The Biomechanics and Muscle Function in Various Squat Techniques with a Rehabilitative and Training Approach: A Narrative Review

Document Type : Review Articles


1 PhD, Centre of Excellence for Support Systems in Health Development, Yazd University, Yazd, Iran

2 Assistant Professor, Department of Mechanical Engineering, School of Mechanical Engineering AND Centre of Excellence for Support Systems in Health Development, Yazd University, Yazd, Iran

3 Assistant Professor, School of Physical Education and Sport Science, Isfahan (Khorasgan) Branch, Islamic Azad University, Isfahan, Iran



Introduction: Nowadays, squat exercises are commonly used in rehabilitation centers to expand muscle power and strength. In this study, biomechanics and muscle function have been reviewed during squats. The aim of this study is to recognize the gaps and deficiencies of previous studies and provide suggestions to improve the application and safety of squats for rehabilitation and training purposes.Materials and Methods: PubMed and ScienceDirect databases were searched for studies published in English between 2000 and 2020. The Google Scholar search engine was also used for this purpose. Adopting from Medical Subject Headings (MeSH) terms, the search was conducted with keywords Squat, Biomechanics, Muscle function, and Optimization as well as the combination of these terms. The final analysis was performed on more than 32 articles with a direct relationship to the review subject.Results: The squat exercise was widely investigated for several purposes such as improving techniques, preventing injuries, and promoting muscle function. The most common parameters in kinematics, kinetics, and muscle function context were joint range of motion (ROM), joint maximum torque, especially maximum torque of the knee joint, and quadriceps and hamstring muscles function, respectively. Despite numerous studies examining muscle function, there was not enough information about profound muscles involved in the squat exercise. Furthermore, none of the squat methods were optimized in terms of motion pattern.Conclusion: Performing wide-stance back squat (≥ shoulder width) with natural foot positioning, unrestricted movement of the knees, and full depth while the lordotic curve is maintained is an optimal technique to perform this exercise. But it should be noted that the use of musculoskeletal models to optimize motion pattern and make knowledge on the deep muscle function are beneficial to find gold standards and more use of the squat for clinical and rehabilitation purposes.


