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A Biomechanical Comparison of the Traditional Squat, Powerlifting Squat, and Box Squat
Abstract
The purpose of this study was to compare the biomechanics of the traditional squat with 2 popular exercise variations commonly referred to as the powerlifting squat and box squat. Twelve male powerlifters performed the exercises with 30, 50, and 70% of their measured 1 repetition maximum (1RM), with instruction to lift the loads as fast as possible. Inverse dynamics and spatial tracking of the external resistance were used to quantify biomechanical variables. A range of significant kinematic and kinetic differences (p < 0.05) emerged between the exercises. The traditional squat was performed with a narrow stance, whereas the powerlifting squat and box squat were performed with similar wide stances (48.3 ± 3.8, 89.6 ± 4.9, 92.1 ± 5.1 cm, respectively). During the eccentric phase of the traditional squat, the knee traveled past the toes resulting in anterior displacement of the system center of mass (COM). In contrast, during the powerlifting squat and box squat, a more vertical shin position was maintained, resulting in posterior displacements of the system COM. These differences in linear displacements had a significant effect (p < 0.05) on a number of peak joint moments, with the greatest effects measured at the spine and ankle. For both joints, the largest peak moment was produced during the traditional squat, followed by the powerlifting squat, then box squat. Significant differences (p < 0.05) were also noted at the hip joint where the largest moment in all 3 planes were produced during the powerlifting squat. Coaches and athletes should be aware of the biomechanical differences between the squatting variations and select according to the kinematic and kinetic profile that best match the training goals.
... muscular power), or ambiguous descriptor (e.g. explosive) will be used to classify exercises (11,20,26,34). An advantage of using of kinetic and kinematic terms for exercise classifications allow the ability for objective units of measurement (e.g. ...
... (20) • Movement of lighter loads with more acceleration. (26) • Strength-speed: ...
... (20) • Movements with a relatively heavy load lifted as fast as possible. (26) • Starting strength: ...
The field of strength and conditioning (S&C) has been adulterated with numerous, overlapping terms leading to miscommunication between athletes, sport coaches, strength and conditioning coaches (SCC) and sport scientists. Specifically, the use of various hyphenated terms to describe strength, in combination with contention associated with the proper definition and use of power, warrants the necessity to come to agreement on consistent terminology usage. Considerations should be based on the level of applicability and understanding of those most effected (athlete, sport coach, SCC, sport scientist). Moreover, while the use of kinetic and kinematic variables in describing strength and power related qualities is not incorrect, the population receiving the information must be considered. Athletes and sport coaches may be more influenced by simple cues and descriptors used to create movement intent and overall “buy in” to the S&C plan. Furthermore, SCC may be more concerned with how an exercise or movement will relate to improved sport performance while sport scientists may be more interested with how a specific variable(s) can be measured and quantified. Should the use of ambiguous, overlapping, or complex terminology persist, each of the various populations listed may continue to talk past one another instead of striving to be in agreeance with one another. Additionally, SCC may struggle with exercise selection and muddled programming due to the “paralysis by analysis” phenomenon when attempting to disseminate which exercises and movements to prescribe. Ultimately, the athlete may be most affected due to limited physiological improvement in turn leading to sub-par performance outcomes. Thus, the primary objectives of this article are to advance the field by creating an open discourse between the various individuals involved with the S&C profession while simultaneously shedding light on uncertainty associated with overlapping terms used to describe strength, power and other physical qualities associated with sports performance.
... In this scenario, both LPTs and LVTs have different limitations inherent to their technology, which can alter the resulting velocity data depending on the exercises evaluated and the way they are performed (Król & Gołaś, 2017;Swinton et al., 2012Swinton et al., , 2011. To date, despite the wide spectrum of linear transducers´ (LTs) validation articles (Courel-Ibáñez et al., 2019;Crewther et al., 2011;Fernandes et al., 2018;Gonzalez et al., 2019;Mitter et al., 2019;Pérez-Castilla et al., 2019), to the author´s knowledge, there is only one systematic review in this regard (Weakley et al., 2021). ...
... Furthermore, the authors only took into account whether the LTs were compared with a gold standard and the plane in which the exercise was performed (2D or 3D), without investigating factors such as the nature (plyometric or non-plyometric) of the evaluated exercises nor the mode of execution of the movement (contraction regimes). These variables have been shown to alter the kinetic and kinematic parameters (Cormie et al., 2007;Król & Gołaś, 2017;Swinton et al., 2012Swinton et al., , 2011. Therefore, the objective of this systematic review is to summarise and analyse the validity and reliability of LPT and LVT, in exercises of a diverse nature and with different forms of execution. ...
... m/s), GymAware, FitroDyne (Fitronic), Tendo Weightlifting Analyser System, Chronojump, and Speed4Lift LPT devices extracted less accurate velocity values during those movement without isometric pause or eccentric controlled phase (0.04-0.194 m/s) (Askow et al., 2018;Lorenzetti et al., 2017) (see Table 4). The main reason that lead to this fact may be the greater sampling frequencies (the amount of data reported per second and expressed in Hertz (Hz) (Rico-González et al., 2020)) of the LTs when identify the real start of the push phase, which is dependent on the sampling frequency (Cormie et al., 2007;Król & Gołaś, 2017;Swinton et al., 2012Swinton et al., , 2011. Tables 3 and 4). ...
This systematic review aimed to summarise and analyse the evidence on the reliability and validity of linear tranducers (LTs) in exercises of different nature and different modes of execution. This systematic review was carried out under PRISMA guidelines, and was carried out using three databases (PubMed, Web of Sciences, and Scopus). Of the 351 initially found, 21 were included in the qualitative synthesis. The results reflected that linear position transducers (LPTs) were valid and reliable in monitoring movement velocity in non-plyometric exercises. However, precision and reliability were lower in execution protocols without isometric phase and in the execution of exercises in multiple planes of movement, with greater measurement errors at higher sampling frequencies. On the other hand, linear velocity transducers (LVTs) proved to be valid and reliable in measuring velocity during plyometric and non-plyometric exercises performed on the Smith machine, with less variation in measurement in the latter. Finally, the use of peak values is recommended, since they are less dependent on the technological errors of LTs. Therefore, the performance of non-plyometric exercises, carried out in the Smith machine and with an isometric phase in the execution of the movement, will help to minimise the technological error of the LTs.
... The two most common back squat bar placements are the high-bar and the low-bar placement, characterized by the bar placed along the top of the upper trapezius or across the midtrapezius, over the spine of the scapulae and posterior deltoid, respectively (Glassbrook et al., 2017). Several studies have investigated the effect of barbell placements on squat performance and biomechanics (Benz and West Chester, 1989;Fry et al., 1993;Wretenberg et al., 1996;Swinton et al., 2012;Glassbrook et al., 2017Glassbrook et al., , 2019. Furthermore, when squatting with loads corresponding to greater than 85% of 1-RM, a sticking region has been observed (Elliott et al., 1989). ...
... In the sticking region, the gluteus medius and maximus myoelectric activity increased for both barbell placements, whereas myoelectric activity decreased in the quadriceps and soleus muscles. Also, the low-bar squat can result in a more anterior projection of the center of mass than the high-bar squat (Swinton et al., 2012). This may be explained by the observation that squatting with a low-bar technique often leads to greater forward lean and thereby a greater horizontal distance between the barbell and the hip joint, creating greater external hip joint moments and moment arms as speculated by van den Tillaar and . ...
... This occurred since ankle flexion angles were 4 • -9 • greater during all events for the narrow stance widths and were not influenced much by barbell placement. Similar findings were reported by Swinton et al. (2012), who found that peak ankle flexion was ∼10 • greater for narrow stance widths, whereas the present study reported 5 • -7 • greater ankle flexion for the narrow stance. ...
Barbell placement and stance width both affect lifting performance in the back squat around the sticking region. However, little is known about how these squat conditions separately could affect the lifting performance. Therefore, this study investigated the effects of stance width and barbell placement upon kinematics, kinetics, and myoelectric activity around the sticking region during a three-repetition maximum back squat. Nine men and nine women (body mass: 76.2 ±11.1, age: 24.9 ± 2.6) performed back squats with four different techniques, such as: high-bar narrow stance (HBNS), high-bar wide stance, low-bar narrow stance, and low-bar wide stance where they lifted 99.2 ± 23.6, 92.9 ± 23.6, 102.5 ± 24.7, and 97.1 ± 25.6 kg, respectively. The main findings were that squatting with a low-bar wide stance condition resulted in larger hip contributions to the total moment than the other squat conditions, whereas squatting with an HBNS resulted in greater knee contributions to the total moment together with higher vastus lateralis and less gluteus maximus myoelectric activity. Our findings suggest that training with an HBNS could be beneficial when targeting the knee extensors and plantar flexors, whereas a low-bar wide stance could be beneficial when targeting the hip extensors.
... 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.
... 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. ...
... N m�kg -1 ) and hexagonal-(1.46 N m�kg -1 ) bar deadlift against the same 70% 1RM external load [19,20]. Therefore, whilst the hip thrust preferentially loads the hip extensors (as expected), there is also considerable demand placed on the knee extensors during the lift. ...
... The range of pelvic-trunk joint motion was small (12 ± 21˚) and the extensor work done was more than 6-fold smaller than the hip joint ( Table 2), indicating that the extensor moment at the pelvic-trunk joint was predominantly acting to resist pelvic-trunk flexion. The magnitude of peak pelvic-trunk extensor moment (4.93 ± 1.53 N m�kg -1 ) was comparable with those reported during back squat and deadlift variations at similar relative loading conditions [19,20]. However, whilst standing exercises such as the back squat will elicit both compressive and shear forces across the lumbar spine [22], the non-axial loading nature of the hip thrust may offer a means of training the hip extensor musculature with reduced compressive forces at the lumbar spine, although further investigation is required. ...
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.
... Each participant was guided to perform two CKC motions ( Fig. 1 a, b)., including a box squat (BS) and a deep lunge, as well as two OKC motions ( Fig. 1 c, d) including non-weight bearing active knee extension (OKC-0) and active knee extension with 10 kg loading around the ankle (OKC-10). For the box squat, participants were asked to maintain their hips posteriorly and hold a near-vertical shin position (McBride et al., 2010;Swinton et al., 2012). Considering that the toe direction would affect the knee kinematics, we asked the participants to place their feet in the neutral toe position (Swinton et al., 2012). ...
... For the box squat, participants were asked to maintain their hips posteriorly and hold a near-vertical shin position (McBride et al., 2010;Swinton et al., 2012). Considering that the toe direction would affect the knee kinematics, we asked the participants to place their feet in the neutral toe position (Swinton et al., 2012). When performing the lunge motion, each participant started from a natural standing position and ended around ∼90°of flexion with their knee maintaining an isometric hold at the bottom. ...
Background:
Usage of open-kinetic-chain (OKC) or closed-kinetic-chain (CKC) exercises during rehabilitation planning after anterior cruciate ligament (ACL) reconstruction has been debated for decades. However, the ACL elongation pattern during different rehabilitation exercises at different loadings remains unclear.
Objectives:
This study aimed to determine the effects of OKC and CKC exercises on the length of ACL anteromedial bundle (AMB) and posterolateral bundle (PLB) to provide biomechanical support for making rehabilitation schedules.
Design:
Laboratory Descriptive Study.
Method:
Eighteen healthy volunteers were asked to perform two OKC motions, including non-weight-bearing and 10 kg loaded seated knee extension (OKC-0, OKC-10), as well as two CKC motions, including box squat (BS) and deep single-legged lunge (Lunge). Techniques of 2D-to-3D image registration and 3D ligament simulation were used to quantify length changes of ACL.
Results:
The motion which led to the least and most ACL elongation were OKC-0 and OKC-10, respectively. The AMB and PLB were significantly longer in OKC-10 than those in OKC-0 during 0-60° and 0-55° of knee flexion (p < 0.01). Compared with reference length, the AMB and PLB were stretched during 0-30° and 0-10° respectively during OKC-10. During CKC exercises, the AMB and PLB were also stretched from 0 to 25°and 0-5°, respectively. Additionally, no significant difference was found in the length change of ACL bundles between BS and lunge.
Conclusions:
OKC-0 may be safe for the rehabilitation program after ACL reconstruction, and loaded exercises shall be applied when restricted with >30° in early-stage rehabilitation.
... Bodyweight squats are a common exercise in athletic training due to their biomechanical and neuromuscular similarities to fundamental movements in a variety of sports (Almosnino et al., 2013;Schoenfeld, 2010). Additionally, the coordination of major joints and numerous muscle groups in squat performance allows such movement to be frequently used in rehabilitation for improvement in quality of life and evaluation of movement competency (Schoenfeld, 2010;Swinton et al., 2012). However, due to its requirements of mobility and stability of multiple joints, poor technique can lead to an increased risk of injury (Krause et al., 2015;Schoenfeld, 2010). ...
