of the traditional squat, powerlifting squat, and box squat. J Strength Cond Res. 2012;26(7):1805-16.
  4. Gullett JC, Tillman MD, Gutierrez GM, Chow JW. A biomechanical comparison of back and front squats in healthy trained individuals. J Strength Cond Res. 2009;23(1):284-92.
  5. Bloomquist K, Langberg H, Karlsen S, Madsgaard S, Boesen M, Raastad T. Effect of range of motion in heavy load squatting on muscle and tendon adaptations. Eur J Appl Physiol. 2013;113(8):2133-42.
  6. Hartmann H, Wirth K, Klusemann M, Dalic J, Matuschek C, Schmidtbleicher D. Influence of squatting depth on jumping performance. J Strength Cond Res. 2012;26(12):3243-61.
  7. Goodin, Jacob, “Comparison of External Kinetic and Kinematic Variables between High Barbell Back Squats and Low Barbell Back Squats across a Range of Loads” (2015). Electronic Theses and Dissertations.Paper 2539. http://dc.etsu.edu/etd/2539



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