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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.
... Back squat: The free weight back squat is the most commonly performed squatting movement [40,41] and is considered to have the greatest potential to increase lower body strength [27,42]. Because of its ability to impact overall strength, the back squat and its variants have been considered to be one of the cornerstones of sports performance-based strength training interventions used by both professional and amateur athletes [9,10,[13][14][15]43]. ...
... An additional derivative of the free weight back squat that is often performed by powerlifters is the box squat [41,48]. The box squat requires the athlete to perform an eccentric phase (i.e., descent) followed by sitting on a box, typically for a minimum of 1 s, prior to executing the concentric phase (i.e., ascent) of the movement [41,48]. ...
... An additional derivative of the free weight back squat that is often performed by powerlifters is the box squat [41,48]. The box squat requires the athlete to perform an eccentric phase (i.e., descent) followed by sitting on a box, typically for a minimum of 1 s, prior to executing the concentric phase (i.e., ascent) of the movement [41,48]. The box squat can be performed in a full movement, in parallel movements, or in partial movements. ...
There is substantial evidence indicating that increased maximum strength as a result of training with squats, particularly full and parallel squats, is associated with superior athletic capabilities, such as sprinting, jumping and agility. Although full and parallel squats have been strongly associated with sport performance, there is also some evidence that the use of partial squats may provide angle specific adaptations that are likely advantageous for specific sporting activities. Partial squats may be particularly advantageous when trained in conjunction with full or parallel squats, as this practice results in a greater training effect. There is a paucity of evidence that squatting is associated with excessive injuries to the knees, lower back, or other structures. Evidence does indicate that squatting, including full squats, can be undertaken safely, provided an appropriate training methodology is applied. Indeed, based on scientific data, the cost/benefit ratio indicates that squats should be recommended and should be a central strength training exercise for the preparation of athletes in most sports, particularly those requiring strong and powerful whole body and lower body movements.
... As the knee flexion increases, the ability to absorb energy will further increase, especially when the knee joint angle exceeds 30 • (Lam, Liao, Kwok, & Pang, 2016). However, greater knee flexion or squatting leads to horizontal posterior displacement, posterior tilt of the pelvis, and a backward shift in the COM (Swinton, Lloyd, Keogh, Agouris, & Stewart, 2012). A previous study has found that the deep squatting posture has smaller functional stability limits (Sugama, Tonoike, & Seo, 2020), although the knee flexion angle was not reported, which suggests that lower COM postures can be more unstable and potentially dangerous for activities of daily living (Sugama et al., 2020) and working postures (gardening, welding, cutting large steel structures, etc.) related to the squatting posture (Jebelli, Ahn, & Stentz, 2016). ...
... Furthermore, as squat depth increases, the functional stability limits tend to decrease further (Sugama et al., 2020). Therefore, the significant reduction in COM height associated with a deeply flexed knee at 65 • is also important to explore (Jebelli et al., 2016;Sugama et al., 2020;Swinton et al., 2012). This research aims to understand the impact of suspensory strategy on postural stability, considering the effects on joint structure and the potential advantages of lowering the center of gravity. ...
... Additionally, in a deep squat, ankle motion is significantly limited in the lateral direction because the trochlea of the talus is tucked between the lateral malleolus of the fibula and the medial malleolus of the tibia. Previous studies also found that the COP position shifted more rearward compared to the erect standing posture (Swinton et al., 2012), with small functional stability limits (Sugama et al., 2020), suggesting that excessively deep squats were unstable (Jebelli et al., 2016;Sugama et al., 2020). Based on our findings, slight knee flexion is recommended for postural stabilization during the initial phase of sudden perturbation rather than a larger degree of knee flexion or lower COM height. ...
Postural stability is essential for performing daily activities and preventing falls, whereby suspensory strategy with knee flexion may play a role in postural control. However, the contribution of the suspensory strategy for postural control during sudden lateral perturbation remains unclear. We aimed to determine how suspensory strategy contributed to postural adjustment during sudden perturbation in the lateral direction and what knee flexion setting maximized its effect. Eighteen healthy young adults (10 male and 8 female) participated in this study. Kinematic data during lateral perturbation at three velocities (7, 15, and 20 cm/s) were collected under three knee flexion angle conditions (0 • , 15 • , and 65 •) using motion capture technology. Postural adjustments to the external perturbation were assessed by four parameters related to the temporal aspects of the center of mass (COM): reaction time, peak displacement/time and reversal time, and minimum value of the margin of stability (minimum-MOS). Our results showed that the COM height before the perturbation significantly lowered with increasing knee flexion angle. The COM reaction times for low and mid perturbation velocities were delayed at 65 • of knee flexion compared to 0 • and 15 • , and the COM reversal times were significantly shorter at 65 • of knee flexion than at 0 • and 15 • across all perturbation velocities. The minimum-MOS at the high-velocity of perturbation was significantly smaller at 65 • of knee flexion than at 0 • and 15 •. In conclusion, the adoption of a suspensory strategy with slight knee flexion induced enhanced stability during sudden external and lateral perturbations. However, excessive knee flexion induced instability.
... 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.
... It has been found that RIDs can result in different kinetic and kinematic outcomes depending on the intensity and design of the shaft shape (14). With regard to TRT, vertical force curves demonstrate a first peak associated with the beginning of the concentric phase, in the transition period between eccentric and concentric, followed by a short period of decreased force production and, ultimately, a second peak (32), which intensifies with heavier loads (28). The second peak is consistently associated with a higher barbell velocity for loads between 30 and 70% RM (32). ...
... Waveform analyses revealed that TRT generated higher vGRF and lower velocity during the first half of the concentric phase, and lower vGRF and higher velocity during the last quarter compared with RID (resulting in the matched overall MPV). The shape of vGRF observed in both devices was aligned with previous findings from the loaded squat exercise (Figure 2), marked by high initial values and low terminal values during the concentric phase (28,32). Despite the similar shape, RID exhibited a lower development of vGRF than TRT throughout the concentric phase, except in the final segment (70-95%), where RID achieved higher vGRF values. ...
Although rotary inertial devices (RIDs) have been used in resistance training for many years, there is still limited knowledge of the specific biomechanics that distinguish them from traditional resistance training (TRT) methods. The aim of this study is to
compare the serial data of force, velocity, and displacement over time in half-squats performed with both devices when the intensity is based on the concentric mean propulsive velocity (MPV). A total of 20 experienced subjects completed 3 sets of 6 half-squats using both RID and TRT. To ensure a similar load intensity, the concentric phase was matched according to the MPV. Measurements of vertical ground reaction force (vGRF), velocity, and displacement were taken for each repetition of the half-squat. The results showed that TRT exhibited a higher vGRF than RID during 0–57% of the concentric phase but a lower vGRF during 74–93% (p,0.001). Eccentric vGRF was also higher for TRT throughout much of the eccentric phase (0–13%, 38–54%, and 68–100%, p, 0.001). Rotary inertial device demonstrated faster vertical velocity than TRT during 31–52% of the concentric phase and 1–40% of the eccentric phase (p , 0.001). However, during the latter part of the concentric phase (72–99%), TRT exhibited faster vertical velocity compared with RID. In addition, TRT resulted in a higher vertical position than RID at the end (67–100%) of the concentric phase (p 5 0.036). Coaches should be aware of these biomechanical differences when prescribing resistance training with RID or TRT, as even with similar loads, distinct patterns in vGRF and velocity over time can lead to different effects on the athlete.
... In addition, when the pig is lying down, the ankle joint is in excessive dorsiflexion 54 , so the sensing line shows an upward broad peak, of course, the width of this peak depends on its squatting duration, and when the pig is standing up, the ankle joint changes from dorsiflexion to plantarflexion, and the trajectory of the sensing line decreases. However, due to the complexity of the squatting and rising process, the activities involved in the process are not only dorsiflexion and plantarflexion of the ankle joint 55 , so there are many small and miscellaneous peaks in the monitoring curves to be analyzed further (Fig. 6g). Of note, when the pig turned to the right, the sensor recorded a broad downward peak, reflecting the substantial supination movement of the right ankle joint during the turn 55 . ...