... (± 6.00o) to 32.50o (± 5.00o), which overlapped with both the 2D angles (21.80 ± 5.52o) as well as the 3D angles (26.12 ± 6.72o). Additionally, knee 2D horizontal (anteroposterior) displacements (0.23 ± 0.06 m) supported data reported by Swinton et al. (2012) (0.22 ± 0.04 m) whereas 3D knee anteroposterior displacements (0.15 ± 0.04 m) were slightly smaller. The lesser knee flexion and ankle dorsiflexion were likely caused by reduction in physical activities during the COVID-19 pandemic since five out 12 participants reported a drop in exercise. ...
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.
... 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.
... Similarly, theoretical [4], [32], [33] and computational studies [29]- [31] studies also identified the importance of the ankle during squatting and suggests that an ankle exoskeleton may be able to reduce the squat effort. Realizing effective squat assistance using an ankle exoskeleton, however, is challenging due to subject-specific biomechanical movements and muscle activation patterns as well as a subjective range of motion [49]. Perhaps, subjectspecific assistance can reduce the squat effort across users. ...
... The optimized assistance was widely varied across participants, which suggests the importance of personalization. The biomechanics of squatting can be varied due to subject-specific biomechanics [4] and natural range of motion [49], [69]. These subject-specific characteristics appear to contribute to a unique metabolic rate landscape for each user ( Figure 5), resulting in personalized assistance parameters for both ascending and descending conditions ( Figure 4D) and unique torque profile ( Figure 4E). ...
Exoskeletons can assist humans during squatting and the assistance has the potential to reduce the physical demands. Although several squat assistance methods are available, the effect of personalized assistance on physical effort has not been examined. We hypothesize that personalized assistance will reduce the physical effort of squatting. We developed a human-in-the-loop Bayesian optimization scheme to minimize the metabolic cost of squatting using a unilateral ankle exoskeleton. The optimization identified subject-specific assistance parameters for ascending and descending during squatting and took 15.6 min on average to converge. The subject-specific optimized condition reduced metabolic cost by 19.9% and rectus femoris muscle activity by 28.7% compared to the condition without the exoskeleton with a higher probability of improvement compared to a generic condition. In an additional study with two participants, the personalized condition presented higher metabolic cost reduction than the generic condition. These reductions illustrate the importance of personalized ankle assistance using an exoskeleton for squatting, a physically intensive activity, and suggest that such a method can be applied to minimize the physical effort of squatting. Future work can investigate the effect of personalized squat assistance on fatigue and the potential risk of injury.
... For the box squat, participants were asked to move their hips posteriorly and try to hold a near-vertical shin position. [17,18] The height of the plyometric box was adjusted to allow all the knees of participants to be at a 90-degree angle when they sit on the box. Considering that the toe direction would affect the knee kinematics, we asked the participants to place their feet in the neutral toe position [18]. ...
... [17,18] The height of the plyometric box was adjusted to allow all the knees of participants to be at a 90-degree angle when they sit on the box. Considering that the toe direction would affect the knee kinematics, we asked the participants to place their feet in the neutral toe position [18]. For the seated knee extension, participants were asked to extend and flex the knee in a whole cycle under unloaded and loaded (against 10 kg of mass on the ankle) conditions. ...
A rehabilitation program after anterior cruciate ligament reconstruction is of great importance to obtain a satisfactory prognosis after surgery. However, there is still an onging debate over whether closed kinetic chain or open kinetic chain exercises should be chosen. Our study was designed to compare the in vivo tibiofemoral kinematics during closed kinetic chain and open kinetic chain exercises.
Eighteen healthy volunteers were asked to perform box squat and unloaded/10 kg-loaded seated knee extension. In vivo 3-dimensional analysis of tibiofemoral kinematics of different motions were determined using a dual fluoroscopic imaging system.
The study found significantly more tibial anterior displacement during loaded seated knee extension than during unloaded seated knee extension from 25°–50° of knee flexion (p ≤ 0.031). The knees exhibited significantly more internal tibial rotation and lateral tibial translation during the box squat than both seated knee extensions during mid-flexion. In addition, the knees showed less internal-external (IE) range of motion (ROM) from 20°– 75° of flexion (p < 0.001) and medial-lateral (ML) ROM from 75° to full extension (p ≤ 0.006) during box squat than both extensions. This knowledge may help optimize rehabilitation plans for patients post ACL reconstruction.
... Some impact in swimming may occur during the push-off phase of turning against the pool wall, but its reaction force and loading rate are essentially smaller (<1.5 BW, and <10 BW s -1 respectively) [75,76]. Despite the extreme weights lifted, the peak GRF in the H-M exercise (e.g. a squat and deadlift) is comparable (2-3 times BW) [77] to those in the O-I and R-I exercises. Besides, due to the nature of H-M exercises (inherent slow movement and the low number of repetitions), the loading rate (5-6 BW s -1 ) as well as the loading frequency remain marginal compared to the impact exercises [77]. ...
... Despite the extreme weights lifted, the peak GRF in the H-M exercise (e.g. a squat and deadlift) is comparable (2-3 times BW) [77] to those in the O-I and R-I exercises. Besides, due to the nature of H-M exercises (inherent slow movement and the low number of repetitions), the loading rate (5-6 BW s -1 ) as well as the loading frequency remain marginal compared to the impact exercises [77]. Overall, the moderate-to-high GRF alone J o u r n a l P r e -p r o o f may not be sufficient but it needs to be applied at a high loading rate or frequency to trigger the beneficial structural adaptations within the cortical bone of the proximal femur. ...
Physical loading makes bones stronger through structural adaptation. Finding effective modes of exercise to improve proximal femur strength has the potential to decrease hip fracture risk. Previous proximal femur finite element (FE) modeling studies have indicated that the loading history comprising impact exercises is associated with substantially higher fracture load. However, those results were limited only to one specified fall direction. It remains thus unclear whether exercise-induced higher fracture load depends on the fall direction. To address this, using magnetic resonance images of proximal femora from 91 female athletes (mean age 24.7 years with >8 years competitive career) and their 20 non-athletic but physically active controls (mean age 23.7 years), proximal femur FE models were created in 12 different sideways fall configurations. The athletes were divided into five groups by typical loading patterns of their sports: high-impact (H-I: 9 triple- and 10 high-jumpers), odd-impact (O-I: 9 soccer and 10 squash players), high-magnitude (H-M: 17 powerlifters), repetitive-impact (R-I: 18 endurance runners), and repetitive non-impact (R-NI: 18 swimmers). Compared to the controls, the FE models showed that the HI and R-I groups had significantly (p < 0.05) higher fracture loads, 11–17% and 22–28% respectively, in all fall directions while the OI group had significantly 10–11% higher fracture loads in four fall directions. The H-M and R-NI groups did not show significant benefit in any direction. Also, the analyses of the minimum fall strength (MFS) among these multiple fall configurations confirmed significantly 15%, 11%, and 14% higher MFSs in these impact groups, respectively, compared to the controls. These results suggest that the lower hip fracture risk indicated by higher fracture loads in athletes engaged in high impact or repetitive impact sports is independent of fall direction whereas the lower fracture risk attributed to odd-impact exercise is more modest and specific to the fall direction. Moreover, in concordance with the literature, the present study also confirmed that the fracture risk increases if the impact is imposed on the more posterolateral aspect of the hip. The present results highlight the importance of engaging in the impact exercises to prevent hip fractures and call for retrospective studies to investigate whether specific impact exercise history in adolescence and young adulthood is also associated with lower incidence of hip fractures in later life.
... It was a priori hypothesized that ISq reliability would be influenced by maximal ISq strength. Secondly, we sought to compare the reliability of PF in the ISq at a deeper squat position, which approximates the criteria for full depth in the back squat exercise (i.e., a 65 • knee angle [ISq 65 ]) [14,[19][20][21]. We hypothesized that test-retest reliability of PF in the ISq would be correlated with baseline ISq strength and that both PF output in the ISq and test-retest reliability would be greater as the knee angle moved closer to full extension (i.e., ISq 120 > ISq 90 > ISq 65 ). ...
... The second objective of this study was to determine the reliability of PF measurement in the ISq 65 , compared to the ISq 120 and ISq 90 , in a sub-sample of eligible subjects. To the authors' knowledge, this is the first study to investigate the use of an ISq position at a 65 • knee angle, which is somewhat surprising given it closely approximates the bottom position of the back squat (Hales et al., 2009;Swinton et al., 2012). All positions including ISq 65 displayed acceptable reliability based on ICC values (>0.8) [23][24][25]. ...
This study aimed to investigate the test-retest reliability of peak force in the isometric squat across the strength spectrum using coefficient of variation (CV) and intra-class correlation coefficient (ICC). On two separate days, 59 healthy men (mean (SD) age 23.0 (4.1) years; height 1.79 (0.7) m; body mass 84.0 (15.2) kg) performed three maximal effort isometric squats in two positions (at a 120° and a 90° knee angle). Acceptable reliability was observed at both the 120° (CV = 7.5 (6.7), ICC = 0.960 [0.933, 0.977]) and 90° positions (CV = 9.2 (8.8), ICC = 0.920 [0.865, 0.953]). There was no relationship between peak force in the isometric squat and the test-retest reliability at either the 120° (r = 0.052, p = 0.327) or 90° (r = 0.014, p = 0.613) positions. A subgroup of subjects (n = 17) also completed the isometric squat test at a 65° knee angle. Acceptable reliability was observed in this position (CV = 9.6 (9.3), ICC = 0.916 [0.766, 0.970]) and reliability was comparable to the 120° and 90° positions. Therefore, we deem isometric squat peak force output to be a valid and reliable measure across the strength spectrum and in different isometric squat positions.
... 3,4 However, poor technique or improper exercise prescription can lead to conditions/injuries such as patellofemoral pain, menisci/articular cartilage injury, and spondylolysis. 5e11 Thus, several experimental factors during the squat have been investigated because of their potential influences on squat performance including foot placement, 1,12 speed, 13e15 style, 16 and bar position. 2 It was reported that squat performance can also be related to individual's physical characteristics, such as leg length ratio and joint flexibility. ...
... 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.
... Previous kinetic studies limited assessing lumbosacral, hip and knee joint moments in the standing resistance exercises [32][33][34][35][36][37][38][39][40][41][42]; for instance, deadlift is conducted by hip extensor moment, while back squat is conducted by knee extension moment [43]. One possibility of hip or knee domination is likely to be caused by the different joint angles in which the peak joint moments were generated in the lower limb. ...
... These may demonstrate that a barbell hip thrust can be a lower back and hip extension exercise for strength training, accompanied by a slight knee extension. Few previous studies calculated the lumbosacral, hip and knee joint moments during the resistance exercises [32][33][34][35][36][37][38][39][40][41][42]. It is not easy to discuss whether our calculated value of the joint moment is valid, compared to that in previous studies on the resistance exercise. ...
Joint kinetic characteristics during the eccentric phase are important in resistance exercises because eccentric actions with elastic potential energy storage lead to the energy recoil with large joint moment and power generation during the subsequent concentric phase. Previous studies assessed the force production capacity in the barbell hip thrust; however, these were reported by the methodology using only surface electromyographic amplitudes recorded in the lower back and thigh muscles and did not focus on eccentric action. This study aimed to determine kinetic characteristics of lumbosacral, hip and knee joints of sprinters during the eccentric and concentric phases in a barbell hip thrust, compared to those of deadlift and back squat. Eleven well-trained male sprinters participated in this study. Each participant performed two full ranges of motion repetition using their previously determined six-repetition maximum loads. During strength exercises, reflective marker displacements attached to the body and a barbell were captured using 22 high-speed cameras, and ground reaction forces were captured using 4 force plates simultaneously. In the barbell hip thrust, as well as deadlift, the peak values of the lumbosacral and hip extension moments were generated almost immediately after the eccentric phase and were 24% and 42% larger than those in the back squat, respectively. In the knee joint, the largest was the peak extension moment in the back squat (155 ± 28 Nm), followed in order by that in the barbell hip thrust (66 ± 33 Nm) and that in the deadlift (24 ± 27 Nm). These demonstrated that a barbell hip thrust, as well as deadlift, can be a resistance exercise to strengthen the lower back and posterior thigh muscles. Thus, these resistance exercises may be able to be used separately according to their intended purposes, enabling transformations of strength training to specific dynamic motions such as sprint running.
... Adapted from van den Tillaar et al. (2014). performance (Benz and West Chester, 1989;Fry et al., 1993;Wretenberg et al., 1996;Anderson et al., 1998;Mccaw and Melose, 1999;Escamilla et al., 2001a,b;Pereira et al., 2010;Bryanton et al., 2012;Swinton et al., 2012;Saeterbakken et al., 2016;Glassbrook et al., 2019;Lahti et al., 2019;van den Tillaar, 2019;Maddox et al., 2020;Maddox and Bennett, 2021). ...
