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Does segment length influence the hip, knee and ankle coordination during the squat movement?
Abstract
Background: The back squat exercise is a common and essential clinical rehabilitation exercise. As a compound movement of the lower limbs the cues to optimal movement technique are complex and difficult to identify. The aim of this study was to determine the influence of lower limb segment lengths on the biomechanics of movement when performing the back squat exercise.
Methods: Using 3D kinematic analysis the 28 subjects (male n= 16, female n= 12) performed four sets of eight squats. The four independent variables were: load – (i) body-weight with no external load, and (ii) body-weight plus 50% body-weight external load; and width of stance – (iii) narrow stance equal to ASIS width; and (iv) wide equal to twice ASIS width.
Findings: The total squat pattern was different for genders and limb length correlations showed that genders created movement patterns of the lower body in squatting, which may have resulted due to these limb length differences. Males typically lean more forward allowing their spine to create greater movement and depth during the squat. Females utilise the knees and sacrum to adjust for depth, achieve greater hip flexion, and remain upright during the squat. The frequent correlations for limb lengths with the knees in females suggest females utilise the knees as a strategy to maintain synchronisation of the squat.
Interpretation: Taller women typically achieved greater knee angles, and taller men achieved smaller hip angles. Males and females do create different movement strategies for the squat movement and coaches and trainers should allow for this in both teaching and cueing of the squat movement pattern.
... Experiments conducted exclusively with male volunteers showed variations in the range of motion lead to changes in strength development, activation, and synchronization of motor units [11,12]. However, men and women have different strategies to perform the squat in addition to the range of motion, with women presenting greater knee flexion and men presenting greater trunk flexion while performing the squat with greater range of motion [13]. Still regarding squat kinematics, differences between men and women were reported in the hip joint amplitude (greater flexion) and knee joint amplitude (increase in valgus). ...
... Contreras et al. [19] found no differences in the activation of the vastus lateralis (VL), gluteus maximus (GM), and BF muscles relative to the range of motion in the squat. To our knowledge, this is one of the few studies that try to relate these variables exclusively to females, but the studies did not report in their findings the relationship between activation and muscle actions [13,18,20]. ...
... [21], who found higher VL activation with increasing squat range. The higher VL activation during the concentric action of 140 • squats occurred because women perform higher knee flexion when the objective is to perform greater squat depth than men [13]. According to these authors, women tend to flex the knee more at the expense of the hip joint when performing 140 • squats. ...
Purpose: To analyze the muscle activation of the rectus femoris (RF), vastus lateralis (VL), gluteus maximus (GM), and biceps femoris (BF) in concentric and eccentric actions in the squat at 90 • and 140 • range of motion. Methods: Thirty-five women (32.9 ± 7.4 years; 64.5 ± 11.5 kg; 1.63 ± 0.1 m; BMI: 24.2 ± 2.9 kg/m 2 ; %fat: 24.9 ± 6.5%) experienced exercise for at least eight weeks. Electrodes were positioned in standardized locations. The signals were acquired by an A/D SAS1000 V8 converter and the electromyographic activity normalized in the percentage of the highest produced value (%RMS). The data were analyzed using repeated measures two-way ANOVA, with effect size (η 2) and differences calculated in percentage points (∆ p.p.). Results: The RF (p = 0.001; ∆ = 5.1 p.p.) and BF activation (p = 0.020; ∆ = 4.0 p.p.) was higher at 90 • in the eccentric action. The RF showed an interaction between the range of motion and %RMS, with a large effect size (F = 37.9; p = 0.001; η 2 = 0.485). The VL activation was higher at 140 • (p = 0.005; ∆ = 3.9 p.p.) in the concentric action and higher at 90 • (p = 0.006; ∆ = 3.7 p.p.) in the eccentric action, with a large effect size significant interaction (F = 21.3; p = 0.001; η 2 = 0.485). The GM activation was higher at 90 • in the concentric (p = 0.020; ∆ = 5.4 p.p.) and eccentric action (p = 0.022; ∆ = 41 p.p.). Conclusions: The biarticular muscles were influenced by the squat range only in the eccentric action of the movement, while the monoarticular muscles were influenced by the squat in both concentric and eccentric muscle action.
