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Tuesday, June 6, 2023

Squat Depth Recommendations

Squat Depth Recommendations
Brent Brookbush

Brent Brookbush


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Review and commentary on research comparing the effects of squat depth on hypertrophy, strength, and performance.

by Dr. Brent Brookbush DPT, PT, MS, CPT, HMS, IMT

How Deep Should You Squat?

What is the optimal range of motion (ROM) for squats? "Ass to Grass" has become the battle cry of every self-proclaimed "strength coach", but are deep squats really better? Deep squats are definitely harder, and they require a significant amount of work and dedication to perform well. Training with deep squats is certainly necessary for sports that require deep squatting (powerlifting and Olympic lifting). However, the body of research on squat ROM suggests that "squat deep" may be the most over-rated cue in the history of fitness and performance!

Full Squat or Partial Squat Research Summary:

Note, you do not need to take our word for it. We have attempted to locate every relevant research study and included those studies in an annotated bibliography below. Please feel free to read the research and develop your own conclusions (and if you know of additional peer-reviewed, published, original research studies, please leave them in the comments; we will add them). We hope that you find the following conclusions to be a reasonably objective summary of all research findings.

Comparing Squats (Single Set/Session Comparisons)

  • Research findings comparing squat ROM are not congruent, suggesting squats with any ROM may be beneficial, and/or that squat ROM is less influential than other variables (e.g. load, velocity, volume, etc.).
  • Muscle electromyography (EMG) activity for quarter-squats, half-squat, parallel-squats, and full squats are similar. Glute activity may increase with deeper squats, quadriceps activity is likely similar throughout ROM, and calf activity is likely more influenced by the load.
  • Less range of motion is likely to increase the load that can be lifted for a pre-determined rep range, as well as increase the average and peak amount of force and power per set. Increasing ROM is likely to result in more work (force x distance) per set.
  • The increase in load that can be achieved when performing squats with less ROM is likely to result in a larger increase in EMG activity than the increase in EMG activity noted with increasing ROM.

Comparing Training Outcomes (Weeks of Strength Training including Squats)

  • Squat strength is ROM specific. Training a specific ROM will result in the largest increase in strength for that ROM; however, deep squats are likely to result in the widest range of increased strength.
  • Parallel and deep squats are likely to result in similar outcomes (strength, hypertrophy, and power).
  • Although the differences are relatively small, the increase in work/set resulting from deep squats may result in larger improvements in hypertrophy, strength, and power.
  • The increase in load and velocity that can be achieved when performing quarter or half squats may result in larger improvements in power (e.g. vertical jump height).

Potential Issues with "Forcing Deep Squats"

  • Less dorsiflexion range of motion, hip flexion range of motion, and dorsiflexor strength is correlated with a decrease in squat depth. It is unlikely that cues during squat would address these issues.
  • Knee valgus, knee varus, tibial external rotation (feet turn-out), and excessive pronation have been correlated with pain, dysfunction, and/or an increase in the risk of future injury.

Back squat with feet, knees and hips in alignment.
Caption: Back squat with feet, knees and hips in alignment.

A Better Squat Depth Recommendation

The research on deep squats implies that we need a more nuanced recommendation for squat ROM than "squat deep." There are several benefits that may be achieved via deep squats, and deep squats are obviously necessary for sports that require deep squatting (powerlifting and Olympic lifting). However, the research suggests that the benefits of squatting can be achieved with quarter-squats, half-squats, parallel squats, or deep squats. Further, due to the relationship between load (and potentially velocity), total work, and range of motion-specific strength, it is likely that the best recommendations will consider the goal, form (compensation), pain/discomfort, and risk of injury. Although there are more variables to consider, the recommendation does not need to be complicated. The following is our recommendation for exercise range of motion, which we believe to be a very moderate/conservative (scientifically conservative, not a political statement) position that implies ROM can be challenged, but not at the expense of form or pain.

  • Brookbush Institute’s Position Statement on ROM: Exercise (including squats) should be performed through the largest range of motion (ROM) that can be attained with good form and without pain.

We define "good form" below, to aid in clarifying our definition above. Note, the Brookbush Institute's definition of good form (optimal posture) may appear a bit complex, but it is essential that the definition reflects the body of research, and is robust and measurable so that it may be tested in a research setting.