... However, due to the complexity of the squatting and rising process, the activities involved in the process are not only dorsiflexion and plantarflexion of the ankle joint 55 , so there are many small and miscellaneous peaks in the monitoring curves to be analyzed further (Fig. 6g). Of note, when the pig turned to the right, the sensor recorded a broad downward peak, reflecting the substantial supination movement of the right ankle joint during the turn 55 . Subsequent walking activity following the turn was also clearly captured (Fig. 6h). ...
Temporomandibular disorders (TMD) intelligent diagnosis promises to elevate clinical efficiency and facilitate timely TMD management for patients. However, development of TMD intelligent diagnostic tools with high accuracy and sensitivity presents challenges, particularly in sensing minute deformations and ensuring rapid self-recovery. Here we report a biocompatible hydrogel electronic sensor with instantaneous self-recovery (within 2.1 s) and ultra-low detection limit (0.005% strain). It could efficiently diagnose disc displacement with reduction (DDwR) with satisfactory accuracy of 90.00%, and also had a clear indication of the typical clinical manifestations of DDwR and the timing of temporomandibular joint (TMJ) clicking, with a sensitivity of up to 100% in human compared to the diagnostic criteria for TMD (DC/TMD). Furthermore, a predictive model based on waveform features achieved 84.4% accuracy and 86% sensitivity, reducing dependence on physicians. In summary, the hydrogel sensor is expected to become a radiation-free, non-invasive, practical and effective tool for future TMD diagnosis.
... Once the individual is able to recognize the neutral spine alignment in static standing posture, our recommendation is to start with the box squat exercise as it requires less lower extremity (LE) range of motion (ROM) and center of mass (COM) displacement and lower ground reaction forces [59]. Compared to the back squat, the box squat generates a lower extension peak moment at the L5/S1 level [59]. ...
... Once the individual is able to recognize the neutral spine alignment in static standing posture, our recommendation is to start with the box squat exercise as it requires less lower extremity (LE) range of motion (ROM) and center of mass (COM) displacement and lower ground reaction forces [59]. Compared to the back squat, the box squat generates a lower extension peak moment at the L5/S1 level [59]. When the client successfully performs the box squat, the health/fitness expert can progress the older client gradually to a back squat (Figure 3). ...
Background/Objectives: Falls pose a significant health risk for older adults, often due to balance disorders and decreased mobility. Methods: The ability to perform sit-to-stand transfers, which involve squatting, is crucial for daily independence. Incorporating squats into exercise routines can enhance lower body strength, reduce fall risk, and improve overall quality of life. Results: While the back squat is beneficial, proper form is essential to avoid biomechanical errors, like lumbar hyperlordosis and knee valgus. Conclusions: Health and fitness professionals, such as physical therapists and/or clinical exercise physiologists, should carefully guide older adults in performing the back squat, addressing any functional deficits, and ensuring proper technique to minimize the risk of injury and maximize the benefits.
... In addition, when the pig is lying down, the ankle joint is in excessive dorsiflexion 54 , so the sensing line shows an upward broad peak, of course, the width of this peak depends on its squatting duration, and when the pig is standing up, the ankle joint changes from dorsiflexion to plantarflexion, and the trajectory of the sensing line decreases. However, due to the complexity of the squatting and rising process, the activities involved in the process are not only dorsiflexion and plantarflexion of the ankle joint 55 , so there are many small and miscellaneous peaks in the monitoring curves to be analyzed further (Figure 6g). Of note, when the pig turned to the right, the sensor recorded a broad downward peak, reflecting the substantial supination movement of the right ankle joint during the turn 55 . ...
... However, due to the complexity of the squatting and rising process, the activities involved in the process are not only dorsiflexion and plantarflexion of the ankle joint 55 , so there are many small and miscellaneous peaks in the monitoring curves to be analyzed further (Figure 6g). Of note, when the pig turned to the right, the sensor recorded a broad downward peak, reflecting the substantial supination movement of the right ankle joint during the turn 55 . Subsequent walking activity following the turn was also clearly captured (Figure 6h). ...
Temporomandibular disorders (TMD) intelligent diagnosis promises to elevate clinical efficiency, facilitating timely TMD management for patients and staving off the emergence of severe TMJ disability and pain. However, development of TMD intelligent diagnostic tools with high accuracy and sensitivity faces challenges, particularly in sensing minute deformations and ensuring rapid self-healing. Here, inspired by clinical joint palpation, based on the minute facial deformations (0.31-1.62 mm) caused by subtle TMJ movements, we report a biocompatible hydrogel electronic sensor that is capable of instantaneous self-healing (within 2.1 s) and ultra-low detection limit (0.005% strain). The clinical trials involving 120 cases demonstrated that it can efficiently identify the typical clinical manifestations of TMD, such as joint clicking, the adjunctive diagnosis of TMD with repeatability (Kappa=0.86) and a satisfactory accuracy of 90.00%, and it also had a clear indication of other uncoordinated TMJ activity and the timing of TMJ clicking, with a sensitivity of up to 100% for the diagnosis of TMD. Furthermore, to mitigate the reliance on physicians for the diagnostic tool, a predictive model based on sensing waveform features was constructed, achieving high accuracy of 84.4% and sensitivity of 0.86. In summary, the hydrogel sensor, to the best of our knowledge, is the first hydrogel-based strain sensor used for TMD monitoring and is expected to become a radiation-free, non-invasive, convenient and efficient examination tool for clinical TMD diagnosis in the future.
... In examining biomechanical differences between the resistance exercises, previous research has focused on differences in levels of maximum trunk and knee flexion, as well as lower-body net joint moments between the exercises (25,26). Subsequently, maximum trunk (u trunk ) and knee (u knee ) flexion and maximum net internal joint extension moments at the hip (M hip ) and knee (M knee ) occurring throughout the entire movement were identified and used for analysis for both techniques. ...
... and an average u knee of 78.8°( 611.2°). Under BS conditions, Swinton et al. (25) and Cotter et al. (8) found average maximum u knee values of 121.1°(63.4°) and 123.7°(62.0°), ...
Stahl, CA, Regni, G, Tanguay, J, McElfresh, M, Trihy, E, Diggin, D, and King, DL. A biomechanical comparison of the back squat and hexagonal barbell deadlift. J Strength Cond Res 38(5): 815–824, 2024—Coaches often use different exercises to encourage similar strength adaptations and limit monotony. Anecdotally, the hexagonal barbell deadlift (HBD) exhibits similarities to the back squat (BS). To date, research has not examined the empirical differences between these exercises. This study examined kinematic and kinetic differences between the BS and the HBD across different loads. Sixteen resistance-trained individuals (6 men and 10 women) volunteered to participate. Subjects performed 1-repetition maximum (1RM) testing under BS and HBD conditions. Kinematic and kinetic data were collected during performance of both exercises at submaximal (warm-up sets) and maximal (1RM) loads using a 3D motion capture and force-plate system. Results showed that subjects lifted greater 1RM loads in the HBD relative to the BS ( p < 0.05; d = −1.75). Kinematic data indicated that subjects exhibited greater maximum forward lean of the trunk and decreased maximum knee flexion while performing the HBD compared with the BS. The BS resulted in higher maximum extension moments at the hip joint than the HBD. Maximum extension moments at the knee joint showed no difference between the exercises. Data suggest that bar design and position facilitate balanced moment arm length at hip and knee joints during performance of the HBD. By contrast, bar position during performance of the BS increases moment arm length at the hip joint, making it a hip-dominant exercise. The present data have implications for the programming of both exercises. Future research should examine differences in muscle-activation strategies between the 2 exercises.
... With the exception of knee rehabilitation patients, the contemporary literature suggests it should not be practiced on a general basis. stance [11], avoiding AKD cannot be achieved by most athletes performing different barbell squat techniques [7,9,11,12]. Given that deep barbell squat variations, such as deep high-bar back squats (DHBBSs) and deep front squats (DFSs), provide several fundamental benefits, including greater muscle activation, improved functional capacity, and higher athletic performance, as well as performance-enhancing transfer effects of dynamic maximal strength to dynamic speed-strength of hip and knee extensors [13][14][15], they are likely to be preferred over variations where the range of motion is deliberately limited under most circumstances. ...
