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Effect of Knee Position on Hip and Knee Torques During the Barbell Squat
Abstract
Unlabelled:
Some recommendations suggest keeping the shank as vertical as possible during the barbell squat, thus keeping the knees from moving past the toes. This study examined joint kinetics occurring when forward displacement of the knees is restricted vs. when such movement is not restricted. Seven weight-trained men (mean +/- SD; age = 27.9 +/- 5.2 years) were videotaped while performing 2 variations of parallel barbell squats (barbell load = body weight). Either the knees were permitted to move anteriorly past the toes (unrestricted) or a wooden barrier prevented the knees from moving anteriorly past the toes (restricted). Differences resulted between static knee and hip torques for both types of squat as well as when both squat variations were compared with each other (p < 0.05). For the unrestricted squat, knee torque (N.m; mean +/- SD) = 150.1 +/- 50.8 and hip torque = 28.2 +/- 65.0. For the restricted squat, knee torque = 117.3 +/- 34.2 and hip torque = 302.7 +/- 71.2. Restricted squats also produced more anterior lean of the trunk and shank and a greater internal angle at the knees and ankles. The squat technique used can affect the distribution of forces between the knees and hips and on the kinematic properties of the exercise.
Practical applications:
Although restricting forward movement of the knees may minimize stress on the knees, it is likely that forces are inappropriately transferred to the hips and low-back region. Thus, appropriate joint loading during this exercise may require the knees to move slightly past the toes.
... Since the 1980s, there has been a widespread perception that the barbell squat should be performed with an upright posture and that the knees should not be moved beyond the tips of the toes. According to this traditional dogma, anterior knee movement should be limited in the sagittal plane once a vertical line with the tips of the feet is achieved [1,2]. Widely accepted instructions for proper knee positioning during barbell squats [2,3] are based on previous studies [4][5][6] that showed that anterior knee displacement (AKD) past the toes is associated with greater shearing forces in the knees, specifically the tibiofemoral joints [4], and that moving the knees anteriorly to a lesser extent during squatting generates lower knee extensor torque [5]. ...
... According to this traditional dogma, anterior knee movement should be limited in the sagittal plane once a vertical line with the tips of the feet is achieved [1,2]. Widely accepted instructions for proper knee positioning during barbell squats [2,3] are based on previous studies [4][5][6] that showed that anterior knee displacement (AKD) past the toes is associated with greater shearing forces in the knees, specifically the tibiofemoral joints [4], and that moving the knees anteriorly to a lesser extent during squatting generates lower knee extensor torque [5]. Based on these findings, it has become standard practice to maintain the shin as vertical as possible and that "maximal forward movement of the knees should place them no more than slightly in front of the toes" when squatting in order to lessen the shear stress placed on the knee [3]. ...
... Based on these findings, it has become standard practice to maintain the shin as vertical as possible and that "maximal forward movement of the knees should place them no more than slightly in front of the toes" when squatting in order to lessen the shear stress placed on the knee [3]. From a practical standpoint, these guidelines advise against allowing the knees to displace anteriorly past the toes [1][2][3]. Although not reported in the literature, the recommendation to not or only slightly push the knees over the tips of the toes seems to be a very vague statement, as disproportionately large feet in relation to the lower extremities of an individual will likely not lead to reduced shearing forces. ...
Based on seminal research from the 1970s and 1980s, the myth that the knees should only move as far anterior during the barbell squat until they vertically align with the tips of the feet in the sagittal plane still exists today. However, the role of both the hip joint and the lumbar spine, which are exposed to high peak torques during this deliberate restriction in range of motion, has remained largely unnoticed in the traditional literature. More recent anthropometric and biomechanical studies have found disparate results regarding anterior knee displacement during barbell squatting. For a large number of athletes, it may be favorable or even necessary to allow a certain degree of anterior knee displacement in order to achieve optimal training outcomes and minimize the biomechanical stress imparted on the lumbar spine and hip. Overall, restricting this natural movement is likely not an effective strategy for healthy trained individuals. With the exception of knee rehabilitation patients, the contemporary literature suggests it should not be practiced on a general basis.
... It is believed that a training protocol with high loads and a low number of repetitions is effective for improving muscle strength and one with medium loads and a high number of repetitions is effective when the aim is muscle hypertrophy (Choi et al., 1998). For squats, in addition to the lifted load and the number of repetitions, stance width (Escamilla et al., 2001), squatting depth (Bryanton et al., 2012), and the knee position (Fry et al., 2003) are variables to be considered depending on the training objective (Rippetoe, 2011). The load characteristics of the body during squats vary depending on these variables; especially, the posture at the bottom position would be an important variable. ...
... The bottom position posture is defined not only by the squat depth, but also by the knee position. Fry et al. (2003) compared the lower limb joint kinetics during squats in different knee positions at the bottom position, and reported that greater knee joint torque and the lower hip joint torque were produced when in the knee dominant posture (i.e., the knee placed past the toe at the bottom position). Consequently, there is no doubt that the bottom position posture has a major effect on the load characteristics of the squat. ...
... In addition, the mechanical work of the knee joint was significantly greater in the knee posture than in the hip posture, but its value was not twice as high. Fry et al. (2003) reported the effect of the posture on barbell squats, with the knee extension torque being greater and the hip extension torque being less in the knee dominant posture than in the hip dominant posture. In the knee posture, the knee joint is located within 80% of the length of the foot anterior to the toe. ...
This study aimed to investigate squat jump and countermovement jump kinetics in the knee dominant and hip dominant postures. Participants included 12 male sports science students. They were instructed to perform a squat jump and a countermovement jump with two squat postures: knee-and hip-dominant postures. The jumping motion and ground reaction force were recorded using a motion capture system and a force plate, respectively. A p-value of 0.05 was considered statistically significant. There was a significant interaction for the maximal knee joint extension torque, with the knee-countermovement jump being more than twice higher than that of other conditions, but not for mechanical work of the knee joint, which was significantly greater in the knee posture than in the hip posture. No significant interactions were found in mechanical work and maximal extension torque of the hip joint, both of which were significantly greater in the hip posture than in the knee posture, and in the countermovement jump than in the squat jump. This study showed that the effects of countermovement and posture were different for joints and that these effects were independent in the hip joint, but interacted in the knee joint. In the knee joint, the posture increased the effect of countermovement on extension torque, but the effect on mechanical work was small. This suggests that countermovement in the knee posture has little effect on the lifting work, but results in a great load on the knee extensors.
... The main risk factor occurs during knee flexion, when the vertical line that passes through the anterior region of the tibia crosses the vertical line that passes through the toe's tips (of the same side) (Bolgla et al. 2018;Crossley et al. 2019;Fry et al. 2003;Pereira et al. 2020;2022b, c;Powers et al. 2017). Another risk factor that can be pointed out is the difference in strength between the thigh and hip muscles (of the same side), which makes the syndrome symptomatic (Narici et al. 2021;Pereira et al. 2020;Scott et al. 2020;Søgaard and Sjøgaard 2017). ...
... The risk assessed was that of the tibial translation movement in the anterior plane in front of the ipsilateral fingers, as reported in the literature as harmful (Brechter and Powers 2002;Collins et al. 2013;Crossley et al. 2004;Fry et al. 2003;Lorenzetti et al. 2018;Pereira et al. 2022b;Powers et al. 2017;Schütz et al. 2014). ...
... According to the literature, such a movement justifies the implementation of prevention measures (Brechter and Powers 2002;Collins et al. 2013;Crossley et al. 2004;Fry et al. 2003;Neal et al. 2019;Pereira et al. 2022b;Powers et al. 2017;Willy et al. 2019). ...
Patellofemoral pain syndrome (PFPS) is a musculoskeletal disorder in the anterior region of the knee, affecting people of different ages. When it is necessary to go up and down many stairs in a work context, there is a risk of increased wear on the knee joint and, consequently, PFPS. The main objective of this work was to identify the risk of contracting PFPS associated with the action of going up and down stairs in the workplace. An analysis of workers’ movement on an oil platform without lifts was carried out in the circulation by stairs between the different floors. It has been found that leg movements made when going up and down stairs can be harmful to the knee joints. A recommendation was made to change the way workers go up and down stairs to reduce the overload on the joint knee and the risk of contracting or worsening PFPS.
... The first one is based on the knowledge about the degrees of knee flexion, considering its anterior translational movement over the anterior tibial line as the main factor of PFPS worsening [22,40,45,49,53,54,65]. ...
... The anterior translation of the knee with the anterior tibial line in front of the ipsilateral toes line during any squat type [22,24,33,46,49,53,65]. Thus, a difference of strength on the patellar tendon of 18.8% compared to 11.5% was found during the forward lunge squat exercise when the anterior tibial line was translocated from the knee to the front tibial line anterior to the ipsilateral toes line [34]. ...
... This syndrome may or may not be symptomatic. It occurs mainly due to tension overload on the patellofemoral ligament in knee flexion between 60 • and 90 • , and when, during knee flexion, the vertical line passing through the anterior region of the tibia crosses the vertical line passing through the tips of the toes (on the same side) [22,40,45,49,53,54,65]. ...
Patellofemoral pain syndrome (PFPS) is highly prevalent; it can cause severe pain and evolve into progressive functional loss, leading to difficulties performing daily tasks such as climbing and descending stairs and squatting. This systematic review aimed to find evidence, in the literature, of squat movements that can cause or worsen PFPS. This work was based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement, and its protocol was registered in PROSPERO (CRD42019128711). From the 6570 collected records, 37 were included. From these 37 articles, 27 present a causal relationship between knee flexion and PFPS, 8 describe a relationship, considering the greater existence of muscle contractions, and one article did not describe this relationship in its results. The main limitations stem from the fact that different studies used different evaluation parameters to compare the force exerted on the patellofemoral joint. Furthermore, most studies are focused on sports populations. After analysing the included works, it was concluded that all squat exercises can cause tension overload in the knee, especially with a knee flexion between 60° and 90° degrees. The main causal/worsening factors of PFPS symptoms are the knee translocation forward the toes (on the same body side) when flexing the knee, and the muscle imbalance between the thigh muscles.
... The effects of ankle dorsiflexion and the resulting anterior knee position on the knee extensor moment during double-leg squatting, as well as the effects of trunk flexion, have been well studied [7][8][9][10][11]. Reduced ankle dorsiflexion and increased trunk flexion decrease the knee extensor moment while increasing the hip extensor moment during double-leg squatting [7][8][9][10][11]. ...
... The effects of ankle dorsiflexion and the resulting anterior knee position on the knee extensor moment during double-leg squatting, as well as the effects of trunk flexion, have been well studied [7][8][9][10][11]. Reduced ankle dorsiflexion and increased trunk flexion decrease the knee extensor moment while increasing the hip extensor moment during double-leg squatting [7][8][9][10][11]. However, increased trunk flexion is concerned about the increase in the load on the low back [10,12]. ...
... Reduced ankle dorsiflexion and increased trunk flexion decrease the knee extensor moment while increasing the hip extensor moment during double-leg squatting [7][8][9][10][11]. However, increased trunk flexion is concerned about the increase in the load on the low back [10,12]. Reduced ankle dorsiflexion is also associated with an increase in hip flexion angle, hip extensor moment and lumbar lordosis [7,10,12], which is related to the increase in the load on the hip joint and low back [10,12]. ...
Abstract Background Squatting exercises are commonly used in rehabilitation for knee joint disorders; in these exercises, control of knee extensor moment is important to enhance training effects and to avoid adverse effects. Ankle dorsiflexion and trunk flexion are widely used to reduce knee extensor moments during squatting, but the increased load on the low back is a concern. The purpose of this study was to determine whether the anterior–posterior (AP) center-of-pressure (COP) position and the AP-COP position in combination with ankle dorsiflexion and trunk flexion angles can predict the contribution of the knee extensor moment during double-leg squatting. Methods Twenty-eight healthy individuals (14 female and 14 male participants, age 22.8 ± 1.3 years) performed three sets of five consecutive double-leg squats. Kinematics and kinetics were analyzed using a three-dimensional motion analysis system with force plates. Univariate and multivariate regression analyses were performed to predict the contribution of the knee extensor moment (% total support moment) from AP-COP position, ankle dorsiflexion, and trunk flexion. Results The AP-COP position was a significant predictor of the knee extensor moment contribution (R 2 = 0.168, P = 0.030). Multivariate analysis showed that the ankle dorsiflexion angle (ΔR 2 = 0.561, β = 0.842) and AP-COP position (ΔR 2 = 0.296, β = − 0.499) predicted the knee extensor moment contribution (model R 2 = 0.857, P
... Trunk flexion, anterior-posterior knee positioning, shank inclination and the ankle dorsiflexion angle have been widely studied for their effects on the knee extensor moment, patellofemoral joint stress and anterior tibial force during double-leg squatting (Biscarini et al., 2011;Fry et al., 2003;Kernozek et al., 2018;Lorenzetti et al., 2012;Straub et al., 2021). Greater trunk flexion decreases the knee extensor moment (Biscarini et al., 2011;Straub et al., 2021), and restriction of anterior knee shifting decreases the knee extensor moment and increases the hip extensor moment (Fry et al., 2003;Lorenzetti et al., 2012;Straub et al., 2021). ...