... Analyzing its kinematics can help participants understand the correct form and improve their performance. Researchers analyzed the squatting motion to gain insights into different aspects of the movement and its performance (Almosnino et al., 2013;Crowe et al., 2019;Demers et al., 2018;Esformes & Bampouras, 2013;Kim et al., 2015;Lorenzetti et al., 2018;McKean & Burkett, 2012;Moore et al., 2016;Sato & Heise, 2012;Severin et al., 2017;Sorensen et al., 2001). Also, because of its exercise efficiency, squats are often added to core exercise routines to improve lower extremity muscular endurance, strength, and overall conditioning (Escamilla et al., 2000;Escamilla et al., 2001;Schoenfeld, 2010). ...
... In the current study, hip flexion had an average of 106.57o (±13.38o) in 2D analysis and 91.40⁰ (± 11.60o) in 3D analysis. Both values for hip flexion fell into the range of 86.67o (± 8.30o) to 117.02o (± 9.88o) established by previous studies (Demers et al., 2018;Escamilla et al., 2001;Han et al., 2014;Mauntel et al., 2015;McKean & Burkett, 2012). Knee flexion in the current study also agreed with previous results. ...
... Knee flexion in the current study also agreed with previous results. Past studies found that knee flexion in a narrow squat was generally between 92.67o (± 12.67o) to 147.10o (± 9.20o) (Demers et al., 2018;Escamilla et al., 2001;McKean & Burkett, 2012). While located at the lower limit of the range, both results in 2D analysis (83.24 ± 11.67o) and 3D analysis (95.29 ± 16.21o) were included in the established range. ...
Bodyweight squats are a common exercise in athletic training and rehabilitation due to their biomechanical and neuromuscular similarities to fundamental movements in a variety of sports and their requirements of coordination of major joints and numerous muscle groups (Schoenfeld, 2010). They are essential for kinesiology students, whose future careers often include athletic training and rehabilitation, to learn how to analyze the kinematics of a squat. While 3D movement analysis is considered the gold standard for motion capture (Chung & Ng, 2012), 2D digital video analysis is more commonly chosen in education environments to provide hands-on experience. However, few studies have investigated the differences between 2D and 3D analysis of squats (Escamilla et al., 2001; Krause et al., 2015; Schmitz et al., 2015). Therefore, the current study aims to compare 2D and 3D measurements of narrow-stance squats while enhancing learning by engaging students with hands-on experience using free, open-source software. Fifteen healthy adults (nine females, six males, 26.93 ± 9.04 years old) participated in this study. Following proper COVID safety guidelines, 2D analyses were performed by undergraduate students at home while 3D analyses were performed using a motion capture system in the laboratory. Lower extremity joint angles and displacements were calculated using 2D and 3D methods. Statistical significances were found when comparing the differences between both measurements except for hip flexion. Nonetheless, the resulting angular and linear measurements from both 2D and 3D analyses aligned with previous research, suggesting that 2D digital video analysis is a viable option for educational purposes despite the significant differences.
... Similar to the box lifting study of Trafimow et al. (1993), the transferability of these observations to the atlas stone lift are uncertain due to the substantial difference in loading (male: 12.8 kg; female: 8.7 kg) and study populations (healthy office employees) compared to male and female strongman athletes performing the atlas stone lift. Of greater relevance to the atlas stone lift may be the studies of McKean & Burkett (2012) and Lisman et al. (2021), where between-sex kinematic differences were observed in trained persons performing the back squat (50% body mass) and over-head squat (un-loaded), respectively. In these studies, female athletes displayed a more upright trunk position during the overhead squat (Lisman et al., 2021) and back squat (McKean & Burkett, 2012) than male athletes. ...
... Of greater relevance to the atlas stone lift may be the studies of McKean & Burkett (2012) and Lisman et al. (2021), where between-sex kinematic differences were observed in trained persons performing the back squat (50% body mass) and over-head squat (un-loaded), respectively. In these studies, female athletes displayed a more upright trunk position during the overhead squat (Lisman et al., 2021) and back squat (McKean & Burkett, 2012) than male athletes. Male athletes displayed greater peak hip flexion in the overhead squat than female athletes (Lisman et al., 2021), while females displayed greater peak hip flexion in the back squat than male athletes (McKean & Burkett, 2012). ...
