INTRODUCTON
The squat is an effective training tool when performed correctly. It can challenge your upper extremities, trunk, and lower extremities all at the same time leading to important sport specific muscle adaptations. In this blog I will dive into what current research says about the differences between each type of squat, squat depth, muscle activation, and external cues for squats. By the end of this article my hope is that you feel more confident and knowledgeable about choosing when to use a squat, with which type or technique to use, how to properly screen for proper movement or movement faults, and utilize the best current evidence to aid in your decision making. Check out the video to learn more about how to set up the squat and correct its most common movement faults.
The human body functions as a complete system during any athletic movement and thus in our sports training we should eventually train the athlete with whole body sport specificity in mind. That brings us to this analysis on the squat, as it can be an explosive full body power motion that can be translated into a plethora of sport specific motions. If squats are to be used as an ancillary conditioning tool, we as medical professionals must assess the sports movement and utilize the best research in order to train the muscles needed in that sport with the same activation patterning in order to build optimal movement patterns under load. In order to have the most effective lift have the athlete perform the strengthening activity throughout their safe and sport specific full range of motion, with proper form, while at the same time expending the least amount of energy possible per lift. The goal is not only to build strength and power, but also control and technique to improve performance, and decrease risk of injury.
There are three main types of squats, they are named by where the bar is positioned on the body. There is a Front Squat where the bar is placed in front of the torso resting on the patients’ anterior shoulders. There is a High Bar Back Squat where the bar is placed just below the spinous process of the C7 vertebrae and finally, there is a Low Bar Back Squat where the bar is placed just above the spine of the scapula and rests on the posterior deltoid muscle bellies. Many people choose their squat type based on the belief that the different bar positions lead to different lower extremity muscle activation. You will see later that current evidence does not support these claims. Therefore, go back to function! First, which of the three squats can they perform correctly, and which most closely simulates the full body motions of their sport or activity. Will they have to be upright jumping or will they be bent over hitting, pushing, or pulling? Is there any part of their body that we are trying to rehab in specific or reduce the load on during the motion (neck, back, knee, hip, ankle)? The athletes’ objective movement fault, tissue breakdown, and sports specificity of a training mode should always be the guide to choose the correct exercise. I challenge the reader of this article to pick the squat that most closely correlates to the athlete’s body position in their chosen sport so that the loaded myofibril histological adaptations will translate into truly useful sport-specific movement patterns. Happy squatting!
THE SCREEN
Prior to the squat, a thorough subjective and objective screen should be completed to assess the appropriateness of this training mode for each individual due to its complexities and inherent combined motions under load. I know what you’re thinking, people go to gyms and start squatting every day, but just because you can do something does not mean you’re doing it right or safely. With the vast majority of low back and lower extremity injuries I have seen from the gym, are due to motions such as the squat. Once the subjective is complete and it is found that the patient will benefit from squats we must objectively prescreen the patient to find out if they can perform the combined motion correctly. Now, I know there are tons of efficient ways to do this, so if you have a preferred method just make sure it at least touches on the crucial components identified below, as I have already narrowed it down to address only the top faults and minimum body requirements to perform the squat safely and correctly.
Upper extremity, thoracic and shoulder mobility should be assessed to see that the patient can assume the correct squat bar position. For the upper extremities, the front squat will require a combined motion of midrange glenohumeral joint flexion, end range elbow flexion, end range forearm pronation, and full wrist extension. The high bar back squat will require slight thoracic extension, scapular adduction/posterior tilting with combined mid-range glenohumeral external rotation and abduction in order to hold the bar in the correct position. The low bar back squat will require more thoracic extension, scapular adduction/posterior tilting with combined end-range glenohumeral external rotation and midrange abduction in order to hold the bar in the correct position.
Next the lumbar spine, pelvis, and lower extremities must be assessed. For the lower extremities the patients’ lumbar spine range of motion and stability, passive and loaded hip flexion, and ankle dorsiflexion mobility will be of utmost importance as these joints will greatly affect the start and end/bottom position of all three lifts.