... Although the deliberate restriction of AKD can reduce the torque on the knees, traditional recommendations of AKD result in altered knee and hip coordination [7], with a stronger upper body inclination [2,8,9], enhanced trunk flexion in the thoracic and lumbar spine [10], and consequently, disproportionately high forces transferred towards the hip joints and lower back. Additionally, most athletes employing various barbell squat techniques cannot prevent AKD when using a moderate foot stance, which is indicated by an outward-directed foot angle of roughly 20 • , with the toes pointed laterally in conjunction with a shoulder-width stance [7,9,11,12]. As deep barbell squat variations, such as DHBBSs and DFSs, offer a number of fundamental advantages, such as increased muscular activation, improved functional capacity, superior athletic performance, and performance-enhancing transfer effects of dynamic maximum strength to dynamic speed-strength of hip and knee extensors, these techniques are likely to be chosen over variations where the range of motion is deliberately limited [13][14][15]. ...
Based on seminal research from the 1970s and 1980s, the myth that the knees should only move as far anterior during the barbell squat until they vertically align with the tips of the feet in the sagittal plane still exists today. However, the role of both the hip joint and the lumbar spine, which are exposed to high peak torques during this deliberate restriction in range of motion, has remained largely unnoticed in the traditional literature. More recent anthropometric and biomechanical studies have found disparate results regarding anterior knee displacement during barbell squatting. For a large number of athletes, it may be favorable or even necessary to allow a certain degree of anterior knee displacement in order to achieve optimal training outcomes and minimize the biomechanical stress imparted on the lumbar spine and hip. Overall, restricting this natural movement is likely not an effective strategy for healthy trained individuals. With the exception of knee rehabilitation patients, the contemporary literature suggests it should not be practiced on a general basis.
... 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.
... Box squat and seated box squat jump: The box squat, in which athletes sit back onto a box before driving upward, is commonly used to strengthen the squat pattern and develop power (55) and RFD (94). When performed with a brief pause at the bottom position (replicating the zero-velocity point in a countermovement), the exercise minimizes elastic energy contributions, requiring the muscle groups involved in the propulsive phase to generate force independently (55). ...
Volleyball, with its global popularity and rigorous competition schedules, presents unique challenges in athlete conditioning and injury risk reduction. This narrative review synthesizes the current understanding of the physical demands and injury risks associated with elite volleyball play, offering a detailed analysis of match play dynamics and prevalent injury mechanisms. It emphasizes the important role of strength and conditioning (S&C) coaches in developing training programs to enhance performance and mitigate injury risks through strategic exercise selection and periodization. The review provides a thorough needs analysis, highlighting specific conditioning requirements for different player positions and detailing effective physical testing protocols. Recommendations are made for implementing structured S&C programs, which are vital for preparing athletes for the physical challenges of competitive volleyball. Practical guidelines are outlined for S&C coaches to optimize training outcomes, including suggestions for drill sequences and conditioning routines that reflect the sport-specific demands of volleyball. Thus, this review aims to equip coaches, trainers, and athletes with the knowledge and tools necessary to elevate their performance and safeguard against injuries, thereby contributing to the advancement and sustainability of volleyball as a high-intensity competitive sport.
... Under conditions resulting in greater forward trunk flexion, moment forces increase about the hip. These reduced joint moments would be beneficial as they would require less internal moments being generated, which would reduce joint reaction forces [13,14,[31][32][33]. For novice athletes, modifications to the squat mechanism, such as EHs or squat widths, may be beneficial [17,[34][35][36][37]. Collectively, these findings indicate that EHs can improve squat stability by reducing the trunk lean and COP excursion. ...
The back squat (BS) is one of the most effective exercises for enhancing lower limb strength, but an unstable squat can increase shear forces in the lower back. Understanding how to assess the squat stability is useful for avoiding potential sports injury. During the BS, the trunk lean and center of pressure (COP) are relevant to squat safety, and these kinematics can be altered by elevating the heel. However, there is no relevant meta-analysis on the impact of different heel heights on squat stability. This study aims to bridge the gap in the literature by conducting a systematic review and network meta-analysis on how heel elevation affects squat stability. By quantifying the influence of different heel heights on key biomechanical parameters, such as the center of pressure deviation and ankle dorsiflexion, the study provides actionable insights for athletes, trainers, and clinicians. Fourteen articles were included, and the majority of these studies demonstrated that elevated heels (EHs) can reduce COP deviation and trunk lean. In addition, 25 mm heels may be the preferred option for squat stability in the AP direction when COP data and network meta-analysis are combined. However, in the ML direction, the capacity to maintain balance is rather questionable; when ankle peak dorsiflexion is combined, 8 mm heels have higher COP deviation values and 5 mm heels have lower COP deviation values. Regarding limitations, reliance on a single bias assessment tool (Cochrane Risk of Bias Tool) might not fully capture methodological variability across non-RCT studies. Future systematic reviews could consider using multiple bias assessment tools for robust assessment.
... This further demonstrates the active role of the hip joint in the squat, providing effective supportive assistance to the knee joint [32,49,50]. The hip joint primarily provides the necessary force support during the squat and helps adjust the COM position during knee flexion-extension [46,51]. The control of hip external and internal rotation is particularly crucial during significant knee flexion-extension, as it helps maintain a stable pelvic and trunk posture, preventing excessive anterior displacement or a posterior tilting of the COM [52]. ...
Background: Barbell squats are commonly used in strength training, but the anterior–posterior displacement of the Center of Mass (COM) may impair joint stability and increase injury risk. This study investigates the key factors influencing COM displacement during different squat modes.; Methods: This study recruited 15 male strength training enthusiasts, who performed 60% of their one-repetition maximum (1RM) in the Front Barbell Squat (FBS), High Bar Back Squat (HBBS), and Low Bar Back Squat (LBBS). Joint moments at both the hip, knee, and ankle were collected using a motion capture system and force plates, and a factor regression analysis was conducted using SPSS.; Results: In the FBS, primary factors influencing COM displacement included right knee adduction–abduction (38.59%), knee flexion–extension (31.08%), and hip internal–external rotation (29.83%). In the HBBS, they were right ankle internal–external rotation (19.13%), hip flexion–extension (−19.07%), and left knee flexion–extension (19.05%). In the LBBS, the key factors were left knee adduction–abduction (27.82%), right ankle internal–external rotation (27.59%), and left ankle internal–external rotation (26.12%).; Conclusion: The study identifies key factors affecting COM displacement across squat modes, with knee flexion–extension being dominant in the FBS and hip moments more significant in the HBBS and LBBS. These findings have implications for optimizing squat training and injury prevention strategies.
... In support of this, Andersen et al. (1) reported increased hip extensor sEMG amplitudes in conventional compared with hex-bar deadlifts during 1RM. Anecdotally, this may lead practitioners to equate hex-bar deadlifts with back squats because of the increased knee flexion angle, which may not be the case as the back squat is reported in several studies to have different hip and knee flexion angles (28,30) than studies on the hex-bar (31). ...
Gundersen, AH, van den Tillaar, R, Falch, HN, Fredriksen, AB, and Larsen, S. A biomechanical comparison between conventional,
sumo, and hex-bar deadlifts among resistance trained women. J Strength Cond Res XX(X): 000–000, 2024—The deadlift is
a multijoint exercise frequently used to strengthen the lower extremities and spinal erectors. Despite variations, such as the
conventional, sumo, and hex-bar deadlifts, little is known about how these techniques affect the concentric phase of maximal
deadlifts among strength trained women. Therefore, this study used statistical parametric mapping to compare kinematics, net joint moments (NJMs), and surface electromyography amplitude between these deadlift variations during the last repetition of a 3
repetition maximum (3RM) in strength trained women. Eleven women (body mass: 67.64 6 7.27 kg, height: 161.91 6 3.05 cm, age: 23.18 6 3.46 years) performed 3RM deadlifts in conventional, sumo, and hex-bar deadlifts, lifting 103.18 6 18.47, 101.54 6 15.01, and 99.70 6 15.94 kg, respectively. The main findings showed that deadlifting with conventional and sumo techniques resulted in larger hip NJMs near the lockout. Conversely, deadlifting with the hex-bar technique resulted in greater barbell velocity, knee NJMs, and increased hip and knee flexion angles. Therefore, when training maximal 3RM deadlifts, we suggest that hex-bar deadlifts may be beneficial for targeting knee extensors and enhancing barbell velocity among strength trained women. Conversely, sumo and conventional deadlifts may be more effective for targeting the hip extensors near the lockout during the last repetition of 3RM deadlifts.