... In these studies, female athletes displayed a more upright trunk position during the overhead squat (Lisman et al., 2021) and back squat (McKean & Burkett, 2012) than male athletes. Male athletes displayed greater peak hip flexion in the overhead squat than female athletes (Lisman et al., 2021), while females displayed greater peak hip flexion in the back squat than male athletes (McKean & Burkett, 2012). ...
Background
The atlas stone lift is a popular strongman exercise where athletes are required to pick up a large, spherical, concrete stone and pass it over a bar or place it on to a ledge. The aim of this study was to use ecologically realistic training loads and set formats to (1) establish the preliminary biomechanical characteristics of athletes performing the atlas stone lift; (2) identify any biomechanical differences between male and female athletes performing the atlas stone lift; and (3) determine temporal and kinematic differences between repetitions of a set of atlas stones of incremental mass.
Methods
Kinematic measures of hip, knee and ankle joint angle, and temporal measures of phase and repetition duration were collected whilst 20 experienced strongman athletes (female: n = 8, male: n = 12) performed three sets of four stone lifts of incremental mass (up to 85% one repetition maximum) over a fixed-height bar.
Results
The atlas stone lift was categorised in to five phases: the recovery, initial grip, first pull, lap and second pull phase. The atlas stone lift could be biomechanically characterised by maximal hip and moderate knee flexion and ankle dorsiflexion at the beginning of the first pull; moderate hip and knee flexion and moderate ankle plantarflexion at the beginning of the lap phase; moderate hip and maximal knee flexion and ankle dorsiflexion at the beginning of the second pull phase; and maximal hip, knee extension and ankle plantarflexion at lift completion. When compared with male athletes, female athletes most notably exhibited: greater hip flexion at the beginning of the first pull, lap and second pull phase and at lift completion; and a shorter second pull phase duration. Independent of sex, first pull and lap phase hip and ankle range of motion (ROM) were generally smaller in repetition one than the final three repetitions, while phase and total repetition duration increased throughout the set. Two-way interactions between sex and repetition were identified. Male athletes displayed smaller hip ROM during the second pull phase of the first three repetitions when compared with the final repetition and smaller hip extension at lift completion during the first two repetitions when compared with the final two repetitions. Female athletes did not display these between-repetition differences.
Conclusions
Some of the between-sex biomechanical differences observed were suggested to be the result of between-sex anthropometric differences. Between-repetition differences observed may be attributed to the increase in stone mass and acute fatigue. The biomechanical characteristics of the atlas stone lift shared similarities with the previously researched Romanian deadlift and front squat. Strongman athletes, coaches and strength and conditioning coaches are recommended to take advantage of these similarities to achieve greater training adaptations and thus performance in the atlas stone lift and its similar movements.
... In addition to frontal plane kinematics, sex differences have been investigated in a variety of movements (landing [19], running [15], and jumping [16]) inherent to sports where squats are commonly included in training. Many studies have investigated sex differences in the single-leg squat [20][21][22][23], with fewer examining a bilateral (regular) back squat [8,24,25]. When performing bilateral squats with and without weight, males displayed greater lumbar trunk flexion, smaller hip flexion, and greater knee flexion angles during the descent phase of the squat [25]. ...
... Many studies have investigated sex differences in the single-leg squat [20][21][22][23], with fewer examining a bilateral (regular) back squat [8,24,25]. When performing bilateral squats with and without weight, males displayed greater lumbar trunk flexion, smaller hip flexion, and greater knee flexion angles during the descent phase of the squat [25]. This indicates different movement strategies between sexes, possibly due to altered muscle activation. ...