... Trunk flexion, anterior-posterior knee positioning, shank inclination and the ankle dorsiflexion angle have been widely studied for their effects on the knee extensor moment, patellofemoral joint stress and anterior tibial force during double-leg squatting (Biscarini et al., 2011;Fry et al., 2003;Kernozek et al., 2018;Lorenzetti et al., 2012;Straub et al., 2021). Greater trunk flexion decreases the knee extensor moment (Biscarini et al., 2011;Straub et al., 2021), and restriction of anterior knee shifting decreases the knee extensor moment and increases the hip extensor moment (Fry et al., 2003;Lorenzetti et al., 2012;Straub et al., 2021). On the other hand, a few studies reported that the anterior-posterior center of pressure (AP-COP) is also associated with lower limb joint moment coordination during squatting, showing that side-to-side differences in the AP-COP position were associated with those in the ankle extensor moment during double-leg squatting (Flanagan and Salem, 2007) and that the AP-COP position predicted hip-to-knee and ankle-to-knee extensor moment ratios for patients after anterior cruciate ligament reconstruction (Chan and Sigward, 2020). ...
... The knee extensor moment was significantly smaller under the anterior COP condition than under the posterior COP condition. Trunk flexion and anteriorposterior knee position (or shank inclination) are well studied as indicators of the knee extensor moment (Biscarini et al., 2011;Fry et al., 2003;Kernozek et al., 2018;Lorenzetti et al., 2012;Straub et al., 2021). The present finding adds the AP-COP position as a new indicator of the knee extensor moment. ...
The effects of changes in the anterior-posterior center of pressure (AP-COP) position on the lower limb joint moments during double-leg squatting remain unclear. The purpose of this study was to determine the effects of AP-COP positional changes on the hip, knee, and ankle extensor moments during double-leg squatting. Sixteen male participants (22.1 ± 1.5 years) performed double-leg squatting under two conditions (anterior and posterior COP conditions) with visual feedback on their COP positions. Kinematics and kinetics were analyzed using a three-dimensional motion analysis system and force plates. The hip, knee and ankle flexion angles and extensor moments at peak vertical ground reaction force were compared between the two conditions using paired t tests. The COP position was 53.5 ± 2.4% of the foot length, starting from the heel, under the anterior condition and 44.4 ± 2.1% under the posterior condition (P < 0.001). The knee extensor moment was significantly smaller under the anterior than the posterior COP condition (P = 0.003, 95% confidence interval (CI) -0.087 to -0.021 Nm/kg/m), while the ankle extensor moment significantly larger under the anterior COP condition than under the posterior COP condition (P < 0.001, 95% CI 0.113 to 0.147 Nm/kg/m). There was no significant difference in hip extensor moment (P = 0.431). The ankle dorsiflexion angle was significantly larger under the anterior than the posterior COP condition (P = 0.003, 95% CI 0.6 to 2.6°), while there was no difference in trunk, hip, or knee flexion angle. The present results indicate that changes in the AP-COP position mainly affect the ankle and knee extensor moments during double-leg squatting, while the effect on the lower limb joint and trunk flexion angles was limited. Visual feedback on the AP-COP position could be useful for modifying the ankle and knee extensor moments during double-leg squatting.
... Specifically, manipulation of stance width, bar position, foot rotation, trunk position, knee position, and squat depth have been shown to influence demand of the hip and knee extensors during the barbell back squat. [1][2][3][4][5][6][7][8][9] Sagittal plane inclination of the trunk and tibia are of particular interest as both have been reported to independently influence the demand on the hip and knee extensors during squatting. Specifically, increasing forward trunk lean during squatting has been shown to increase the hip extensor moment, while simultaneously decreasing the knee extensor moment. ...
... Specifically, increasing forward trunk lean during squatting has been shown to increase the hip extensor moment, while simultaneously decreasing the knee extensor moment. [1][2][3]5 Conversely, forward inclination of the tibia has been reported to increase the knee extensor moment while simultaneously decreasing the hip extensor moment. [1][2][3]5,7 Previous investigations related to the biomechanical demands of squatting are limited for two primary reasons. ...
... [1][2][3]5 Conversely, forward inclination of the tibia has been reported to increase the knee extensor moment while simultaneously decreasing the hip extensor moment. [1][2][3]5,7 Previous investigations related to the biomechanical demands of squatting are limited for two primary reasons. First, many biomechanical studies do not control for confounding variables known to influence hip and knee extensor demand in the squat, such as stance width or foot rotation, 5,7,10,11 limiting interpretation and application of their results. ...
Sagittal plane inclination of the trunk and tibia have been shown to independently modulate hip and knee extensor moments during squatting. The purpose of this study was to determine if the difference between sagittal plane trunk and tibia inclinations can be used to approximate the relative demand of the hip and knee extensors across a range of squatting conditions. Kinematic and kinetic data were obtained from 16 participants during 8 squat conditions in which trunk and tibia inclination were manipulated. The average hip/knee extensor moment ratio (HKR) was calculated during the lowering (eccentric) phase of each squat condition using inverse dynamics equations. Linear regression evaluated the association between the difference in trunk and tibia inclination at peak knee flexion and the average HKR. Across all squat conditions, the difference between trunk and tibia inclinations explained 70% of the variance in the average HKR (p < 0.001). The squat was knee extensor biased (HKR ≤ 1.0) when the tibia was at least 8 degrees more inclined than the trunk. The results of this study indicate that the relationship between sagittal plane trunk and tibia inclination can be used to estimate the relative demand of the hip and knee extensors.
... A long-held theory within the clinical and strength and conditioning setting is that shank inclination during squatting should be minimized to reduce loading on the knee. 1 Although it is unknown what level of loading is injurious to the knee, previous studies have shown that squatting with the knees forward of the toes (ie, forward shank position) increases the knee-extensor moment (KEM). [1][2][3] Squatting in a way that results in higher KEMs can result in increased patellofemoral joint stress, 4,5 patellar tendon loading, 6,7 and strain on the anterior cruciate ligament (ACL). 8 In contrast to the known relationship between the forward shank position and the KEM, it also has been reported that a forward trunk lean can lessen the KEM during squatting. ...
... To participate, subjects had to confirm that they had participated in an exercise program during the past 5 years that included squatting exercises. Exclusion criteria included the following: (1) history of lower-extremity surgery or other major lower-extremity injury in the previous 12 months, (2) knee pain or knee pathology in the past 12 months, (3) any pain when squatting, (4) any previous injury that would prevent the ability to perform a barbell squat with 35% body weight, and (5) pregnancy. Prior to data collection, written informed consent was obtained from all individual subjects. ...
... It should be noted, however, that greater degrees of forward trunk lean would also increase the demand on the back extensors. 2,18,19 The results of our study need to be interpreted in light of several limitations. First, we collapsed data for all subjects across 8 separate conditions (aimed at producing diverse combinations of trunk and shank positions). ...
Context:
A limitation of previous studies on squatting mechanics is that the influence of trunk and shank inclination on the knee-extensor moment (KEM) has been studied in isolation.
Objective:
The purpose of the current study was to determine the influence of segment orientation on the KEM during freestanding barbell squatting.
Design:
Repeated-measures cross sectional.
Setting:
University research laboratory.
Participants:
Sixteen healthy individuals (8 males and 8 females).
Intervention:
Each participant performed 8 squat conditions in which shank and trunk inclinations were manipulated.
Main outcome measures:
3D kinematic and kinetic data were collected at 250 and 1500 Hz, respectively. Regression analysis was conducted to identify the individual relationships between the KEM and the trunk and shank inclination at 60° and 90° of knee flexion. To identify the best predictor(s) of the KEM, stepwise regression was implemented.
Results:
Increased shank inclination increased the KEM (P < .001, R2 = .21-.25). Conversely, increased trunk inclination decreased the KEM (P < .001, R2 = .49-.50). For the stepwise regression, trunk inclination entered first and explained the greatest variance in the KEM (all P < .001, R2 = .49-.50). Shank inclination entered second (all P < .010, R2 = .53-.54) and explained an additional 3% to 5% of the variance.
Conclusions:
Our results confirm that inclination of the trunk and shank have an opposing relationship with the KEM. Increased forward shank posture increases the KEM, while increased forward trunk posture decreases the KEM. However, when viewed in combination, the trunk was the superior predictor of the KEM, highlighting the fact that increased quadriceps demand created by a forward shank can be offset by trunk inclination.
... [19]. It has been suggested that this compensation occurs due to decreased hip mobility or limited dorsiflexion angle [52,53]. More horizontal posture was adopted to compensate for changes in positioning of the lower leg and maintain the system center of mass over the base of support [53]. ...
... It has been suggested that this compensation occurs due to decreased hip mobility or limited dorsiflexion angle [52,53]. More horizontal posture was adopted to compensate for changes in positioning of the lower leg and maintain the system center of mass over the base of support [53]. In our study, tibia-torso angle variable was not found to be in correlation with running torso sagittal plane movements. ...
Purpose
Overhead squat assessment (OHSA) is a pre-activity dynamic movement analysis tool used to define deviations from an ideal motion pattern which known as compensation. Compensatory movements may result from abnormality in myofascial activity, length-tension relationships, neuro-motor control strategies, osteokinematics and arthrokinematics. The aim of this study is to identify the association between selected biomechanical variables of the ankle, knee, hip, pelvis, torso during OHSA and 16 km/h treadmill running tasks.
Methods
Thirteen national long distance male runners (17.3 ± 0.5 age (years); 5.89 ± 1.95 experience (years), 57.9 ± 3.7 body mass (kg); 175.4 ± 5.7 height (cm)) participated in this 2controlled laboratory study. Three-dimensional kinematics were collected at 250 Hz using a 9-camera Qualisys motion analysis system (Qualisys AB, Goteborg, Sweden) while participants performed 16 km/h treadmill running and OHSA tasks.
Results
Correlation coefficients demonstrated that OHSA pelvic anterior tilt angle was in a positive association with foot strike (FS), mid-stance (MS), and toe-off (TO) pelvic anterior tilt angles and MS tibial internal rotation on talus, MS ankle pronation, MS hip internal rotation. OHSA pelvic anterior tilt angle was in a negative association with TO hip extension. OHSA maximal hip adduction was positively correlated with MS and stance maximal knee adduction. FS, MS, stance maximal angular dorsiflexion values were positively correlated with OHSA dorsiflexion. Increased OHSA dorsiflexion angle was negatively associated with TO plantar flexion. OHSA pronation was positively associated with MS and stance pronation. MS hip internal rotation, MS hip adduction angles were increased, and MS ankle dorsiflexion was significantly decreased with the increase of trunk forward lean relative to tibia during OHSA.
Conclusions
OHSA was associated with some important and dysfunction-related hip, knee and ankle kinematics. Running coaches, may use OHSA as an assessment tool before the corrective training plan to detect injury-related compensation patterns to reduce the risk of injury and improve running technique.
... Limited ankle dorsiflexion has been found to negatively alter squat mechanics and is associated with increased knee valgus while squatting and aberrant flexion of the hips and lumbar spine, which may result in excessive compressive force on the lumbar discs (12,23,65,79,91). Furthermore, decreased hip ROM may also lead to compensatory movement patterns, which increase the risk of low back injury (50). In a deep squat, the hip crease is required to travel below the knee, with similar requirements relating to a successful catch position during a snatch (17,50,65). ...