... Therefore, further research should use musculoskeletal modeling techniques to calculate joint contact forces and moments experienced by the musculoskeletal system. Also, this study only investigated kinematics and kinetics in the high-bar back squat, whereas both stance width and barbell placement have been shown to affect lifting performance (Escamilla et al., 2001a;Swinton et al., 2012;Glassbrook et al., 2017Glassbrook et al., , 2019Lahti et al., 2019;. Therefore, further studies should also investigate how changing barbell placement together with stance width could change the kinematics, kinetics, and myoelectric activity around the sticking region in back squats. ...
The aim of this study was to investigate barbell, joint kinematics, joint kinetics of hip, knee, and ankle in tandem with myoelectric activity around the sticking region in three-repetition maximum (3-RM) back squats among recreationally trained lifters. Unlike previous literature, this study also investigated the event of first-peak deacceleration, which was expected to be the event with the lowest force output. Twenty-five recreationally trained lifters (body mass: 70.8 ± 10.5, age: 24.6 ± 3.4, height: 172 ± 8.5) were tested in 3-RM back squats. A repeated one-way analysis of variance showed that ground reaction force output decreased at first peak deacceleration compared with the other events. Moreover, torso forward lean, hip moment arm, and hip contribution to total moment increased, whereas the knee moment arms and moment contribution to total moment decreased in the sticking region. Also, stable moment arms and moment contributions to total moment were observed for the ankle in the sticking region. Furthermore, the knee extensors together with the soleus muscle decreased myoelectric activity in the post-sticking region, while the gluteus maximus and biceps femoris increased myoelectric activity in the post-sticking region. Our findings suggest that the large hip moment arms and hip contributions to total moment together with a lower myoelectric activity for the hip extensors contribute to a poor biomechanical region for force output and, thereby, to the sticking region among recreationally trained lifters in 3-RM back squats.
... This may explain why powerlifters have even greater forward trunk lean of 10 • (smaller hip joint angle) and less knee flexion (≈7 • ) during low bar lifts, when compared with Olympic lifters with high bar loads at the same percentage of lifting loads. A wider stance, probably used in low bar conditions, can cause lower moment arms of the barbell in comparison with the center of pressure (COP), as indicated by Glassbrook et al. (2019), which influences knee and hip joint angles (Swinton et al., 2012). However, the joint angles during the low bar squats were similar to those of regional and international leveled powerlifters from earlier low bar squat studies (Hales et al., 2009;Swinton et al., 2012;Glassbrook et al., 2019), indicating that the kinematics in our study are comparable with regional to international leveled powerlifters. ...
... A wider stance, probably used in low bar conditions, can cause lower moment arms of the barbell in comparison with the center of pressure (COP), as indicated by Glassbrook et al. (2019), which influences knee and hip joint angles (Swinton et al., 2012). However, the joint angles during the low bar squats were similar to those of regional and international leveled powerlifters from earlier low bar squat studies (Hales et al., 2009;Swinton et al., 2012;Glassbrook et al., 2019), indicating that the kinematics in our study are comparable with regional to international leveled powerlifters. Additionally, in the systematic review by Glassbrook et al. (2017), studies reporting joint kinematics in high bar variations often reported that participants squatted deeper when compared with studies reporting kinematics from a low bar variation. ...
The current study investigated the effects of barbell placement on kinematics and muscle activity during the sticking region of back squats. Ten healthy medium- to well-trained male powerlifters [age 26.1 ± 11.2 years, body mass 90.2 ± 18.3 kg, height 1.83 ± 0.09 m, five repetition maximum (5RM) 158 ± 29 kg] with at least 3 years of resistance-training experience were recruited. In a single session, participants performed 5RM movements using high bar and low bar squats, where absolute load, descent depth, and stance width were matched between squat conditions. The final repetition was analyzed using 3D kinematics and electromyography (EMG) around the sticking region. No differences in barbell and joint kinematics were observed in any phase, between both barbell modalities. Increased muscle activity in the rectus femoris, vastus medialis, and lower part of the erector spinae with the high bar, when compared with low bar conditions, was recorded. Furthermore, the gluteus maximus and medius had increased muscle activity over the three regions (pre-sticking > sticking > post-sticking), while the erector spinae, soleus, vastus lateralis, and rectus femoris experienced decreased muscle activity during the ascending phase. When depth and stance width were matched, the low bar technique was associated with lower erector spinae and quadriceps activity than the high bar technique. Thus, when the goal is to maximally activate knee extensors and the external load is matched, high bar placement would appear preferable.
... Anecdotally, Powerlifters can lift more weight using this variation of the squat, which has also been observed in previous research comparing the traditional "high bar" back squat placement to the low bar position (Glassbrook et al., 2019). Other unique aspects of the powerlifting squat are that typically wider stances are used (Swinton et al., 2012), and a greater relative degree of hip flexion occurs rather than knee and ankle flexion (Glassbrook et al., 2017); thus, the lifter sits "back and down" reaching the required competition depth (the hip crease traveling below the top of the knee when viewed laterally by a referee (IPF, 2019). This is in contrast to how the back squat is performed by weightlifters, who utilize a high bar position, typically a closer stance width, maintained as upright a torso position as possible, and emphasize greater flexion at the knee and ankle in comparison (Glassbrook et al., 2017)ostensibly, this technique difference is to better replicate the snatch and clean. ...
... Rather, only the Powerlifters performed low bar back squat and weightlifters only the high bar back squat, and each was allowed to selfselect their stance width and overall style of squatting. Thus, EMG differences reported by Wretenberg et al. (1996) may not be specifically caused by bar placement per se but possibly by secondary aspects of the techniques used by powerlifters and weightlifters; specifically, powerlifters not only use a low bar position but also a wider stance width, different cues (sitting back vs down), and slightly different depths (Swinton et al., 2012). With that said, previous research on squat stance width has repeatedly found a lack of significant differences in quadriceps muscle activity Paoli et al., 2009); however, some data suggest it may influence glute and adductor EMG (McCaw and Melrose, 1999). ...
The aim of this study was to compare 6-RM muscle activation and kinematics in back squats with low and high barbell placements. Twelve resistance-trained males (23.5 ± 2.6 years, 86.8 ± 21.3 kg, 1.81 ± 0.08 m) with a minimum of 2 years of squatting experience performed a 6-RM using high and low barbell placements while muscle activation of eight muscles and joint kinematics were measured. During high barbell placement squats, lifting time was longer, with lower average velocity than low barbell placement. This was accompanied by a lesser knee flexion angle at the lowest point of the squat, and larger hip flexion angles during high, compared to low barbell squats. Furthermore, peak angular ankle, knee and hip velocities in the descending phase developed differently between conditions. No significant differences in muscle activation were found between conditions. Thus, our data suggests gross muscular adaptations between barbell placements may be similar over time, and therefore, from a muscular development standpoint, both squat styles are valid. Furthermore, unlike the low barbell placement, fatigue may manifest earlier itself in the high barbell squats during 6-RMs as sets progress toward a lifter's maximal capacity, altering kinematics, especially in the last repetition.
... Using dynamic testing conditions, standardization is mostly performed for range of motion (69). The squat ROM varies between different studies (mostly 70-110°) ( Table 1), (36,44,73,121,122). ...
Measuring maximal strength (MSt) is a very common performance diagnoses, especially in elite and competitive sports. The most popular procedure in test batteries is to test the one repetition maximum (1RM). Since testing maximum dynamic strength is very time consuming, it often suggested to use isometric testing conditions instead. This suggestion is based on the assumption that the high Pearson correlation coefficients of r = 0.7 between isometric and dynamic conditions indicate that both tests would provide similar measures of MSt. However, calculating r provides information about the relationship between two parameters, but does not provide any statement about the agreement or concordance of two testing procedures. Hence, to assess replaceability, the concordance correlation coefficient (rhoc) and the Bland-Altman analysis including the mean absolute error (MAE) and the mean absolute percentage error (MAPE) seem to be more appropriate. Therefore, an exemplary model based on r=0.55 showed rhoc = 0.53, A MAE of 413.58N and a MAPE = 23.6% with a range of -1000 – 800N within 95% Confidence interval (95%CI), while r=0.7 and 0.92 showed rhoc =0.68 with a MAE = 304.51N/MAPE = 17.4% with a range of -750N – 600N within a 95% CI and rhoc =0.9 with a MAE = 139.99/MAPE =7.1% with a range of -200-450N within a 95% CI, respectively. This model illustrates the limited validity of correlation coefficients to evaluate the replaceability of two testing procedures. Interpretation and classification of rhoc, MAE and MAPE seem to depend on expected changes of the measured parameter. A MAPE of about 17% between two testing procedures can be assumed to be intolerably high.
... The second type of this squat is the low bar back squat, in which the barbell rests in the lower region of the quadriceps muscles [15]. When performing the low bar back squat, the athlete is able to lift a much heavier load [3, 15, 16 ,17], while the high bar back squat is considered to be safer in terms of intervertebral spinal loads [15,17]. The third type of squat is the front squat with the barbell held on the chest. ...
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.
... The type of squat is chosen on the basis of training/rehabilitation goals, with each type of squat having different biomechanics that require varying degrees of mobility, strength, balance and coordination. While each squat will generally challenge muscles of the lower body, core and trunk, each variation will have certain emphases ( [8] [9] [11] [12] [14] [15] [18] [19] [21]- [31] Table 1). ...
... During traditional (TRAD) squatting (i.e., same absolute load for the concentric and eccentric phase), ground reaction forces have been reported to be greater during the concentric vs. the eccentric phase [19], given the load must be accelerated against gravity in the concentric phase. Consequently, the load during the eccentric phase in TRAD squatting is significantly below the maximum eccentric capacity, potentially under-loading the musculature and therefore providing sub-optimal mechanical tension to promote adaptation. ...
Introduction:
Accentuated-eccentric loading (AEL) takes advantage of the high force producing potential of eccentric muscle contractions, potentially maximising mechanical tension within the muscle. However, evidence is lacking on how AEL squatting may load the involved musculature, limiting scientifically justified programming recommendations. The purpose of this study was to investigate the effects of concentric and eccentric loads on joint loading and muscle activity of the lower limbs.
Methods:
Resistance trained males performed traditional squatting (20-100% of concentric one-repetition maximum [1RM]) and AEL squatting with eccentric loads (110-150% of 1RM) provided by a novel motorised isotonic resistance machine (Kineo). Kinetics and kinematics of the hip, knee, and ankle joints were collected, with electromyography from the gluteus maximus, vastus lateralis, biceps femoris, and gastrocnemius medialis. A secondary cohort underwent a kinematic and electromyography analysis of squatting technique to compare Kineo and back and front barbell squatting.
Results:
Knee joint peak eccentric moments occurred at 120% 1RM (P = 0.045), with no further increase thereafter. As eccentric load increased, the time course of moment development occurred earlier in the eccentric phase. This resulted in a 37% increase in eccentric knee extensor work from the 80% 1RM trial to the 120% 1RM trial (P<0.001). Neither hip nor ankle joints displayed further change in kinetics as eccentric load increased above 100% 1RM. Electromyographic activity during traditional squatting was ~15-30% lower in all eccentric trials than in concentric trials for all muscles. EMG plateaued between a load of 80-100% 1RM during the eccentric trials and did not increase with AEL. No significant differences in kinematics were found between Kineo and barbell squatting.
Conclusions:
The knee extensors appear to be preferentially loaded during AEL squatting. The greater work performed during the eccentric phase of the squat as eccentric load increased suggests greater total mechanical tension could be the cause of adaptations from AEL. Our data suggest that AEL should be programmed with a load of 120% of 1RM. Further studies are needed to confirm the longer-term training effects of AEL.
... Compared to stationary machine exercises, free-weight exercises rely on additional activation of the stabilizers, plantar and knee flexors, and enhanced quadriceps and knee extensor activation to enhance gait speed [93]. Biomechanical studies reveal that squatting, whether traditional, goblet squat, or box squat, provides an array of shear stresses and linear displacement on the long bones and joints through varying moment arms at the hips, knees, ankles, and lumbosacral spine (Fig. 3) requiring intense coordination and core activation for stability [94]. ...
There are many benefits to the addition of exercise to cancer treatment and survivorship, particularly with resistance training regimens that target hypertrophy, bone mineral density, strength, functional mobility, and body composition. These goals are best achieved through a series of individualized high-intensity compound movements that mirror functional mobility patterns and sufficiently stress the musculoskeletal system. As a result of adequate stress, the body will engage compensatory cellular mechanisms that improve the structural integrity of bones and muscles, stimulate metabolism and the immune system, optimize functional performance, and minimize mechanical injury risk. The current evidence suggests that application of the above exercise principles, practiced in a safe environment under expert observation, may offer patients with cancer an effective means of improving overall health and cancer-specific outcomes. The following article poses several important questions certified exercise specialists and physicians should consider when prescribing resistance exercise for patients with cancer.