  • Brookbush Institute's Definition of Optimal Posture (a.k.a. good form): A mean range of segment alignment that is absent of signs correlated with dysfunction, pain, or an increased risk injury. Additionally, "good form" may include alignment recommendations influenced by optimal length-tension relationships, biomechanical advantage, or force generation capacity.

And, just for a little humor here is a funny term we created for the deep squat die-hards who have decided that evidence and reason have no place at the altar of the "squat deep or die" religion.

  • "Ass to Grassholes" - A group of individuals who think squat depth is more important than alignment, pain-free motion, or the client’s goals.

Comparing squat form, the hip morphology myth, and the strange assumption that foot position and hip morphology are related.
Caption: Comparing squat form, the hip morphology myth, and the strange assumption that foot position and hip morphology are related.

If you think the squat on the left looks better than the squat on the right, you may be jumping to conclusions. The individual on the left is clearly exhibiting knee varus, feet turn out (tibial external rotation), and excessive pronation. All of which are compensations that have been correlated with pain and injury.

The individual on the right is a basketball player with a history of microdiscectomy. He is squatting as far as he can without compensation or pain (note the near-perfect trunk and lower extremity alignment). Are we going to take squats away from him because he cannot achieve "ass to grass" ROM? The research suggests that quarter-and-half squats are very beneficial for performance.

Ridiculous “coaching” tips we have heard:

“If you can’t get deep, it doesn’t count”

  • As the research implies, in general squatting is very effective, and depth does not seem to have a large effect on any outcome.

“Just go lighter, work on your depth, and then you can add load.”

  • This rarely if ever works. For example, how would lighter weight improve a dorsiflexion restriction?

“If you can’t squat deep, work on your flexibility.”

  • Not all mobility issues are related to flexibility (at least, in the sense that you should "stretch more"). Motor control, joint stiffness, apprehension, and various injuries can influence ROM. And, mobility intervention recommendations should be based on a reliable, objective movement assessment .

“Just put your feet wider and turn them out.”

  • This is both an excuse for individuals too lazy to learn corrective interventions, and willful dismissal of research demonstrating that excessive pronation, feet turn out, and knee varus are correlated with pain, dysfunction, and an increased risk of injury.

"You must be a terrible coach if you or your clients cannot squat deep."

  • Coaches are not magicians. Squat depth should be recommended based on the client's goals and mobility, and not the coach’s goals or biases.

Additional Strength and Performance Articles

Strength Progressions

Trainer teaches a woman how to perform a back squat. Is a half-squat a good place to start?
Caption: Trainer teaches a woman how to perform a back squat. Is a half-squat a good place to start?

Annotated Bibliography: Squat Range of Motion

Single Session: EMG, Biomechanics, Force, Power, etc.

da Silva, Josinaldo J., et al. "Muscle activation differs between partial and full back squat exercise with external load equated." The Journal of Strength & Conditioning Research 31.6 (2017): 1688-1693.

  • da Silva et al. compared the 15 resistance-trained men (age: 26±5 years) performing back squats with their 10-RM during partial and full range of motion squats. The findings demonstrated that both conditions resulted in similar activity for the vastus lateralis, vastus medialis, rectus femoris, semitendinosus, and erector spinae; however, the partial range of motion squat (likely due to the increase in load) resulted in an increase in the activity of the gluteus maximus, biceps femoris, and soleus.

Contreras B, Vigotsky AD, Schoenfeld BJ, Beardsley C, Cronin J (2016) A comparison of gluteus maximus, biceps femoris, and vastus lateralis electromyography amplitude in the parallel, full, and front squat variations in resistance-trained females. J Appl Biomech 32:16–22

  • Contreras et al. compared 13 healthy women (age: 28.9 ± 5.1 years), and the mean and peak electromyography (EMG) of their upper gluteus maximus, lower gluteus maximus, biceps femoris, and vastus lateralis, during front, full, and parallel squats with 10 reps or a 10-RM load. The findings indicated that the mean and peak EMG activity for all muscles was similar during all 3 variations of the squat.