The squat is an essential exercise for strengthening lower body musculature. Although squats are frequently employed to improve lower extremity strength and neuromuscular control, differences between sexes and slight modifications, such as squat depth, can dramatically alter muscle recruitment and thus the foci of the exercise. The purpose of this study was to assess the effect of sex and squat depth on lower extremity coactivation and kinematics. Twenty recreationally active (women=10) participants were recruited. The first visit consisted of one repetition maximum testing. For the second visit, muscle activation was recorded of the gluteus maximus, semitendinosus, biceps femoris, vastus medialis, vastus lateralis, rectus femoris, and gastrocnemius. Reflective markers were placed on the lower body for 3D motion capture. Participants performed a series of squats to 90° knee flexion and 120° knee flexion. Benjamin-Hochberg procedure was employed and the alpha level was set at .05. Knee flexion (p<.001), adduction (p<.001), and external rotation (p=.008) were reduced during 90° compared to deep squats. Hip flexion, abduction, and external rotation were greater in deep squats (p<.001). Males had greater hip extensor to quad (HE:Q) co-contraction in 90° compared to deep squats (p=.007); females produced greater posterior chain activation in deep squats (p=.001) on ascent. When comparing sexes, males displayed greater HE:Q in the 90° squat during ascent (p=.013). The addition of deep squats into a preventative training program could be beneficial in reducing deficits prevalent in females and decrease injury incidence.
... A wide stance width, due to the effective shortening of the thigh in the sagittal plane and the resulting favorable thigh-to-lower-leg-ratio, decreases the required range of ADF which, when reduced, limits AKD during squatting [68]. Moreover, squatting patterns diverge between genders, which may be a result of differences in limb length and limb-to-torso-ratio between men and women [69]. Underlying anthropometric differences consequently impact AKD (Figure 3) [37]. ...
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.
... However, correlation of these values with squat depth indicate that there was no statistically significant relationship between them. A previous study by Mckean and Burkett reported that body height can be related to kinematic parameters in males and females during the two-leg back squat 48 . Thus, anthropometric parameters seem to be linked to SLS depth affecting kinematics. ...
The purpose of this study is to compare recreationally physically active females and males with regard to spine, pelvis and lower limb joints peak angles in each plane of motion during a single leg squat (SLS). The second aim is to investigate the relationship between kinematics and SLS depth in females and males. Fifty-eight healthy, young adults performed 5 repetitions of a single right leg squat to maximal depth while keeping their balance. Kinematic data were obtained using an optical motion capture system. At the hip, greater adduction and greater internal rotation were observed in females than in males. Females had more extended spines and less outward bended knees throughout the SLS than did men. In males, squat depth was significantly, positively correlated with the maximal angle of the ankle (r = 0.60, p < 0.001), the knee (r = 0.87, p < 0.001), the hip (r = 0.73, p < 0.001) and the pelvis (r = 0.40, p = 0.02) in the sagittal plane. A positive significant correlation was found between SLS depth and maximal angle of the knee (r = 0.88, p < 0.001) and the ankle (r = 0.53, p = 0.01) in the sagittal plane in females. Males and females used different motor strategies at all levels of the kinematic chain during SLS.
... This is consistent with the findings of McKean et al., who showed a similar relation in the timing of lumbar flexion (McKean et al., 2010b) This author also reported that maximum hip and knee angles are achieved almost simultaneously with the deepest part of the squat (M. McKean and Burkett, 2012). To the best of the authors' knowledge, this is the first report of a correlation between the timing parameters of joints' motion and squat depth. ...
The aim of this study was to analyze the relationship of range of motion (ROM) in the sagittal plane and timing parameters during a bodyweight squat to the depth of the squat. Sixty participants (20 females and 40 males) took part in this study. They were instructed to perform a bodyweight squat to the maximal depth position. Kinematic data were obtained using the optical motion capture system. The time for the descent phase of squatting was normalized from 0% (initial position, start of movement) to 100% (squat position-stop of movement). The ROM of ankle, knee, hip, pelvis and spine in the sagittal plane and the normalized time when the maximum joint angles occurred during the descent were analyzed to investigate the relationship between them and the squat depth in males and females. The knee ROM contributed most significantly, from all joints to squatting depth in both females and males (r = 0.92, p < 0.001). The squat depth was related to lumbar, hip and knee motion in females and to all kinematics parameters in males. Maximal ankle dorsiflexion and pelvis anterior tilt were reached earlier than the maximal angles of knee, hip and spine during squatting. Pelvis and ankle timing was negatively correlated with the squat depth (rs =-0.64, p < 0.001 and rs =-0.29, p = 0.02, respectively). This suggests that pelvis and ankle timing can be important to keeping balance during squatting and can lead to achieving the desired depth.