... The squat is considered one of the best exercises to improve physical fitness as its execution requires the simultaneous recruitment and coordination of multiple muscle groups of the trunk and lower limbs (1). In fact, it is a multijoint exercise that mainly involves the hips, knees, and ankles, and which athletes of different sports perform to train the strength of lower limbs and back muscles (2)(3)(4). The squat can be a bodyweight exercise, or it can be performed with a barbell. ...
Introduction
This study aimed to evaluate the angular kinematics of the hip, knee, ankle, and the linear kinematics of the barbell during the back squat (BS) at different load intensities in powerlifters and weightlifters.
Methods
Seventeen athletes were recruited (n = 14 powerlifters; n = 3 weightlifters). The 1-RM of the BS of each participant was calculated and, 1-week after, each participant was asked to perform 5 trials of the BS at different load intensities (i.e., 60%, 70%, 80%, 90%, 100%) of the 1-RM. An action camera recorded the execution of each BS trial in the sagittal plane and, afterward, the videos were analyzed by measuring the range of motion (ROM) of hip, knee, and ankle for the angular kinematics, and the timing, distances, speeds, and accelerations of the barbell for the linear kinematics.
Results
Regarding the angular kinematics, no significant differences were found in the parameters in the starting and ending positions among the 5 trials, while a significant decrease was found in the hip relative angle (p = 0.026) in the maximum flexion position as load intensity increased. Regarding the linear kinematics, a significant difference was found in the descent acceleration (p = 0.049) in the descent phase, while a significant difference was found in the ascent speed (p < .001) and vertical speed of ascent (p < .001) in the ascent phase, which decreased as load intensity increased.
Discussion
Our findings show that the angular and linear kinematics of BS change as load intensity increases.
... al. 5 examined the effect of knee position on hip and knee torques during the back squat, while Escamilla et al. 6 explored biomechanical parameters while performing the back squat with varying stance widths, and Swinton et. al. 7 compared the biomechanics of the box squat, traditional squat, and powerlifting squat. ...
Background
It is important to assess the quality of fundamental movements, to discover deficits, evaluate mobility, balance, and stability, and identify movement dysfunction and asymmetries. However, little research has been performed on the assessment of fundamental movements with bodybuilders.
Purpose
The purpose of this research was to examine the quality of professional and amateur bodybuilders’ functional movements and the quality of the back squat performance. A secondary purpose was to discern whether greater experience in bodybuilding was associated with better scores on the back squat assessement (BSA).
Study design
Cross-Sectional Cohort
Methods
Twenty-six athletes were recruited to participate. The group of professional bodybuilders consisted of five men and six women, a total of 11 athletes. The group of amateur bodybuilders consisted of seven men and eight women, a total of 15 athletes. The Functional Movement Screen™ (FMS™) was used to assess the seven included fundamental patterns that evaluate an individual’s neuromuscular control, mobility, balance, and stability. The BSA was used to assess the quality of movement, dysfunction, deficit, or compensation during the squat exercise. Statistical analyses applied non-parametric tests (Wilcoxon, Mann-Whitney U, and Friedman’s) for dependent and independent samples, with significance set at p<0.05, and the Spearman correlation coefficient and Chi-square test were used to assess relationships between quantitative and qualitative variables.
Results
Overall, athletes with a higher total FMS™ score performed better on the BSA as well. The professional athletes scored 2.58 points higher than the amateurs on total FMS™ scores (p<0.001).
Professional athletes scored better on the BSA than amateurs (p<0.001). A statistically significant, positive moderate correlation was revealed between the FMS™ total score and the squat total score (r=0.68; p=0.005).
Conclusions
A higher FMS™ score in bodybuilders is associated with a higher BSA score. Professional bodybuilders have higher FMS™ scores and higher BSA scores than amateurs. Greater experience in bodybuilding is associated with the compliance with several BSA criteria: trunk position, frontal knee alignment, tibial translation angle, foot position in all three back squat variations with different external loads, and descent with the training weight.
Level of Evidence
3b
... For the back squat exercise much research has examined squat variations [e.g., front squat, box squat, unilateral variants (3, 8,22,24,[33][34][35]37)], placement of the barbell [e.g., high-bar and low-bar (13,21)], body positioning [e.g., variances in the hip, knees, feet, torso, depth (5,6,8,33)], muscle activation (7,8,33), and even squat visual cues (2,8), to name a few. However, much less is known about the effects of the loading implement itself on back squat outcomes, especially regarding specific barbell variations beyond the traditional OL barbell (16,22). ...
This study examined using a traditional Olympic (OL) or safety squat bar (SSB) barbell on force, velocity, and perceived exertion during an acute session of high-intensity back squats in adults. Twelve recreationally trained men (23.0±2.6 years; 88.3±19.1 kg) randomly completed two sessions of 3 sets of 6 repetitions at the same absolute load using the OL barbell or SSB barbell. Force and velocity were measured on every repetition and rating of perceived exertion (RPE) was assessed for each set. A two-way ANOVA (set x barbell) with repeated measures and Sidak post-hoc test (repetitions set-by-set) or paired t-test (repetitions independent of set) were used (p<0.05). Compared to a traditional OL barbell, using a SSB barbell resulted in no significant differences in peak force (2443.0±46.6 vs 2622.9±65.8 N, respectively; d=0.28) or average set RPE (7.8±0.8 vs 8.0±1.2, respectively; d=0.15) during an acute multi-set high-intensity back squat session. In contrast, compared to a traditional OL barbell, using a SSB barbell resulted in significantly (p<0.05) lower average velocity (0.42±0.04 vs 0.38±0.05 m/s, respectively; d=0.27) during the same parameters. When performing the back squat exercise recreationally resistance-trained adults exhibit similar peak force and perceived effort with OL or SSB barbells, but greater velocities can be achieved with the OL barbell. Practitioners working with adults to develop lower body strength and power with the back squat exercise across multiple sets can interchangeably use the OL or SSB barbells to similarly train force, but training velocity is trivially better with the OL barbell acutely.
... the hBBs is commonly used by weightlifting athletes while the lBBs by powerlifting athletes [7]. Regardless of two different variations of the back squat, several studies analysed different aspects of the back squat such as kinematics, kinetics and electromyographic activities of the recruited muscles during the execution of the exercise in both powerlifting and weightlifting athletes, regardless of gender, weight and age categories [7][8][9][10][11][12][13]. a seminal study reported that the execution of the back squat with high weights, approaching the 1-RM, is a measure of different lower body characteristics such as strength, power, balance and coordination [14]. ...
Background
The movement of the barbell has been detected as success factor for the snatch and the clean and jerk events. As the barbell’s movement has been shown to be related to the athlete’s body movement, we hypothesized that the latter could be a success factor also for the back squat (BS) event. Hence, this study aimed to investigate postural control during the execution of the BS at different load intensities in powerlifters and weightlifters.
Methods
Seventeen powerlifters and weightlifters were enrolled and the one-repetition maximum (1-RM) of the BS of each participant was measured. Afterwards, the assessment of postural control during the execution of the BS at different load intensities (i.e. 60%, 70%, 80%, 90%, 100%) of the 1-RM of each participant was carried out through a posturographic platform to measure the displacement of the centre of pressure (CoP). The following parameters were considered: sway path length (SPL), sway ellipse surface (SES), length/surface (LFS ratio), sway mean speed (SMS), CoP coordinates along X and Y planes.
Results
We found a significant increase in SPL and LFS ratio, and a significant decrease in SMS as the load intensity increased. In detail, we detected a significant difference in: (a) SPL between the BS at 60% and 80%, 60% and 90%, 60% and 100%; between the BS at 70% and 90%, 70% and 100%; between the BS at 80% and 100%; and between the BS at 90% and 100%; (b) SMS between the BS at 60% and 80%, 60% and 90%; (c) LFS ratio between the BS at 60% and 90%, 60% and 100%.
Conclusions
These results suggest that powerlifters and weightlifters adopt different postural control strategies depending on the load intensity when performing the BS. Our findings showed that higher effort could affect postural control during the BS. Thus, postural control could be considered a success factor for the BS.