... The squat is one of the most used exercises in S&C, with different styles used for different reasons (Jones, Smith, Macneughton, & French, 2016). However, there are differences between these variations, e.g. in the kinetics and kinematics of the traditional back squat, powerlifting squat and the box squat (Swinton, Lloyd, Keogh, Agouris, & Stewart, 2012), and in the kinematics and electromyographic activity of the back and front squat (Yavuz, Erdağ, Amca, & Aritan, 2015). Therefore, future research should examine the effect of head position on performance during these different squatting styles. ...
... In addition, unlike single-joint movements where kinematics are constrained, the kinematics of squatting can differ between the concentric and eccentric phase (Swinton et al. 2012), which may prevent the hip and knee joints simultaneously being at their optimal angle to produce maximal joint moments, despite squat depth remaining constant. The combined contribution of the two joints to the ground reaction force could, therefore, be reduced (Beckham et al. 2018), in particular during the eccentric trials compared to the concentric trials, reducing the eccentric squatting force. ...
Purpose
The force–velocity relationship of muscular contraction has been extensively studied. However, previous research has focussed either on isolated muscle or single-joint movements, whereas human movement consists of multi-joint movements (e.g. squatting). Therefore, the purpose of this study was to investigate the force–velocity relationship of isovelocity squatting.
Methods
Fifteen male participants (24 ± 2 years, 79.8 ± 9.1 kg, 177.5 ± 6 cm) performed isovelocity squats on a novel motorised isovelocity device (Kineo Training System) at three concentric (0.25, 0.5, and 0.75 m s⁻¹) and three eccentric velocities (− 0.25, − 0.5, and − 0.75 m s⁻¹). Peak vertical ground reaction forces, that occurred during the isovelocity phase, were collected using dual force plates (2000 Hz) (Kistler, Switzerland).
Results
The group mean squat force–velocity profile conformed to the typical in vivo profile, with peak vertical ground reaction forces during eccentric squatting being 9.5 ± 19% greater than isometric (P = 0.037), and occurring between − 0.5 and − 0.75 m s⁻¹. However, large inter-participant variability was identified (0.84–1.62 × isometric force), with some participants being unable to produce eccentric forces greater than isometric. Sub-group analyses could not identify differences between individuals who could/could not produce eccentric forces above isometric, although those who could not tended to be taller.
Conclusions
These finding suggest that variability exists between participants in the ability to generate maximum eccentric forces during squatting, and the magnitude of eccentric increase above isometric cannot be predicted solely based on a concentric assessment. Therefore, an assessment of eccentric capabilities may be required prior to prescribing eccentric-specific resistance training.
... In the studies of Agarwal et al. [11] and Rhea et al. [38], they indicated that with the increase of squatting depth, when the movement ability of the ankle joint was not enough to maintain the contact between the foot and the ground, the torso showed a more forward posture to maintain the stability of the center of gravity. This compensation mechanism may lead to an increase in the sheer force received by the lumbar vertebrae, thus increasing the risk of injury [39,40]. In addition, it is worth noting that in F-SQ, when the flexion angle of the knee joint reached the maximum, i.e., squatting to the deepest, the femur and tibia was in a state of internal rotation, the knee joint showed a slight abduction angle, the hip joint showed a transient trend of adduction, which meant that when squatting to the deepest point, the subject's knee joint showed valgus, which was a common postural error. ...
Background:
Females with different practice experience may show different body postures and movement patterns while squatting in different depths, which may lead to changes of biomechanical loadings and increase the risks of injuries.
Methods:
Sixteen novice female participants without squat training experience participated in this study. A 3D motion capture system was used to collect the marker trajectory and ground reaction force data during bodyweight squatting in different depths. The participants' kinematic data and joint moment were calculated using OpenSim's inverse kinematics and inverse dynamics algorithm. In this study, authors adapted a model especially developed for squatting and customized the knee joint with extra Degree-of-Freedom (DoF) in the coronal and horizontal plane with adduction/abduction and internal/external rotation. A paired-sample t-test was used to analyze the difference of joint range of motions (ROM) and peak moments between full-squat (F-SQ) and half-squat (H-SQ). One-Dimensional Statistical Parametric Mapping (SPM1D) is used to analyze the difference of joint angle and moment between the process of squatting F-SQ and H-SQ.
Results:
(1) Compared with H-SQ, F-SQ showed larger ROM in sagittal, coronal, and transverse planes (p < 0.05). (2) SPM1D found that the difference in joint angles and joint moments between F-SQ and H-SQ was mainly concentrated in the mid-stance during squatting, which suggested the difference is greatly pronounced during deeper squat. (3) Peak hip extension moment, knee extension moment, hip adduction moment, and plantar flexion moment of F-SQ were significantly higher than H-SQ (p < 0.05). (4) Difference of hip and knee extension moments and rotation moments between the F-SQ and H-SQ were exhibited during descending and ascending.
Conclusions:
The study found that novice women had larger range of joint motion during the F-SQ than H-SQ group, and knee valgus was observed during squatting to the deepest point. Greater joint moment was found during F-SQ and reached a peak during ascending after squatting to the deepest point. Novice women may have better movement control during H-SQ. The findings may provide implications for the selection of lower limb strength training programs, assist the scientific development of training movements, and provide reference for squat movement correction, thus reducing the risk of injury for novice women in squatting practice.
... It's noteworthy that both BL and HL events have higher densities (higher peak) at eccentric contraction. This might be because the subjects tend to perform eccentric contraction slower than concentric contraction [42], and therefore in eccentric contraction joint sound events had a higher density. The BL and HL event distributions were significantly distinct (p < 0.001) in both two-leg squats and in one-leg squats. ...
Objective:
Considering the knee as a fluid-lubricated system, articulating surfaces undergo different lubrication modes and generate joint acoustic emissions (JAEs). The goal of this study is to compare knee biomechanical signals against synchronously recorded joint sounds and assess the hypothesis that JAEs are attributed to tribological origins.
Methods:
JAE, electromyography, ground reaction force signals, and motion capture markers were synchronously recorded from ten healthy subjects while performing two-leg and one-leg squat exercises. The biomechanical signals were processed to calculate a tribological parameter, lubrication coefficient, and JAEs were divided into short windows and processed to extract 64-time-frequency features. The lubrication coefficients and JAE features of two-leg squats were used to label the windows and train a classifier that discriminates the knee lubrication modes only based on JAE features.
Results:
The classifier was used to predict the label of one-leg squat JAE windows and it achieved a high test-accuracy of 84%. The Pearson correlation coefficient between the estimated friction coefficient and predicted JAE scores was 0.83 ± 0.08. Furthermore, the lubrication coefficient threshold, separating two lubrication modes, decreased by half from two-leg to one-leg squats. This result was consistent with tribological changes in the knee load as it was inversely doubled in one-leg squats.
Significance:
This study supports the potential use of JAEs as a quantitative biomarker to extract tribological information. Since arthritis and similar disease impact the roughness of the joint cartilage, the use of JAEs could have broad implications for studying joint frictions and monitoring joint structural changes with wearable devices.
... Furthermore, these dynamics influence how a suitable, safe movement may look like (e.g., higher knee flexion in boxes with low handle). Research has shown heterogeneity in flexion-extension movements across healthy participants Zwambag et al., 2019) and also that different lifting techniques are required to accomplish different lifting tasks in different contexts (van Dieën et al., 1999;Swinton et al., 2012). It follows then that the optimal lifting technique for all individuals (i.e., one size fits all) does not exist and cannot be taught in educational programs. ...
Spine posture during repetitive lifting is one of the main risk factors for low-back injuries in the occupational sector. It is thus critical to design appropriate intervention strategies for training workers to improve their posture, reducing load on the spine during lifting. The main approach to train safe lifting to workers has been educational; however, systematic reviews and meta-analyses have shown that this approach does not improve lifting movement nor reduces the risk of low back injury. One of the main limitations of this approach lies in the amount, quality and context of practice of the lifting movement. In this article, first we argue for integrating psychologically-grounded perspectives of practice design in the development of training interventions for safe lifting. Principles from deliberate practice and motor learning are combined and integrated. Given the complexity of lifting, a training intervention should occur in the workplace and invite workers to repeatedly practice/perform the lifting movement with the clear goal of improving their lifting-related body posture. Augmented feedback has a central role in creating the suitable condition for achieving such intervention. Second, we focus on spine bending as risk factor and present a pilot study examining the benefits and boundary conditions of different feedback modalities for reducing bending during lifting. The results showed how feedback modalities meet differently key requirements of deliberate practice conditions, i.e., feedback has to be informative, individualized and actionable. Following the proposed approach, psychology will gain an active role in the development of training interventions, contributing to finding solutions for a reduction of risk factors for workers.
... A short ROM, double knee bend technique was used sporadically by some athletes to initiate a stretch shortening cycle just prior to the beginning of the second pull phase. While the stretch-shortening cycle is commonly used in weightlifting events to ensure maximal force and power can be rapidly applied to the barbell (Enoka, 1979;Gourgoulis et al., 2000;Winwood et al., 2015b), evidence supporting its effectiveness for heavy/ strength-based lifts performed over an extended duration, such as the atlas stone lift, is conflicting (McBride et al., 2010;Swinton et al., 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.
... Biomechanical analysis has improved our understanding of the performance of RT movements by identifying interactions between joints and the forces acting on them [4][5][6]. The recent development of portable data collection devices, such as inertial measurement units (IMU) and markerless motion capture cameras, has provided accessible data collection outside of research and commercial sectors and the means to easily acquire large amounts of movement data. ...
The technical performance of resistance-training (RT) movement is commonly monitored through visual assessment and feedback by trained practitioners or by individual self-evaluation. However, both approaches are limited due to their subjectivity, inability to monitor multiple joints simultaneously, and dependency on the assessor’s or exerciser’s experience and skill. Portable data collection devices and machine learning (ML) have been combined to overcome these limitations by providing objective assessments for RT movement performance. This systematic review evaluates systems developed for providing objective, automatic assessment for RT movements used to improve physical performance and/or rehabilitation in otherwise healthy individuals. Databases searched included Scopus, PubMed and Engineering Village. From 363 papers initially identified, 13 met the inclusion and exclusion criteria. Information extracted from the collated papers included the experimental protocols, data processing, ML model development methodology and movement classification performance. Identified movement assessment systems ranged in classification performance (accuracy of 70%–90% for most classifiers). However, several methodological errors in the development of the ML models were identified, and additional aspects such as model interpretability or generalisability were often neglected. Future ML models should adopt the correct developmental methodology and provide interpretable and generalisable models for application in the RT environment.
... The squat is one of the most used exercises in S&C, with different styles used for different reasons (Jones, Smith, Macneughton, & French, 2016). However, there are differences between these variations, e.g. in the kinetics and kinematics of the traditional back squat, powerlifting squat and the box squat (Swinton, Lloyd, Keogh, Agouris, & Stewart, 2012), and in the kinematics and electromyographic activity of the back and front squat (Yavuz, Erdağ, Amca, & Aritan, 2015). Therefore, future research should examine the effect of head position on performance during these different squatting styles. ...
The effect of head positioning is often not accounted for when optimising performance in the back squat exercise. The primary aim of the study was to identify the most advantageous head position for peak power (PP), peak velocity (PV) and peak force (PF) performance in the back squat exercise. A secondary aim was to identify the most favourable head position. Twenty male rugby union players performed 1x3 repetitions at 75% one repetition maximum (1RM) to determine their preferred pre-intervention head position, followed by 1x3 at 75% 1RM in a flexed (FP), extended (EP) and neutral (NP) neck position, performed in a counterbalanced and randomised order. PP, PV, PF and comfort level (CL) were measured during each repetition. FP resulted in significantly higher PP (3147.50 ± 464.70 W; p<0.05) compared to EP (2730 ± 427.83 W) and NP (2912.95 ± 441.16 W). However, NP resulted in significantly greater CL than FP and EP (3.65 ± 0.59; p<0.05). Therefore, when performing the back squat at 75% 1RM, the FP can be adopted to optimise power performance if there is no pain and no detriment to movement kinematics.
... The passive SpringExo in Figure 2 is a 3D-printed nylon spring coil attached to a photopolymer resin 3D-printed thigh cuff and shank cuff, which can strap to the thigh and shank of the user. The coil spring can accommodate extreme knee flexion in squat kinematics, such as in Tewart (2012). The cuffs are mechanically connected to the spring ends and attached to the leg via Velcro straps covering the skin to avoid discomfort. ...