Bryanton MA, Kennedy MD, Carey JP, Chiu LZF (2012) Effect of squat depth and barbell load on relative muscular effort in squatting. J Strength Cond Res 26:2820–2828

  • Bryanton et al. compared 10 strength-trained women (age: 22.5 ± 2.1 years) while performing squats with 50 - 90% or 1-RM loads in a motion analysis laboratory to determine hip extensor, knee extensor, and ankle plantar flexor the "relative muscular effect (RME). The RME was determined as the ratio of net joint moment to maximum voluntary torque matched for joint angle. Knee extensor RME increased with increases in squat depth but not increases in load, and ankle plantar flexor RME increased with increases in load but not squat depth. Both greater squat depth and load increased hip extensor RME. These findings suggest that optimizing lower extremity strength may require more squat depth for knee extensors, more load for ankle plantar flexors, and either or both load and depth for hip extensors.

Caterisano A, Moss RF, Pellinger TK, Woodruf K, Lewis VC, Booth W, Khadra T (2002) The effect of back squat depth on the EMG activity of 4 superfcial hip and thigh muscles. J Strength Cond Res 16:428–432

  • Caterisano et al. compared 10 experienced weight lifters (age: 24.3 ± 5.6 years) and the EMG activity of their vastus medialis (VMO), vastus lateralis, biceps femoris, and gluteus maximus, during back squats at 3 depths with 100-125% of body weight resistance. The findings demonstrated that although the contribution of the biceps femoris, vastus medialis, and vastus lateralis were similar, the contribution of the gluteus maximus during the concentric phases among increase with range of motion: partial (16.9%), parallel (28.0%), and deep (35.4%).

Gorsuch J, Long J, Miller K, Primeau K, Rutledge S, Sossong A, Durocher JJ (2013) The effect of squat depth on multiarticular muscle activation in collegiate cross-country runners. J Strength Cond Res 27:2619–2625

  • Gorsuch et al. compared 20 Division I collegiate cross-country runners (10 males and 10 females, age: 19.2 ± 0.4 years) in a randomized crossover design, performing partial squats and parallel squats for 6 reps with 10-RM loads. The findings demonstrated that parallel squats resulted in significantly higher average EMG activity of the rectus femoris and erector spinae; however, biceps femoris and gastrocnemius activity were similar for both conditions.

Drinkwater, E. J., Moore, N. R., & Bird, S. P. (2012). Effects of changing from full range of motion to partial range of motion on squat kinetics. The Journal of Strength & Conditioning Research, 26(4), 890-896.

  • Drinkwater et al. compared 10 men with at least 1 year of resistance training experience (21.4 ±1.14) during 4 separate sessions comparing squat ROM and load. All exercisers performed squats with partial range motion (hips and knee in the horizontal plane) or a full range of motion (120° of knee flexion), with 67% of 1-RM for 10 reps/set or 83% of 1-RM loads for 5 reps/set, for 4 sets/session, with a moderate (90 sec) rest between sets. The results of the study demonstrated that the highest peak force and peak power were exhibited during the partial range of motion squats with heavier loads, and the largest amount of work was performed during full range of motion squats with heavier loads.

Comparing Training Periods with Quarter, Half, and Deep Squats

Bloomquist K, Langberg H, Karlsen S, Madsgaard S, Boesen M, Raastad T (2013) Effect of range of motion in heavy load squatting on muscle and tendon adaptations. Eur J Appl Physiol 113:2133–2142

  • Bloomquist et al. compared 17 male exercise science students (age: 25 ± 6 years) randomly assigned to perform deep squats (0–120° of knee flexion) or shallow squats (0–60° of knee flexion). All participants performed squats for 12 weeks, with a daily undulating and progressive program, 3 sessions/week including 3-5 sets/session, 3-10 RM/set, with a max velocity concentric tempo (2-4:0:maxV). The findings demonstrated that neither group exhibited significant increases in patellar tendon CSA. The shallow squat group exhibited superior increases in shallow squat 1-RM strength. The deep squat group exhibited significantly larger increases in deep squat 1-RM strength, as well as small but significantly larger increases in thigh muscle CSA, knee extension strength at 75˚ and 105˚ knee flexion, and squat jump performance.

