The effect of stance on muscle activation in the squat
WIDE STANCE:
The Journal of Strength and Conditioning, by William and Kraemer (2010) suggests that the squat is one of the most frequently used exercises in the field of strength and conditioning. Considering the complexity of the exercise and the many variables related to performance, understanding the squats biomechanics is of great importance for both achieving optimal muscular development as well as reducing the prospect of training-related injury (Medline 2014).
The squat also is becoming increasingly popular in clinical settings as a means to strengthen lower-body muscles and connective tissue after joint-related injury (Merrit, 2010). It has been used extensively for therapeutic treatment of ligament lesions, patellofemoral dysfunctions, total joint replacement, and ankle instability. Furthermore the loosed-chain stance required for performance reduces anterior cruciate ligament (ACL) strain, making it superior to the knee extension for rehabilitation of the ACL injury.
During squat performance, the talocrucial joint (articulation of the tibia and fibula with the talus) facilitates movement through the actions of dorsiflexion and plantar flexion, whereas the primary action at the subtalar joint is to maintain postural stability and contributes significant support and aids in power generation during squat performance (Kingston, 2010).
The knee joint consists of the tibiofemoral, which carries out sagittal plane movement throughout a range of motion of 0 to approximately 160 degrees of flexion Merrit, (2010). The tiofemoral joint can be classified as a modified hinge joint that comprises the articulation of the tibia and femur. A small amount of axial rotation is also present at the joint during dynamic movement, with femur rotating laterally during flexion and medially during extension with respect to the tibia. This causes the instant centre of rotation at the knee to shift slightly throughout performance of the squat. The knee is supported by an array of ligaments and cartilage. Of these structures, the AL is often considered the most important stabilizer of the joint it primary role is to prevent anterior tibial translation at the knee, particularly at lower flexion angles. It also plays a role in limiting internal and external rotation of the knee and inhibiting varus/valgus motion Medline, (2014). The posterior cruciate ligament (PCL) can be considered the counterpart to the ACL. Its primary function is to restrain posterior tibial translation.
Hemmerich et al., (2006) suggest that during the squat, hip torques increase in conjunction with increased hip flexion, with maximal torque occurring near the bottom phase of movement. The primary hip muscles involved during the squat are the glutes maximus (GM) and the hamstrings. The gluteus maximus is a powerful hip extensor, acting eccentrically to control the squatdescent and concentrically to overcome external resistance. Given its attachment at the iliotibial band, the GM is also thought to play a role in stabilizing knee and pelvis during squatting on the ascent.
Although weightlifters may choose to variant their stance, research indicates that the optimal squat technique is a wide stance (> shoulder width) with natural foot positioning, unrestricted movement of the knees, and full depth while the lordotic curve of the lumbar spine (referring to the inward curvature, just above the buttocks Medline, (2014) is maintained with a forward or upward gaze (Comfort and Kasim, 2007). Two, independent studies indicated that stance width
variation does alter muscle recruitment patterns. Esamilla, et al., (2001) define muscle recruitment asthe ability to convert additional motor units as the resistance is increased), increasing activity of the adductor longus. Healthline, (2014) suggests that when a wide stance is used, thus it is valuable considering
muscles may increase force production, therefore performance during the execution of the lift. Paoli et al., (2009) when a wider stance squat (i.e. stance at 140–150 per cent of shoulder width) is performed, it allows for greater posterior displacement of the hips, while maintaining a vertical posture with the torso, thus enabling the lifter to achieve greater glute activation when depth is reached in comparison to a narrow stance (i.e. stance at 100 percent of shoulder width; 1–3). Wide stance squats are achieved with a posterior tracking of the hips, which leads to greater hip extension to return the bar back up. Further, wide stance squats have been shown to have greater abduction and adduction with greater internal and external rotation of the femur during the lift. Mcmaw and Melrose, (2000) however states that the lateral anterior thigh muscle (vastus lateralis0 is more active when a lifter adducts the thighs to assume a narrow stance.