Screening for each patient’s true safe full end range motion during the squat is very important after each joint is assessed due to the increased chance of injury towards the bottom position of the squat. The end range for the squat can be defined as the lowest position of the squat where there is no excessive overload and stress given on any one joint that could promote tissue damage. As movement experts, we must specifically focus on a screen that can find the correct ending position for the squat as this is when the low back/ hips are most compromised and susceptible to injury. All athletic training squats should end their downward motion just before the lordotic curvature of the lumbar spine can no longer be maintained or just above the point that a “butt wink” can be seen. This is the true safe and smart end range of motion of that athlete. But how about butt to ground/ATG squats? Or if I don’t have pain and I can go lower even after my back has rounded? Yes you are right, everyone most likely can squat lower after their pelvis posterior pelvic tilt (butt wink) occurs while squatting, but they will do it using this poor compensatory pattern which is putting their low back at risk for injury while it is under load. Again, you are trying to load the body and system for integrated athletic motion and strength built to last and avoid increased stress and eventual tissue breakdown, leading to injury. If a patient is allowed to posterior pelvic tilt under load at the bottom of the squat the iliocostalis lumborum and longissimus thoracic muscle fibers will align themselves with the compressive axis of the spine, due to the flexed lumbar spine posture, instead of counteracting the anterior shearing component of the lift. The patient will no longer have the proper anterior to posterior muscular support needed and the spine will be susceptible to injury via loaded flexion and compression (13). In order to find the correct ending position, place the athlete in quadruped. Then have them rock back to assess where the posterior pelvic tilt occurs. If they make it back to the required sport specific depth without a posterior pelvic tilt then you are done, and you have found the proper ending point, which can be confirmed with a standing un-weighted and weighted squat. If not and the goal is to perform a deeper squat due to sport specific needs then in this quadruped position we can now try to see if small changes can be made to their form in order to achieve this depth such as abduction/ external rotation of the hips, various trunk bracing and motor awareness cues, pushing into the table in order to activate trunk/ scapulohumeral muscles, ankle plantarflexion or dorsiflexion as well as any number of small changes to see if their fault is easily fixed and a lower depth can be achieved without a posterior pelvic tilt. If all of these small changes are exhausted then the remaining limited motion can be safely contributed to either a soft tissue shortness/ stiffness which needs specific focus to change or a true mobility deficit of the hip/ lumbar spine/ knee, or limiting the motion which may not be able to be changed (12). This may be hard for your patient/client to hear, but the vast majority of the western population does not have the anthropomorphics to allow what the current population considers a full butt to floor squat without poor compensation, myself included. But not to worry, you will soon see that this thought of “butt to floor” for full squat motion at any cost and its association with improved muscle activation is not supported by current evidence and in most sport training is not a necessity or even advantageous. A caveat to this is if you are training for Olympic weightlifting as your sport. In this case, if you cannot get to the bottom of the squat with a relatively flat back you will not last long and your tissue will most likely fail as the load is increased to competition weight. Sorry to say this, but it might behoove of you to take up a different sport.
After separate joints have been screened for appropriateness, and the safe bottom ending position of the squat is identified in quadruped, the athlete should first practice un-weighted squatting form, stopping before the posterior pelvic tilt. This should be done with and then without external cueing as you and the athlete assess the full-unloaded motion for proper form. I have uploaded videos and have a checklist at the bottom of this article, which focuses on form from the lateral and anterior views. Don’t get overwhelmed, as this may seem like a lot, but I would say on average it takes all of 10-15 minutes to subjectively and objectively assess an athlete for the appropriateness of squatting with correct form.
THE EVIDENCE
Now I have to say, for an exercise as popular as the squat, the research was rather limited when taking into account only the best quality controlled studies. But here is the section that will recap the current reliable research as it pertains to muscle activation and joint loading with the different types of squats, depths, and weight with different muscle activation, and the use of external. In the first study, in from 2016 we take a look at 13 women, mean age 29 years old performing a ten repetition maximum (RM) squat. This study compared mean and peak electromyography (EMG) amplitude of the upper gluteus maximus, lower gluteus maximus, biceps femoris, and vastus lateralis muscles of a front, parallel depth high bar back squat, and full depth high bar back squat. The study found that there were no significant differences between front, parallel depth high bar back squats and full depth high bar back squat in any of the tested muscles. Given these findings, it can be suggested that the front, and high bar back squat (parallel and full depth) will have similar levels of EMG activity with this age group of females when squatting with a weight equaling a ten repetition maximum (1).