Passive wearable exoskeletons are desirable as they can provide assistance during user movements while still maintaining a simple and low-profile design. These can be useful in industrial tasks where an ergonomic device could aid in load lifting without inconveniencing them and reducing fatigue and stress in the lower limbs. The SpringExo is a coil-spring design that aids in knee extension. In this paper, we describe the muscle activation of the knee flexors and extensors from seven healthy participants during repeated squats. The outcome measures are the timings of the key events during squat, flexion angle, muscle activation of rectus femoris and bicep femoris, and foot pressure characteristics of the participants. These outcome measures assess the possible effects of the device during lifting operations where reduced effort in the muscles is desired during ascent phase of the squat, without changing the knee and foot kinematics. The results show that the SpringExo significantly decreased rectus femoris activation during ascent (−2%) without significantly affecting either the bicep femoris or rectus femoris muscle activations in descent. This implies that the user could perform a descent without added effort and ascent with reduced effort. The exoskeleton showed other effects on the biomechanics of the user, increasing average squat time (+0.02 s) and maximum squat time (+0.1 s), and decreasing average knee flexion angle (−4°). The exoskeleton has no effect on foot loading or placement, that is, the user did not have to revise their stance while using the device.
... As the gluteus maximus and hamstring muscles are the primary hip extensors during bilateral lifting exercises (57,80), their capacity to produce a high internal extensor moment is vital to performance. However, when hip flexion angle increases beyond 35° as it does during most full range of motion lifting exercises (105,106), the hip extensor muscle moment arm length decreases significantly (15,79). As such, some lumbar flexion during lifting may preserve the effectiveness of the hip extensor muscles for generating high internal extensor moments at the hip joint by reducing peak hip flexion angles. ...
Lifting exercises are essential for the development of strength qualities in the lower extremity. Traditionally, coaches encourage a neutral lumbar spine posture during these exercises in order to reduce injury risk and maximise performance. However, evidence suggests that significant amounts of lumbar spine flexion occur during lifting exercises, and appears to be unavoidable even when coached. It is the aim of this article to discuss the potential risks and advantages for allowing moderate amounts of lumbar spine flexion during lifting exercises.
... Two to four minutes of recovery was provided between 1RM attempts (19). The back squat was deemed successful if the athlete lowered to a depth denoted by a box underneath the players buttocks (height 56-62 cm), by bending of the knees, and then recover to an upright stance with knees locked, without any assistance (35). Maximal back squat testing has been shown to have high test-retest reliability (ICC 5 0.99; coefficient of variation [CV] 5 0.35) (34). ...
Glassbrook, DJ, Fuller, JT, Wade, JA, and Doyle, TLA. Not all physical performance tests are related to early season match running performance in professional rugby league. J Strength Cond Res 36(7): 1944-1950, 2022-This study aimed to determine which physical tests correlate with early season running performance. Sixteen professional rugby league players performed the 30-15 intermittent fitness test (IFT), 1.2-km time trial, 1 repetition maximum (RM) barbell back squat, isometric midthigh pull (IMTP), countermovement jump (CMJ), barbell squat jump (SJ), and ballistic bench press throw (BBP). Bivariate Pearson's correlations and linear regression were used to compare physical tests with peak match running intensities recorded by a portable Global Positioning System and represented by peak match velocity and acceleration, as well as peak 1-, 4-, 6-, and 8-minute instantaneous acceleration/deceleration periods of play. Significant (p < 0.05) negative correlations (r = -0.55 to -0.60) were observed between the IFT and relative 1-, 4-, 6-, and 8-minute peaks, and between the relative 1RM back squat and relative 1-, 4-, 6-, and 8-minute peaks. Significant positive correlations (r = 0.52-0.84) were observed between the following physical tests and match performance pairs: IFT and peak acceleration; relative 1RM back squat and peak acceleration; SJ peak power (relative and absolute) and peak acceleration; CMJ peak force (relative and absolute) and peak acceleration; CMJ peak power (relative and absolute) and peak acceleration and 1-, 4-, 6-, and 8-minute peaks; and relative BBP peak power and peak velocity and peak acceleration. The results of this study highlight that not all generic tests of physical qualities are related to peak match running performance and only those with significant correlations are likely to be able to indicate how players may perform during match-play.
... Many studies report NJMs during performance of lower-body strength exercises, such as the deadlift and the squat (34). ...
Mausehund, L, Werkhausen, A, Bartsch, J, and Krosshaug, T. Understanding bench press biomechanics-The necessity of measuring lateral barbell forces. J Strength Cond Res XX(X): 000-000, 2020-The purpose of this study was to advance the expertise of the bench press exercise by complementing electromyographic (EMG) with net joint moment (NJM) and strength normalized NJM (nNJM) measurements, thus establishing the magnitude of the elbow and shoulder muscular loads and efforts. Normalized NJMs were determined as the ratio of the bench press NJMs to the maximum NJMs produced during maximum voluntary isokinetic contractions. Furthermore, we wanted to assess how changes in grip width and elbow positioning affected elbow and shoulder NJMs and nNJMs, and muscle activity of the primary movers. Thirty-five strength-trained adults performed a 6-8 repetition maximum set of each bench press variation, while elbow and shoulder NJMs and EMG activity of 7 upper extremity muscles were recorded. The results show that all bench press variations achieved high elbow and shoulder muscular efforts. A decrease in grip width induced larger elbow NJMs, and larger EMG activity of the lateral head of the triceps brachii, anterior deltoid, and clavicular head of the pectoralis major (p ≤ 0.05). An increase in grip width elicited larger shoulder NJMs and nNJMs, and larger EMG activity of the abdominal head of the pectoralis major (p ≤ 0.05). In conclusion, all bench press variations may stimulate strength gains and hypertrophy of the elbow extensors and shoulder flexors and horizontal adductors. However, greater adaptations of the elbow extensors and shoulder flexors may be expected when selecting narrower grip widths, whereas wider grip widths may induce greater adaptations of the shoulder horizontal adductors.
... As a closed chain exercise, the squat has gained wide acceptance for core stabilization and strengthening the lower body muscles [236]. Previously, the lower limb joint kinematics have been described as well as the impact of variations in squatting technique [96,251]. Most of these studies have focused on the knee biomechanics with the aim of enhancing the strength performance and minimizing the injury risk [4,37,228,280]. ...
The hip functions as a ball and socket joint, with cartilage layers that cover the joint surfaces on both sides protecting it from impacts and permitting smooth movements. When the cartilage is impaired by mechanical, infectious or inflammatory causes, the joint might eventually wear down - a disabling condition known as osteoarthritis. Recent literature indicates that up to 80\% of all osteoarthritis cases are potentially caused by subtle hip variations: the round shape of the ball (femur head) that is disturbed by a bump or/and the socket (acetabulum) that overcovers the femur head. These abnormal variants can give rise to conflicts and altered load distribution in the hip joint. When the load on the joint is no longer evenly distributed, peak stresses can arise in certain areas of the hip posing a risk of developing focal cartilage damage. Since the apparent prevalence of these morphological hip abnormalities is reported to be much higher than the number of actual patients, the question remains how to differentiate potential patients from incidental findings.The aim of this thesis was to describe and explore the impact of shape variation in the hip joint and by doing so improve the understanding of the mechanical environment of the hip joint. First differences in hip anatomy between white and Chinese subjects were mapped using a cross sectional design. Pelvic computed tomography scans of 201 subjects (99 white Belgians and 102 Chinese; 105 men and 96 women; 18-40 years old) were assessed. Ten radiographic parameters predisposing to femoroacetabular impingement were evaluated. The white subjects had a less spherical femoral head than the Chinese subjects. The Chinese subjects had less lateral acetabular coverage than the white subjects. A shallower acetabular configuration was predominantly present in Chinese women. Static and dynamic variation in hip joint reaction forces was evaluated using an experimental computational modeling design. We therefore calculated the hip joint reaction force and hip flexion angle in a virtual representative male Caucasian population by means of musculoskeletal modeling of three distinct sitting configurations: a simple chair, a car seat and a kneeling chair configuration. The observed median hip joint reaction force in relation to body weight and hip flexion angle, respectively, was 22.3$\%$ body weight and 63° for the simple chair, 22.5$\%$ body weight and 79° for the car seat and 8.7$\%$ body weight and 50° for the kneeling chair. The kneeling chair appears to hold the greatest potential as an ergonomic sitting configuration for the hip joint since it requires the lowest hip flexion angle and hip joint reaction force of these 3 distinct sitting configurations. Dynamic mapping of deep squat hip kinetics was performed in young, athletic adults using a personalized numerical model solution based on inverse dynamics. Thirty-five healthy subjects underwent deep squat motion capture acquisitions and MRI scans of the lower extremities. Musculoskeletal models were personalized using each subject’s lower limb anatomy. The average peak hip joint reaction force was found to be 274$\%$ body weight. Average peak hip and knee flexion angles were 107° and 112° respectively. Deep squatting kinetics in the younger population differ substantially from the previously reported in vivo data in older subjects. In order to map variation in cartilage stress, a numerical discrete element analysis algorithm was developed. A validation study with hip joint contact stress data from 10 healthy subjects calculated by means of subject-specific finite element analysis was performed. Furthermore an efficient cartilage anatomy prediction tool was defined that does not require manual cartilage image segmentation. We showed that this novel population-averaged cartilage anatomy prediction method, integrated with the discrete element analysis algorithm could provide an efficient platform to predict cartilage contact stresses in large populations compared to subject specific finite element analysis. The mechanical effect of arthroscopic cam resection in femoroacetabular impingement was explored with a case-control study design. For this purpose, patient-specific discrete element models from 10 cam type femoroacetabular patients (all male, aged 18-40 years old) were defined based on preoperative CT and postoperative MRI scans. Complete cam resection postoperatively on MRI was confirmed with alpha angles $<$ 55°. The preoperative and postoperative peak contact stress findings during impingement testing were compared against a matched virtual control group. Peak contact stress was significantly elevated in patients with cam type femoroacetabular impingement during impingement testing with increasing amount of internal rotation. This effect was however normalized following arthroscopic cam resection and loading patterns matched those of the control group. Using multidimensional statistics and personalized load and stress predictions, we were able to demonstrate that the important population variation in shape and joint mechanics adds to differences in the onset and progression of cartilage lesions of the hip joint. Further, our work contributes to an improved identification and classification of patients who are truly at risk for developing cartilage damage. The final step of this thesis was to gradually transfer these findings into practice at the operating theater. We demonstrated that an accurate surgical treatment of cam lesions has the potential to effectively restore the normal mechanical environment of the hip.
... Powerlifting research has primarily focused on anthropometry (Keogh et al., 2007), muscle morphology (Abe et al., 2018), biomechanics (Swinton et al., 2012), injuries (Str€ omb€ ack et al., 2018), and programming . However, until recently, powerlifting studies have not addressed pre-competition and competition day practices. ...
This study provides the first comparison of weight selection attempt strategies used by powerlifters competing at the international level. We observed attempts selected by elite male and female classic powerlifters and compared weight selection attempts between sexes. Male (n = 66) and female (n = 43) powerlifters who completed all lifts successfully at an International Powerlifting Federation Classic World Championship between 2012-2019 were included in the analysis. We calculated the percentage weight increase from first attempts (A1) to second attempts (A2) and from A2 to third attempts (A3). For purposes of comparison, A1 values were expressed as a percentage of A3 values. We calculated non-parametric statistics with effect sizes for between and within-group comparisons. Relative to A3, males selected greater A1s compared to females for bench press (η2 = 0.16; p = 0.004) and deadlift (η2 = 0.06; p = 0.036) for each lift. Alternatively, females selected greater A1 to A2 and A2 to A3 progressions for bench press (η2 = 0.06; p = 0.026; η2 = 0.21; p = 0.005, respectively), and A2 to A3 for deadlift (η2 = 0.04; p = 0.035) compared to males. Within-group comparisons showed that males selected greater A1s on bench press compared to deadlift (η2 = 0.06; p = 0.046), whereas females selected greater A1s on squat compared to deadlift (η2 = 0.13; p = 0.038) relative to A3. Males also selected greater A2 to A3 progressions on deadlift compared to bench press (η2 = 0.10; p = 0.044), whereas females selected greater A2 to A3 progressions for bench press (η2 = 0.15; p = 0.039) and deadlift compared to squat (η2 = 0.10; p = 0.041). In conclusion, selecting an opener of ∼91% of the expected A3 weight, followed by ∼5% increase from A1 to A2, and ∼3% increase from A2 to A3 represent the typical weight selection attempts used across lifts by elite classic powerlifters competing in the World Championships. The results of this study provide novel insight into the weight selection attempts of elite classic powerlifters.
... Furthermore, the largest peak moment in all three planes were produced at the hip joint during the powerlifting squat (57) and that greater loads can be lifted with a low bar squat as it targets the stronger hip musculature (17). In addition, the sticking point in the bench press does not seem to be affected by a change in the moment arm (12), a narrow grip bench press produces greater barbell velocity (18) and a wider grip bench press shows similar muscle activation except for the biceps brachii (48). ...