Merritt, (2010) found that the muscle activation of the gluteus maximus changed in relation to the amount of weight used, not the width of the stance. An independent study by McCaw, and Melrose, (2000) discovered that the rectus femoris, vastus medialis, and the vastus laterlis, exhibited significantly greater IEMG (Integrated Electromyography) values with 75% 1RM load compared with a 60% 1RM load. In conclusion IEMG values were 20% greater when lifting the high load compared with the low load.
Kingston, (2010) found that foot rotation increased the knee flexion moment in both wide and normal stances. During a squat there is a tendency for the knee to internally rotate and adduct which strains the knee's connective tissues. A wide stance stresses the biomechanical structure of the lower limb and increases the knee's adduction moment. When squatting with a wide stance, external foot rotation reduces the internal rotation moment, meaning the knees are less likely to move together, therefore it aids to keep the knee (leg and thigh segments) properly aligned.
Conclusion
Research to date is still debating the effects of the stance width during a squat on muscle recruitment. A number of researchers have concluded that stance width does not affect the degree of muscular recruitment of the quadriceps or hamstrings during the back squat. However, it has been noted that a greater stance width does lead to increased gluteus maximus activity, which may be the reason for why weightlifters choose to adopt this stance. Comfort and Kasim, (20070 however disagrees with such findings and has discovered that the stance width variation does alter the muscle recruitment patterns of the rectus femoris, vastus medialis and the vastus laterlis during a squat.
Current research implies that each individuals stance is unique, due to the biomechanics for performing a squat changes for every individual. Research suggests that the biomechanics for each individual may have an effect on the stance taken when performing a squat, thus causing muscle such as the gluteus maximus to become more active when performing the exercise. Over all due to the clear debate that is on-going with regards to squat stance, muscle recruitment and muscle activation. Further research is clearly needed to aid to aid in coming to a definitive conclusion to this question. However currently there seems to be a larger amount of recent research supporting the idea that width does not affect the amount of muscular recruitment during a back squat and that by using a wider stance will lead to an increased activity of the gluteus maximus.
Reference List
Comfort, P. and Kasim, P. (2007) Optimizing Squat Technique.. Strength & Conditioning Journal (Allen Press). Vol. 29, No. 6: 10-13.
Dionisio, V, Almeida, G, Duarte, M, and Hirata, R. (2008) Kinematic, Kinetic and EMG patterns during downward squatting. Journal of Eletomyogr-Kinesiol 18:134-143.
Escamilla, R, Fleisig, G, Lowery, T, Barrentine, S, and Andrews, J. (2001) A three-dimensional biomechanical analysis of the squat during varying stance widths. Med Science Sports Exercise 33: 984-998
Healthline . (2014) Adductor longus. [Online] Available from: http://www.healthline.com/human-body-maps/adductor-longus-muscle#3/2[accessed 24 March
2014]
Hemmerich, A, Brown, H, Smith, S, Marthandam, S, and Wyss, U. (2006) Hip, knee and ankle kinematics of high range of motion activities of daily living. Journal of Orthopaedic Res 24:770-781
Kingston, D. et al. (2010) Knee Loading during Bodyweight Squat Performance: Effects of Stance Width and Foot Rotation. Sports Research Intelligence Sportive. Vol. 17, No. 8: 22.
McCaw, S. and Melrose, D. (2000) Stance Width and Bar Load Effects on Leg Muscle Activity During the Parallel Squat. (1st ed.) Illinois: Apllied Sciences.
Medline Plus . (2014) Lordosis. [Online] Available from:http://www.nlm.nih.gov/medlineplus/ency/article/003278.htm [accessed 24 March2014]
Merritt, G. (210) You Don't Know Squat!. Flex. Vol. 30, No. 12: 100.
Paoli A, Marcolin G, Petrone N (2009) The Effect of Stance Width on the Electromyographical Activity of Eight Superficial Thigh Muscles During Back Squat With Different Bar Loads. The Journal of Strength& Conditioning Research 23(1):246–50.