McMahon GE, Morse CI, Burden A, Winwood K, Onambele GL (2014) Impact of range of motion during ecologically valid European Journal of Applied Physiology 1 3 resistance training protocols on muscle size, subcutaneous fat, and strength. J Strength Cond Res 28:245–255

  • An RCT by McMahon et al. compared 26 male and female experienced exercisers (age: 19 ± 3.4 years) randomly assigned to a control group (no additional activity, a short-range group (50°), or a larger range group (90°). All participants performed a lower body resistance training routine with either 50° or 90° of knee flexion during all lower body exercises (including back squats, knee extensions, Bulgarian split squats, bilateral and unilateral Sampson chair, leg press, dumbbell lunges) for 8 weeks (followed by 4 weeks of de-training), 3x/week (including 1 home session), 4 exercises/session, 3 sets/exercise, 10 reps/set, 80% of 1-RM loads, moderate (2:0:1) rep tempo, and moderate (60-90 sec) rest between sets. The findings of the study demonstrated that both exercise groups exhibited significant increases in muscle cross-sectional area (CSA) and pennation angle, and that the longer range group exhibited a trend toward larger improvement; however, following 4 weeks of detraining both groups had returned to baseline values similar to the control group. Both groups exhibited significant increases in range of motion specific strength with the larger range of motion group exhibiting an increase in strength over a larger range and maintaining more of the strength increase during the de-training period. Additionally, both groups exhibited a significant and similar difference in subcutaneous fat that persisted during the detraining period.

Weiss, L. W., FRX, A. C., WOOD, L. E., RELYEA, G. E., & MELTON, C. (2000). Comparative effects of deep versus shallow squat and leg-press training on vertical jumping ability and related factors. The Journal of Strength & Conditioning Research, 14(3), 241-247.

  • An RCT by Weiss et al. compared 19 novice exercisers (10 men, 9 women, age: 23.7 ± 6.1 years) randomly assigned to a control group (no exercise), a deep squat group (half-squats), or a shallow squat group (quarter-squats). All exercisers performed Bear Machine and Nautilaus Plate-loaded squats for 9 weeks, 3x/week, in a daily-undulating program of 2-5 sets/session, and1-10 RM/set. The findings demonstrated that neither exercise group exhibited significant increases in vertical jump or velocity during squats; however, the deep squat group exhibited a significant increase in deep and shallow squat 1-RM strength.

Rhea, M. R., Kenn, J. G., Peterson, M. D., Massey, D., Simão, R., Marin, P. J., ... & Krein, D. (2016). Joint-angle specific strength adaptations influence improvements in power in highly trained athletes. Human movement, 17(1), 43-49.

  • Rhea et al. compared 28 Division 1, 2, and 3 male college athletes (age: 21.4 ± 3.2 years) randomly assigned to a quarter squat group (knee flexion 55-65°), half squat group (knee flexion 85-95°), and a full squat group (knee flexion exceeding 110°). All exercisers performed a split routine including lower body exercises on Monday and Thursday (squats, power cleans, lunges, reverse hamstring curls, and step-ups) for 16 weeks, periodized intensity, 4-8 sets squats/session, 2-4 sets clean/session, 1-3 sets of other exercisers/session, 2-8RM/set, and a long (3 min) rest between sessions. The findings demonstrated that increases in 1-RM strength were correlated with the range of motion that was trained; however, the quarter squat group exhibited larger improvements in vertical jump height and 40m sprint time.

Hartmann, H., Wirth, K., Klusemann, M., Dalic, J., Matuschek, C., & Schmidtbleicher, D. (2012). Influence of squatting depth on jumping performance. The Journal of Strength & Conditioning Research, 26(12), 3243-3261.

  • An RCT by Hartmann et al. compared 23 female and 36 male experienced exercisers (age: 24.11 ± 2.88 years) parallelized by their counter-movement jump height into 3 groups including a deep back squat group, a deep front squat group, and a quarter back squat group, which were compared to a group of 16 controls. The experimental groups trained for 10 weeks with a strength/power block periodization program, 2x/week, 5 sets/session, 2-10 RM/set, long (5 min) rest between sets, and a maxV concentric with no bouncing tempo. The findings demonstrated that both the deep front squat and deep back squat groups exhibited significant and similar increases in vertical jump height, as well as deep front squat, deep back squat, and quarter back squat 1-RM strength. The quarter-back squat group only exhibited significant increases in quarter-back squat 1-RM strength.

Kubo, K., Ikebukuro, T., & Yata, H. (2019). Effects of squat training with different depths on lower limb muscle volumes. European journal of applied physiology, 1-10.