International Journal of Exercise Science 13(4): 1512-1531, 2020. Several studies have determined the influence of physical characteristics on strength. The present quantified the relationships between anthropometry and maximal strength. Male classic powerlifters (n=59) were measured before a championship. Two-tailed Pearson correlation analysis was used. Powerlifters that presented higher relative maximal strength (RMS) in the squat and bench generally had higher body weight (BW), body mass index (BMI), torso circumference (C), waist C/height, torso C/height (r=0.26 to 0.49, p<0.05), and smaller lower leg length (L)/height and forearm L/torso C (r=-0.31 to-0.45, p<0.05) ratios. Powerlifters with a higher % of their deadlift on their total generally presented a smaller BW, BMI, body fat percentage (BF%), waist and torso C, trunk L, waist C/height, torso C/height, trunk L/height, waist C/hip C, thigh L/ lower leg L, trunk L/thigh L ratios (r=-0.26 to-0.49, p<0.05) and higher lower leg L, lower leg L/height, reach/height, and forearm L/torso C ratios (r=0.32 to 0.51, p<0.05). Stepwise regressions revealed that a bigger torso positively predicted absolute maximal strength (AMS) in the squat (β=0.41, p=0.04), the bench (β=0.77, p<0.01), the deadlift (β=0.88, p<0.01) and the total (β=0.89, p<0.01), that a higher torso C/height ratio positively predicted RMS in the squat(β=0.48, p<0.01), the bench (β=-0.87, p<0.01) and the total (β=0.66, p<0.01), and that reach/height positively predicted RMS in the deadlift (β=0.37, p<0.01) and it's % on the total (β=0.31, p<0.01), but negatively predicted RMS in the bench (β=-0.25, p=0.02) and its % on the total (β=-0.24, p=0.04) As all of the stronger correlations came from AMS, powerlifters should focus on increasing AMS (weight lifted) instead of RMS (Wilks pts).
... Analyzed movements were selected based on their transferability to a range of exercise-related movement patterns [39,40] and their ability to be performed in a laboratory environment ( Figure 1). The following subsection provides a description of these five movements. ...
This study proposes a minimal modeling magnetic, angular rate and gravity (MARG) methodology for assessing spatiotemporal and kinematic measures of functional fitness exercises. Thirteen healthy persons performed repetitions of the squat, box squat, sandbag pickup, shuffle-walk, and bear crawl. Sagittal plane hip, knee, and ankle range of motion (ROM) and stride length, stride time, and stance time measures were compared for the MARG method and an optical motion capture (OMC) system. The root mean square error (RMSE), mean absolute percentage error (MAPE), and Bland–Altman plots and limits of agreement were used to assess agreement between methods. Hip and knee ROM showed good to excellent agreement with the OMC system during the squat, box squat, and sandbag pickup (RMSE: 4.4–9.8°), while ankle ROM agreement ranged from good to unacceptable (RMSE: 2.7–7.2°). Unacceptable hip and knee ROM agreement was observed for the shuffle-walk and bear crawl (RMSE: 3.3–8.6°). The stride length, stride time, and stance time showed good to excellent agreement between methods (MAPE: (3.2 ± 2.8)%–(8.2 ± 7.9)%). Although the proposed MARG-based method is a valid means of assessing spatiotemporal and kinematic measures during various exercises, further development is required to assess the joint kinematics of small ROM, high velocity movements.
... The rope was adjusted to a height where the participants' thighs were parallel to the ground at the bottom of their squat. Participants were instructed to keep their chests up and weight over the heels and to not allow their knees to fall into a valgus position (5,53,78). Given that the back squat is used much more commonly compared with its front squat variation (89), and since the front squat requires higher ankle mobility (loss of ankle dorsiflexion is a common feature in young and old populations; see Ref. 69), the back squat was selected for the current study. ...
Purpose
The skeletal muscle is an integrated multi-component system with complex dynamics of continuous myoelectrical activation of various muscle types across timescales to facilitate muscle coordination among units and adaptation to physiological states. To understand the multi-scale dynamics of neuromuscular activity, we investigate spectral characteristics of different muscle types across timescales and their evolution with physiological states. We hypothesize that each muscle type is characterized by a specific spectral profile, reflecting muscle composition and function, that remains invariant over timescales and is universal across subjects. Further, we hypothesize that the myoelectrical activation and corresponding spectral profile during certain movements exhibit an evolution path in time that is unique for each muscle type, and reflects responses in muscle dynamics to exercise, fatigue, and aging.
Methods
To probe the multi-scale mechanism of neuromuscular regulation, we develop a novel protocol of repeated squat exercise segments, each performed until exhaustion, and we analyze differentiated spectral power responses over a range of frequency bands for leg and back muscle activation in young and old subjects.
Results
We find that leg and back muscle activation is characterized by muscle-specific spectral profiles, with differentiated frequency bands contribution, and a muscle-specific evolution path in response to fatigue and aging that is universal across subjects in each age group.
Conclusion
The uncovered universality among subjects in the spectral profile of each muscle at a given physiological state, as well as the robustness in the evolution of these profiles over a range of timescales and states, reveals a previously unrecognized multi-scale mechanism underlying the differentiated response of distinct muscle types to exercise-induced fatigue and aging.
Keywords: muscle fibers, spectral power, time scales, fatigue, aging.
Objectives: To assess style and themes of feedback provided by artificial intelligence (AI) mobile application and physical therapist (PT) to participants during bodyweight squat exercise. Methods: Research population was age 20–35, without any pre-existing condition that precluded participation in bodyweight exercise. Qualitative methodology followed directed content analysis. Cohen's kappa coefficient verified consistency between coders. Results: Both AI and PT groups had seven female and eight male participants. Three themes emerged: affirmation schema, correction paradigms and physical assessments. Average kappa coefficient calculated for all codes was 0.96, a value that indicates almost perfect agreement. Conclusion: Themes generated highlight the AI focus on congruent, descriptive and prescriptive feedback, while the PT demonstrated multipoint improvement capabilities. Further research should establish feedback comparisons with multiple PTs and correlate qualitative data with additional quantitative data on performance outcomes based on feedback.
Neurological traumas can impair motor function and compromise the ability to perform activities of daily living. Physical rehabilitation can aid in motor recovery, but these practices are frustrating due to their rigorous and repetitive nature. Emerging rehabilitation technologies utilize computerized interfaces, such as virtual reality to increase participant engagement and better train muscle-level control. These interfaces can readily provide enhanced augmented sensory feedback, especially at visual levels, to accelerate motor outcomes. Still, there remains a lack of understanding in optimizing the deployment of augmented sensory feedback for clinical motor rehabilitation. In this research, I investigated how specific features of augmented visual feedback can improve motor performance during rehabilitation training. The two primary features of interest were complexity and intermittency, which vary the amount and frequency of visual guidance provided, respectively. A key supplementary feature of augmented visual feedback is the level of body representation to leverage visual embodiment, which was also examined. I evaluated unique combinations of these features to improve functional performance of two different motor rehabilitation exercises, representing either a motion- or force-based task. For a two-legged squat exercise (motion-based), augmented visual feedback that was relatively complex with more body-discernible guidance cues produced the best performance during and after training. The dynamic embodiment may have facilitated the ability to effectively synthesize more feedback information during a synergistic, multi-segment movement. Alternatively, training with simple feedback demonstrated a greater potential for motor learning of a task utilizing isometric muscle control (force-based). Complex feedback may have been interpreted as superfluous to this task, given the shifted emphasis to force control without dynamic embodiment. Thus, the additional cues may have hindered both learning and user experience, reflected in reduced performance and significant physical and cognitive stress changes. For training of either experimental task, intermittently providing visual feedback about real-time performance errors (i.e., concurrent bandwidth feedback) suggested a greater potential for motor learning. In conclusion, systematic variation of specific features in augmented feedback can significantly improve motor performance. Thus, optimizing computerized interfaces for motor rehabilitation requires a greater understanding of how sensory feedback affects the user for a given functional task.
Squatting has received considerable attention in sports and is commonly utilized in daily activities. Knowledge of the squatting biomechanics in terms of its speed and depth may enhance exercise selection when targeting for sport-specific performance improvement and injury avoidance. Nonetheless, these perspectives have not been consistently reported. Hence, this preliminary study intends to quantify the kinematics, kinetics, and energetics in squat with different depths and speeds among healthy young adults with different physical activity levels; i.e., between active and sedentary groups. Twenty participants were administered to squat at varying depths (deep, normal, and half) and speeds (fast, normal, and slow). Motion-capture system and force plates were employed to acquire motion trajectories and ground reaction force. Joint moment was obtained via inverse dynamics, while power was derived as a product of moment and angular velocity. Higher speeds and deeper squats greatly influence higher joint moments and powers at the hip ([Formula: see text]) and knee ([Formula: see text]) than ankle, signifying these joints as the prime movers with knee as the predominant contributor. These preliminary findings show that the knee-strategy and hip-strategy were employed in compensating speed and depth manipulations during squatting. In certain contexts, appreciating these findings may provide clinically relevant implications, from the performance and injury avoidance viewpoint, which will ameliorate the physical activity level of practitioners.
Systematic overload, which is a training characteristic of powerlifters with visual impairments of high qualification has a negative impact on the functioning of body systems and the course of the underlying and comorbidities. This determines the relevance of the scientific substantiation of training programs for athletes with visual impairments as the most important component of ensuring the achievement of sports results in powerlifting. This study aimed to experimentally substantiate the effectiveness of the impact of various training programs on physical fitness and athletic performance of powerlifters with visual impairments of high qualification. To solve the goal we used methods of analysis of scientific and methodological literature, pedagogical observation, pedagogical experiment and methods of mathematical statistics. The study involved 16 visually impaired athletes who were members of the national powerlifting team. The pedagogical experiment was based on testing the effectiveness of two training programs, which differed in the parameters of the load components in the annual training and macrocycle periods. After the pedagogical experiment, the experimental group showed reliable indicators of growth on all tests and improvement of sports results, and athletes of the control group increased physical fitness in three tests out of five and sports results are available only in squat and bench press. In both groups, the highest growth rates in the level of development of physical qualities were found in tests aimed at determining the level of development of strength and flexibility. Comparing the results of the introduction of various training programs in the training process of powerlifters with visual impairments, we can conclude that the performance of the experimental group is much higher than among the powerlifters of the control group.
Sistematsko preopterećenje, koje je karakteristika treninga powerliftera sa oštećenjima vida visoke kvalifikacije, negativno utiče na funkcionisanje tijela i tok osnovnog stanja vida i na pojavu komorbiditeta. Time se utvrđuje relevantnost naučnog utemeljenja programa treninga za sportiste sa oštećenjem vida kao najvažnije komponente osiguravanja postizanja sportskih rezultata u powerliftingu.
Ovo istraživanje imalo je za cilj eksperimentalno potkrijepiti učinkovitost uticaja različitih programa treninga na tjelesnu spremnost i atletske performanse powerliftera sa oštećenjem vida visoke kvalifikacije. Da bi se cilj ostvario, korištene su metode analize naučne i metodičke literature, pedagoško posmatranje, pedagoški eksperiment i metode matematičke statistike. U istraživanju je učestvovalo 16 slabovidnih sportista koji su bili članovi nacionalnog powerlifting tima. Eksperiment se temeljio na testiranju učinkovitosti dva programa treninga koji su se razlikovali u parametrima komponenti opterećenja u godišnjem trenažnom i makrociklusnom razdoblju. Eksperimentalna grupa je nakon eksperimenta pokazala pouzdane pokazatelje povećanja na svim testovima i poboljšanja sportskih rezultata, a sportisti kontrolne grupe povećali su fizičku spremnost u tri od pet testova (sportski rezultati dostupni su samo u čučnju i bench pressu). U obje grupe najveće stope rasta nivoa razvijenosti tjelesnih osobina utvrđene su u testovima za utvrđivanje stepena razvoja snage i fleksibilnosti. Upoređujući rezultate uvođenja različitih programa treninga u trenažni proces powerliftera sa oštećenjem vida, može se zaključiti da je učinak eksperimentalne grupe znatno veći nego kod powerliftera kontrolne grupe.