... Specifically, the box squat exercise showed less medial tibial translation and less range of motion of the tibiofemoral joint in internal-external rotation and medial-lateral translation than other knee extension motions (Li et al., 2022). Regarding the differences between the squat and box squat, the shin maintained a less inclined position during box squat, resulting in lower peak joint moments at the spine and ankle (Swinton, Stewart, Lloyd, Keogh, & Agouris, 2012). Nevertheless, the peak force and power were similar, and minimal differences were observed for muscle activity (Mcbride, Szkinner, Schafer, Haines, & Kirby, 2010). ...
The aims of this study were to assess (i) the load–velocity relationship during the box squat exercise in women survivors of breast cancer, (ii) which velocity variable (mean velocity [MV], mean propulsive velocity [MPV], or peak velocity [PV]) shows stronger relationship with the relative load (%1RM), and (iii) which regression model (linear [LA] or polynomic [PA]) provides a greater fit for predicting the velocities associated with each %1RM. Nineteen women survivors of breast cancer (age: 53.2 ± 6.9 years, weight: 70.9 ± 13.1 kg, and height: 163.5 ± 7.4 cm) completed an incremental load test up to one‐repetition maximum in the box squat exercise. The MV, MPV, and the PV were measured during the concentric phase of each repetition with a linear velocity transducer. These measurements were analyzed by regression models using LA and PA. Strong correlations of MV with %1RM (R² = 0.903/0.904; the standard error of the estimate (SEE) = 0.05 m.s⁻¹ by LA/PA) and MPV (R² = 0.900; SEE = 0.06 m.s⁻¹ by LA and PA) were observed. In contrast, PV showed a weaker association with %1RM (R² = 0.704; SEE = 0.15 m.s⁻¹ by LA and PA). The MV and MPV of 1RM was 0.22 ± 0.04 m·s⁻¹, whereas the PV at 1RM was 0.63 ± 0.18 m.s⁻¹. These findings suggest that the use of MV to prescribe relative loads during resistance training, as well as LA and PA regression models, accurately predicted velocities for each %1RM. Assessing and prescribing resistance exercises during breast cancer rehabilitation can be facilitated through the monitoring of movement velocity.
... In the deep squat following the half squat, the contribution of other joint motions except for the ankle would be necessarily increased more because the ankle motion is limited by the anatomical motion restrictions of the ankle. Furthermore, with increasing squat depth (i.e., deep squatting), the horizontal posterior displacement and posterior tilt of the pelvis increased, and the COM shifted backward (Swinton et al., 2012). In cases where heel-off is not permitted, the ankle motion turns from dorsiflexion to plantarflexion (Dionisio et al., 2008;Schoenfeld, 2010). ...
Squatting is a common motion in activities of daily living and is frequently used in training programs. Squatting requires a shift of the body in both vertical and anterior-posterior directions. Postural control during squatting is considered a mixed strategy; however, details and roles of the trunk and lower limb joints are unclear. The purpose of this study was to investigate the relationship among the kinematics of the lower limb, the trunk and the center of mass (COM) descent during squatting. Twenty-six healthy young adults performed repeated parallel squats. Lower limb joint and trunk angles and the COM were analyzed using a 3D motion analysis system. We evaluated the relationship between the kinematics and the squat depth by performing correlation analysis and multiple linear regression analysis. The ankle was the first to reach its maximum angle, and the remaining joints reached their maximum angles at the maximum squat depth. The knee joint motion and the squat depth were significantly correlated and there was a correlation between the hip and the ankle joint motion and the anteroposterior displacement of the COM during squatting. Multivariate linear regression analysis indicated that squat depth was predicted by both the knee and ankle motion and that anteroposterior displacement of the COM was predicted by the hip, ankle, and knee joint motion. The knees contributed to the vertical COM motion during squatting, while the hips contributed to the COM motion in the anteroposterior direction. On the other hand, the ankles contributed to COM motions in both the vertical and anteroposterior directions during squatting.
... For example, doubling the load will double the extensor torques at the hip, knee, and ankle. (Further details concerning the static stick figure and its limitations are provided in Appendix A.) Despite its limitations, the static stick figure in Appendix A can explain the findings of studies that examined many variations of the squat exercise, such as comparing the high-bar with the lowbar back squat (20,21,36), the front squat with the back squat (11,23,37), restricted with unrestricted squats (18), and the back squat with the box squat (33). However, less is known about the squat using the safety-squat bar (SSB). ...
Johansson, DG, Marchetti, PH, Stecyk, SD, and Flanagan, SP. A biomechanical comparison between the safety-squat bar and traditional barbell back squat. J Strength Cond Res 38(5): 825-834, 2024-The primary objectives for this investigation were to compare the kinematic and kinetic differences between performing a parallel back squat using a traditional barbell (TB) or a safety-squat bar (SSB). Fifteen healthy, recreationally trained male subjects (23 + 4 years of age) performed the back squat with a TB and an SSB at 85% of their respective 1 repetition maximum with each barbell while instrumented for biomechanical analysis. Standard inverse dynamics techniques were used to determine joint kinematic and kinetic measures. A 2 3 3 (exercise 3 joint) factorial analysis of variance with repeated measures was used to determine the kinetic and kinematic differences between the squats while using the different barbells. Fisher's least significant difference post hoc comparisons showed that the TB resulted in significantly greater maximum hip flexion angle (129.33 6 11.8˚vs. 122.11 6 12.1˚; p , 0.001; d 5 1.80), peak hip net joint extensor torque (2.54 6 0.4 Nm·kg 21 vs. 2.40 6 0.4 Nm·kg 21 ; p 5 0.001; d 5 1.10), hip net extensor torque mechanical energy expenditure (MEE; 2.81 6 0.5 Nm·kg 21 vs. 2.58 6 0.6 Nm·kg 21 ; p 5 0.002; d 5 0.97), and ankle net joint plantar flexor torque MEE (0.32 6 0.09 J·kg 21 vs. 0.28 6 0.06 J·kg 21 ; p 5 0.029; d 5 0.63), while also lifting significantly (123.17 6 20.8 kg vs. 117.17 6 20.8 kg; p 5 0.005; d 5 0.858) more weight than the SSB. The SSB resulted in significantly higher maximum knee flexion angles (116.82 6 5.8˚vs. 115.65 6 5.6˚; p 5 0.011; d 5 0.75) than the TB, with no significant difference in kinetics at the knee. The TB may be preferred to the SSB for developing the hip extensors and lifting higher maximum loads. The SSB may be advantageous in situations where a more upright posture or a lower load is preferred while creating a similar demand for the knee joint.
... Paul. reported differences in lower limb kinematics and kinetics using different percentages of 1RM squat methods (Swinton et al., 2012). This indicates that different training strategies effectively enhance performance levels with different resistances within an 8-week timeframe. ...
Objective: To assess the effects of 8 weeks of unilateral (UNI), bilateral (BI), and combined unilateral + bilateral (UNI + BI) resistance training on bench press and squat strength in adolescent boxers.
Methods: Using the Gym Aware linear accelerometer, free-weight squat and bench press strength exercises were evaluated after an 8-week training intervention. Thirty adolescent boxers were randomly assigned to three groups: UNI, height: 1.73 ± 0.08 m, weight: 55.42 ± 5.85 kg; UNI + BI, height: 1.7 ± 0.06 m, weight: 54.73 ± 5.33 kg; and BI, height: 1.74 ± 0.06 m, weight: 59.67 ± 8.39 kg. Each group followed their designated UNI/BI/UNI + BI compound resistance training protocols, and the effects of 8 weeks of single-sided and bilateral intervention training on the performance of free-weight squat and bench press exercises at 30%, 50%, and 80% of 1-repetition maximum (1RM) were evaluated.
Results: Significant improvements were observed in the 30% 1RM, 50% 1RM, and 80% 1RM outcomes for both squat and bench press exercises before and after the interventions (p < 0.05, p < 0.01). In the intergroup comparison, GymAware measurements revealed that the UNI and UNI + BI groups exhibited superior peak power values for squat and bench press exercises at 30% 1RM compared to the BI group.
Discussion: UNI and UNI + BI training led to significantly higher output power values in bench press and squat exercises at 30% 1RM compared to the BI training group.