  1. Kubo K, Ikebukuro T, Yata H. Effects of squat training with different depths on lower limb muscle volumes. Eur J Appl Physiol 2019; 119(9): 1933-42.
  2. Toutoungi DE, Lu TW, Leardini A, Catani F, O'Connor JJ. Cruciate ligament forces in the human knee during rehabilitation exercises. Clin Biomech (Bristol, Avon) 2000; 15(3): 176-87.
  3. Rutland M, O'Connell D, Brismee JM, Sizer P, Apte G, O'Connell J. Evidence-supported rehabilitation of patellar tendinopathy. N Am J Sports Phys Ther 2010; 5(3): 166-78.
  4. Frohm A, Saartok T, Halvorsen K, Renstrom P. Eccentric treatment for patellar tendinopathy: A prospective randomised short-term pilot study of two rehabilitation protocols. Br J Sports Med 2007; 41(7): e7.
  5. Behm D, Colado JC. The effectiveness of resistance training using unstable surfaces and devices for rehabilitation. Int J Sports Phys Ther 2012; 7(2): 226-41.
  6. Glaviano NR, Baellow A, Saliba S. Elevated fear avoidance affects lower extremity strength and squatting kinematics in women with patellofemoral pain. Athl Train Sports Health Car 2019; 11(4): 192-200.
  7. dos Santos AN, Pavao SL, Rocha NA. Sit-to-stand movement in children with cerebral palsy: A critical review. Res Dev Disabil 2011; 32(6): 2243-52.
  8. Mak MK, Hui-Chan CW. The speed of sit-to-stand can be modulated in Parkinson's disease. Clin Neurophysiol 2005; 116(4): 780-9.
  9. Bahrami F, Riener R, Jabedar-Maralani P, Schmidt G. Biomechanical analysis of sit-to-stand transfer in healthy and paraplegic subjects. Clin Biomech (Bristol, Avon) 2000; 15(2): 123-33.
  10. Galli M, Cimolin V, Crivellini M, Campanini I. Quantitative analysis of sit to stand movement: experimental set-up definition and application to healthy and hemiplegic adults. Gait Posture 2008; 28(1): 80-5.
  11. Escamilla RF, Fleisig GS, Lowry TM, Barrentine SW, Andrews JR. A three-dimensional biomechanical analysis of the squat during varying stance widths. Med Sci Sports Exerc 2001; 33(6): 984-98.
  12. Escamilla RF, Fleisig GS, Zheng N, Lander JE, Barrentine SW, Andrews JR, et al. Effects of technique variations on knee biomechanics during the squat and leg press. Med Sci Sports Exerc 2001; 33(9): 1552-66.
  13. Yeadon MR, King MA, Wilson C. Modelling the maximum voluntary joint torque/angular velocity relationship in human movement. J Biomech 2006; 39(3): 476-82.
  14. Comfort P, McMahon J, Suchomel T. Optimizing squat technique-revisited. Strength Cond J 2020 40(6):68-74.
  15. Caterisano A, Moss R, Pellinger T, Woodruff K, Lewis V, Booth W, et al. The effect of back squat depth on the EMG Activity of 4 Superficial Hip and thigh muscles. J Strength Cond Res 2002; 16(3): 428-32.
  16. Anderson K, Behm DG. Trunk muscle activity increases with unstable squat movements. Can J Appl Physiol 2005; 30(1): 33-45.
  17. Cotterman ML, Darby LA, Skelly WA. Comparison of muscle force production using the Smith machine and free weights for bench press and squat exercises. J Strength Cond Res 2005; 19(1): 169-76.
  18. Hemmerich A, Brown H, Smith S, Marthandam SS, Wyss UP. Hip, knee, and ankle kinematics of high range of motion activities of daily living. J Orthop Res 2006; 24(4): 770-81.
  19. 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.
  20. Pereira GR, Leporace G, Chagas D, Furtado LF, Praxedes J, Batista LA. Influence of hip external rotation on hip adductor and rectus femoris myoelectric activity during a dynamic parallel squat. J Strength Cond Res 2010; 24(10): 2749-54.
  21. McBride JM, Skinner JW, Schafer PC, Haines TL, Kirby TJ. Comparison of kinetic variables and muscle activity during a squat vs. a box squat. J Strength Cond Res 2010; 24(12): 3195-9.
  22. Schoenfeld BJ. Squatting kinematics and kinetics and their application to exercise performance. J Strength Cond Res 2010; 24(12): 3497-506.
  23. Lamontagne M, Brisson N, Kennedy MJ, Beaule PE. Preoperative and postoperative lower-extremity joint and pelvic kinematics during maximal squatting of patients with cam femoro-acetabular impingement. J Bone Joint Surg Am 2011; 93(Suppl 2): 40-5.
  24. Drinkwater EJ, Moore NR, Bird SP. Effects of changing from full range of motion to partial range of motion on squat kinetics. J Strength Cond Res 2012; 26(4): 890-6.
  25. Lorenzetti S, Gulay T, Stoop M, List R, Gerber H, Schellenberg F, et al. Comparison of the angles and corresponding moments in the knee and hip during restricted and unrestricted squats. J Strength Cond Res 2012; 26(10): 2829-36.
  26. Fry AC, Smith JC, Schilling BK. Effect of knee position on hip and knee torques during the barbell squat. J Strength Cond Res 2003; 17(4): 629-33.
  27. Aspe RR, Swinton PA. Electromyographic and kinetic comparison of the back squat and overhead squat. J Strength Cond Res 2014; 28(10): 2827-36.
  28. Demers E, Pendenza J, Radevich V, Preuss R. The effect of stance width and anthropometrics on joint range of motion in the lower extremities during a back squat. Int J Exerc Sci 2018; 11(1): 764-75.
  29. Lee SP, Gillis CB, Ibarra JJ, Oldroyd DF, Zane RS. Heel-raised foot posture does not affect trunk and lower extremity biomechanics during a barbell back squat in recreational weight lifters. J Strength Cond Res 2019; 33(3): 606-14.
  30. Nisell R, Ekholm J. Joint load during the parallel squat in powerlifting and force analysis of in vivo bilateral quadriceps tendon rupture. Scand J Med Sci Sports 1986; 8(2): 63-70.