  • Kubo et al. compared 17 physical active males (age: 20.9 ± 0.8 years) who were not participating in organized exercise, matched by strength and physical characteristics, and randomly assigned to either a half squat group (90° of knee flexion) or full squat group (140° of knee flexion). All exercisers performed squat training for 10 weeks, 2x/week, 3 sets/session, a progressive program of 8-10 reps/set, with 60 - 80% of 1-RM loads. The findings demonstrated that both groups exhibited similar increases in half-squat 1-RM strength, but the full-squat group exhibited superior increases in full-squat 1-RM strength. The full squat also exhibited significantly larger increases in muscle volume for the knee extensors, gluteus maximus, and adductors, and neither group exhibited significant increases in rectus femoris or hamstring volume.

Pallarés, J. G., Cava, A. M., Courel-Ibáñez, J., González-Badillo, J. J., & Morán-Navarro, R. (2019). Full squat produces greater neuromuscular and functional adaptations and lower pain than partial squats after prolonged resistance training. European journal of sport science, 1-10.

  • Pallarés et al. compared 53 experienced male exercisers (age: 23.0 ± 4.4 years) randomly assigned to a control group (no training), a half-squat group, a parallel squat group, and a full-squat group. All exercisers completed 10 weeks of periodized squat training, 2 sessions/week, 4-5 sets/session, 4-8 reps/set, with 60-80 1RM loads, long (4 min) rest between sets, and a maximum velocity (maxV) concentric tempo. The findings demonstrated that the full-squat group exhibited an increase in 1-RM strength for all ranges; however, each group improved most for the range of motion they trained. The full squat and parallel-squat group exhibited significant and similar improvements during the re-assessment of the counter-movement jump (CMJ) and Wingate performance tests, but the half-squat group did not exhibit significant improvements.

A Loss of Ankle Dorsiflexion Correlated with a Loss of Squat Depth

Kim, S. H., Kwon, O. Y., Park, K. N., Jeon, I. C., & Weon, J. H. (2015). Lower extremity strength and the range of motion in relation to squat depth. Journal of human kinetics45, 59.

  • Kim et al. compared 101 healthy participants (64 males, 37 females; age: 25.69 ± 5.93 years) following hip flexion and dorsiflexion goniometric assessment, hip flexion, hip rotation, and dorsiflexion MVIC, and performance of the deepest bodyweight (hands behind head), shoulder-width stance, squat that could be maintained for 5 sec. The findings demonstrated that a decrease in ankle dorsiflexion ROM, hip flexion ROM, hip internal rotation ROM, or dorsiflexor strength was correlated with a decrease in squat depth. Whereas a decrease in hip external rotation and hip flexor strength was not correlated with a decrease in squat depth.

Mauntel, T. C., Begalle, R. L., Cram, T. R., Frank, B. S., Hirth, C. J., Blackburn, T., & Padua, D. A. (2013). The effects of lower extremity muscle activation and passive range of motion on single leg squat performance. The Journal of Strength & Conditioning Research27(7), 1813-1823.

  • Mauntel et al. selected 40 healthy recreationally active individuals (age: 18-35 years) from a larger group to compare the lower extremity passive range of motion and EMG of 20 individuals with visual knee valgus, and 20 individuals without medial during 5 single leg squats. The results demonstrated that individuals with knee valgus exhibited a relative reduction in gluteus medius and gluteus maximus activity relative to adductor activity, and a reduction in passive dorsiflexion.

Macrum, E., Bell, D. R., Boling, M., Lewek, M., & Padua, D. (2012). Effect of limiting ankle-dorsiflexion range of motion on lower extremity kinematics and muscle-activation patterns during a squat. Journal of sport rehabilitation, 21(2), 144-150.

  • Macrum et al. compared 15 male and 15 female recreationally active individuals without a history of lower extremity injury (age: 18 - 30 years) during 7 trials of squats with feet flat and 7 trials of squats with a 12° forefoot wedge (simulating reduced dorsiflexion). The findings demonstrated the wedge decreased knee flexion, increased knee valgus, decreased quadriceps activity, and increased soleus activity. These changes are similar to those noted in individuals with patellofemoral pain syndrome (PFPS).

© 2023 Brent Brookbush (B2C Fitness, LLC d.b.a. Brookbush Institute )

Comments, critiques, and questions are welcome!