The Journal of Strength and Conditioning, by William and Kraemer (2010) suggests that the squat is one of the most frequently used exercises in the field of strength and conditioning. Considering the complexity of the exercise and the many variables related to performance, understanding the squats biomechanics is of great importance for both achieving optimal muscular development as well as reducing the prospect of training-related injury (Medline 2014).
The squat also is becoming increasingly popular in clinical settings as a means to strengthen lower-body muscles and connective tissue after joint-related injury (Merrit, 2010). It has been used extensively for therapeutic treatment of ligament lesions, patellofemoral dysfunctions, total joint replacement, and ankle instability. Furthermore the loosed-chain stance required for performance reduces anterior cruciate ligament (ACL) strain, making it superior to the knee extension for rehabilitation of the ACL injury.
During squat performance, the talocrucial joint (articulation of the tibia and fibula with the talus) facilitates movement through the actions of dorsiflexion and plantar flexion, whereas the primary action at the subtalar joint is to maintain postural stability and contributes significant support and aids in power generation during squat performance (Kingston, 2010).
The knee joint consists of the tibiofemoral, which carries out sagittal plane movement throughout a range of motion of 0 to approximately 160 degrees of flexion Merrit, (2010). The tiofemoral joint can be classified as a modified hinge joint that comprises the articulation of the tibia and femur. A small amount of axial rotation is also present at the joint during dynamic movement, with femur rotating laterally during flexion and medially during extension with respect to the tibia. This causes the instant centre of rotation at the knee to shift slightly throughout performance of the squat. The knee is supported by an array of ligaments and cartilage. Of these structures, the AL is often considered the most important stabilizer of the joint it primary role is to prevent anterior tibial translation at the knee, particularly at lower flexion angles. It also plays a role in limiting internal and external rotation of the knee and inhibiting varus/valgus motion Medline, (2014). The posterior cruciate ligament (PCL) can be considered the counterpart to the ACL. Its primary function is to restrain posterior tibial translation.
Hemmerich et al., (2006) suggest that during the squat, hip torques increase in conjunction with increased hip flexion, with maximal torque occurring near the bottom phase of movement. The primary hip muscles involved during the squat are the glutes maximus (GM) and the hamstrings. The gluteus maximus is a powerful hip extensor, acting eccentrically to control the squatdescent and concentrically to overcome external resistance. Given its attachment at the iliotibial band, the GM is also thought to play a role in stabilizing knee and pelvis during squatting on the ascent.
Although weightlifters may choose to variant their stance, research indicates that the optimal squat technique is a wide stance (> shoulder width) with natural foot positioning, unrestricted movement of the knees, and full depth while the lordotic curve of the lumbar spine (referring to the inward curvature, just above the buttocks Medline, (2014) is maintained with a forward or upward gaze (Comfort and Kasim, 2007). Two, independent studies indicated that stance width
variation does alter muscle recruitment patterns. Esamilla, et al., (2001) define muscle recruitment asthe ability to convert additional motor units as the resistance is increased), increasing activity of the adductor longus. Healthline, (2014) suggests that when a wide stance is used, thus it is valuable considering
muscles may increase force production, therefore performance during the execution of the lift. Paoli et al., (2009) when a wider stance squat (i.e. stance at 140–150 per cent of shoulder width) is performed, it allows for greater posterior displacement of the hips, while maintaining a vertical posture with the torso, thus enabling the lifter to achieve greater glute activation when depth is reached in comparison to a narrow stance (i.e. stance at 100 percent of shoulder width; 1–3). Wide stance squats are achieved with a posterior tracking of the hips, which leads to greater hip extension to return the bar back up. Further, wide stance squats have been shown to have greater abduction and adduction with greater internal and external rotation of the femur during the lift. Mcmaw and Melrose, (2000) however states that the lateral anterior thigh muscle (vastus lateralis0 is more active when a lifter adducts the thighs to assume a narrow stance.