... The traditional back squat is frequently used in training programs to activate and strengthen both the anterior and posterior chain (6). It has been shown that men and women do adopt different movement patterns during the traditional back squat, which could initiate the activation of different musculature during squat execution and have exercise prescription implications (12,19). Currently, the physiological explanation for this disparity is unknown because analysis from the aforementioned study was limited to the kinematic variables of the back squat and reports of the muscle activation patterns of women during the traditional back squat are sparse (4). ...
Mehls, K, Grubbs, B, Jin, Y, and Coons, J. Electromyography comparison of sex differences during the back squat. J Strength Cond Res XX(X): 000-000, 2020-Currently, there is limited information regarding the muscle activity differences between men and women during the traditional back squat. The back squat is a widely used exercise which stimulates lower-body musculature; thus, information regarding the muscle activity patterns during this exercise is pertinent when prescribing resistance training. This study evaluated muscle activity differences (using surface electromyography) in men and women during the traditional back squat with a load prescribed to elicit strength gains. Resistance-trained men (n = 14) and women (n = 14) performed 3 sets of 4 repetitions in the traditional back squat using 85% of their pretest 1 repetition maximum. Muscle activity data were collected for 6 muscles including the vastus lateralis, vastus medialis, rectus femoris, gluteus maximus, semitendinosus, and biceps femoris (BF). Independent sample t tests revealed a significantly higher normalized muscle activity men in the BF muscle during the descending phase of the back squat. No other muscle activity differences were present between men and women. These results indicate that men activate the BF muscle during the traditional back squat to a greater extent than women. For women, it may be necessary to consider other exercises to optimally stimulate and strengthen the BF muscle during resistance training.
Background: The lumbopelvic-hip complex, also referred to as the “core”, is composed of every muscle between the knees and sternum. The back squat (BS) and front squat (FS) are both staple exercises that challenge the core in different ways. Possessing a properly balanced squat ratio (SR = 1-RM FS/1-RM BS; 1-RM = one-repetition maximum) could lead to a more stable core. Objective: This study attempted to determine if there was a meaningful relationship between the SR and core strength (CS) in resistance-trained males. If a strong relation exists between the SR and CS, strength and conditioning professionals would have a readily available assessment tool for examining CS by simply viewing the SR. Method: Twenty-one resistance-trained males (age = 28.3 ± 6.2 years; body mass = 93.1 ± 13.1 kg; height = 181.9 ± 7.6 cm; weight training experience with FS & BS = 6.4 ± 3.7 years) performed CS tests (flexor endurance, extensor endurance, prone bridge, left side-bridge, and right side-bridge), along with a 1-RM in the BS and FS. An aggregate of the CS test times (CSA) was also calculated for comparison with the SR. A Pearson product-moment correlation coefficient (r) was used to compare the SR with the CS tests and the CSA. Results: The CS test results were as follows (secs): flexor endurance 228.2±93.0, extensor endurance 137.0±28.2, prone bridge 166.7±51.3, left side-bridge 97.36±31.0, right side-bridge 100.2±28.3, and CSA 729.8±165.4. The 1-RM BS, 1-RM FS, and SR were: 157.5±29.7 kgs, 132.2±24.3 kgs, and 0.84±0.06 respectively. A moderate correlation was found between total CSA and the SR (r = 0.50, CD2 = 0.25, p<0.05). In addition, a moderate correlation was found between the prone bridge test and the SR (r = 0.49, CD2 = 0.24, p<0.05). A very strong positive correlation was also found between 1-RM BS and 1-RM FS (r = 0.93, CD2 = 0.86, p<0.05). Conclusions: The results of this study suggest that the CSA and prone bridge test are moderately related to the SR. However, the low coefficient of determination between the SR and CS times suggests that the SR is not a suitable estimate of CS. The very strong relationship between the 1-RM FS and 1-RM BS provides strong evidence for the interchangeable use of these modalities within a resistance training protocol.