Artificial intelligence technology is becoming more prevalent in health care as a tool to improve practice patterns and patient outcomes. This study assessed ability of a commercialized artificial intelligence (AI) mobile application to identify and improve bodyweight squat form in adult participants when compared to a physical therapist (PT). Participants randomized to AI group (n = 15) performed 3 squat sets: 10 unassisted control squats, 10 squats with performance feedback from AI, and 10 additional unassisted test squats. Participants randomized to PT group (n = 15) also performed 3 identical sets, but instead received performance feedback from PT. AI group intervention did not differ from PT group (log ratio of two odds ratios = − 0.462, 95% confidence interval (CI) (− 1.394, 0.471), p = 0.332). AI ability to identify a correct squat generated sensitivity 0.840 (95% CI (0.753, 0.901)), specificity 0.276 (95% CI (0.191, 0.382)), PPV 0.549 (95% CI (0.423, 0.669)), NPV 0.623 (95% CI (0.436, 0.780)), and accuracy 0.565 95% CI (0.477, 0.649)). There was no statistically significant association between group allocation and improved squat performance. Current AI had satisfactory ability to identify correct squat form and limited ability to identify incorrect squat form, which reduced diagnostic capabilities.
Trial Registration NCT04624594, 12/11/2020, retrospectively registered.
Collins, KS, Klawitter, LA, Waldera, RW, Mahoney, SJ, and Christensen, BK. Differences in muscle activity and kinetics between the goblet squat and landmine squat in men and women. J Strength Cond Res XX(X): 000-000, 2021-Squat exercise variations are widely used and extensively researched. However, little information exists on the goblet squat (GBS) and landmine squat (LMS) and differences between men and women. This study investigated the differences in muscle activity and kinetics between the GBS and the LMS in 16 men and 16 women. Five repetitions of each squat type were performed loaded at 30% of their body mass. Vertical and anteroposterior ground reaction forces for the eccentric and concentric phases and peak vertical force were recorded with a force plate. Electromyographic (EMG) signals were recorded for the vastus medialis (VM), vastus lateralis (VL), semitendinosus (ST), and biceps femoris (BF). Normalized mean EMG values and ground reaction forces were analyzed with repeated measures analysis of variance (p < 0.05). Significant main effects for squat condition and sex were found. The LMS reduced activity in the quadriceps (VM and VL) muscles and vertical forces, while increasing posterior horizontal forces. In the LMS, men showed decreased ST activity, whereas women had decreased BF activity. Women exhibited greater quadriceps activity in both the GBS and LMS and greater ST in the LMS. Women also produced greater eccentric vertical force in both the GBS and LMS and less posterior horizontal forces in the LMS. The LMS may be useful to balance hamstring to quadriceps activity, increase horizontal loading, and reduce vertical loading. Conversely, the GBS can better target quadriceps activity and increase vertical loading. Sex differences should be considered for training programs that include the GBS and LMS.
O levantamento olímpico (LPO) se tornou comum na preparação física de atletas de alto nível devido a sua similaridade entre a tripla extensão de joelho, tornozelo e quadril em relação relevante com o salto contra movimento em diversos esportes. Objetivo: Essa revisão tem por objetivo, fazer um levantamento dos estudos que verificaram os efeitos do levantamento olímpico sobre ganhos de desempenho no salto contra movimento em atletas de alto nível. Método: Para a pesquisa, foram feitas buscas em base de dados nacionais e internacionais usando os termos pertinentes ao tema. Após a busca e aplicabilidade dos critérios de inclusão e exclusão, foram selecionados quatro artigos que mais se aproximaram do tema proposto por esta pesquisa. Resultados e discussão: Dentre os estudos analisados, foi possível observar que os protocolos e os desenhos foram bastante semelhantes, nos permitindo assim, observar a melhora do desempenho de atletas de esportes coletivos em pré e até mesmo no meio da temporada com o incremento do LPO em seus treinamentos físicos. Conclusão: Podemos concluir que, o levantamento olímpico se mostra um importante exercício para performance do salto contra movimento utilizado em diversos esportes coletivos e individuais no que tange à potência, força e espessura muscular de membros inferiores. Palavras-Chaves: Levantamento de peso, Salto contra movimento, Atletas, Performance.
The composition of routines used in the training process of qualified powerlifters is still determined in accordance with the experience and intuition of a coach, rather than with a deep metrological assessment of the key parameters of movements. The purpose: to determine the compliance of bench press types with the powerlifting competitive exercise in accordance with the dynamic characteristics of movements and to reveal their hierarchical dependencies. Methods and organization of the research: theoretical analysis and generalization of scientific and methodological literature on the research subject, accelerometry, methods of mathematical statistics. The experimental site of the research is the “Children's and Youth Sports School named after the Olympic champion V.S. Sokolov", Cheboksary. Testing was performed in December 2019. The group of experimental subjects included 7 athletes with qualifications from the 1st category to the Master of Sports. Metrological assessment covered 8 variants of training and competition bench press. The total number of measurements was 78. Results and discussion. Bench press tests revealed the following levels of compliance: maximum (wide grip press, spring-loaded press and narrow grip press), high (press with chains, press without bridging and standing press), medium (face down on incline bench). Conclusion. The comparative analysis revealed routines with different compliance with the competitive exercise. The determination of priority of routines will provide evidence-based approach to the selection of routines for tackling the issues of bench press training among qualified powerlifters.
The squat is one of the most frequently used exercises in the field of strength and conditioning. Considering the complexity of the exercise and the many variables related to performance, understanding squat biomechanics is of great importance for both achieving optimal muscular development as well as reducing the prospect of a training-related injury. Therefore, the purpose of this article is 2-fold: first, to examine kinematics and kinetics of the dynamic squat with respect to the ankle, knee, hip and spinal joints and, second, to provide recommendations based on these biomechanical factors for optimizing exercise performance.
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.
Decreased lumbo-pelvic (or core) stability has been suggested to contribute to the etiology of lower extremity injuries, particularly in females. This prospective study compares core stability measures between genders and between athletes who reported an injury during their season versus those who did not. Finally, we looked for one or a combination of these strength measures that could be used to identify athletes at risk for lower extremity injury.
Before their season, 80 female (mean age = 19.1 +/- 1.37 yr, mean weight 65.1 +/- 10.0 kg) and 60 male (mean age = 19.0 +/- 0.90 yr, mean weight 78.8 +/- 13.3 kg) intercollegiate basketball and track athletes were studied. Hip abduction and external rotation strength, abdominal muscle function, and back extensor and quadratus lumborum endurance was tested for each athlete.
Males produced greater hip abduction (males = 32.6 +/- 7.3%BW, females = 29.2 +/- 6.1%BW), hip external rotation (males = 21.6 +/- 4.3%BW, females = 18.4 +/- 4.1%BW), and quadratus lumborum measures (males = 84.3 +/- 32.5 s, females = 58.9 +/- 26.0 s). Athletes who did not sustain an injury were significantly stronger in hip abduction (males = 31.6 +/- 7.1%BW, females = 28.6 +/- 5.5%BW) and external rotation (males = 20.6 +/- 4.2%BW, females = 17.9 +/- 4.4%BW). Logistic regression analysis revealed that hip external rotation strength was the only useful predictor of injury status (OR = 0.86, 95% CI = 0.77, 0.097).
Core stability has an important role in injury prevention. Future study may reveal that differences in postural stability partially explain the gender bias among female athletes.
Barbell squat can improve the lower body strength for weightlifter to enhance their performance. Previous studies mentioned that the full three-dimensional biomechanical analysis of lower limbs is greatly helpful for understanding the musculoskeletal mechanism in barbell squat exercise. The purpose of this study was to estimate the joint kinetics of lower limbs during the barbell squat. Thirteen male weightlifters from college weightlifting team members performed barbell squat with 85% weight of his one repetition maximum in the motion analysis laboratory. Motion analysis system and two force plateforms were used to collect the kinematic and kinetic data. The results showed that the major joint movements were not only occurred in the sagittal plane, but also in the frontal plane and transverse plane. The knee and hip joints suffered high compression forces and shear forces. The results also showed that ankle plantarflexor, knee extensor, hip flexor, and abductor were dominant muscles in barbell squat exercise. These finding could provide the additional guidelines for sports injury prevention and treatment, as well as guidelines of strength training program design for the coaches and athletic trainer. System Ltd., UK) was used to collect the trajectories of the markers at 250 Hz. Two force plateforms (Kistler Instrumente AG, Switzerland) were synchronized with the motion analysis system to collect ground reaction forces and moments at 1000 Hz. The events of barbell squat were defined by movements in truck and knee. Three events include initial movement, maximum knee flexion, and end point in this study. The descending phase is from initial movement to maximum knee flexion. The ascending phase is from maximum flexion to end point.
SUMMARY In order to stimulate further adaptation toward specific training goals, progressive resistance training (RT) protocols are necessary. The optimal characteristics of strength-specific programs include the use of concentric (CON), eccentric (ECC), and isometric muscle actions and the performance of bilateral and unilateral single- and multiple-joint exercises. In addition, it is recommended that strength programs sequence exercises to optimize the preservation of exercise intensity (large before small muscle group exercises, multiple-joint exercises before single-joint exercises, and higher-intensity before lower-intensity exercises). For novice (untrained individuals with no RT experience or who have not trained for several years) training, it is recommended that loads correspond to a repetition range of an 8-12 repetition maximum (RM). For intermediate (individuals with approximately 6 months of consistent RT experience) to advanced (individuals with years of RT experience) training, it is recommended that individuals use a wider loading range from 1 to 12 RM in a periodized fashion with eventual emphasis on heavy loading (1-6 RM) using 3- to 5-min rest periods between sets performed at a moderate contraction velocity (1-2 s CON; 1-2 s ECC). When training at a specific RM load, it is recommended that 2-10% increase in load be applied when the individual can perform the current workload for one to two repetitions over the desired number. The recommendation for training frequency is 2-3 dIwkj1 for novice training, 3-4 dIwkj1 for intermediate training, and 4-5 dIwkj1 for advanced training. Similar program designs are recom- mended for hypertrophy training with respect to exercise selection and frequency. For loading, it is recommended that loads corresponding to 1-12 RM be used in periodized fashion with emphasis on the 6-12 RM zone using 1- to 2-min rest periods between sets at a moderate velocity. Higher volume, multiple-set programs are recommended for maximizing hypertrophy. Progression in power training entails two general loading strategies: 1) strength training and 2) use of light loads (0-60% of 1 RM for lower body exercises; 30-60% of 1 RM for upper body exercises) performed at a fast contraction velocity with 3-5 min of rest between sets for multiple sets per exercise (three to five sets). It is also recommended that emphasis be placed on multiple-joint exercises especially those involving the total body. For local muscular endurance training, it is recommended that light to moderate loads (40-60% of 1 RM) be performed for high repetitions (915) using short rest periods (G90 s). In the interpretation of this position stand as with prior ones, recommendations should be applied in context and should be contingent upon an individual's target goals, physical capacity, and training
SQUATTING AND ITS VARIATIONS ARE PERHAPS THE MOST USED EXERCISE IN STRENGTH AND CONDITIONING. HOWEVER, THERE IS CONTROVERSY ON THE PROPER METHOD OF PERFORMING THE SQUATTING EXERCISE. WHEN COACHING THE SQUATTING EXERCISE, MECHANICS OF THE JOINTS AND SEGMENTS SHOULD BE CAREFULLY CONSIDERED TO OPTIMIZE THE TRAINING STIMULUS AND MINIMIZE INJURY POTENTIAL.
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
Many strength trainers believe that varying the foot position during the parallel squat or knee extension can target specific muscles of the quadriceps group. To test this theory, 10 men performed 3 parallel squats at added resistance equal to their body weight and 3 knee extensions at 8- to 10-RM resistance under 3 treatment conditions: toes pointed out, lateral rotation of the tibia (LR); toes straight forward, no rotation of the tibia (N); and inward, medial rotation of the tibia (MR). Lifts were separated by a 5-min rest. Bipolar surface electrodes placed on the bellies of the v. lateralis and v. medialis and on the lateral and medial portions of the rectus femoris revealed no significant differences in electrical activity for any muscle due to changes in foot position during the squat. During the knee extension, however, LR produced a significantly greater mean rmsEMG than the other foot positions across all muscles. Thus for the squat a lifter should choose the most stable and comfortable position. For the knee extension, however, maintaining a laterally rotated position is best.
(C) 1995 National Strength and Conditioning Association
The purpose of this investigation was to determine if there was a difference in kinetic variables and muscle activity when comparing a squat to a box squat. A box squat removes the stretch-shortening cycle component from the squat, and thus, the possible influence of the box squat on concentric phase performance is of interest. Eight resistance trained men (Height: 179.61 ± 13.43 cm; Body Mass: 107.65 ± 29.79 kg; Age: 24.77 ± 3.22 years; 1 repetition maximum [1RM]: 200.11 ± 58.91 kg) performed 1 repetition of squats and box squats using 60, 70, and 80% of their 1RM in a randomized fashion. Subjects completed the movement while standing on a force plate and with 2 linear position transducers attached to the bar. Force and velocity were used to calculate power. Peak force and peak power were determined from the force-time and power-time curves during the concentric phase of the lift. Muscle activity (electromyography) was recorded from the vastus lateralis, vastus medialis, biceps femoris, and longissimus. Results indicate that peak force and peak power are similar between the squat and box squat. However, during the 70% of 1RM trials, the squat resulted in a significantly lower peak force in comparison to the box squat (squat = 3,269 ± 573 N, box squat = 3,364 ± 575 N). In addition, during the 80% of 1RM trials, the squat resulted in significantly lower peak power in comparison to the box squat (squat = 2,050 ± 486 W, box squat = 2,197 ± 544 W). Muscle activity was generally higher during the squat in comparison to the box squat. In conclusion, minimal differences were observed in kinetic variables and muscle activity between the squat and box squat. Removing the stretch-shortening cycle during the squat (using a box) appears to have limited negative consequences on performance.