... Furthermore, decreased hip ROM may also lead to compensatory movement patterns, which increase the risk of low back injury (50). In a deep squat, the hip crease is required to travel below the knee, with similar requirements relating to a successful catch position during a snatch (17,50,65). Improving ankle dorsiflexion may reduce lower limb injury rates with improved joint mobility shown to be beneficial in reducing the risk of sustaining musculoskeletal injury (64,76). ...
Fascial restrictions that occur in response to myofascial trigger points (MTrP), exercise-induced muscle damage (EIMD) and delayed onset of muscle soreness (DOMS) cause soft tissue to lose extensibility which contributes to abnormal muscle mechanics, reduced muscle length and decrements in joint range of motion (ROM) and actively contributes to musculoskeletal pain. Resistance training and in particular, weightlifting movements have unique mobility requirements imperative for movement efficacy and safety with ROM restrictions resulting in ineffective volume and intensity tolerance and dampened force output and power which may lead
to a failed lift or injury. Self-massage (SM) provides an expedient method to promote movement efficiency and reduce injury risk by improving ROM, muscular function and reducing pain and allows athletes to continue to train at their desired frequency with minimal disruption from MTrPs associated adverse effects. Thus, the aim of this review was to determine the efficacy of various self-massage tools in managing pain and mobility and to explore the potential benefits of SM on resistance training performance. Many SM devices are available for athletes to manage ROM restrictions and pain including differing densities of foam rollers, roller massagers, tennis balls and vibrating devices. To attenuate adverse training effects, a 10-to-20-minute bout consisting of 2-minute bouts of SM on the affected area may be beneficial. When selecting a SM device, athletes should note that foam rollers appear to be more effective than roller massagers, with vibrating
foam rollers eliciting an increased reduction to pain perception and tennis balls and soft massage balls shown to be efficacious in targeting smaller affected areas.
... The third type of squat is the front squat with the barbell held on the chest. The front squat is considered a safe exercise often used in rehabilitation or by beginners [16,18]. Studies of both types of squats indicate greater trunk verticalisation in the front squat, which translates into lower shear forces in the lumbar spine [16,18]. ...
... The front squat is considered a safe exercise often used in rehabilitation or by beginners [16,18]. Studies of both types of squats indicate greater trunk verticalisation in the front squat, which translates into lower shear forces in the lumbar spine [16,18]. On the other hand, Spitz [19] did not confirm a significant difference in barbell velocities, nor Davis [20] a significant difference in energy expenditure of the body during front and back squat performance. ...
Introduction. Front and back squats are multi-joint exercises used in sports to develop strength, power and muscle mass. Due to their movement structure and involvement of the main muscle groups, they are training measures that are used in strength training in various sports. A long-term training process leading to sports mastery requires the correct selection of loads as well as objective control of the training effects to date, both short-term and long-term. The aim of this study was to create a statistical model and to determine with it the character of the changes in the record scores in the front and back squat of young weight-lifters over a two-year training cycle.
Material and Methods. The study included 17 young athletes training in competitive weightlifting. Recorded scores in the front squat and back squat were measured seven times (every three months over a two-year training cycle). The progression method was used to determine the maximum load, and the repetition with the highest load (1RM) was used in the calculations.
Results. The subjects performed better in the back squat, but the difference between the results for both squats was approximately constant over the two-year training cycle. The time courses of both squats were similar over the analysed period. Systematic increases in maximum results were observed. The first statistically non-significant differences between the mean record values in successive measurements were found between the sixth and seventh measurements for both squats.
Conclusions. Determining the relationship between front and back squat record scores can contribute to the optimisation of training loads in sports using strength training. Obtaining an analytical form of the course of record scores over time for both squats helps to assess the skill level of athletes and predict their performance in the next training macro-cycle.
... This study has limitations. First, the knee and hip joint moments in squats depend on the patterns of lifting movement (4,7,10,11,19,21,33). In particular, the degrees of shank and trunk inclination could affect the distribution of joint extension moments between knee and hip (11,33). ...
... First, the knee and hip joint moments in squats depend on the patterns of lifting movement (4,7,10,11,19,21,33). In particular, the degrees of shank and trunk inclination could affect the distribution of joint extension moments between knee and hip (11,33). For this reason, the 4-month familiarization period was provided to attain potential maximum external loads and joint moments at 10RM. ...
Arakawa, H, Mori, M, and Tanimoto, M. Greater hip moments in rear-foot-elevated split squats than in conventional back squats with the same relative intensity of loads. J Strength Cond Res XX(X): 000-000, 2022-Rear-foot-elevated split squat (RFESS) is often performed as an alternative to conventional double-leg back squat (DLBS). This study aimed to compare 3-dimensional joint kinetics of DLBS and RFESS using the same relative intensity of loads. Eight male college rugby players performed 3 repetitions of DLBS and RFESS at 10-repetition-maximum (RM) loading. Before testing, both exercises were incorporated into the subjects' training program with a progressive increase in loads for 4 months. A 3-dimensional optical motion capture system and force platform were used for data collection. The 3-dimensional moments at the knee and hip joints in each of the 3 axes were calculated based on the inverse dynamic procedure. p values < 0.05 were considered statistically significant. The hip extension moment was 44% greater in the RFESS than in the DLBS at the bottom position (p < 0.01) and 47% greater for the peak value (p < 0.01) on harmonic averages. The hip abduction and external rotation moments at the bottom position were also greater in the RFESS than in the DLBS. The findings suggest that the magnitude of hip extension moment per leg in DLBS tends to be restricted to less than that expected from the given strength level. In conclusion, the mechanical contribution of hip extensors per leg can be greater in RFESS than in DLBS when using respective 10RM loads, even if the absolute load is smaller and the trunk is more upright in RFESS.
... It is the ability to perform and maintain efficient and accurate movement patterns that are fundamental to daily life [22]. The ability to perform functional movements is indispensable because it can prevent injuries [23] and pain [24]. To achieve functional movement, muscle strength, endurance, coordination, flexibility, balance, and movement efficiency are imperative [18]. ...
... Squats are an example of a functional movement in which humans adapt variations to accomplish tasks of activities of daily living [25]. Squats can also be used as an essential functional training because they recruit multiple muscle groups during a single movement [23,24]. Lunge is also regarded as a functional activity and is used to assess hip muscle and knee performances [26][27][28]. ...
(1) Background: The present study investigated the agreement between the Azure Kinect and marker-based motion analysis during functional movements. (2) Methods: Twelve healthy adults participated in this study and performed a total of six different tasks including front view squat, side view squat, forward reach, lateral reach, front view lunge, and side view lunge. Movement data were collected using an Azure Kinect and 12 infrared cameras while the participants performed the movements. The comparability between marker-based motion analysis and Azure Kinect was visualized using Bland–Altman plots and scatter plots. (3) Results: During the front view of squat motions, hip and knee joint angles showed moderate and high level of concurrent validity, respectively. The side view of squat motions showed moderate to good in the visible hip joint angles, whereas hidden hip joint angle showed poor concurrent validity. The knee joint angles showed variation between excellent and moderate concurrent validity depending on the visibility. The forward reach motions showed moderate concurrent validity for both shoulder angles, whereas the lateral reach motions showed excellent concurrent validity. During the front view of lunge motions, both the hip and knee joint angles showed moderate concurrent validity. The side view of lunge motions showed variations in concurrent validity, while the right hip joint angle showed good concurrent validity; the left hip joint showed poor concurrent validity. (4) Conclusions: The overall agreement between the Azure Kinect and marker-based motion analysis system was moderate to good when the body segments were visible to the Azure Kinect, yet the accuracy of tracking hidden body parts is still a concern.
... The barbell squat is one of the most effective exercises for building lower extremity strength [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] and is widely used for strength training and rehabilitation. During barbell squat training or competition, athletes often wear a type of heel lift shoe or use other means to elevate the heel, which is thought to improve the range of motion (ROM) of the lower extremity joints and improve stability of movement during the deep squat [16][17][18][19][20][21]. ...
... Barbell squats are commonly used for strength training and rehabilitation [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. Heel elevation during a barbell squat is thought to improve deep squat movement patterns. ...
The effect of heel elevation on the barbell squat remains controversial, and further exploration of muscle activity might help find additional evidence. Therefore, 20 healthy adult participants (10 males and 10 females) were recruited for this study to analyze the effects of heel height on lower extremity kinematics, kinetics, and muscle activity using the OpenSim individualized musculoskeletal model. One-way repeated measures ANOVA was used for statistical analysis. The results showed that when the heel was raised, the participant’s ankle dorsiflexion angle significantly decreased, and the percentage of ankle work was increased (p < 0.05). In addition, there was a significant increase in activation of the vastus lateralis, biceps femoris, and gastrocnemius muscles and a decrease in muscle activation of the anterior tibialis muscle (p < 0.05). An increase in knee moments and work done and a reduction in hip work were observed in male subjects (p < 0.05). In conclusion, heel raises affect lower extremity kinematics and kinetics during the barbell squat and alter the distribution of muscle activation and biomechanical loading of the joints in the lower extremity of participants to some extent, and there were gender differences in the results.
... However, varying performance responses have been found following these activities (38,59,69). Differences in exercise range of motion have been shown to affect mechanical and physiological demands (52) and may also influence postpriming performance responses after squatting tasks. When intensity is equated, a deeper squat will result in greater mechanical work compared with more shallow variations (104). ...
... The authors suggested that the oxidative potential of MHC IIa muscle fibers may be important in restoring adenosine triphosphate (ATP) postexercise to elicit a same-day potentiation response that offsets fatigue (22,62). A higher percentage of these fibers strongly correlates with greater relative MHC IIa area, an indicator of the strength training history (51,52,54,142). As such, the magnitude of potentiation or fatigue following resistance priming exercise completed on the same day may be influenced by training status (21,22). Nevertheless, further research examining the relationship between these muscle adaptations and the postexercise response subsequent to resistance priming strategies with lower exercise volumes that may be effective to improve performance within this time frame is needed. ...
“Priming exercises” are gaining popularity as a precompetition strategy to improve subsequent performance. Although priming exercise has been shown to improve various neuromuscular performance measures within 48 hours, a number of studies have also found no change or significant decreases in performance following priming interventions. Inconsistencies in findings are likely due to the many different variables used in the research. In addition, evidence suggests that the potential performance response following a priming stimulus is likely to be influenced by individual characteristics. Therefore, the purpose of this review is to examine the available evidence and identify those variables that most strongly determine whether priming stimuli involving resistance and stretch-shortening cycle exercise tasks are likely to improve performance within 48 hours of that stimulus. In addition to making recommendations based on the evidence to date, directions for future research are also identified.
... 6 If the knee exceeds the toe, the compression load and shear force applied to the knee will increase, increasing the possibility of knee injuries. 7 Also, as the trunk leans in the forward direction, the shear force on the knee increases. 2 To prevent knee injury due to this, motor learning by training with a physical therapist and personal trainer or athletic trainer is necessary, and repetitive practice and provision of sensory feedback are essential for efficient motor learning. ...
Various sensory feedback methods are considered important for motor learning, but the effect of each sensory feedback method on effective squat learning still needs to be clarified. This study aimed to investigate the effect of sensory feedback types on the acquisition and retention of a squat. A double‐blinded, randomized controlled trial was carried out. Thirty‐healthy people were recruited and randomly assigned to the visual feedback group (VFG = 10), tactile feedback group (TFG = 10), and control group (CG = 10). VFG received visual feedback through video data of the participant performing squats, and TFG received tactile feedback through manual contact with a physical therapist. Both groups received feedback on the movements that needed correction after each set was completed. CG maintained rest without receiving any feedback. The retro‐reflexive marker, force plate, and electromyography were used to measure body angle, foot center of pressure (COP), and muscle activity. All assessments were measured to confirm a squat acquisition. VFG and TFG showed significant differences in neutral knee position (NKP), trunk forward lean (TFL), anterior knee displacement (AKD), and anteroposterior (AP) foot COP (p < 0.050). In addition, the acquisition was retained until 3 days later for NKP and a week later for TFL, AKD, and AP foot COP in VFG (p < 0.050), while the acquisition was not retained in TFG (p > 0.050). There was no statistically significant change in CG (p > 0.050). This study demonstrated that visual feedback positively affects the acquisition and retention of squats. Therefore, we recommend the use of visual feedback for squat acquisition and retention in exercise novices.