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.
ABSTRACT An effective and often prescribed compound exercise for the lower limb is the squat movement. The purpose of this research was to determine if the leading joint hypothesis exists when squatting, that is one joint creates a dynamic foundation for motion of the entire limb. To contribute to future exercise prescription guidelines the influence of mediolateral and anteroposterior movement, the timing of the knees, and the influence of segment lengths were investigated in 29 subjects from a cross sectional back ground of sport and strength training. Subjects performed two types of squats; unloaded body weight squats and barbell squats with 50% body weight added. The 3D kinematics of the lower limb and torso were assessed with the independent variables of load, stance, phase and gender. The movement of the knees when squatting was found to support the leading joint hypothesis. The knee changed mediolateral and anteroposterior position to accommodate variations in load and stance width. The knee was also found to move past the alignment of the anteroposterior displacement of the knee, did not remain aligned with heel width, direction of the toes or anterior position of the toes. The amount of anteriorposterior displacement of the knee, with respect to the foot, varied between gender and this movement is considered anatomically appropriate and therefore should be encouraged in exercise prescription. Despite the literature, and this current research, generally supporting deep squats and the freedom for the knee to move anterior of the toes, there exists an inappropriate perception in some practical settings to restrict this movement pattern. Based on this research practitioners should allow an athletes' knees move in both mediolateral and anteroposterior direction when squatting and not remain aligned with heel width, direction of the toes, or anterior position of toes. Knee behaviour in squatting appears to be strategic and occurs in a specific order of the timing in the squat movement. Movement anterior of the toes is a normal and required part of the squat movement that should be encouraged where appropriate and when practitioners feel the clients' knees are healthy or normal.
When walking, step length provides critical information on traveled distance along the ongoing path [corrected] Little is known on the role that knowledge about body dimensions plays within this process. Here we directly addressed this question by evaluating whether changes in body proportions interfere with computation of traveled distance for targets located outside the reaching space. We studied locomotion and distance estimation in an achondroplastic child (ACH, 11 yr) before and after surgical elongation of the shank segments of both lower limbs and in healthy adults walking on stilts, designed to mimic shank-segment elongation. Kinematic analysis of gait revealed that dynamic coupling of the thigh, shank, and foot segments changed substantially as a result of elongation. Step length remained unvaried, in spite of the significant increase in total limb length ( approximately 1.5-fold). These relatively shorter strides resulted from smaller oscillations of the shank segment, as would be predicted by proportional increments in limb size and not by asymmetrical segmental increment as in the present case (length of thighs was not modified). Distance estimation was measured by walking with eyes closed toward a memorized target. Before surgery, the behavior of ACH was comparable to that of typically developing participants. In contrast, following shank elongation, the ACH walked significantly shorter distances when aiming at the same targets. Comparable changes in limb kinematics, stride length, and estimation of traveled distance were found in adults wearing on stilts, suggesting that path integration errors in both cases were related to alterations in the intersegmental coordination of the walking limbs. The results are consistent with a dynamic locomotor body schema used for controlling step length and path estimation, based on inherent relationships between gait parameters and body proportions.
Altering foot stance is often prescribed as a method of isolating muscles during the parallel squat. The purpose of this study was to compare activity in six muscles crossing the hip and/or knee joints when the parallel squat is performed with different stances and bar loads.
Nine male lifters served as subjects. Within 7 d of determining IRM on the squat with shoulder width stance, surface EMG data were collected (800 Hz) from the rectus femoris, vastus medialis, vastus lateralis, adductor longus, gluteus maximus, and biceps femoris while subjects completed five nonconsecutive reps of the squat using shoulder width, narrow (75% shoulder width), and wide (140% shoulder width) stances with low and high loads (60% and 75% 1RM, respectively). Rep time was controlled. A goniometer on the right knee was used to identify descent and ascent phases. Integrated EMG values were calculated for each muscle during phases of each rep, and the 5-rep means for each subject were used in a repeated measures ANOVA (phase x load x stance, alpha = 0.05).
