Journal of Human Sport and Exercise

Electromyographic analysis of lower extremity muscle activities during modified squat exercise: Preliminary study

SunHae Song, SeungHoo Lee, DongGeon Lee, SoungKyun Hong, GyuChang Lee



The squat is a movement that keeps the knee angle at 90° while keeping the weight of the one's shoulder to the shoulder width and maintaining equal weight load on the left and right legs. However, sufficient muscle activation of the lower limb is necessary to maintain a knee angle of 90 degrees. Thus, this study has been conducted to confirm the possibility that a modified squat exercise compared to traditional squat exercise can be recommended for elderly or patients. Two healthy adult males participated in this study. They performed a traditional squat exercise and a modified squat exercise. The modified squat exercise was performed in a general squat exercise posture while keeping the knee at 90 degrees and extending the hip joint with leaning the ball behind the back (supine position). The muscle activity of rectus femoris, vastus medialis, vastus lateralis, and gastrocnemius during exercises was measured by surface electromyography. As a result of this study, it was found that muscle activities were less in the right and left rectus femoris, vastus lateralis, vastus medialis during the modified squat exercise compared to the traditional squat exercise. The results showed that the muscle strength of the lower limb was activated to less than 50% compared with the traditional squat exercise during the modified squat exercise. These results may be used as an effective rehabilitation method for patients with weak muscles in the lower limb.


Squat exercise; Muscle activity; Electromyographic analysis


Bynum EB, Barrack RL, Alexander AH. Open versus closed chain kinetic exercises after anterior cruciate ligament reconstruction: a prospective randomized study. The American journal of sports medicine. 1995; 23(4): 401-6.

Cheron G, Bengoetxea A, Pozzo T, Bourgeois M, Draye JP. Evidence of a preprogrammed deactivation of the hamstring muscles for triggering rapid changes of posture in humans. Electroencephalography and Clinical Neurophysiology/ Electromyography and Motor Control. 1997; 105(1): 58–71.

Choi YA, Kim JS, Lee DY. Effects of fast and slow squat exercises on the muscle activity of the paretic lower extremity in patients with chronic stroke. Journal of physical therapy science. 2015; 27(8): 2597-9.

Dahlkvist NJ, Mayo P, Seedhom BB. Forces during squatting and rising from a deep squat. Engineering in medicine. 1982; 11(2): 69-76.

Dan B, Bouillot E, Bengoetxea A, Nöel P, Kahn A, Cheron G. Adaptive motor strategy for squatting in spastic diplegia. European journal of paediatric neurology. 1999; 3(4): 159-65.

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. International journal of exercise science. 2018; 11(1): 764-75. PMID: 29997725.

de Souza LML, da Fonseca DB, da Veiga Cabral H, de Oliveira LF, Vieira TM. Is myoelectric activity distributed equally within the rectus femoris muscle during loaded, squat exercises?. Journal of Electromyography and Kinesiology. 2017; 33: 10-9.

Dionisio VC, Almeida GL, Duarte M, Hirata RP. Kinematic, kinetic and EMG patterns during downward squatting. Journal of Electromyography and Kinesiology. 2008; 18(1): 134-43.

Earl JE, Schmitz RJ, Arnold BL. Activation of the VMO and VL during dynamic mini-squat exercises with and without isometric hip adduction. Journal of electromyography and kinesiology. 2001; 11(6): 381-6.

Escamilla RF. Knee biomechanics of the dynamic squat exercise. Medicine and science in sports and exercise. 2001; 33(1): 127-41

Escamilla RF, Fleisig GS, Zheng N, Barrentine SW, Wilk KE, Andrews JR. Biomechanics of the knee during closed kinetic chain and open kinetic chain exercises. Medicine and science in sports and exercise. 1998; 30(4): 556-69.

Escamilla RF, Fleisig GS, Zheng N, et al. Effects of technique variations on knee biomechanics during the squat and leg press. Medicine and science in sports and exercise. 2001; 33(9): 1552-66.

Flanagan S, Salem Gj, Wang MY, Sanker SE, Greendale GA. Squatting exercises in older adults: kinematic and kinetic comparisons. Medicine and science in sports and exercise. 2003; 35(4): 635-43.

Franco-Márquez F, Rodríguez-Rosell D, Gonzalez-Suarez JM, Pareja-Blanco F, Mora-Custodio R, Yañez-García JM, González-Badillo JJ. Effects of combined resistance training and plyometrics on physical performance in young soccer players. International journal of sports medicine. 2015; 94(11): 906-14.