... This exercise demands high levels of body balance control and explosive joint torque. To improve the forces distribution on all involved joints and lift heavier loads, it is commonly recommended to avoid moving the knees forward past the toes too much or to maintain a near-vertical position of the shank [15], [16]. Restricting the shank-gravity angle within a certain range ensures that the majority of the weight is primarily supported by the shinbone, as the orange bar shown in Fig. 3(b), enhancing overall body stability and minimizing strain on the knees [17]. ...
Wheeled bipedal robots have the capability to execute agile and versatile locomotion tasks in unknown terrains, with balancing being a key criteria in evaluating their dynamic performance. This paper focuses on enhancing the balancing performance of wheeled bipedal robots through innovations in both hardware and software aspects. A bio-inspired mechanical design, inspired by the human barbell squat, is proposed and implemented to achieve an efficient distribution of load onto the limb joints. This design improves knee torque joint efficiency and facilitates control over the distribution of the center of mass (CoM). Meanwhile, a customized balance model, namely the wheeled linear inverted pendulum (wLIP), is developed. The wLIP surpasses other alternatives by providing a more accurate estimation of wheeled robot dynamics while ensuring balancing stability. Experimental results demonstrate that the robot is capable of maintaining balance while manipulating pelvis states and CoM velocity; furthermore, it exhibits robustness against external disturbances and unknown terrains.
... The risk of injury in the knee areas is particularly high when performing barbell squats [9], making strengthening and conditioning essential [10]. Squat motions must be performed correctly to reduce the risk of knee and back injuries [11]. The biomechanical elements of barbell squats are associated with high levels of knee flexion, which increases the likelihood of injury to the knee joint itself [3]. ...
Background:
Squats are one of the most widely used weight training methods worldwide, and the single most ubiquitous with regard to multi-joint resistance training.
Objective:
The objective of the present study was to investigate kinematic and kinetic changes in the lower extremities as a result of load increases during a back squat exercise, and to propose an association between back squats and lower extremity injuries.
Methods:
Eight individuals with experience of back squat training were recruited. The subjects performed back squats with loads of 25%, 50%, 100%, and 125% of their body weight. During the performance, the center of pressure (COP) sway; vertical center of mass (COM) velocity; joint moment; joint range of motion (ROM) of flexion/extension and adduction/abduction; and rotation of the ankle, knee, and hip joints were measured.
Results:
The participants' lower extremity joint ROM, vertical COM velocity, and COP variability did not change significantly with changes in weight loading. However, the moments applied to the lower extremity joints differed according to changes in barbell weight. The moments of plantar flexion (f= 54.362, p< 0.001), dorsiflexion (f= 8.475, p< 0.001), knee flexion (f= 12.013, p< 0.001), knee extension (f= 8.581, p< 0.001), hip flexion (f= 5.111, p< 0.001), and hip extension (f= 11.053, p< 0.001) increased in the sagittal plane (flexion/extension). There was also a significant increase in ankle eversion (f= 5.612, p= 0.004), hip abduction (f= 3.242, p= 0.037), and adduction (f= 5.846, p= 0.003) in the frontal plane (adduction/abduction). Among the moment variables in the transverse plane (rotation), there were significant differences in ankle internal rotation (f= 7.043, p= 0.001) and hip external rotation (f= 11.070, p< 0.001).
Conclusion:
As the barbell load increased, posture and performance were maintained, but rotational moments of the joints differed. It is expected that the joint directions that showed significant differences in this study are likely to be vulnerable to the risk of injury when an excessive load is applied to the body. Examples include the hip adduction moment, hip external rotation moment, and ankle internal rotation moment, and apply regardless of the increase in the rotational moments of joints from load increases.
... The squat is a widely performed exercise which builds lower body strength and induces muscle hypertrophy for athletes [1,2] as well as non-athlete individuals and is commonly prescribed for rehabilitation [3,4]. However, squats may cause pain in individuals with back and knee problems [5,6]. In addition, there are concerns over the effectiveness of the squat, a bilateral exercise, in sports that require brief temporary weight support with only a unilateral lower extremity. ...
... Hence, when fatigue of the elbow flexors accumulates, trainees are restricted in their ability to involve other muscle groups to assist in completing further repetitions. Conversely, when squatting, trainees are less restricted in their movements and can thus alter exercise execution and increase the involvement of different muscle groups [16,17], for example, to compensate for quadriceps fatigue, trainees may implement greater hip flexion, which leads to increased involvement of the hamstring and gluteal muscles [18,19]. We therefore speculate that exercises that offer fewer opportunities for exercise modifications lead to better RIR predictions. ...
Background
A key role of resistance training (RT) coaches is to personalize programs based on their trainees’ abilities and goals. Specifically, coaches often assess how many repetitions in reserve (RIR) their trainees have until task-failure. Coaches can then modify the number of repetitions assigned per set accordingly. However, coaches’ ability to predict the number of RIR is unknown.
Methods
Certified RT coaches ( n = 259) were randomly assigned to watch a video of one of eight trainees. The trainees performed two sets of barbell squats and preacher biceps-curls, using 70% or 80% of their 1RM, to task-failure. The coaches predicted trainees’ RIR at 33%, 66%, and 90% of the total number of repetitions the trainees completed in each set. We fitted a linear mixed model with various predictors to the prediction errors as the outcomes (i.e., signed and unsigned values of the predicted minus actual repetitions to task-failure).
Results
The overall average number of repetitions completed by the trainees was 13.9. The average absolute errors were 4.8, 2.0, and 1.2 repetitions for the 33%, 66%, and 90% time-points, respectively. The absolute prediction error increased for the biceps-curl compared to the squat (1.43, 95% CI [1.13, 1.74]), but decreased for heavier loads (− 1.17, 95% CI [− 2.16, − 0.19]), and in the second set of each exercise (− 1.20, 95% CI [− 1.38, − 1.02]). Surprisingly, coaches’ years of experience had a negligible effect on the absolute error (− 0.020, 95% CI [− 0.039, − 0.0007]). Finally, coaches underpredicted the RIR at early time-points but reverted to slight overprediction at later time-points.
Conclusions
Prior coaching experience seems to play a minor role in RIR predictions. However, even short-term exposures to new trainees performing different exercises can substantially improve coaches’ RIR predictions.
... On the other hand, in LBBS, the trunk is inclined more forward than in HBBS, and the moment arm of the hip joint is larger [17]. This indicates that the degree of trunk bending and the change in the moment arm of the lower extremity joints are related to the muscle activity of the trunk [18]. ...
This study aimed to investigate the effect of the load and bar position on trunk and lower extremity muscle activity during squat exercise. High bar back squats (HBBS) and low bar back squats (LBBS) were performed in random order at 50%, 60%, and 70% loads of one repetition maximum by 28 experienced healthy adult men who had been performing squats for at least one year. Before the experiment, the maximal voluntary contraction of the vastus medialis, vastus lateralis, rectus femoris, biceps femoris, rectus abdominis, transverse abdominis, external oblique, and erector spinae muscles was measured by means of surface electromyography. In addition, eccentric and concentric exercises were performed for 3 s each to measure the muscle activity. There was a significant difference in muscle activity according to the load for all muscles in the eccentric and concentric phases (p < 0.05), indicating that muscle activity increased as the load increased. In addition, in the comparison between HBBS and LBBS, significant differences were shown in all lower extremity muscles and all trunk muscles except for the external oblique in the concentric phase according to the bar position (p < 0.05). HBBS showed a higher muscle activity of the lower extremity in the eccentric and concentric phases than in LBBS, while LBBS showed a higher muscle activity of the trunk muscle in the eccentric and concentric phases than in HBBS (p < 0.05). HBBS requires more force in the lower extremity than LBBS and is particularly advantageous in strengthening the muscular strength of the quadriceps. In contrast, LBBS requires more muscle activity in the trunk than HBBS and is more effective in carrying heavier loads because of the advantage of body stability. This study suggests that rehabilitation experts apply the bar position and load as important variables affecting the intensity and method of training for target muscle strengthening of the lower extremities and trunk.
... Squatting is a commonly performed exercise for the athletes. [3,4] Another squat variation which is commonly used in athlete population is the overhead http://annalsofrscb.ro squat. [5] Wrong movement patterns such as medio lateral rotation of the hip, the knee alignment inside or outside the hip during the movement provokes the amount of compressive and shear forces at the ankle, knee and hip joints [6,7] and this likely increases the chances of injuries. ...
Background: Altered or poor mechanics of movement creates tissue damage and stress leading to overuse injuries. It was observed that athletes with muscle imbalance had decreased playing performance and were at risk for injuries. Tight post chain structures could probably lead to altered mechanics of the overhead squat. Aim: To know whether giving a wedge beneath the heels partly nullifies the tightness in the posterior chain and improves the mechanics of the overhead squat. Methods: 30 collegiate male athletes from cricket, football and basketball were taken with a mean age of (21.37 + 2.34) years. All of them performed five overhead squats with and without a two inch wooden wedge kept beneath the heels. Results: We found shoulder flexion to improve by 3.27⁰ (+ 7. 79⁰) with the presence of a two inch wedge. Statistically significant (p = 0.024) difference was noted in shoulder flexion (46.32+ 9.58), Hip flexion (98.88+ 17.43) and (p= 0.0002), Knee flexion (114.27+ 21.79) and (p= 0.006), Ankle dorsiflexion (46.32+ 9.58) and (p= <0.0001) and the results were statistically significant. Conclusion: Based on our results, there was an increase in the range available for dorsiflexion at the ankle with the use of two inch wedge resulted in following kinematic changes: decreased shoulder flexion, increased knee flexion and increased hip flexion. The significant change in hip flexion after the use of wedge can be attributed to the shift in the center of gravity entirely.
... The squat is an exercise that indirectly improves the quality of life of sports and non-sports people by increasing the hip and knee extensor strength [8]. Squats can recruit multiple muscle groups in a single movement and is related to many daily activities, such as lifting heavy objects [9]. Exercise is also included as a core in many sports to improve athletic performance [10]. ...
Background: Life in modern society has become convenient, but the lack of exercise due to a sedentary lifestyle has led to muscle weakness. The quadriceps femoris is essential for walking, standing, and using stairs in daily life. Muscle weakness can lead directly to impaired function. Squatting is the most representative exercise for effective muscle development and increasing the knee extensor strength. This study examined the effects of ankle angle during wall squats on the muscle activity of the vastus medialis oblique (VMO), vastus lateralis (VL), rectus femoris (RF), biceps femoris (BF), rectus abdominis (RA), and erector spinae (ES) to determine which ankle angle can better strengthen the vastus medialis oblique as a method of rehabilitation training after a knee joint injury. Methods: All subjects (n = 20) performed the following three types of wall squats randomly: (1) GWS (General Wall Squat), (2) WSD 10° (Wall Squat with dorsiflexion 10°), and (3) WSP 10° (Wall Squat with plantarflexion 10°). Each subject completed all three kinds of wall squatting exercises three different times, and the muscle activity data of the VMO, VL, RF, BL, RA, and ES were recorded. Results: Compared to GWS exercise, the VMO and RF muscle activity increased significantly under WSP 10° exercise (p < 0.05), whereas the VL, BF, RA, and ES activity did not increase significantly (p > 0.05). No significant change between WSD 10° and WSP 10° was observed (p > 0.05). Conclusions: WSP 10° can help increase the quadriceps muscle activity. Wall squat exercise with different ankle angles can be used for quadriceps muscle strengthening training for normal people and for recovery training for patellofemoral pain syndrome (PFPS) patients in the rehabilitation stage.
... 25 NJT and flexions of the lower extremity joints were selected as the dependent variables because both have been key variables in previous squat studies. 1,7,15,16 The ASISs for dynamic trials were calculated using the rigid body method. 26 The hip joint center was located using the Tylkowski eAndriacchi hybrid method 27 and the joint between the fourth and fifth lumbar vertebrae (L4/5) was located using the MacKinnon method. ...
Background/objective
There is a lack of information about relationship between physical characteristics and biomechanics of the lower extremity during the squat. Additionally, studies did not examine sex-related differences. The purpose of this study was to investigate relationships between physical characteristics and biomechanics of the lower extremity during the squat, and to determine if any sex differences are present.