For rectus femoris, vastus medialis, and vastus lateralis, only the load effect was significant. Adductor longus exhibited a stance by phase interaction and a load effect. Gluteus maximus exhibited a load by stance interaction and a phase effect. Biceps femoris activity was highest during the ascent phase.
The results suggest that stance width does not cause isolation within the quadriceps but does influence muscle activity on the medial thigh and buttocks.
The squat is used extensively in strength and conditioning, physical therapy, rehabilitation, and fitness programs. However, the movement pattern of the hip and knee is still relatively unknown, in particular, the timing of when maximum angles is reached. The purpose of this study was to quantify the hip and knee movements of the squat and establish if load alters these movements. Twenty-eight subjects (16 men and 12 women) performed 2 sets of 8 squats. Load was applied in random order as no additional weight (body weight [BW]) or an additional load of 50% of the subject's weight (BW+50%). Joint angles and time for hip and knee, as well as forward knee, displacement in the descent and ascent phases were measured with significance at p<0.05. Regardless of gender, phase, and load, all subjects achieved their maximum hip and knee angles within 2% of the deepest position. Load significantly increased the flexion angle at the hip and knee joints in men. The knees movement forward of the toes ranged from 63.8 to 64.7 mm in men and 93.2 to 96.6 mm in women. A significant difference in the timing of when the maximum forward knee movement occurred was observed because of gender. The overriding factor for the practical prescription of squat technique was regardless of load, gender, or phase; the maximum angles of the hip and knee are reached almost simultaneously at the bottom of the squat. Furthermore, for all subjects, the knee moved forward of the toes when squatting with men reaching their maximum forward knee position around 84% of the descent phase, whereas this occurred for women around 93%.
Many strength trainers believe that varying the stance width during the back squat can target specific muscles of the thigh. The aim of the present work was to test this theory measuring the activation of 8 thigh muscles while performing back squats at 3 stance widths and with 3 different bar loads. Six experienced lifters performed 3 sets of 10 repetitions of squats, each one with a different stance width, using 3 resistances: no load, 30% of 1-repetition maximum (1RM), and 70% 1RM. Sets were separated by 6 minutes of rest. Electromyographic (EMG) surface electrodes were placed on the vastus medialis, vastus lateralis, rectus femoris, semitendinosus, biceps femoris, gluteus maximus, gluteus medium, and adductor maior. Analysis of variance and Scheffè post hoc tests indicated a significant difference in EMG activity only for the gluteus maximus; in particular, there was a higher electrical activity of this muscle when back squats were performed at the maximum stance widths at 0 and 70% 1RM. There were no significant differences concerning the EMG activity of the other analyzed muscles. These findings suggest that a large width is necessary for a greater activation of the gluteus maximus during back squats.
The joint and muscle forces arising from and generated in the knee during the activity of squatting, and rising from a deep squat have been calculated. The analysis involved the consideration of a two-dimensional model. Data was then collected from each of the subjects performing the activity using: a force platform; a ciné film used in conjunction with the X-rays to describe accurately the configuration of the lower limb; EMG data; anthropometric data. A computer program was developed to analyse the data and compute the forces in the leg. Six subjects were tested and graphs of joint and muscle forces versus knee angle were obtained for each of them. A discussion follows. The results for ascent and descent, and slow and fast activities are compared.
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.
To compare trunk muscle coordination in people with and without low back pain with varying speeds of limb movement.
Abdominal and back extensor muscle activity in association with upper limb movement was compared among three speeds of movement and between people with and without low back pain.
Fourteen subjects with a history of recurrent low back pain and a group of age- and sex-matched control subjects.
The onsets of electromyographic activity of the trunk and limb muscles, frequency of trunk muscle responses, and angular velocity of arm movements.
Early activation of transversus abdominis (TrA) and obliquus internus abdominis (OI) occurred in the majority of trials, with movement at both the fast and intermediate speeds for the control group. In contrast, subjects with low back pain failed to recruit TrA or OI in advance of limb movement with fast movement, and no activity of the abdominal muscles was recorded in the majority of intermediate speed trials. There was no difference between groups for slow movement.
The results indicate that the mechanism of preparatory spinal control is altered in people with lower back pain for movement at a variety of speeds.