In another study in from 2017, focusing on high bar back squat, fifteen young, healthy, resistance trained men, mean age 26, performed a high bar back squat at their ten repetition maximum weight using two different ranges of motion, partial range or 90 degrees knee flexion and full range or 140 degrees of knee flexion. Surface electromyography was used to measure muscle activation of the vastus lateralis, vastus medialis rectus femoris, biceps femoris, semitendinosus, erector spinae, soleus, and gluteus maximus. The results show that muscle activity was highest during the partial back squat for gluteus maximus, biceps femoris, and soleus when compared to the full range of motion with all other muscles being insignificant. So the deeper the range, did not equate to increased muscle EMG activity. The study postulated that the higher activation of the gluteus maximus during the shallower squat could be due to its inherent attachment points as a single joint muscle positioned at the hip, which creates a longer lever arm during a partial squat (3). Also, it is purposed that at the greater depth, the gluteus maximus is not needed as a pelvic stabilizer due to the passive trunk stability provided by the inherent increased hip joint flexion and tissue stability created in this position. The variance in muscle activation as it relates to squat depth between the men and women in these two studies may be due to the fact that trained females have been shown to have increased hip mobility when compared to men. Taking this into account females should need gluteal stability/activity lower in the squat due to reduced static joint/ passive tissue tension stability whereas the males will lock into their end range of hip/ knee and/ ankle motion earlier thus reducing their need for this dynamic hip stability provided by the glutes. Also, anthropomorphically males have larger upper body weight with larger average shoulder span leading to an increased need for trunk stability through gluteal activation when passive joint stability is not available in the shallower depths of the squat as opposed to those in the all-female study.
In 2009 the lower extremity muscle activation of 15 healthy trained individuals was tested and they were all shown to be the same when comparing front vs. high bar back squats. Unfortunately, gluteal muscles were omitted from this study. However, in this same study, the high bar back squat resulted in significantly higher compressive forces at the tibiofemoral joint and knee extensor moments than the front squat (9).
In an isometric study in 2016 fifteen young, healthy, resistance-trained men performed an isometric back squat at three knee joint angles (20°, 90°, 140°). Surface electromyography was used to measure muscle activation of the vastus lateralis, vastus medialis, rectus femoris, biceps femoris, semitendinosus, and gluteus maximus. In general, muscle activity was the highest at 90° for the three quadriceps muscles. Activity of the gluteus maximus was significantly greater at 20° and 90° compared to 140°. An isometric back squat at 90° generates the highest overall muscle activation, yet an isometric back squat at 140° generates the lowest overall muscle activation of the vastus lateralis and gluteus maximus (11). Again, the lower the angle, did not equate to higher EMG activity.
So now we have a grasp of what research says about the lower extremity muscles, but what about the low back? Results of two studies from 2011 and 2015 showed that the back squat exhibited a significantly greater trunk lean and torque force than the front squat throughout the motion with no differences occurring in knee joint kinematics (4, 8). It has been shown in a study on 15 healthy trained individuals that the low back erector spinae had higher EMG which was correlated to increased torque and stress with the high bar back squat when compared to the front squat (9).
In a 2017 study focusing on the aid of resistance bands with squatting, sixteen healthy, male, university aged-participants were split into two groups of eight. One group consisted of a “trained” (defined as regularly participating in barbell back squat training for the last year) and the other was an “untrained” group (no barbell back squatting experience, but who were able to squat a bodyweight load). The study looked at a three-repetition maximum and a bodyweight loaded squat for repetitions to failure using a medium resistance band (4.5lbs of pull to double a 12-inch band) vs. a no resistance band group. The band increased gluteus max and gluteus medius muscle activity but only with consistency in the untrained participants. It was hypothesized that only untrained participants benefitted from the resistance band due to the fact that the trained participants had already achieved the muscle activation patterns required to promote neutral knee alignment and to resist medial collapse (6).