Methods
Fifty three participants recruited (21.82 ± 2.3 years; 75.56 ± 14.98 kg; 171.57 ± 8.38 cm) performed three squats with 75% of one repetition maximum. Femur to tibia length ratio, hip and ankle joints’ flexibilities, and relative muscular strength were measured and used as physical characteristics. Net joint torques (NJT) and flexion angles of the lower extremity were extracted as dependent variables. Multiple regression (stepwise) analysis was conducted to examine the relationships with physical characteristics being factors. Pearson correlation coefficients were calculated to determine intercorrelations among the dependent variables.
Results
Relative muscular strength was related to hip NJT and knee flexion angle, and hip flexibility was related to ankle dorsiflexion. Hip and knee NJT showed moderate correlations with the corresponding flexion angles (r = .48-.53; p < .01). Ankle dorsiflexion angle showed weak to moderate correlations with hip NJT and hip flexion angle (r = -.36-.50; p <.01) and a moderate correlation with knee NJT. No significant sex difference was observed (r = .52; p < .05).
Conclusion
Biomechanics of the lower extremity has been shown to correlate more with relative muscular strength and joint flexibility than with leg length ratio.
... Characteristics of movement behavior associated with higher knee extensor moments (or quadriceps muscle activity) during athletic tasks include an upright trunk [21][22][23] and forward displacement of the tibia (knee pass the toe). [23][24][25][26] In a previous publication, our group reported that the relative orientation of the trunk and tibia in the sagittal plane could be used to estimate the average HKR during various squat conditions. 27 More specifically, the difference between the sagittal plane trunk and tibia inclination at peak knee flexion explained 70% of the variance in the average HKR during the lowering phase of the squat. ...
Given that increased use of the knee extensors relative to the hip extensors may contribute to various knee injuries, there is a need for a practical method to characterize movement behavior indicative of how individuals utilize the hip and knee extensors during dynamic tasks. The purpose of the current study was to determine whether the difference between sagittal plane trunk and tibia orientations obtained from 2D video (2D trunk–tibia) could be used to predict the average hip/knee extensor moment ratio during athletic movements. Thirty-nine healthy athletes (15 males and 24 females) performed 6 tasks (step down, drop jump, lateral shuffle, deceleration, triple hop, and side-step-cut). Lower-extremity kinetics (3D) and sagittal plane video (2D) were collected simultaneously. Linear regression analysis was performed to determine if the 2D trunk–tibia angle at peak knee flexion predicted the average hip/knee extensor moment ratio during the deceleration phase of each task. For each task, an increase in the 2D trunk–tibia angle predicted an increase in the average hip/knee extensor moment ratio when adjusted for body mass (all P < .013, R ² = .17–.77). The 2D trunk–tibia angle represents a practical method to characterize movement behavior that is indicative of how individuals utilize the hip and knee extensors during dynamic tasks.
... Correct technical performance is crucial to getting the benefits of squatting (Schoenfeld et al., 2010;Yavuz & Edgar, 2017). On the contrary, deviations are associated with the risk of overloading and accidents (Fry et al. 2003, Hartmann & Wirth, 2014. The entire movement must be controlled. ...
PURPOSE Squats are among the basic exercises that have become an integral part of exercise programs. It is commonly used by athletes in many sports. Its potential is shown in the development of strength, power, and overall sports performance. The aim of the study was to verify inconsistent views on deep squats, technical design, and related health risks. METHODS For the purposes of the review, the terms "squat, knee, biomechanics, deep, patellofemoral, back squat, performance, arthritis, health, injury, risk" were used. RESULTS It turns out that the technique of performing a deep squat has its strict principles, which must be respected and which have a significant impact on the benefits and risks. From loading, the lower position represents an increase in compressive and shear forces on the patellofemoral joint, however, this is a natural state that is not risky. Health hazards cannot be based on analytical-mathematical models, which are insufficient in this aspect. Extreme long-term exposure carries the risk of permanent consequences in the form of osteoarthritis. For prophylaxis or convalescence, it is possible to use effective aids like sleeves, kinesio taping, bandage or "knee savers". CONCLUSIONS With optimal technique and sensible exercise selection, there is no greater risk in healthy individuals without degenerative anatomical changes. In order to assess the effects of the squat forces on the ankle, knee, hip, spine, it is necessary to consider the technique and also individual anatomical differences.
... Therefore, incorrect head movements can cause incorrect body compensation, resulting in injury [2,7,8]. Changes in the gaze direction and head position can affect the spine kinematics [1]; there have been many discussions on the expected effect and safety of squat exercise. ...
... It was found that the total squat score for the younger group was significantly higher than the middle and the older groups, but we surprisingly found that there was no difference between the middle and older aged participants. Squat performance has been studied between the younger and the older population, and squat is known as an appropriate rehabilitation exercise for post-ligament reconstruction surgery (44,45). To the best of our knowledge, this is the first time that squat exercise has been studied among younger, middle-aged, and older populations in Japan. ...
COVID-19 has changed our lives and limited our ability to have adequate physical activity (PA). It is necessary to replace outdoor PA with home-based fitness. However, people lack access, skills, and even motivation for home-based fitness. To address these issues, we designed a free access self-monitoring and coaching and music-based interactive online squat fitness system. Body weight squat was utilized for fitness exercise and evaluated based on three indices: knee width, hip depth, and rhythm. An online survey on changes in exercise due to the COVID-19 pandemic and exercise habits was conducted to investigate the effect of the COVID-19 pandemic on PA. We collected data from 557 respondents 5 months after the system first released and analyzed 200 visitors' performance on squat exercise and the other relevant parameters. Visitors were divided into three groups according to their age: younger, middle, and older groups. Results showed that the younger group had better squat performance than the middle and older groups in terms of hip depth and rhythm. We highlighted the lessons learned about the system design, fitness performance evaluation, and social aspects, for future study of the design and development of similar home-based fitness systems. We provided first-hand results on the relation between the COVID-19 pandemic and physical exercise among different age groups in Japan, which was valuable for policy making in the post-COVID-19 era.
... The average hip extension in the second section remained the same as in the first section, while the flexion value increased. It may be concluded that only the hip may not be held responsible for the shifting of the weight distribution, which is contrary to some studies [27,31,32]. The ROM of the ankle significantly increased by 10% compared to the first section. ...
Citation: Erman, B.; Ozkol, M.Z.; Ivanović, J.; Arslan, H.;Ćosić, M.; Yuzbasioglu, Y.; Dopsaj, M.; Aksit, T. The purpose of this study was to analyse in detail body weight squat (BWS)’ fatigue effect on the range of motions (ROM) of the hip, knee, ankle and ground reaction forces (GRF). Twenty male recreational athletes (24.0 ± 3.1 years, 178.85 ± 7.12 cm and 78.7 ± 11.45 kg) participated in this study. BWS were performed on four load cell platforms until the participants failed to continue. Participants performed 73 ± 27 repetitions and the duration to complete of the repetitions was 140.72 ± 62.28 s during the BWS exercise. The forefoot and hindfoot of the feet were on two load cells, thus, there were two under each foot. All of the data collected was divided into three sections for analysis (24 ± 9 repetitions for each). In terms of GRF of the fore feet and hind feet, significant differences and medium to large effect size were found between each section (p = 0.006~0.040, ES = 0.693~0.492). No significant differences were found between right and left leg in all sections. Significant differences were found in the ROM of the hip between the sections of first-third (p = 0.044, ES = 0.482) and second-third (p = 0.034, ES = 0.510), the ROM of the knee first-third (p = 0.014, ES = 0.602) and second-third (p = 0.005, ES = 0.701) and for the ROM of the ankle first-second (p = 0.045, ES = 0.479). As a result, end-of-exercise fatigue caused an increase in the ROM of the hip, knee and ankle. Thus, it is observed that fatigue induced increased ROM, also increases the GRF towards the forefeet.
... Sitting, lifting, and other movements and postures similar to the squat are often used in daily life, and as such, the squat is often used as an exercise to improve activities of daily living. It has been reported that the squatting strategy differs between the lower back pain group and the non-lower back pain group 10) , and it is known that the load on the lumbar region varies with the squatting strategy 11,12) . During the downward phase of the squat, the extensors of the lower extremities perform eccentric contractions, and during the upward phase, the extensors of the lower extremities perform concentric contractions to control the vertical movement of the center of gravity. ...
[Purpose] This study aimed to investigate the relationships among the changes in iliopsoas muscle thickness, hip angle, and lower limb joint moment during squatting in different pelvic positions to help in performing hip-dominant squatting exercises. [Participants and Methods] The participants were seven healthy adult males. The measurement task consisted of squatting with 60 degrees of knee flexion in three positions: the anterior, neutral, and posterior pelvic tilt positions. The iliopsoas muscle thickness was measured in the center of the inguinal region using ultrasonography. A three-dimensional motion analysis system was used to measure the joint angles and joint moments. [Results] There were no significant differences in pelvic angles between the pelvic positions. The hip angle differences were significantly higher in the anterior and neutral pelvic tilt positions compared to those in the posterior tilt position. Only the anterior pelvic tilt position had a significantly positive correlation with iliopsoas muscle thickness and hip angle differences. [Conclusion] Squatting in the neutral or posterior pelvic tilt position was not associated with hip angle and iliopsoas muscle thickness changes, whereas squatting in an anterior pelvic tilt position was associated with changes in the iliopsoas muscle thickness and hip flexion angle. Our findings suggest that activation of the iliopsoas muscle might be necessary to promote hip-dominant squatting.
... Biomechanical analysis offers insight to the underlying kinematics and kinetics of a training exercise, providing coaches and athletes conceptual understanding to bring objectivity to sport-specific exercise selection [16]. Investigating the musculoskeletal demand placed on the lower limb and pelvic-trunk joints is fundamental to biomechanical analyses of strength training exercises [17][18][19][20][21][22], although has yet to be undertaken for the hip thrust. Specifically, for the hip joint, whilst authors have proposed that the hip thrust requires a consistent hip extension moment and greater muscular "tension" when hip joint is close to full extension [4,5,7,8], there is currently no joint kinetic evidence to support these ideas. ...
Barbell hip thrust exercises have risen in popularity within the biomechanics and strength and conditioning literature over recent years, as a method of developing the hip extensor musculature. Biomechanical analysis of the hip thrust beyond electromyography is yet to be conducted. The aim of this study was therefore to perform the first comprehensive biomechanical analysis the barbell hip thrust. Nineteen resistance trained males performed three repetitions of the barbell hip thrust at 70% one-repetition maximum. Kinematic (250 Hz) and kinetic (1000 Hz) data were used to calculate angle, angular velocity, moment and power data at the ankle, knee, hip and pelvic-trunk joint during the lifting phase. Results highlighted that the hip thrust elicits significantly ( p < 0.05) greater bilateral extensor demand at the hip joint in comparison with the knee and pelvic-trunk joints, whilst ankle joint kinetics were found to be negligible. Against contemporary belief, hip extensor moments were not found to be consistent throughout the repetition and instead diminished throughout the lifting phase. The current study provides unique insight to joint kinematics and kinetics of the barbell hip thrust, based on a novel approach, that offers a robust evidence base for practitioners to guide exercise selection.
... These strategies are associated with changes in joint moments between the knee and the hip joint. For example, during the barbell back squat and landing tasks, a smaller trunk flexion will lead to an increase in the internal knee extension moment [32] which will likely be accompanied by an increase in quadriceps activation [33]. Future studies should investigate the effect of these different sagittal plane strategies during the single-leg squat on hip and knee loads in the frontal and transverse planes. ...
Background
Limited passive ankle dorsiflexion range has been associated with increased knee valgus during functional tasks. Increased knee valgus is considered a contributing factor for musculoskeletal disorders in the lower limb. There is conflicting evidence supporting this association. The extent of passive ankle dorsiflexion range is associated with dynamic ankle dorsiflexion range and the way how these variables are related to lower limb or trunk kinematics is unclear.
Research question
What is the association between passive ankle dorsiflexion range or dynamic ankle dorsiflexion range with shank, thigh, pelvis or trunk movements during the single-leg squat?
Methods
This is a cross-sectional study with a convenience sample. Thirty uninjured participants performed the single-leg squat with their dominant limb. Ankle, shank, thigh, pelvis and trunk 3D kinematics were recorded. Passive ankle dorsiflexion range was assessed through the weight-bearing lunge test and the dynamic ankle dorsiflexion range was defined as the ankle dorsiflexion range of motion in the sagittal plane during the single-leg squat.