This study sought to compare the myoelectric activity of the hip adductors (HAs) and rectus femoris (RF) when the hip was in a neutral position or externally rotated by 30° or 50° (H0, H30, and H50, respectively) during a parallel squat. Ten healthy subjects performed 10 repetitions of squats in each of the 3 hip positions and the myoelectric activities of the HAs and RF were recorded. The signal was then divided into categories representing concentric (C) and eccentric (E) contractions in the following ranges of motion: 0-30° (C1 and E1), 30-60° (C2 and E2), and 60-90° (C3 and E3) of knee flexion. From those signals, an root mean square (RMS) value for each range of motion in each hip position was obtained. All values were normalized to those obtained during maximum voluntary isometric contraction. We found that HAs showed a significant increase in myoelectric activity during C3 and E3 in the H30 and H50 positions, as compared with H0. Meanwhile, RF activity did not significantly differ between hip positions. Both muscles showed higher activation during 60-90° (C3 and E3) of knee flexion, as compared with 0-30° (C1 and E1) and 30-60° (C2 and E2). The results suggest that if the aim is to increase HA activity despite the low percentage of muscle activation, squats should be performed with 30° of external rotation and at least 90° of knee flexion.
Many individuals involved in the sport of powerlifting believe that the squat and deadlift have such similar lifting characteristics that the lifts yield comparable training results. The aim of this study was to compare and contrast biomechanical parameters between the conventional style deadlift and the back squat performed by 25 lifters competing in regional powerlifting championship. The 3-dimensional analysis incorporated 4 60 Hz synchronized video cameras for collecting data from 25 participants. Parameters were quantified at the sticking point specific to each lift. Kinematic variables were calculated at the hip, knee, and ankle. Paired (samples) t-tests were used to detect significant differences in the kinematic mean scores for the different lift types. The statistical analysis revealed significant differences exist between the squat (0.09 m/s) and the deadlift (0.20 m/s) vertical bar velocities. Differences were found for angular position of the hip, knee, and ankle between lifts. The sticking point thigh angles were quantified as 32.54 +/- 3.02 and 57.42 +/- 4.57 for the squat and deadlift, respectively. Trunk angles were 40.58 +/- 6.29 (squat) and 58.30 +/- 7.15 (deadlift). The results indicate the back squat represents a synergistic or simultaneous movement, whereas the deadlift demonstrates a sequential or segmented movement. The kinematic analysis of the squat and the conventional deadlift indicate that the individual lifts are markedly different (p < 0.01), implying that no direct or specific cross-over effect exists between the individual lifts.
The primary objective of this study was to investigate current powerlifting training methods in light of anecdotal evidence purporting increased similarity with the explosive training practices of weightlifters. The study also assessed the prevalence of contemporary training practices frequently recommended for powerlifters in the popular literature. A 20-item survey was distributed to 32 elite British powerlifters at an International competition. The subject group included multiple national, international, and commonwealth champions and record holders. Based on 2007 competition results, the average Wilks score of the group was 450.26 +/- 34.7. The response rate for the surveys was 88% (28 of 32). The survey was sectioned into 6 areas of inquiry: a) repetition speed, b) explosive training load, c) resistance materials used, d) adjunct power training methods, e) exercise selection, and f) training organization. The results demonstrate that the majority of powerlifters train with the intention to explosively lift maximal and submaximal loads (79 and 82%, respectively). Results revealed that 39% of the lifters regularly used elastic bands and that 57% incorporated chains in their training. Evidence for convergence of training practices between powerlifters and weightlifters was found when 69% of the subjects reported using the Olympic lifts or their derivatives as part of their powerlifting training. Collectively, the results demonstrate that previous notions of how powerlifters train are outdated. Contemporary powerlifters incorporate a variety of training practices that are focused on developing both explosive and maximal strength.
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 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.
A simple external marker system and algorithms for computing lower extremity joint angle motion during level walking were developed and implemented on a computer-aided video motion analysis system (VICON). The concept of embedded axes and Euler rotation angles was used to define the three-dimensional joint angle motion based on a set of body surface markers. Gait analysis was performed on 40 normal young adults three times on three different test days at least 1 week apart using the marker system. Angular motion of the hip, knee, and ankle joints and of the pelvis were obtained throughout a gait cycle utilizing the three-dimensional trajectories of markers. The effect of uncertainties in defining the embedded axis on joint angles was demonstrated using sensitivity analysis. The errors in the estimation of joint angle motion were quantified with respect to the degree of error in the construction of embedded axes. The limitations of the model and the marker system in evaluating pathologic gait are discussed. The relatively small number of body surface markers used in the system render it easy to implement for use in routine clinical gait evaluations. Additionally, data presented in this paper should be a useful reference for describing and comparing pathologic gait patterns.
The purpose of this study was to quantify the relationship between musculotendinous stiffness and performance in eccentric, isometric, and concentric activities. Thirteen trained subjects performed a series of maximal effort eccentric, concentric, and isometric muscular contractions in a bench press-type movement. Additionally, subjects performed a series of quasi-static muscular contractions in a bench press movement. A brief perturbation was applied to the bar while these isometric efforts were maintained, and the resulting damped oscillations provided data pertaining to each subject's musculotendinous stiffness. Musculotendinous stiffness was significantly related to isometric and concentric performance (r = 0.57-0.78) but not to eccentric performance. These results are interpreted as demonstrating that the optimal musculotendinous stiffness for maximum concentric and isometric activities was toward the stiff end of the elasticity continuum. A stiffer musculotendinous unit may facilitate such performances by improving the force production capabilities of the contractile component, due to a combination of improved length and rate of shortening, and additionally by enhancing initial force transmission.
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.
The purpose of this study was to quantify biomechanical parameters employing two-dimensional (2-D) and three-dimensional (3-D) analyses while performing the squat with varying stance widths.
Two 60-Hz cameras recorded 39 lifters during a national powerlifting championship. Stance width was normalized by shoulder width (SW), and three stance groups were defined: 1) narrow stance squat (NS), 107 +/- 10% SW; 2) medium stance squat (MS), 142 +/- 12% SW; and 3) wide stance squat (WS), 169 +/- 12% SW.
Most biomechanical differences among the three stance groups and between 2-D and 3-D analyses occurred between the NS and WS. Compared with the NS at 45 degrees and 90 degrees knee flexion angle (KF), the hips flexed 6-11 degrees more and the thighs were 7-12 degrees more horizontal during the MS and WS. Compared with the NS at 90 degrees and maximum KF, the shanks were 5-9 degrees more vertical and the feet were turned out 6 degrees more during the WS. No significant differences occurred in trunk positions. Hip and thigh angles were 3-13 degrees less in 2-D compared with 3-D analyses. Ankle plantar flexor (10-51 N.m), knee extensor (359-573 N.m), and hip extensor (275-577 N.m) net muscle moments were generated for the NS, whereas ankle dorsiflexor (34-284 N.m), knee extensor (447-756 N.m), and hip extensor (382-628 N.m) net muscle moments were generated for the MS and WS. Significant differences in ankle and knee moment arms between 2-D and 3-D analyses were 7-9 cm during the NS, 12-14 cm during the MS, and 16-18 cm during the WS.
Ankle plantar flexor net muscle moments were generated during the NS, ankle dorsiflexor net muscle moments were produced during the MS and WS, and knee and hip moments were greater during the WS compared with the NS. A 3-D biomechanical analysis of the squat is more accurate than a 2-D biomechanical analysis, especially during the WS.
The specific aim of this project was to quantify knee forces and muscle activity while performing squat and leg press exercises with technique variations.
Ten experienced male lifters performed the squat, a high foot placement leg press (LPH), and a low foot placement leg press (LPL) employing a wide stance (WS), narrow stance (NS), and two foot angle positions (feet straight and feet turned out 30 degrees ).
No differences were found in muscle activity or knee forces between foot angle variations. The squat generated greater quadriceps and hamstrings activity than the LPH and LPL, the WS-LPH generated greater hamstrings activity than the NS-LPH, whereas the NS squat produced greater gastrocnemius activity than the WS squat. No ACL forces were produced for any exercise variation. Tibiofemoral (TF) compressive forces, PCL tensile forces, and patellofemoral (PF) compressive forces were generally greater in the squat than the LPH and LPL, and there were no differences in knee forces between the LPH and LPL. For all exercises, the WS generated greater PCL tensile forces than the NS, the NS produced greater TF and PF compressive forces than the WS during the LPH and LPL, whereas the WS generated greater TF and PF compressive forces than the NS during the squat. For all exercises, muscle activity and knee forces were generally greater in the knee extending phase than the knee flexing phase.
The greater muscle activity and knee forces in the squat compared with the LPL and LPH implies the squat may be more effective in muscle development but should be used cautiously in those with PCL and PF disorders, especially at greater knee flexion angles. Because all forces increased with knee flexion, training within the functional 0-50 degrees range may be efficacious for those whose goal is to minimize knee forces. The lack of ACL forces implies that all exercises may be effective during ACL rehabilitation.
Multiple factors are responsible for ACL tears. The key factor in the gender discrepancy appears to be dynamic, not static, and proximal, not distal. The factors involved in evaluating the female ACL are multiple. However, it is the dynamic movement patterns ot hip and knee position with increased flexion and a coordinated proximal muscle firing pattern to keep the body in a safe landing position that are the most critical factors. An ACL injury at an early age is a life-changing event. We can very successfully reconstruct and rehabilitate an ACL, but we cannot stop there. We must now go into the prevention arena. In the United States there is tremendous variation in the exposure and acquisition of skills of physical activities in our youth. Today, children are often playing inside, using computers and watching television-missing out on the opportunity to learn safe movement patterns. Therefore, physical movement classes should occur very early in life, teaching children to land safely and in control, similar to the cry of "get down, stay down" routinely heard during youth soccer. Similarly, specific strength training programs can address landing as well as foot movements during cutting in basketball. Coaches should issue stern warnings when athletes demonstrate a high-risk movement patterns such as one-leg landings, out-of-control baseline landings, or straight-leg landings. The warnings may serve to keep the athlete from "touching the hot stove again" for fear of getting burned. No athlete feels she will be the one to get injured. Therefore, prospective analysis is likely to be received more warmly by the athletes if the program is presented with an emphasis on performance improvement rather than injury prevention. With increased participation in these programs, multiple-center analysis will have the power necessary to determine which factors significantly predispose athletes to ACL injury. The future for injury prevention is bright. We must rise to the challenge.
The ability to optimise muscular power output is considered fundamental to successful performance of many athletic and sporting activities. Consequently, a great deal of research has investigated methods to improve power output and its transference to athletic performance. One issue that makes comparisons between studies difficult is the different modes of dynamometry (isometric, isokinetic and isoinertial) used to measure strength and power. However, it is recognised that isokinetic and isometric assessment bear little resemblance to the accelerative/decelerative motion implicit in limb movement during resistance training and sporting performance. Furthermore, most people who train to increase power would have limited or no access to isometric and/or isokinetic dynamometry. It is for these reasons and for the sake of brevity that the findings of isoinertial (constant gravitational load) research will provide the focus of much of the discussion in this review.
One variable that is considered important in increasing power and performance in explosive tasks such as running and jumping is the training load that maximises the mechanical power output (Pmax) of muscle. However, there are discrepancies in the research as to which load maximises power output during various resistance exercises and whether training at Pmax improves functional performance is debatable. There is also some evidence suggesting that Pmax is affected by the training status of the individuals; however, other strength variables could quite possibly be of greater importance for improving functional performance. If Pmax is found to be important in improving athletic performance, then each individual’s Pmax needs to be determined and they then train at this load. The predilection of research to train all subjects at one load (e.g. 30% one repetition maximum [1RM]) is fundamentally flawed due to inter-individual Pmax differences, which may be ascribed to factors such as training status (strength level) and the exercise (muscle groups) used. Pmax needs to be constantly monitored and adjusted as research suggests that it is transient. In terms of training studies, experienced subjects should be used, volume equated and the outcome measures clearly defined and measured (i.e. mean power and/or peak power). Sport scientists are urged to formulate research designs that result in meaningful and practical information that assists coaches and strength and conditioning practitioners in the development of their athletes.