Galvin CR, Perriman DM, Newman PM, Lynch JT, Smith PN, Scarvell JM.. Squatting, lunging and kneeling provided similar kinematic profiles in healthy knees—A systematic review and meta-analysis of the literature on deep knee flexion kinematics. The Knee. 2018; 25(4): 514-30.

Hase K, Sako M, Ushiba J, Chino J. Motor strategies for initiating downward-oriented movements during standing in adults. Experimental brain research. 2004;158(1):18-27.

Hermens HJ, Freriks B, Disselhorst-Klug C, Rau G. Development of recommendations for SEMG sensors and sensor placement procedures. Journal of electromyography and Kinesiology. 2000; 10(5): 361-74.

Isear JJ, Erickson JC, Worrell TW. EMG analysis of lower extremity muscle recruitment patterns during an unloaded squat. Medicine and science in sports and exercise. 1997; 29(4): 532-9.

Kang JY, Kim TG, Kim KY. The effects of closed kinetic chain exercise using EMG biofeedback on PFPS patients pain and muscle functions. International Journal of Bio-Science and Bio-Technology. 2014; 6(3): 55-62.

Koh EK, Lee KH, Jung DY. The effect of isometric hip adduction and abduction on the muscle activities of vastus medialis oblique and vastus lateralis during leg squat exercises. Korean journal of sport biomechanics. 2011; 21(3): 361-8.

Lee D, Lee S, Park J. Impact of decline-board squat exercises and knee joint angles on the muscle activity of the lower limbs. Journal of physical therapy science. 2015; 27(8): 2617-9.

Lee TK, Park SM, Yun SB, Lee AR, Lee YS, Yong MS. Analysis of vastus lateralis and vastus medialis oblique muscle activation during squat exercise with and without a variety of tools in normal adults. Journal of physical therapy science. 2016; 28(3): 1071-3.

Liu MF, Chou PH, Liaw LJ, Su FC. Lower-limb adaptation during squatting after isolated posterior cruciate ligament injuries. Clinical Biomechanics. 2010; 25(9): 909-13.

Marques MC, Gabbett TJ, Marinho DA, Blazevich AJ, Sousa A, Tillaar RV, Izquierdo M. Influence of strength, sprint running, and combined strength and sprint running training on short sprint performance in young adults. International journal of sports medicine. 2015; 94(10): 789-95.

Miyaji T, Gamada K, Kidera K, Ikuta F, Yoneta K, Shindo H, Osaki M, Yonekura A. In vivo kinematics of the anterior cruciate ligament deficient knee during wide-based squat using a 2D/3D registration technique. Journal of sports science & medicine. 2012; 11(4): 695. PMCID:PMC3763317.

Nagura T, Dyrby CO, Alexander EJ, Andriacchi TP. Mechanical loads at the knee joint during deep flexion. Journal of Orthopaedic Research. 2002; 20(4): 881-6.

Padua DA, Bell DR, Clark MA. Neuromuscular characteristics of individuals displaying excessive medial knee displacement. Journal of athletic training. 2012; 47(5): 525-36.

Park CH, Yoo SW, Park JW, et al. The study for muscle activating of lower extremities, according various squatting. Journal of Korean Physical Therapy Science. 2015; 22: 43-8.

Perchthaler D, Horstmann T, Grau S. Variations in neuromuscular activity of thigh muscles during whole-body vibration in consideration of different biomechanical variables. Journal of sports science & medicine. 2013;12(3):439. PMCID:PMC3772586.

Rønnestad BR, Hansen J, Hollan I, et al. Strength training improves performance and pedaling characteristics in elite cyclists. Scandinavian journal of medicine & science in sports. 2015; 25(1): e89-e98.

Saeterbakken AH, Fimland MS. Muscle force output and electromyographic activity in squats with various unstable surfaces. The Journal of Strength & Conditioning Research. 2013; 27(1): 130-6.

Salem GJ, Salinas R, Harding FV. Bilateral kinematic and kinetic analysis of the squat exercise after anterior cruciate ligament reconstruction. Archives of physical medicine and rehabilitation. 2003; 84(8): 1211-6.

Shelbourne KD, Klootwyk TE, DeCarlo MS. Update on accelerated rehabilitation after anterior cruciate ligament reconstruction. Journal of Orthopaedic & Sports Physical Therapy. 1992; 15: 303-8.

Tang SF, Chen CK, Hsu R, Chou SW, Hong WH, Lew HL. Vastus medialis obliquus and vastus lateralis activity in open and closed kinetic chain exercises in patients with patellofemoral pain syndrome: an electromyographic study. Archives of physical medicine and rehabilitation. 2001; 82(10): 1441-5.


Copyright (c) 2018 Journal of Human Sport and Exercise

Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.