  31. Solomonow M, Baratta R, Zhou BH, Shoji H, Bose W, Beck C, et al. The synergistic action of the anterior cruciate ligament and thigh muscles in maintaining joint stability. Am J Sports Med 1987; 15(3): 207-13.
  32. McCaw ST, Melrose DR. Stance width and bar load effects on leg muscle activity during the parallel squat. Med Sci Sports Exerc 1999; 31(3): 428-36.
  33. Zink AJ, Whiting WC, Vincent WJ, McLaine AJ. The effects of a weight belt on trunk and leg muscle activity and joint kinematics during the squat exercise. J Strength Cond Res 2001; 15(2): 235-40.
  34. Caterisano A, Moss RF, Pellinger TK, Woodruff K, Lewis VC, Booth W, et al. The effect of back squat depth on the EMG activity of 4 superficial hip and thigh muscles. J Strength Cond Res 2002; 16(3): 428-32.
  35. McBride JM, Cormie P, Deane R. Isometric squat force output and muscle activity in stable and unstable conditions. J Strength Cond Res 2006; 20(4): 915-8.
  36. Hamlyn N, Behm DG, Young WB. Trunk muscle activation during dynamic weight-training exercises and isometric instability activities. J Strength Cond Res 2007; 21(4): 1108-12.
  37. Paoli A, Marcolin G, Petrone N. The effect of stance width on the electromyographical activity of eight superficial thigh muscles during back squat with different bar loads. J Strength Cond Res 2009; 23(1): 246-50.
  38. Schwanbeck S, Chilibeck PD, Binsted G. A comparison of free weight squat to Smith machine squat using electromyography. J Strength Cond Res 2009; 23(9): 2588-91.
  39. Dionisio VC, Almeida GL, Duarte M, Hirata RP. Kinematic, kinetic and EMG patterns during downward squatting. J Electromyogr Kinesiol 2008; 18(1): 134-43.
  40. Markolf KL, Gorek JF, Kabo JM, Shapiro MS. Direct measurement of resultant forces in the anterior cruciate ligament. An in vitro study performed with a new experimental technique. J Bone Joint Surg Am 1990; 72(4): 557-67.
  41. Lamontagne M, Brisson N, Kennedy MJ, Beaule PE. Preoperative and postoperative lower-extremity joint and pelvic kinematics during maximal squatting of patients with cam femoro-acetabular impingement. J Bone Joint Surg Am 2011; 93(Suppl 2): 40-5.
  42. Hoang HX, Diamond LE, Lloyd DG, Pizzolato C. A calibrated EMG-informed neuromusculoskeletal model can appropriately account for muscle co-contraction in the estimation of hip joint contact forces in people with hip osteoarthritis. J Biomech 2019; 83: 134-42.
  43. Nigg BM, Herzog W. Biomechanics of the Musculo-Skeletal System. Chichester, UK: Wiley; 1999. p. 416-20.
  44. Delp SL, Anderson FC, Arnold AS, Loan P, Habib A, John CT, et al. OpenSim: Open-source software to create and analyze dynamic simulations of movement. IEEE Trans Biomed Eng 2007; 54(11): 1940-50.
  45. Gallo CA, Thompson WK, Lewandowski B, Humphreys BT, Funk JH, Funk NH, et al. Computational Modeling Using Opensim to Simulatea Squat Exercise Motion. National Aeronautics and Space Administratio (NASA) [Online]. [Cited 2015]; Available from: URL:
  46. Goehler CM, Helm K, Prato L, Levenda A. Presenting a performance assessment protocol and full body opensim model for use in identifying risk of injury. Adv Ortho and Sprts Med 2019: AOASM-115.
  47. Christophy M, Faruk Senan NA, Lotz JC, O'Reilly OM. A musculoskeletal model for the lumbar spine. Biomech Model Mechanobiol 2012; 11(1-2): 19-34.
  48. Xiang Y, Arora JS, Abdel-Malek K. Physics-based modeling and simulation of human walking: A review of optimization-based and other approaches. Struct Multidiscipl Optim 2010; 42(1): 1-23.
  49. Hajlotfalian M. Optimization of torque and stability to investigate the effect of exercise in arising control. Proceedings of the 2nd National Congress on Application of Sport Sciences in Health; 2017 Feb 28-29; Shiraz, Iran. [In Persian].
  50. Nishii J, Taniai Y. Evaluation of trajectory planning models for arm-reaching movements based on energy cost. Neural Comput 2009; 21(9): 2634-47.
  51. Friedman J, Flash T. Trajectory of the index finger during grasping. Exp Brain Res 2009; 196(4): 497-509.
  52. Biess A, Liebermann DG, Flash T. A computational model for redundant human three-dimensional pointing movements: Integration of independent spatial and temporal motor plans simplifies movement dynamics. J Neurosci 2007; 27(48): 13045-64.
  53. Gundogdu O, Anderson KS, Parnianpour M. Simulation of manual materials handling: Biomechanial assessment under different lifting conditions. Technol Health Care 2005; 13(1): 57-66.
  54. Anderson FC, Pandy MG. Dynamic optimization of human walking. J Biomech Eng 2001; 123(5): 381-90.
  55. Parnianpour M, Wang JL, Shirazi-Adl A, Khayatian B, Lafferriere G. A computational method for simulation of trunk motion: towards a theoretical based quantitative assessment of trunk performance. ACM 1999; 11.
  56. Hajlotfalian M, Redaei A, Sadeghi H. Biomechanical modeling of selected methods of load carriage to improve military capabilities of troops. J Sport Biomech 2016; 2(3):15-23. [In Persian].
  57. Mostafa HL, Heidar S. Optimal trajectory of squat to stand movement by using different cost function. J Res Sport Rehabil 2018; 5(10): 49-57. [In Persian].
  58. Matsui T, Motegi M, Tani N. Mathematical model for simulating human squat movements based on sequential optimization. Mech Eng J 2016; 3(2): 15-00377.
Volume 15, Issue 5 - Serial Number 5
November 2019
Pages 294-304
  • Receive Date: 08 February 2020
  • Revise Date: 02 June 2022
  • Accept Date: 22 May 2022
  • First Publish Date: 22 May 2022