... Yet, it was possible to estimate the individual patellar tendon strain during squats as a function of the maximum patellar tendon strain during an isometric MVC and the 1RM percentages with high accuracy (R 2 = 0.858), which also confirms our second hypothesis. The resultant knee joint moments during the squats ranged on average from 126 to 226 Nm, which agrees with earlier reported values 20,21 . There was a progressive increase in the resultant knee, hip and ankle joint moment as well as in the EMG-activity of the investigated knee extensor muscles with increasing percentages of the 1RM in all participants, indicating a gradual increase of muscle loading. ...
Tendon strain during exercise is a critical regulatory factor in tendon adaptive responses and there are indications for an optimal range of strain that promotes tendon adaptation. Back squats are used to improve patellar tendon properties in sport and clinical settings. To date, the operating patellar tendon strain during back squats is unknown and current recommendations for individual exercise loading are based on the one repetition maximum (1RM). Here, we quantified patellar tendon strain during loaded back squats at 40, 60 and 80% of the 1RM and during maximum isometric knee extension contractions (MVC) using ultrasonography. Kinematics, ground reaction forces and muscle electromyographic activity were also recorded. Additionally, maximum tendon strain during the MVC and the percentage of 1RM were used as explanatory variables to estimate the individual patellar tendon strain during the squats. Strain increased with increasing 1RM loading (4.7 to 8.2%), indicating that already medium-loading back squats may provide a sufficient stimulus for tendon adaptation. The individual variability was, however, too high to generalize these findings. Yet, there was a high agreement between the individually estimated and measured patellar tendon strain (R² = 0.858) during back squats. We argue that this approach may provide new opportunities for personalized tendon exercise.
... It should be noted that a dichotomous approach in which individuals are labelled as (non-)responders on the basis of a single threshold is not without criticism. A single response threshold is more likely to distinguish a "true" response from an uncertain response than a "true" nonresponse [26,27]. Moreover, classifying subjects as nonresponders on the basis of a single parameter neglects the wide range of possible biological training adaptations [28]. ...
Background
Standardized training prescriptions often result in large variation in training response with a substantial number of individuals that show little or no response at all. The present study examined whether the response in markers of cardiorespiratory fitness (CRF) to moderate intensity endurance training can be elevated by an increase in training intensity.
Methods
Thirty-one healthy, untrained participants (46 ± 8 years, BMI 25.4 ± 3.3 kg m⁻² and V˙O2max 34 ± 4 mL min⁻¹ kg⁻¹) trained for 10 weeks with moderate intensity (3 day week⁻¹ for 50 min per session at 55% HRreserve). Hereafter, the allocation into two groups was performed by stratified randomization for age, gender and VO2max response. CON (continuous moderate intensity) trained for another 16 weeks at moderate intensity, INC (increased intensity) trained energy-equivalent for 8 weeks at 70% HRreserve and then performed high-intensity interval training (4 × 4) for another 8 weeks. Responders were identified as participants with VO2max increase above the technical measurement error.
Results
There was a significant difference in V˙O2max response between INC (3.4 ± 2.7 mL kg⁻¹ min⁻¹) and CON (0.4 ± 2.9 mL kg⁻¹ min⁻¹) after 26 weeks of training (P = 0.020). After 10 weeks of moderate training, in total 16 of 31 participants were classified as VO2max responders (52%). After another 16 weeks continuous moderate intensity training, no further increase of responders was observed in CON. In contrast, the energy equivalent training with increasing training intensity in INC significantly (P = 0.031) increased the number of responders to 13 of 15 (87%). The energy equivalent higher training intensities increased the rate of responders more effectively than continued moderate training intensities (P = 0.012).
Conclusion
High-intensity interval training increases the rate of response in VO2max to endurance training even when the total energy expenditure is held constant. Maintaining moderate endurance training intensities might not be the best choice to optimize training gains.
Trial Registration German Clinical Trials Register, DRKS00031445, Registered 08 March 2023—Retrospectively registered, https://www.drks.de/DRKS00031445
... However, the major challenge involved in exoskeleton-assisted squatting is inter-subject variability. The biomechanical movements, patterns of muscle activation, and range of motion are highly subject-specific and therefore vary across individuals (Swinton et al., 2012). To address this challenge, a personalized assistance technique was developed using the human-in-the-loop (HIL) optimization scheme (Felt et al., 2015;Zhang et al., 2017;Ding et al., 2018;Kim et al., 2019). ...
Introduction: Recent studies found that wearable exoskeletons can reduce physical effort and fatigue during squatting. In particular, subject-specific assistance helped to significantly reduce physical effort, shown by reduced metabolic cost, using human-in-the-loop optimization of the exoskeleton parameters. However, measuring metabolic cost using respiratory data has limitations, such as long estimation times, presence of noise, and user discomfort. A recent study suggests that foot contact forces can address those challenges and be used as an alternative metric to the metabolic cost to personalize wearable robot assistance during walking.
Methods: In this study, we propose that foot center of pressure (CoP) features can be used to estimate the metabolic cost of squatting using a machine learning method. Five subjects’ foot pressure and metabolic cost data were collected as they performed squats with an ankle exoskeleton at different assistance conditions in our prior study. In this study, we extracted statistical features from the CoP squat trajectories and fed them as input to a random forest model, with the metabolic cost as the output.
Results: The model predicted the metabolic cost with a mean error of 0.55 W/kg on unseen test data, with a high correlation (r = 0.89, p < 0.01) between the true and predicted cost. The features of the CoP trajectory in the medial-lateral direction of the foot (xCoP), which relate to ankle eversion-inversion, were found to be important and highly correlated with metabolic cost.
Conclusion: Our findings indicate that increased ankle eversion (outward roll of the ankle), which reflects a suboptimal squatting strategy, results in higher metabolic cost. Higher ankle eversion has been linked with the etiology of chronic lower limb injuries. Hence, a CoP-based cost function in human-in-the-loop optimization could offer several advantages, such as reduced estimation time, injury risk mitigation, and better user comfort.
... 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 (ρc) 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 ρc = 0.53, A MAE of 413.58 N and a MAPE = 23.6% with a range of −1,000–800 N within 95% Confidence interval (95%CI), while r = 0.7 and 0.92 showed ρc = 0.68 with a MAE = 304.51N/MAPE = 17.4% with a range of −750 N–600 N within a 95% CI and ρc = 0.9 with a MAE = 139.99/MAPE = 7.1% with a range of −200–450 N 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 ρc, 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). ...
... The only possible way to assess postural ______________________________ control is to measure the movement of the center of mass (CoM) or center of foot pressure (CoP). According to Swinton et al. [39], during the traditional squat, the knee traveled past the toes resulting in anterior displacement of the system center of mass. In contrast, during the powerlifting and box squat, a more vertical shin position was maintained, resulting in posterior displacements of the CoM. ...
Purpose: The symmetry of feet loading and adequate postural control are crucial aspects of proper squat performance. The study aimed to evaluate the effect of various stance widths during squat on postural control and symmetry of feet loading. Methods: Thirty healthy individuals participated in this study. Each participant performed one type of squat with a narrow stance (NS), hip stance (HS) and wide stance (WS). Results: A significantly higher value of CoP path length, the velocity of sways and Area95 were obtained for the WS squat compared to NS and HS. In addition, the wide feet setting significantly affected not only the feet loading symmetry but also the strategy (high LyE), the amount of irregularities (high SampEn) and the CoP time-series roughness complexity (high FD). It has been shown that as the base of support grew, the asymmetry index grew. Conclusions: The wide squat is less stable, requiring more complex postural control behavior and more flexibility. Performing this squat significantly shifts the pressure to the dominant limb.
... 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.
... Based on pre-existing squat literature descriptions and published squat best practices [17][18][19][20][21][22][23], the PT and three independent raters collectively agreed on this study's official squat definition: "Individual starts in a standing position with feet flat on the floor knees and hips in a neutral, extended anatomical position, spine in an upright position with preservation of its natural curves and hands held in front of body. Squat movement begins with descent phase initiated by 'sitting back' as hips, knees and ankles flex simultaneously. ...
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.
Background
Time to perform 40-yard dash (40-yd) is a performance criterion in American football. Sprinting ability is strongly correlated with maximal values of horizontal power (PHmax), Force (FH0) and Velocity (VH0). While numerous methods for developing sprint speed exist, few studies have focused on the effects of periodizations on the sprinting mechanical variables in young talented American football players.