Results
Greater passive ankle dorsiflexion range was associated with smaller thigh internal rotation (r= -.38). Greater dynamic ankle dorsiflexion range was associated with smaller trunk flexion (r = .59) and pelvis anteversion (r= -.47). Passive ankle dorsiflexion range and dynamic ankle dorsiflexion range were not associated.
Significance
Greater passive ankle dorsiflexion range seems to be associated with a better lower limb alignment during the single-leg squat, while dynamic ankle dorsiflexion range seems to reflect different lower limb and trunk kinematic strategies.
... This is congruent with the nature of the movement and the imposed tempo. Compared to the low-bar squat, the back squat places a greater demand on quadriceps muscles due to a more upright trunk position [81][82][83]. The tempo required participants to control the eccentric phase and pause in a deep squat position. ...
Background:
Self-administered massage interventions with a roller massager are commonly used as part of warm-ups and post-workout recovery routines. There is yet no clear consensus regarding the practical guidelines for efficient embedded interventions.
Objectives:
The present randomized crossover pilot trial aimed at examining the effects of a rolling intervention with a roller massager embedded within the rests periods of a resistance training protocol. The rolling intervention targeted quadriceps muscles.
Setting:
Participants (n = 14) performed two resistance training protocols expected to elicit momentary muscle failure. The protocol consisted in 10 sets of 10 rest-pause repetitions of back squats, with a poundage set up at 50% of the maximal one-repetition. Two min were allocated to recovery between sets. During the recovery periods, participants completed a rolling routine with a roller massager for 60 s (Roller-massager), or underwent passive recovery (Control). The total workload, concentric power, thigh circumference rate of perceived exertion (RPE) and delayed onset of muscle soreness (DOMS) from 24 h to 120 h after completion of the protocol were the dependent variables.
Results:
Roller-massager was associated with a reduction in total workload (-11.6%), concentric power (-5.1%) and an increase in perceived exertion compared to Control (p < 0.05). Roller-massager was also associated with reduced thigh circumference after the resistance training protocol, indicating reduced muscle swelling, and reduced DOMS 24 h to 120 h post-workout (p < 0.001).
Conclusion:
These findings support that embedded rolling with a roller massager hinders performance and increases effort perception. Embedded interventions may not be suitable during conditioning periods designed to maximize training intensity.
... Combined with knee kinematics changes (time to maximal flexion), such results suggest that expectations regarding a weight to lift trigger similar adaptations in patients experiencing mild cLBP and healthy individuals. Although no difference was noted in joint angles, probably due to high heterogeneity and relatively low loads, the current observations seems congruent with the broadly accepted idea that deeper knee flexion during squatting technique contributes to the unloading of hip and the back articulations [41]. Interestingly, minor differences were found in a few kinematic variables indicating that participants with LBP respond similarly, but not exactly as healthy individuals to load expectations. ...
Objective
This study aimed to investigate how load expectations modulate neuromuscular and postural strategies in the anticipation of a freestyle lifting task with varying expected loads in individuals with and without chronic low back pain (cLBP).
Methods
Forty-seven participants, 28 with cLBP pain and 19 without, were recruited and completed a series of freestyle lifting trials (3 sets of box lifted for a total of 36 lifts). Verbal cues were used to modulate their expectations about the boxes’ weight: no expectation, lighter or heavier load expectations. Following each set, participants rated their perceived exertion on a visual analog scale. During the lifting protocol, kinematics (time to maximal flexion, angular velocity and joint angles), electromyography muscle activity (erector spinae and quadriceps) and center of pressure displacement were simultaneously recorded.
Results
Results showed that time to maximal knee flexion was modulated by load expectations in both groups (mean lighter load expectations = 1.15 ± 0.32 sec.; mean heavier load expectations = 1.06 ± 0.31 sec.). Results also showed a load expectations X group interaction for that time to maximal hip and lumbar flexion. Time to maximal hip flexion decreased with heavier load expectations (mean lighter load expectations = 1.20 ± 0.36; mean heavier load expectations = 1.16 ± 0.33) for cLBP only. Time to maximal lumbar flexion increased with heavier load expectation (mean lighter load expectations = 1.41 ± 0.27 sec.; mean lighter load expectations = 1.46 ± 0.29 sec.) for participants without LBP. However, no difference in lumbar, hip nor knee angles were observed between groups or conditions. Results highlighted significant load expectation effects for erector spinae electromyography activity, as lower muscle activations was observed for both groups with heavier load expectations (mean = 0.32 ± 0.15), compared to lighter load expectations (mean = 0.52 ± 0.27). Force plates analyses did not reveal any significant load expectation effects.
Conclusion
Present findings showed that load expectations modulate movement strategies and muscle activation similarly but not identically in individuals with chronic low back pain and healthy adults during freestyle lifting. Results of the present study partially differ from previous studies and suggest only minor differences in lifting strategies between healthy individuals and individuals with cLBP experiencing low level of pain and disability. More studies are needed to investigate the potential role of load expectations in the development and persistence of chronic low back pain.
... The back squat requires participation of every lower extremity muscle in some capacity (isometric, concentric, or eccentric) [6][7][8][9][10][11]. In general, the loads for the hip and knee joints comprise 80-90%, whereas the ankle contributes 0-20% of the total lower extremity moment to lift the system mass during the upward portion of back squats [6,[12][13][14][15][16][17][18]. Various repetition and set schemes for the back squat may be implemented depending on the training goal, including submaximal and supramaximal training [9,19,20]. ...
Previous literature suggests the sticking region, the transition period between an early peak concentric velocity to a local minimum, in barbell movements may be the reason for failing repeated submaximal and maximal squats. This study determined the effects of load on lower extremity biomechanics during back squats. Twenty participants performed the NSCA's one-repetition maximum (1RM) testing protocol, testing to supramaximum loads (failure). After completing the protocol and a 10-minute rest, 80% 1RM squats were performed. Statistical parametric mapping was used to determine vertical velocity, acceleration, ankle, knee, and hip sagittal and frontal plane biomechanics differences between 1RM, submaximum, and supramaximum squats (105% 1RM). Vertical acceleration was a better discriminative measure than velocity, exibiting differences across all conditions. Supramaximum squats emphasized knee moments, whereas 1RM emphasized hip moments during acceleration. Submaximum squats had reduced hip and knee moments compared to supramaximum squats, but similar knee moments to 1RM squats. Across all conditions, knee loads mirrored accelerations and a prominent knee (acceleration) to hip (sticking) transition existed. These results indicate that 1) submaximum squats performed at increased velocities can provide similar moments at the ankle and knee, but not hip, as maximal loads and 2) significant emphasis on hip strength is necessary for heavy back squats.
... In a study done by Escamilla et al. (2001) it was shown that wide stance squats compared to narrow stance squats exhibited substantially larger hip extensor moments at the hip. Additionally, Fry et al. (2009) found that when restricting the squat and causing the shins to stay more vertical, larger torques at the hip than at the knee were detected. Furthermore, when HTs were assessed, Contreras et al. (2015) showed that HT produced substantial recruitment of the gluteal musculature. ...
Increased involvement of the hip musculature during some movements is associated with enhanced performance and reduced injury risk. However, the impact of hip dominant weight training methods on movement strategy has seen limited attention within the literature. The aim of this study was to evaluate if a 9-week hip dominant weight training intervention promotes a more hip dominant movement strategy leading to an improvement in countermovement jump performance. Twenty-two experienced female dancers were recruited and separated into an intervention (age 24.4 ± 6.3 years, body height 165.5 ± 5.8 cm, body mass 65.9 ± 5.6 kg) and a control (age 22.9 ± 5.6 years, body height 163.3 ± 5.4 cm, body mass 57.4 ± 6.8 kg) group. The intervention group participated in a 9-week hip dominant training intervention, which consisted of a wide stance back squat, Romanian deadlift, hip thrusters, and a bent over row. Hip and knee kinematics and kinetics, and countermovement jump performance were assessed pre and post training. Significant interaction effects were found for peak hip joint moment (p = 0.030, η2 = 0.214) and countermovement jump performance (p = 0.003, η2 = 0.356), indicating an increase in peak hip joint moment and countermovement jump performance for the intervention group. Specifically, the intervention group showed a mean increase in jump height of 11.5%. The data show that the use of a hip dominant weight training strategy can improve hip contribution in the propulsion phase of the countermovement jump. Strength and conditioning specialists should incorporate hip dominant weight training exercises to increase hip strength and improve performance.
... 36 Interactively, restricting forward movement of the knees may minimize stress on the knees, and it is likely that forces are inappropriately transferred to the hips and low-back region. 37 Therefore, it is also necessary to strengthen psoas and gluteal muscle exercise after UKA to ensure the stability of the knee. Last but not the least, we have some thoughts about the overall design of this study. ...
Few studies have assessed knee range of motion (ROM) and moments of patients with mobile-bearing unicompartmental knee arthroplasty (MB UKA) during active deep flexion activities. We analyze knee kinematic and kinetic parameters during postoperative squatting-standing activity, aiming to evaluate the efficacy of MB UKA and postoperative rehabilitation progress. This was a clinical cohort study. We followed up with 37 patients diagnosed with medial knee osteoarthritis (OA) with primary UKA. After screening 31 patients were recruited to take gait tests. Squatting-standing activities were performed under the test of 10-camera motion analysis system and force plates preoperatively at different stages after UKA (12, 18, and 24 months). The average duration of follow-up was 24.4 months (from 22.8 to 26.7 months). Hip-knee-ankle angle improved significantly compared with pre-UKA as well as scores of American Knee Society Score, numeric rating scale, ORS, and Western Ontario and McMasters. University Osteoarthritis Index. About 83.6% (31/37) of follow-up patients completed squatting-standing activity independently. At 1-year follow-up, peak varus angle (20.6 ± 2.8 degrees), internal rotation angle (13.6 ± 1.8 degrees), extensor moment (1.44 ± 0.04N*m/kg), and internal rotator moment (0.02 ± 0.005N*m/kg) of UKA knees were inferior to contralateral knees. Peak adductor moment (0.76 ± 0.05N*m/kg) was superior to contralateral knees. At 2-year follow-up, peak flexion angle (125.0 ± 2.8 degrees) showed a growing trend meanwhile extensor (1.70 ± 0.03N*m/kg) and adductor (0.68 ± 0.06 N*m/kg) moment closely resembled those of the contralateral knee. MB UKA could alleviate the affected knee mainly in flexion-extension ROM and moment meanwhile did not affect the biomechanical indicators of healthy limbs. OA knees in the early postoperative period showed decreased extensor moment and increased adductor moment during active deep flexion activity. Better ROM and relatively more natural extensor and adductor moment of UKA knee with rehabilitation time increasing may predict ideal rehabilitation outcome in the medium or longer term.
... the squat has been the subject of many biomechanical evaluations in the areas of kinetics, kinematics, and muscle recruitment and in various stance and load conditions [4]. the primary muscles involved in squats surround the hip and knee joints (e.g. quadriceps, gluteal muscles), which generate 80-90% of the lower extremity moments [2,[6][7][8]. in addition to stance and load variations, many training accessories exist for the squat that athletes and recreational exercisers use for enhancing training or preventing injury. ...
PurposeTo compare the spine hinge evaluated by sacral inertial measurement unit (IMU) versus both lumbar and sacral IMUs and to assess the influence of clinical variables on the spine hinge.Methods
The study included 20 healthy participants (10 men and 10 women) and 18 participants (6 men and 12 women) with low back pain. Participants performed a bodyweight squat with IMU sensors attached to the lumbar spine, sacrum, and lateral thigh. The spine hinge was evaluated by two methods: lumbosacral hinge (LS hinge), defined as an abrupt increase in LS flexion, and sacral hinge, defined as a change in sacral direction from forward to backward. The amount of and ratio (LS ratio) between sacral and lumbar rotations were evaluated.ResultsThe spine hinge detected only from the sacral IMU showed a high degree of agreement with that detected from both IMUs. The LS hinge occurred at a lower depth in females than in males (p = 0.001). Females had greater sacral rotation (p = 0.012) and a higher LS ratio (p < 0.001) than males. A larger passive hip flexion range was associated with later LS hinge occurrence in females (p = 0.041) but not in males (p = 0.965). Trunk muscle strength and presence of low back pain were not significant in either sex.ConclusionIMUs can detect the squat depth when the spine hinge occurs. A single sacral IMU is sufficient to detect the spine hinge. The movement patterns differ between sexes during squats, which should be considered to achieve the optimal squat depth.