Merritt, (2010) found that the muscle activation of the gluteus maximus changed in relation to the amount of weight used, not the width of the stance. An independent study by McCaw, and Melrose, (2000) discovered that the rectus femoris, vastus medialis, and the vastus laterlis, exhibited significantly greater IEMG (Integrated Electromyography) values with 75% 1RM load compared with a 60% 1RM load. In conclusion IEMG values were 20% greater when lifting the high load compared with the low load.
Kingston, (2010) found that foot rotation increased the knee flexion moment in both wide and normal stances. During a squat there is a tendency for the knee to internally rotate and adduct which strains the knee's connective tissues. A wide stance stresses the biomechanical structure of the lower limb and increases the knee's adduction moment. When squatting with a wide stance, external foot rotation reduces the internal rotation moment, meaning the knees are less likely to move together, therefore it aids to keep the knee (leg and thigh segments) properly aligned.
Conclusion
Research to date is still debating the effects of the stance width during a squat on muscle recruitment. A number of researchers have concluded that stance width does not affect the degree of muscular recruitment of the quadriceps or hamstrings during the back squat. However, it has been noted that a greater stance width does lead to increased gluteus maximus activity, which may be the reason for why weightlifters choose to adopt this stance. Comfort and Kasim, (20070 however disagrees with such findings and has discovered that the stance width variation does alter the muscle recruitment patterns of the rectus femoris, vastus medialis and the vastus laterlis during a squat.
Current research implies that each individuals stance is unique, due to the biomechanics for performing a squat changes for every individual. Research suggests that the biomechanics for each individual may have an effect on the stance taken when performing a squat, thus causing muscle such as the gluteus maximus to become more active when performing the exercise. Over all due to the clear debate that is on-going with regards to squat stance, muscle recruitment and muscle activation. Further research is clearly needed to aid to aid in coming to a definitive conclusion to this question. However currently there seems to be a larger amount of recent research supporting the idea that width does not affect the amount of muscular recruitment during a back squat and that by using a wider stance will lead to an increased activity of the gluteus maximus.
Reference List
Comfort, P. and Kasim, P. (2007) Optimizing Squat Technique.. Strength & Conditioning Journal (Allen Press). Vol. 29, No. 6: 10-13.
Dionisio, V, Almeida, G, Duarte, M, and Hirata, R. (2008) Kinematic, Kinetic and EMG patterns during downward squatting. Journal of Eletomyogr-Kinesiol 18:134-143.
Escamilla, R, Fleisig, G, Lowery, T, Barrentine, S, and Andrews, J. (2001) A three-dimensional biomechanical analysis of the squat during varying stance widths. Med Science Sports Exercise 33: 984-998
Healthline . (2014) Adductor longus. [Online] Available from: http://www.healthline.com/human-body-maps/adductor-longus-muscle#3/2[accessed 24 March
2014]
Hemmerich, A, Brown, H, Smith, S, Marthandam, S, and Wyss, U. (2006) Hip, knee and ankle kinematics of high range of motion activities of daily living. Journal of Orthopaedic Res 24:770-781
Kingston, D. et al. (2010) Knee Loading during Bodyweight Squat Performance: Effects of Stance Width and Foot Rotation. Sports Research Intelligence Sportive. Vol. 17, No. 8: 22.
McCaw, S. and Melrose, D. (2000) Stance Width and Bar Load Effects on Leg Muscle Activity During the Parallel Squat. (1st ed.) Illinois: Apllied Sciences.
Medline Plus . (2014) Lordosis. [Online] Available from:http://www.nlm.nih.gov/medlineplus/ency/article/003278.htm [accessed 24 March2014]
Merritt, G. (210) You Don't Know Squat!. Flex. Vol. 30, No. 12: 100.
Paoli A, Marcolin G, Petrone N (2009) The Effect of Stance Width on the Electromyographical Activity of Eight Superficial Thigh Muscles During Back Squat With Different Bar Loads. The Journal of Strength& Conditioning Research 23(1):246–50.