Objective
this study aimed to compare the effects of block (BP) and undulating (UP) training periodization modalities on 40-yard dash performance.
Method
27 players from the Young French League of American football (17.1 ± 0.9 y, 179.9 ± 5.5 cm, 81.1 ± 14.9 kg) were randomly assigned in either the BP (n = 15) or UP (n = 12) group. Anthropometric characteristics, 40-yd performance, maximal velocity (Vmax), PHmax, FH0 and VH0 were assessed before and after 10-wk intervention period.
Results
Training resulted in the 40-yd performance increase of 3.72% (p < 0.001) and significant changes in Vmax (+ = 6.13 ± 5.62%, p < 0.001) and VH0 values (+2.68 ± 4.14%, p = 0.004). BP intervention leaded higher improvements in time to perform 40-yd (4.45 ± 2.06 vs. 3.02 ± 1.93%, p < 0.001) and Vmax (7.30 ± 6.63% vs. 4.54 ± 4.10%, p = 0.002,) compared to UP. No periodization effect was found in changes of VH0 (BP: 3.42 ± 4.31% vs. UP: 1.48 ± 3.88, p = 0.214).
Conclusion
Our results showed that BP and UP were effective to increase sprint performance. Despite a similar training load, the block periodization of training had better effects on 40-yd performance compared to undulating training periodization in this population of talented young American football players.
The lack of training to maximize the patient’s physical performance, especially in weightlifting, can cause various types of musculoskeletal injuries. The biomechanical analysis through motion sensors and machine learning algorithms of an exercise as widely used in any sports discipline as the free squat can be a very helpful tool for both beginners and high-performance athletes. This methodology, using Xsens DOT© motion sensors which internally contain a gyroscope, records the exercise. With the necessary knowledge, the data is processed using feature extraction with statistical moments, allowing for the classification of the exercise execution with prior knowledge in sports and basic anatomy. Additionally, genetic algorithms are used to select the best variables to create a logistic classification model, achieving good performance. The proposed model obtained an accuracy of 0.7885 in a blind evaluation and an area under the receiver operating characteristic curve (AUC) of 0.74.
Objective
To systematically review the literature on the incidence, prevalence, anatomical injury localisation and risk factors in Olympic weightlifting and powerlifting.
Design
Updated systematic review, PROSPERO registration (CRD42022382364).
Data sources
Four databases (PubMed, Embase, SPORTDiscus and Web of Science) were searched on 19 February 2024.
Eligibility
Reports assessing injury incidence and prevalence in Olympic weightlifting and powerlifting, published between January 2015 and February 2024, were included in addition to reports from a previous systematic review. The ‘Quality Assessment Tool for Observational Cohort and Cross-sectional Studies’ was used to assess methodological quality.
Results
Of 1765 screened records, eight new reports were found, resulting in 17 reports in the review. 12 reports covered weightlifting and seven covered powerlifting, with two of the reports included in both categories as they addressed both sports. In weightlifting, the period prevalence of injuries during competitions was 10.7%–68%, the incidence was 2.4–3.3 injuries/1000 hours of training, and the most common injury sites were the knee, lower back, shoulder and hands/fingers. In powerlifting, one report showed a point prevalence of 70%. Injury incidence was 1.0–4.4 injuries/1000 hours of training, and the most common injury sites were the lower back/pelvis, shoulder and elbow/upper arm. Both sports showed a high prevalence of pelvic floor dysfunction (eg, urinary incontinence) among females (50%) compared with males (9.3%).
Conclusions
This updated systematic review supports the conclusions of previous reviews and shows new findings that pelvic floor dysfunction is very common in both sports. Due to the distinctly different study designs and settings, further direct comparisons between sports were difficult. In weightlifting, reports mainly focused on injuries during competitions. In powerlifting, injury incidence was low, but injury prevalence was high when defining injury as a painful condition that impairs training/competition.
Kneeling and half-kneeling training are common positions used in physical therapy. however, research on lower extremity muscle activity is lacking compared to the ergonomic aspects and trunk muscle activity. The purpose of this study is to investigate the effects on lower extremity muscle activity during squats in kneeling and half-kneeling positions. The study was designed as a cross-sectional study with a single group of healthy adults. Participants were instructed to perform squats while assuming 3 positions (standing, kneeling, and half-kneeling). Surface electromyography data were recorded 3 times from the rectus femoris (RF), gluteus maximus (GMax), gluteus medius (GMed), and biceps femoris (BF) on the participant’s dominant side, and the mean values were analyzed. The participants performed squats for 9 seconds, with 4 seconds of the descent phase, 1 second of the maintenance phase, and 4 seconds of the ascent phase. A metronome was used to ensure precise timing. The study included 30 participants (19 males and 11 females). The muscle activities of the RF, GMed, and BF showed statistically significant differences among the 3 positions, being highest in the half-kneeling position (HKP), followed by the standing position (SP) and kneeling position (KP). The muscle activity of the GMax was significantly higher in the HKP than in the SP and KP ( P < .05). The co-contraction ratio was significantly higher with KP than with the SP and HKP ( P < .05). In the SP and KP, there were statistically significant differences between the ascent and descent phases of the RF, GMax, GMed, and BF ( P < .05). In the HKP, there were statistically significant differences between the ascent and descent phases of the RF, GMax, and GMed ( P < .05). The results of this study indicate that squats in the HKP (especially during the ascent phase) require the highest muscle activity, whereas squats in the KP (especially during the descent phase) can be performed with the lowest muscle activity. It can be concluded that these findings could serve as selective indicators for squat exercises and in enhancing postural control, muscle strength, and lower extremity stabilization.
Background and Aims Pyramid and reverse pyramid loading patterns are used to increase the training load in resistance training. Although physiological studies have attempted to compare the two patterns, the difference between the two loading patterns on the biomechanics of the spine and pelvis has not been determined. This study aimed to investigate the effect of pyramid and inverted pyramid loadings on spinal and pelvic coordination variability in squat movement. Methods Twelve bodybuilding athletes in Tehran City, Iran, voluntarily participated in this study. The subjects performed squat movements as the pyramid and reverse pyramid at intensities of 50%, 70%, and 90% of ten maximum repetitions. Then, the kinematic information of the three segments of their spine and pelvis was recorded. Coordination and variability coordination were calculated using a modified vector coding method. Results The results of repeated measures analysis of variance showed a significant difference in the coordination pattern for pelvic-lower back coordination, lower-back to lower-trunk spine, and lower-trunk-to-upper-trunk spine in the intensity of 50%. A significant difference was observed in the coordination pattern, with an intensity of 70% for the lower back and lower trunk spine. Also, no statistical significance was observed between the pyramidal and inverted pyramidal loading types for spine and pelvis coordination. Conclusion According to the results of increasing the load in pyramid loading and decreasing the load in reverse loading, the coordination of distal couplings affected the sagittal plane more than the proximal one. It is recommended to use the reverse pyramid method for exercises and be more careful when performing pyramid exercises.
The squat is one of the most frequently prescribed exercises in the rehabilitative setting. Performance of the squat can be modified by changing parameters such as stance width, foot rotation, trunk position, tibia position, and depth. An understanding of how the various squatting techniques can influence joint loading and muscular demands is important for the proper prescription of this exercise for various clinical conditions. The purpose of this clinical commentary is to discuss how the biomechanical demands of the squat can be influenced by various modifiable parameters. General recommendations for specific clinical conditions are presented.