The three most fundamental variations of the barbell squat with the bar placed on the shoulders are the high-bar back squat (HBBS), the low-bar back squat (LBBS), and the front squat (FS). There are significant kinematic, kinetic, and biomechanical distinctions between these variations that should be considered in the exercise selection. In comparison to the high-bar variations, the LBBS results in a greater hip joint torque and greater activation of the hip extensor muscles. In contrast, during the FS, the m. quadriceps is utilized more compared to the other two variations due to an increased torque in the knee joint. Regarding the relation between hip and knee joint torques, the HBBS is an intermediate and more balanced exercise variation than the LBBS and the FS. The HBBS is a fundamental exercise in athletic conditioning and a suitable starting point for novices, whereas the LBBS is preferred when the primary objective is to maximize weightlifting performance. The FS is crucial for athletes performing the clean and its derivates since it trains the required body position for a successful catch and might be the biomechanically advantageous variation if the goal is to target the knee extensor muscles. However, the differences in terms of knee extensor demands, muscle activation and kinematics between the HBBS and FS seem to be minimal, as the literature indicates similar results when comparing the FS to the HBBS. As far as analysis methods are concerned, even though 3D movement analysis is regarded as the gold standard for motion capture and analyzing kinematics, 2D models seem to serve as a valid initial guide in order to understand the kinematics and biomechanics of different squat variations.
Squatting is a common daily activity and fundamental exercise in resistance training and closed kinetic chain programs. The aim of the present study was to investigate the effects of an experimentally induced weakness of the gluteal muscles on joint kinematics, reactions forces (JRFs), and dynamic balance performance during deep bilateral squats in healthy young adults. Ten healthy adults received sequential blocks of 1) branch of the superior gluteal nerve to the tensor fasciae latae (SGNtfl) muscle, 2) superior gluteal nerve (SGN), and 3) inferior gluteal nerve (IGN) on the dominant right leg. At the control condition and following each block, the participants were instructed to perform deep bilateral squats standing on two force plates. Hip, knee, ankle, and pelvis kinematics did not differ significantly following iatrogenic weakness of gluteal muscles. The most important finding was the significant differences in JRFs following SGN and IGN block, with the affected hip, patellofemoral, and ankle joint demonstrating lower JRFs, whereas the contralateral joints demonstrated significantly higher JRFs, especially the patellofemoral joint which demonstrated an average maximum difference of 1.43 x body weight compared to the control condition. When performing a deep bilateral leg squat under SGN and IGN block, the subjects demonstrated an increased center of pressure (CoP) range and standard deviation (SD) in mediolateral compared to the control condition. These results imply that squat performance changes significantly following weakness of gluteal muscles and should be considered when assessing and training athletes or patients with these injuries. This article is protected by copyright. All rights reserved.
Objectives:
The effect of knee position on joint moments during squats has been studied; however, the effect of trunk angle has been less well investigated. This study evaluated the effect of both trunk and knee sagittal plane position on the distribution of moments between the hip and knee extensors during the bilateral squat.
Design:
Observational study.
Setting:
Biomechanics laboratory.
Participants:
One hundred individuals performed bilateral squats.
Main outcome measures:
Motion and force data were collected using motion capture and force plates. Trunk and shank angles and hip and knee moments were calculated. A linear regression was used to associate the ratio between the hip and knee moments (hip-to-knee moment ratio) with the sagittal plane trunk and shank angles, while accounting for six squat depths (between 60° and 110° of knee flexion) and side.
Results:
Trunk angle and shank angle each contributed to the hip-to-knee moment ratio (P < .001) with trunk accounting for a higher proportion of variance than the other variables. The hip-to-knee moment ratio increased with increasing trunk angle and with decreasing shank angle.
Conclusions:
This large cohort study supports the use of trunk position to instruct squat technique with the goal of modifying hip and knee moments.
The purpose was to specify lower extremity joint angles in different squats for the future development of adequate computational models of the joints.
Methods: We investigated joint angles in the lower extremity joints in 103 athletes in different types of squats with and withoutadded weight (barbell) 75% of 1 repetition maximum.results. the mean knee and hip flexion and ankle dorsiflexion angles in horizontal squats are respectively 113.42°, 128.21°, and 23.27°; in half-squats 70.60°, 87.94°, and 15.60°; in lunges 98.04°, 96.36°, and 8.02°; in Smith machine squats 94.42°, 106.28° and 4.46°. in a horizontal squat with a barbell, the knee joint flexion and the ankle joint dorsiflexion angles are significantly larger(by 4.56° and 3.11°, respectively) than in squats without added weight. the knee joint flexion and ankle dorsiflexion angles inlunges are significantly less in barbell squats (by 4.15° and 4.37°, respectively). the knee flexion angle in horizontal barbellsquats in male athletes is significantly larger than in female athletes (by 4.71°).
Conclusions: The mean knee and hip flexion and ankle dorsiflexion angles in different types of squats are established and maybe used for further research. Horizontal squats produce greater lower extremity joint angles.
Background
Performance asymmetries between the lower limbs have been reported across a variety of variables and for numerous motor tasks including double leg squats. Additionally, the degree of symmetry is often used as a recovery metric during rehabilitation programs.
Hypothesis/Purpose
The purpose of this investigation was to examine leg asymmetry during a bodyweight double leg squat task and assess the effects of squat speed in a physically active population.
Study Design
Cross-over Study Design.
Methods
Eighteen healthy individuals completed two sets of 20 squats at two tempos (preferred tempo and 60 bpm) while ground reaction force and center of pressure data were recorded using dual force plates. Peak vertical ground reaction force, force impulse, and center of pressure (COP) standard deviation in the anterior-posterior (AP) and mediolateral (ML) direction were calculated and analyzed to identify any differences between legs, tempo, and as a function of repetitions. Significance was set at ρ ≤ .05.
Results
The subjects exhibited greater ground reaction forces during the self-paced tempo compared to the metronome-paced tempo ( F 1,79 = 14.48, p < .001) with the preferred leg generating larger values than the non-preferred leg during the self-paced condition. There was also a significant tempo x leg interaction for force impulse ( F 1,79 = 5.927, p = 0.015). A greater amount of COP variability was found in the preferred leg compared to the non-preferred leg in both the AP ( F 1,79 = 30.147, p < 0.001) and ML ( F 1,79 = 41.204, p < 0.001) directions.
Conclusions
These findings highlight the importance of considering multiple levels of analysis when assessing lower limb symmetry as separate variables may provide differential evidence for asymmetry. Practically, these results emphasize the need for coaches and practitioners to consider different degrees of lower limb asymmetries that may impact the development and design of strength and rehabilitation programs.
Level of Evidence
3
The safety squat bar squat (SSBS) is a unique squat variation performed with its namesake barbell. In addition to describing proper SSBS technique, this column reviews SSBS biomechanics, criteria for exercise performance, programming opportunities for special populations, and descriptions of 3 additional exercise variations with suggestions for use.
vonGaza, GL, and Chiu, LZF. Comparison of alternative methods to improve weight-bearing sagittal plane anterior leg rotation. J Strength Cond Res 35(12): 3315-3321, 2021-Promoting rearfoot plantar flexion may permit greater sagittal plane anterior leg rotation in weight-bearing tasks. Anterior leg rotation, where the proximal tibia translates forward, is required for tasks such as squatting and landing from a jump. Twenty-eight individuals with less than 25° anterior leg rotation during a weight-bearing lunge test were enrolled and randomly assigned to self-massage and stretching only (n = 15; 14 subjects retained) or self-massage and stretching plus gastrocnemius exercise (n = 13). Anterior leg rotation was assessed during a weight-bearing lunge test and a partial squat; 95% confidence interval (95% CI) of the change score and Cohen's d effect size were calculated. Anterior leg rotation in the weight-bearing lunge increased in the self-massage and stretching only (left: 95% CI [2.1°-5.4°], d = 1.14; right: 95% CI [2.3°-6.0°], d = 1.22) and self-massage and stretching plus gastrocnemius exercise (left: 95% CI [2.3°-7.5°], d = 1.71; right: 95% CI [4.2°-8.6°], d = 1.48) groups. There were no changes in anterior leg rotation in the partial squat for self-massage and stretching only (left: 95% CI [-1.2° to 2.5°], d = 0.15; right: 95% CI [-0.5° to 2.6°], d = 0.24) or self-massage and stretching plus gastrocnemius exercise (left: 95% CI [-0.2° to 4.8°], d = 0.55; right: 95% CI [-0.2° to 4.0°], d = 0.59) groups. Increases in anterior leg rotation in the weight-bearing lunge may be due to decreased passive stiffness in the plantar structures.
In this paper, we explore the use of numerical optimization techniques to synthesize realistic human-like squat motions. For this purpose, a two-step optimization-based synthesis scheme, inspired by whole-body controllers from robotics, is proposed. In step I, a reduced set of physically-relevant criteria is optimized to produce the state and torque patterns with a joint-actuated model. Afterwards, muscle activities are computed in step II with a muscle-actuated model. To validate the approach, the synthesized kinetic and muscle activities of two squat strategies obtained through the scheme are analyzed and compared to captured movement and electromyographic data. The outcome shows that it is feasible to synthesize human-like squats without motion capture data while exhibiting several main features of the motor function strategies. However, disparities related to the simple modeling of the actuators are observed.
Evaluation of the compressive load acting on the lumbar spine (L3-L4) during half-squat exercises executed with a barbell resting on the subject's shoulders was undertaken. The kinematics of the upper body segments of two male and two female subjects as well as the barbell were described using data obtained by means of an optoelectronic system (CoSTEL). L3-L4 compressive load was calculated using a model of the anatomy of the trunk musculoskeletal system. Filtered surface electromyographic trunk flexor recordings from the obliquus externus and rectus abdominis and trunk extensor erectores spinae muscles as well as measurement of the ground reaction forces were also carried out for predicted result validation. During half-squat exercises with barbell loads in the range 0.8 to 1.6 times body weight the compressive loads on the L3-L4 segment vary between 6 and 10 times body weight. Erectores spinae contraction force was predicted to be between 30 and 50% of the relevant maximal isometric force. The magnitude of trunk flexion was found to be the variable which influenced most spinal compression load.
Three high-skilled powerlifters performed parallel squats with different burden weights. Using a sagittal plane biomechanical model, the moments of force about the bilateral axes of the lumbo-sacral, hip, knee, and ankle joints were determined. A local biomechanical model of the knee was used in order to calculate the knee joint forces induced. The greatest moments were found in the lumbo-sacral joint. The maximum hip moment was greater than that of the knee moment which was greater than the ankle moment. The knee moment had a flexing direction and reached its maximum at the deepest position of the squat, while the lumbo-sacral and hip moments were found to reach their maxima during the first half second of the ascent. One lift that caused a bilateral quadriceps tendon rupture was stimulated and was found to give a maximum knee flexing moment ranging between 335 Nm and 550 Nm. This moment induced a force in each quadriceps tendon of between 10.9 kN and 18.3 kN at the occasion of rupture.
The purpose of this study was to determine whether regression equations could be developed, as an alternative to biochemical models, to predict the peak L4(L5 disc compression force during dynamic, sagittal plane lifting. Eighteen male subjects performed a squat and a stoop lift with loads of 6, 14, 22, 29, and 32 kg. Each lift was analysed with a linked segment biomechanical model that output the compression force time history during the lift. The peak compression served as the dependent variable for two regression models. The independent variables in each model were measures which described the subject's body dimensions, body posture, internal lifting mechanics, load location and load effects. A ‘lab’ model was developed (R=0·93) which required only four inputs and had an RMS error of only 8·3% between the biomechanical model estimate of the peak L4/L5 disc compression force and that predicted from the regression equation. A seven variable ‘field’ model was developed with an R of 0·90 and an RMS error of 9·7%. It was concluded that both of the proposed models were potentially useful to the practising ergonomist interested in easily and quickly estimating lumbar compression forces during dynamic sagittal plane lifting.