Finally let’s look at a 2017 study that compared muscle activation and squat weight with 14 healthy, male, experienced weightlifters. It was found that overall lower extremity muscle activities increased with increasing loads, but significant increases were seen only for vastus medialis and gluteus maximus during the 90% and 100% of the participants’ one repetition maximum, when compared to their 80% one-repetition maximum weight. There was no significant difference between the 90% and 100% 1RM for any muscle (7). Thus as it pertains to muscle activation and this studies specific population there is no increased muscle activation benefit to squatting greater than 90% the athletes 1RM amount with experienced male lifters.
Now, I know there is tons of information out there on squatting, but I have tried to bring you some of the best current evidence in order to make your clinical decisions without bias. I could write a whole paper on each studies’ shortcomings but currently this is some the best we have and we can use it to at least guide our decision-making process for each studies’ gender and age taking into account the weight tested and the lifters experience.
RESEARCH QUICK REFERENCE
For athletic young females the front vs. high bar back squat produced similar muscle activation at all depths (Choose based on sport)
A squat depth of 90 degrees will produce more muscle activation of the gluteus maximus, biceps femoris, and soleus than a lower back squat for young athletic males (Choose based on target muscles, not depth)
For resistance-trained men performing an isometric back squat at 90° generates the highest overall muscle activation (Depth does not increase activation)
High bar back squat will produce increased low back stresses when compared to front squat (Choose based on pathology)
Loop Band around thighs increases gluteal activation for untrained individuals only (Choose based on patient experience)
Muscle activation increases from 80-90% of a patients 1RM, but does not from 90-100% (Possibly limited need to 1RM train)
SQUAT MOVEMENT FAULT GUIDE
Lateral View:
Bar starts on the rack at the level of inferior scapular angle
Chin neck angle 60-90 entire time (Cue: hold a tennis ball under chin- DNF, Stick on back/ head, Allow gaze to follow body motion)
Thumbs always over the bar (To avoid wrist extension and wrist injury, also allows for elbows up for lats engagement)
In Low Bar Back Squat, the bar should fit just below/on the spine of the scapula and on top of the posterior deltoid's (bar shelf).
In High Bar Back Squat, the bar will ALWAYS be just below C7 spinous process
In Front Squat, the bar rests as close to anterior neck as possible on the anterior deltoid bulk with elbows lifted
Elbows back and slightly up (should only see one elbow from the side view if they are in line)
Abdominal Brace (Breath in and out at the top of squat, never at bottom position)
Start the squat with a hip hinge first then allow a knee break and continue with 1:1 knee and hip flexion rate
Avoid butt wink/ posterior pelvic tilt ALWAYS, as this is a poor compensatory pattern which increases risk for lumbar spine injury
Feet 15-30 degrees eversion/external rotation
Bar path must be vertical at all times to avoid increased low back stress and wasted energy
Athlete is ALWAYS to walk bar forward until they hear it hit the crossbar before racking
Anterior view:
Bar starts on the rack at the level of inferior scapular angle
Chin neck angle 60-90 entire time (Cue: hold a tennis ball under chin- DNF, Stick on back/ head, allow gaze to follow body)
No cervical side bend
Thumbs always over the bar (To avoid wrist extension and wrist injury, also allows for elbows up for lats engagement)
In Low Bar Back Squat, the bar should fit just below/on the spine of the scapula and on top of the posterior deltoid's (bar shelf).