Level of Evidence
5
Chiu, LZF. “Knees out” or “Knees in”? Volitional lateral versus medial hip rotation during barbell squats. J Strength Cond Res 38(3): 435–443, 2024—Medial or lateral hip rotation may be present during barbell squats, which could affect the hip frontal and transverse plane moments. Male ( n = 14) and female ( n = 18) subjects performed squats using their normal technique and with volitional medial and lateral hip rotation. Hip net joint moments (NJM) were calculated from 3-dimensional motion capture and force platform measurements. Statistical significance was set for omnibus tests ( α = 0.05) and Bonferroni’s corrected for pairwise comparisons ( α t-test = 0.0056). Normal squats required hip extensor, adductor, and lateral rotator NJM. Lateral rotation squats had smaller hip extensor ( p = 0.002) and lateral rotator ( p < 0.001) NJM and larger hip adductor ( p < 0.001) NJM than normal squats. Medial rotation squats had smaller hip extensor ( p = 0.002) and adductor ( p < 0.001) NJM and larger hip lateral rotator ( p < 0.001) NJM than normal squats. These differences exceeded the minimum effects worth detecting. As gluteus maximus exerts hip extensor and lateral rotator moments, and the adductor magnus exerts hip extensor and adductor moments, these muscles combined would be required to meet these hip demands, supporting previous research that has established these muscles as the primary contributors to the hip extensor NJM. Lateral rotation squats reduce hip lateral rotator and increase hip adductor NJM, which may be hypothesized as preferentially loading adductor magnus. Medial rotation squats increase hip lateral rotator and decrease hip adductor NJM; therefore, this variant may shift loading to the gluteus maximus.
Tasks of daily living are often sporadic, highly variable, and asymmetric. Analyzing these real-world non-cyclic activities is integral for expanding the applicability of exoskeletons, protheses, wearable sensing, and activity classification to real life, and could provide new insights into human biomechanics. Yet, currently available biomechanics datasets focus on either highly consistent, continuous, and symmetric activities, such as walking and running, or only a single specific non-cyclic task. To capture a more holistic picture of lower limb movements in everyday life, we collected data from 12 participants performing 20 non-cyclic activities (e.g. sit-to-stand, jumping, squatting, lunging, cutting) as well as 11 cyclic activities (e.g. walking, running) while kinematics (motion capture and IMUs), kinetics (force plates), and electromyography (EMG) were collected. This dataset provides normative biomechanics for a highly diverse range of activities and common tasks from a consistent set of participants and sensors.
PurposeTo compare the spine hinge evaluated by sacral inertial measurement unit (IMU) versus both lumbar and sacral IMUs and to assess the influence of clinical variables on the spine hinge.Methods
The study included 20 healthy participants (10 men and 10 women) and 18 participants (6 men and 12 women) with low back pain. Participants performed a bodyweight squat with IMU sensors attached to the lumbar spine, sacrum, and lateral thigh. The spine hinge was evaluated by two methods: lumbosacral hinge (LS hinge), defined as an abrupt increase in LS flexion, and sacral hinge, defined as a change in sacral direction from forward to backward. The amount of and ratio (LS ratio) between sacral and lumbar rotations were evaluated.ResultsThe spine hinge detected only from the sacral IMU showed a high degree of agreement with that detected from both IMUs. The LS hinge occurred at a lower depth in females than in males (p = 0.001). Females had greater sacral rotation (p = 0.012) and a higher LS ratio (p < 0.001) than males. A larger passive hip flexion range was associated with later LS hinge occurrence in females (p = 0.041) but not in males (p = 0.965). Trunk muscle strength and presence of low back pain were not significant in either sex.ConclusionIMUs can detect the squat depth when the spine hinge occurs. A single sacral IMU is sufficient to detect the spine hinge. The movement patterns differ between sexes during squats, which should be considered to achieve the optimal squat depth.
The 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.
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.
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.
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.
Center of mass displacement during gait has frequently been used as an indicator of gait efficiency or as a complement to standard gait analysis. With technological advances, measuring the center of mass as the centroid of a multi-segment system is practical and feasible, but must first be compared to the well-established Newtonian computation of double-integrating the ground reaction force. This study aims to verify that the kinematic centroid obtained from a commonly-used model (Vicon Peak Plug-In-Gait) provides at least as reliable measurements of center of mass displacement as those obtained from the ground reaction forces. Gait data was collected for able-bodied children and children with myelomeningocele who use larger lateral center of mass excursions during gait. Reasonable agreement between methods was found in fore-aft and vertical directions, where the methods' excursions differed by an average of less than 10 mm in either direction, and the average RMS differences between methods' computed curves were 6 and 13 mm. Particularly good agreement was observed in the lateral direction, where the calculated excursions differed by an average of less than 2 mm and the RMS difference was 5 mm. Error analyses in computing the center of mass displacement from ground reaction forces were performed. A 5% deviation in mass estimation increased the computed vertical excursion twofold, and a 5% deviation in the integration constant of initial velocity increased the computed fore-aft excursions by 10%. The suitability of calculating center of mass displacement using ground reaction forces in a patient population is questioned. The kinematic centroid is susceptible to errors in segment parameters and marker placement, but results in plausible results that are at least within the range of doubt of the better-established ground reaction force integration, and are more useful when interpreting 3-D gait data.
This study examined the changes in peak power, ground reaction force and velocity with different loads during the performance of the parallel squat movement. Twelve experienced male lifters (26.83 +/- 4.67 years of age) performed the standard parallel squat, using loads equal to 20, 30, 40, 50, 60, 70, 80, and 90% of 1 repetition maximum (1RM). Each subject performed all parallel squats with as much explosiveness as possible using his own technique. Peak power (PP), peak ground reaction force (PGRF), peak barbell velocity (PV), force at the time of PP (FPP), and velocity at the time of PP (VPP) were determined from force, velocity, and power curves calculated using barbell velocity and ground reaction force data. No significant differences were detected among loads for PP; however, the greatest PP values were associated with loads of 40 and 50% of 1RM. Higher loads produced greater PGRF and FPP values than lower loads (p < 0.05) in all cases except between loads equal to 60-50, 50-40, and 40-30% of 1RM for PGRF, and between loads equal to 70-60 and 60-50% of 1RM for FPP. Higher loads produced lower PV and VPP values than lower loads (p < 0.05) in all cases except between the 20-30, 70-80, and 80-90% of 1RM conditions. These results may be helpful in determining loads when prescribing need-specific training protocols targeting different areas of the load-velocity continuum.
Unlabelled:
Some recommendations suggest keeping the shank as vertical as possible during the barbell squat, thus keeping the knees from moving past the toes. This study examined joint kinetics occurring when forward displacement of the knees is restricted vs. when such movement is not restricted. Seven weight-trained men (mean +/- SD; age = 27.9 +/- 5.2 years) were videotaped while performing 2 variations of parallel barbell squats (barbell load = body weight). Either the knees were permitted to move anteriorly past the toes (unrestricted) or a wooden barrier prevented the knees from moving anteriorly past the toes (restricted). Differences resulted between static knee and hip torques for both types of squat as well as when both squat variations were compared with each other (p < 0.05). For the unrestricted squat, knee torque (N.m; mean +/- SD) = 150.1 +/- 50.8 and hip torque = 28.2 +/- 65.0. For the restricted squat, knee torque = 117.3 +/- 34.2 and hip torque = 302.7 +/- 71.2. Restricted squats also produced more anterior lean of the trunk and shank and a greater internal angle at the knees and ankles. The squat technique used can affect the distribution of forces between the knees and hips and on the kinematic properties of the exercise.
Practical applications:
Although restricting forward movement of the knees may minimize stress on the knees, it is likely that forces are inappropriately transferred to the hips and low-back region. Thus, appropriate joint loading during this exercise may require the knees to move slightly past the toes.
The influence of various loads on power output in the jump squat (JS), squat (S), and power clean (PC) was examined to determine the load that maximizes power output in each lift.
Twelve Division I male athletes participated in four testing sessions. The first session involved performing one-repetition maximums (1RM) in the S and PC, followed by three randomized testing sessions involving either the JS, S, or PC. Peak force, velocity, and power were calculated across loads of 0, 12, 27, 42, 56, 71, and 85% of each subject's 1RM in the JS and S and at 10% intervals from 30 to 90% of each subject's 1RM in the PC.
The optimal load for the JS was 0% of 1RM; absolute peak power was significantly lower from the optimal load at 42, 56, 71, and 85% of 1RM (P < or = 0.05), whereas peak power relative to body mass was significantly lower at 27% of 1RM in addition to 42, 56, 71, and 85% of 1RM. Peak power in the S was maximized at 56% of 1RM; however, power was not significantly different across the loading spectrum. The optimal load in the PC occurred at 80% of 1RM. Relative peak power at 80% of 1RM was significantly different from the 30 and 40% of 1RM.
This investigation indicates that the optimal load for maximal power output occurs at various percentages of 1RM in the JS, S, and PC.
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