The purpose of this study was to formulate a kinematic model of performance in the parallel squat, based on the movement characteristics of world class powerlifters, and to determine if the model could be utilized to assess technique differences between high and less-skilled subjects. Two trials were recorded via high-speed cinematography from a side view of twenty-four Ss during the 1974 U.S. Senior National A.A.U. Powerlifting Championships. Vertical and horizontal displacement patterns of three joint centers and the center of the bar were determined for the best trial of each S. These data were subsequently used to calculate desired linear and angular coordinates, velocities and accelerations for body segments and bar. Results indicated that although there was some variability in most kinematic parameters, vertical bar velocity was found to be very similar among competitors, even for Ss of different bodyweight. Consequently, the vertical velocity of the bar was selected as the parameter around which performance could be modeled in the parallel squat. A model was formulated by plotting the mean values in vertical bar velocity for all Ss scaled to a common time base. The resultant model was contrasted with vertical bar velocity data for less-skilled Ss to assess typical performance errors.
(C)1977The American College of Sports Medicine
This study investigated the muscular torques and joint forces during the parallel squat as performed by weightlifters. (JD)
The purpose of this study was to formulate a kinematic model of performance in the parallel squat, based on the movement characteristics of world class powerlifters, and to determine if the model could be utilized to assess technique differences between high and less-skilled subjects. Two trials were recorded via high-speed cinematography from a side view of twenty-four Ss during the 1974 U.S. Senior National A.A.U. Powerlifting Championships. Vertical and horizontal displacement patterns of three joint centers and the center of the bar were determined for the best trial of each S. These data were subsequently used to calculate desired linear and angular coordinates, velocities and accelerations for body segments and bar. Results indicated that although there was some variability in most kinematic parameters, vertical bar velocity was found to be very similar among competitors, even for Ss of different bodyweight. Consequently, the vertical velocity of the bar was selected as the parameter around which performance could be modeled in the parallel squat. A model was formulated by plotting the mean values in vertical bar velocity for all Ss scaled to a common time base. The resultant model was contrasted with vertical bar velocity data for less-skilled Ss to assess typical performance errors.
The structural properties of 27 pairs of human cadaver knees were evaluated. Specimens were equally divided into three groups of nine pairs each based on age: younger (22 to 35 years), middle (40 to 50 years), and older (60 to 97 years). Anterior-posterior displacement tests with the intact knee at 30 degrees and 90 degrees of flexion revealed a significant effect of knee flexion angle, but not of specimen age. Tensile tests of the femur-ACL-tibia complex were performed at 30 degrees of knee flexion with the ACL aligned vertically along the direction of applied tensile load. One knee from each pair was oriented anatomically (anatomical orientation), and the contralateral knee was oriented with the tibia aligned vertically (tibial orientation). Structural properties of the femur-ACL-tibia complex, as represented by the linear stiffness, ultimate load, and energy absorbed, were found to decrease significantly with specimen age and were also found to have higher values in specimens tested in the anatomical orientation. In the younger specimens, linear stiffness (242 +/- 28 N/mm) and ultimate load (2160 +/- 157 N) values found when the femur-ACL-tibia complex was tested in the anatomical orientation were higher than those reported previously in the literature. These values provide new baseline data for the design and selection of grafts for ACL replacement in an attempt to reproduce normal knee kinematics.
The purpose of this study was to compare the knee extensor demands and low back injury risks of the front and back squat exercises. Highly strength-trained college-aged males (n = 8), who performed each type of squat (Load = 75% of front squat one repetition maximum), were filmed (50 fps) from the sagittal view. The body was modeled as a five link system. Film data were digitized and reduced through Newtonian mechanics to obtain joint forces and muscle moments. Mean and individual subject data results were examined. The maximum knee extensor moment comparison indicated similar knee extensor demands, so either squat exercise could be used to develop knee extensor strength. Both exercises had similar low back injury risks for four subjects, but sizable maximum trunk extensor moment and maximum lumbar compressive and shear force differences existed between the squat types for the other subjects. The latter data revealed that with the influence of trunk inclination either exercise had the greatest low back injury risk (i.e., with greater trunk inclination: greater trunk extensor demands and lumbar shear forces, but smaller lumbar compressive forces). For these four subjects low back injury risk was influenced more by trunk inclination than squat exercise type.
Past studies have produced conflicting results as to the effect of squat exercises on knee stability. One hundred male and female college students were measured using a knee ligament arthrometer on nine tests of knee stability. Over an 8-wk training program, full or half squats did not consistently affect knee stability compared to non-squatting controls. To measure the effect of long-term squat training 27 male powerlifters (14 Elite or Master Class) and 28 male weightlifters (8 Elite or Master Class) were measured on the same tests. Powerlifters were significantly tighter than controls on the anterior drawer at 90 degrees of knee flexion. Both powerlifters and weightlifters were significantly tighter than controls on the quadriceps active drawer at 90 degrees of knee flexion. Data on powerlifters and weightlifters were also analyzed by years of experience and skill level. No effect of squat training on knee stability was demonstrated in any of the groups tested.
Virtually all types of collagenous tissues have been transferred in and around the knee joint for intra-articular and extra-articular ligament reconstructions. However, the mechanical properties (in particular, strength) of such grafts have not been determined in tissues from young adult donors, where age and disuse-related effects have been excluded. To provide this information, we subjected ligament graft tissues to high-strain-rate failure tests to determine their strength and elongation properties. The results were compared with the mechanical properties of anterior cruciate ligaments from a similar young-adult donor population. The study indicated that some graft tissues used in ligament reconstructions are markedly weak and therefore are at risk for elongation and failure at low forces. Grafts utilizing prepatellar retinacular tissues (as in certain anterior-cruciate reconstructions) and others in which a somewhat narrow width of fascia lata or distal iliotibial tract is utilized are included in this at-risk group. Wider grafts from the iliotibial tract or fascia lata would of course proportionally increase ultimate strength. The semitendinosus and gracilis tendons are stronger, having 70 and 49 per cent, respectively, of the initial strength of anterior cruciate ligaments. The bone-patellar tendon-bone graft (fourteen to fifteen millimeters wide, medial or central portion) was the strongest, with a mean strength of 159 to 168 per cent of that of anterior cruciate ligaments. Patellar tendon-bone units, based on grip-to-grip motions, were found to be three to four times stiffer than similarly gripped anterior cruciate ligaments, while gracilis and semitendinosus tendon preparations had values that were nearly identical to those of anterior cruciate ligaments.(ABSTRACT TRUNCATED AT 250 WORDS)
Successful reconstruction of ligaments requires knowledge of the properties of the intact ligament. This study examined the strength of the human posterior cruciate ligament (PCL), treating it as two separate fibre bundles. It was hypothesized (i) that the mechanical and material properties of the anterolateral (aPC) and the posteromedial (pPC) bundles of the PCL were significantly different and (ii) that previous studies have underestimated the strength of the whole PCL. The properties of the two bundles were measured in 10 donors (53-98 yr). The mechanical and material properties of the two bundles were found to be significantly different, the aPC was six times as strong as the pPC. The aPC had a mean strength of 1.6 kN. Allowing for age effects this study suggests that the strength of the PCL in young active people is 4 kN, which is higher than that suggested by previous studies. Because of the difference in the strengths of the two bundles, we conclude that the aPC is primarily responsible for the stabilising effect of the PCL. We therefore recommend that PCL reconstructions should be centered on the middle of the aPC bundle.
The purpose of this study was to quantify the amount of anterior tibial displacement occurring in anterior cruciate ligament-deficient knees during two types of rehabilitation exercises: 1) resisted knee extension, an open kinetic chain exercise; and 2) the parallel squat, a closed kinetic chain exercise. An electrogoniometer system was applied to the anterior cruciate ligament-deficient knee of 11 volunteers and to the uninvolved normal knee in 9 of these volunteers. Anterior tibial displacement and the knee flexion angle were measured during each exercise using matched quadriceps loads and during the Lachman test. The anterior cruciate ligament-deficient knee had significantly greater anterior tibial displacement during extension from 64 degrees to 10 degrees in the knee extension exercise as compared to the parallel squat exercise. In addition, the amount of displacement during the Lachman test was significantly less than in the knee extension exercise, but significantly more than in the parallel squat exercise. No significant differences were found between measurements in the normal knee. We concluded that the stress to the anterior cruciate ligament, as indicated by anterior tibial displacement, is minimized by using the parallel squat, a closed kinetic chain exercise, when compared to the relative anterior tibial displacement during knee extension exercise.
Eight Swedish national class weightlifters performed "high-bar" squats and six national class powerlifters performed "low-bar" squats, with a barbell weight of 65% of their 1 RM, and to parallel- and a deep-squatting depth. Ground reaction forces were measured with a Kistler piezo-electric force platform and motion was analyzed from a video record of the squats. A computer program based on free-body mechanics was designed to calculate moments of force about the hip and knee joints. EMG from vastus lateralis, rectus femoris, and biceps femoris was recorded and normalized. The peak moments of force were flexing both for the hip and the knee. The mean peak moments of force at the hip were for the weightlifters 230 Nm (deep) and 216 Nm (parallel), and for the powerlifters 324 Nm (deep), and 309 Nm (parallel). At the knee the mean peak moments for the weightlifters were 191 Nm (deep) and 131 Nm (parallel), and for the powerlifters 139 Nm (deep) and 92 Nm (parallel). The weightlifters had the load more equally distributed between hip and knee, whereas the powerlifters put relatively more load on the hip joint. The thigh muscular activity was slightly higher for the powerlifters.
Although closed (CKCE) and open (OKCE) kinetic chain exercises are used in athletic training and clinical environments, few studies have compared knee joint biomechanics while these exercises are performed dynamically. The purpose of this study was to quantify knee forces and muscle activity in CKCE (squat and leg press) and OKCE (knee extension).
Ten male subjects performed three repetitions of each exercise at their 12-repetition maximum. Kinematic, kinetic, and electromyographic data were calculated using video cameras (60 Hz), force transducers (960 Hz), and EMG (960 Hz). Mathematical muscle modeling and optimization techniques were employed to estimate internal muscle forces.
Overall, the squat generated approximately twice as much hamstring activity as the leg press and knee extensions. Quadriceps muscle activity was greatest in CKCE when the knee was near full flexion and in OKCE when the knee was near full extension. OKCE produced more rectus femoris activity while CKCE produced more vasti muscle activity. Tibiofemoral compressive force was greatest in CKCE near full flexion and in OKCE near full extension. Peak tension in the posterior cruciate ligament was approximately twice as great in CKCE, and increased with knee flexion. Tension in the anterior cruciate ligament was present only in OKCE, and occurred near full extension. Patellofemoral compressive force was greatest in CKCE near full flexion and in the mid-range of the knee extending phase in OKCE.
An understanding of these results can help in choosing appropriate exercises for rehabilitation and training.
Coaches round table: The squat and its application to athletic performance
- K Klein
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- T Mclaughun
- P O Shea
- And D Wathen
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A comparison of methods for determining kinematic properties of three barbell squat exercises
- A C Fry
- T A Aro
- J A Bauer
- And W J Kraemer
FRY, A.C., T.A. ARO, J.A. BAUER, AND W.J. KRAEMER. A comparison of methods for determining kinematic properties of
three barbell squat exercises. J. Hum. Move. Stud. 24:83-95. 1993.
The deep squat exercise as utilized in weight training for athletes and its effect on the ligaments of the knee
KLEIN, K.K. The deep squat exercise as utilized in weight training for athletes and its effect on the ligaments of the knee. J.
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Comparison of closed and open chain kinetic exercise in the anterior cruciate ligament-deficient knee Acknowledgments The authors would like to thank L Scruggs for their assistance with the data collection and their contributions to the preparation of this manuscript. Address correspondence to Dr
- H J Yack
- C E Collins
- T J Whieldon T Ramsey
- G Calhoon
- M Matuszak
- T Ireland
- D Bullen
- L E Wood
- P Grindstaff
YACK, H.J., C.E. COLLINS, AND T.J. WHIELDON. Comparison of closed and open chain kinetic exercise in the anterior cruciate ligament-deficient knee. Am. J. Sports Med. 21:49–54. 1993. Acknowledgments The authors would like to thank L.T. Ramsey, G. Calhoon, M. Matuszak, T. Ireland, D. Bullen, L.E. Wood, P. Grindstaff, and M. Scruggs for their assistance with the data collection and their contributions to the preparation of this manuscript. Address correspondence to Dr. Andrew C. Fry, afry@memphis.edu.