In High Bar Back Squat, the bar will ALWAYS be just below C7 spinous process
In Front Squat, the bar rests as close to anterior neck as possible on the anterior deltoid bulk with elbows lifted
Hands should be the same height and same distance from shoulders and same distance from bar ends
Elbows same height
Abdominal Brace (Breath in and out at the top of squat, never at bottom position)
Start the squat with a hip hinge first then allow a knee break and continue with 1:1 knee and hip flexion rate of flexion
Avoid butt wink/ posterior pelvic tilt ALWAYS as this is a poor compensatory pattern, which increases risk for lumbar spine injury
No Femoral adduction/ IR
Feet 15-30 degrees eversion/external rotation
Feet hip distance apart
Bar path must be vertical at all times to avoid increased low back stress and wasted energy
Athlete is ALWAYS to walk bar forward until they hear it hit the crossbar before racking
Quick Look: Movement
Bar starts on the rack level of inferior scapular angle
Patient steps under and positions bar, patient feels comfortable with bar weight and is ready
Set up Trunk to Floor positioning
Chin neck angle 60-90 entire time
Turn on Brace (Tactile cue/one long controlled pursed lip exhale breath or breath held for entire motion is OK)
Hip hinge initiation with trunk anterior lean to start movement followed by knee flexion
Hip and knee flexion same rate after hip drive
Avoid Femoral adduction/ IR
Motion stopped at bottom position BEFORE posterior pelvic tilt/butt wink
Glute squeeze with hip hinge again to initiate ascent
Sit back into heels, and push through heels with toe box still on the floor (spread floor)
Breath at top and reposition as needed
Patient is ALWAYS to walk bar forward until they hear the bar hit the crossbar before racking
CITATIONS
1. B. Contreras, A. D. Vigotsky, B. J. Schoenfeld, C. Beardsley, and J. Cronin, “A comparison of gluteus maximus, biceps femoris, and vastus lateralis electromyography amplitude in the parallel, full, and front squat variations in resistance- trained females,” Journal of Applied Biomechanics, vol. 32, no. 1, pp. 16–22, 2016.
2. Caterisano, A., R.F. Moss, T.K. Pellin-ger, K. Woodruff, V.C. Lewis, W. Booth, and T. Khadra.The effect of back squat depth on the EMG activity of 4 superficial hip and thigh muscles. J. Strength Cond.Res. 16(3):428–432. 2002.
3. Da Silva JJ, Schoenfeld BJ, Marchetti PN, Pecoraro SL, Greve JMD, Marchetti PH. Muscle Activation Differs Between Partial and Full Back Squat Exercise With External Load Equated. J Strength Cond Res. 2017 Jun; 31(6):1688-1693.
4. Diggin, David & O’Regan, Ciaran & Whelan, Niamh & Daly, Scott & McLoughlin, V & McNamara, L & Reilly, A. (2011). A biomechanical Analysis of front and back squat: injury implications. .
5. Dezewska M, Galuszka R, Sliwinski Z. Hip joint mobility in dancers: preliminary report. Ortop Traumatol Rehabil. 2012;14(5):443-452.
6. Foley, Ryan C.A. et al. “EFFECTS OF A BAND LOOP ON LOWER EXTREMITY MUSCLE ACTIVITY AND KINEMATICS DURING THE BARBELL SQUAT.” International Journal of Sports Physical Therapy 12.4 (2017): 550–559. Print.
7. Hasan U. Yavuz and Deniz Erdag, “Kinematic and Electromyographic Activity Changes during Back Squat with Submaximal and Maximal Loading,” Applied Bionics and Biomechanics, vol. 2017, Article ID 9084725, 8 pages, 2017. doi:10.1155/2017/9084725
8. H. U. Yavuz, D. Erdağ, A. M. Amca, and S. Aritan, “Kinematic and EMG activities during front and back squat variations in maximum loads,” Journal of Sports Sciences, vol. 33, no. 10, pp. 1058–1066, 2015.
9. J. C. Gullett, M. D. Tillman, G. M. Gutierrez, and J. W. Chow, “A biomechanical comparison of back and front squats in healthy trained individuals,” Journal of Strength and Conditioning Research, vol. 23, no. 1, pp. 284–292, 2009.
10. Mangine, Gerald T et al. “The Effect of Training Volume and Intensity on Improvements in Muscular Strength and Size in Resistance-Trained Men.” Physiological Reports 3.8 (2015): e12472. PMC. Web. 8 Feb. 2018.
11. Marchetti, Paulo Henrique et al. “Muscle Activation Differs between Three Different Knee Joint-Angle Positions during a Maximal Isometric Back Squat Exercise.” Journal of Sports Medicine 2016 (2016): 3846123. PMC. Web. 8 Feb. 2018.
12. McGill, Stuart. Low Back Disorders: Evidence-based Prevention and Rehabilitation. Champaign, IL: Human Kinetics, 2002. Print.
13. McGill, Stuart. Ultimate Back Fitness and Performance Fourth Edition .Waterloo, Ontario Canada, 2009. Print. (P.73)
14. Rippetoe, Mark., and Lon Kilgore. Starting Strength: Basic Barbell Training.3rd ed. Wichita falls, Tx: Asagaard Co, 2011. Print.