ArticleLiterature Review

Analysis of the Load on the Knee Joint and Vertebral Column with Changes in Squatting Depth and Weight Load

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Abstract

It has been suggested that deep squats could cause an increased injury risk of the lumbar spine and the knee joints. Avoiding deep flexion has been recommended to minimize the magnitude of knee-joint forces. Unfortunately this suggestion has not taken the influence of the wrapping effect, functional adaptations and soft tissue contact between the back of thigh and calf into account. The aim of this literature review is to assess whether squats with less knee flexion (half/quarter squats) are safer on the musculoskeletal system than deep squats. A search of relevant scientific publications was conducted between March 2011 and January 2013 using PubMed. Over 164 articles were included in the review. There are no realistic estimations of knee-joint forces for knee-flexion angles beyond 50° in the deep squat. Based on biomechanical calculations and measurements of cadaver knee joints, the highest retropatellar compressive forces and stresses can be seen at 90°. With increasing flexion, the wrapping effect contributes to an enhanced load distribution and enhanced force transfer with lower retropatellar compressive forces. Additionally, with further flexion of the knee joint a cranial displacement of facet contact areas with continuous enlargement of the retropatellar articulating surface occurs. Both lead to lower retropatellar compressive stresses. Menisci and cartilage, ligaments and bones are susceptible to anabolic metabolic processes and functional structural adaptations in response to increased activity and mechanical influences. Concerns about degenerative changes of the tendofemoral complex and the apparent higher risk for chondromalacia, osteoarthritis, and osteochondritis in deep squats are unfounded. With the same load configuration as in the deep squat, half and quarter squat training with comparatively supra-maximal loads will favour degenerative changes in the knee joints and spinal joints in the long term. Provided that technique is learned accurately under expert supervision and with progressive training loads, the deep squat presents an effective training exercise for protection against injuries and strengthening of the lower extremity. Contrary to commonly voiced concern, deep squats do not contribute increased risk of injury to passive tissues.

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... n = 9 for all variables except for gluteus maximus activity where n = 7. (Escamilla, 2001). More recent reviews (Hartmann et al., 2013) and experimental studies (Bryanton et al., 2012) do not, however, support this notion. By contrast, the implicit lower external load at deep squat or leg press, in combination with load distribution over a larger area beneath the quadriceps tendon and patella ("wrapping effect"), rather support such routines in individuals without joint disorders (Hartmann et al., 2013). ...
... More recent reviews (Hartmann et al., 2013) and experimental studies (Bryanton et al., 2012) do not, however, support this notion. By contrast, the implicit lower external load at deep squat or leg press, in combination with load distribution over a larger area beneath the quadriceps tendon and patella ("wrapping effect"), rather support such routines in individuals without joint disorders (Hartmann et al., 2013). ...
... The findings of higher total load during squat and a propensity for deeper knee flexion and higher contraction velocity during leg press should also be viewed in a training efficacy perspective. Resistance training studies comparing squats performed at different knee-joint angles do not advocate the exercise type that allows the heaviest load to be lifted; instead, a deep rather than shallow knee-inflexion point appears to be a key factor for strength development and hypertrophy of the quadriceps muscle during squat training regimens (Bryanton et al., 2012;Bloomquist et al., 2013;Hartmann et al., 2013;Kubo et al., 2019). Greater muscle-tendon forces over the knee joint and longer knee-extensor muscles have been postulated as the main stimuli for these increments (Bryanton et al., 2012;Bloomquist et al., 2013). ...
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The aim was to compare the musculoskeletal load distribution and muscle activity in two types of maximal flywheel leg-extension resistance exercises: horizontal leg press, during which the entire load is external, and squat, during which part of the load comprises the body weight. Nine healthy adult habitually strength-training individuals were investigated. Motion analysis and inverse dynamics-based musculoskeletal modelling were used to compute joint loads, muscle forces, and muscle activities. Total exercise load (resultant ground reaction force; rGRF) and the knee-extension net joint moment (NJM) were slightly and considerably greater, respectively, in squat than in leg press ( p ≤ 0.04), whereas the hip-extension NJM was moderately greater in leg press than in squat ( p = 0.03). Leg press was performed at 11° deeper knee-flexion angle than squat ( p = 0.01). Quadriceps muscle activity was similar in squat and leg press. Both exercise modalities showed slightly to moderately greater force in the vastii muscles during the eccentric than concentric phase of a repetition ( p ≤ 0.05), indicating eccentric overload. That the quadriceps muscle activity was similar in squat and leg press, while rGRF and NJM about the knee were greater in squat than leg press, may, together with the finding of a propensity to perform leg press at deeper knee angle than squat, suggest that leg press is the preferable leg-extension resistance exercise, both from a training efficacy and injury risk perspective.
... To facilitate inter-condition comparisons, the present LP and S exercises were performed at a given submaximal load (rGRF), and the participants were instructed to attain a peak knee-flexion angle of 90 degrees. From a training perspective, this may not be an optimal strategy since development of muscle mass and strength is superior when heavy squat resistance training is performed with deep rather than shallow knee angle (Bloomquist et al., 2013;Hartmann et al., 2013). ...
... Since the flywheel force was applied to the torso, joint forces in the lower back were as anticipated higher in LP than in S, particularly the lumbar compressive force, which was more than 80% higher in LP than in S (Figure 4). It has been estimated that during athletic squat exercise with an external bar load of 1.5 BW, the compressive loads of the lumbar vertebrae may exceed 10 BW, approaching a conservative estimation of vertebral failure load (Hartmann et al., 2013). Lumbar compression forces in the present LP exercise are, thus, not so high as to raise concerns for risk of vertebral compression fractures (Cappozzo et al., 1985;Hartmann et al., 2013). ...
... It has been estimated that during athletic squat exercise with an external bar load of 1.5 BW, the compressive loads of the lumbar vertebrae may exceed 10 BW, approaching a conservative estimation of vertebral failure load (Hartmann et al., 2013). Lumbar compression forces in the present LP exercise are, thus, not so high as to raise concerns for risk of vertebral compression fractures (Cappozzo et al., 1985;Hartmann et al., 2013). Also, the anteroposterior lumbar shear force was significantly greater in LP than in S, although in both modalities, the force magnitude was low and most likely of little practical importance for injury risk (Skrzypiec et al., 2012). ...
Article
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Resistance exercise on Earth commonly involves both body weight and external load. When developing exercise routines and devices for use in space, the absence of body weight is not always adequately considered. This study compared musculoskeletal load distribution during two flywheel resistance knee-extension exercises, performed in the direction of (vertical squat; S) or perpendicular to (horizontal leg press; LP) the gravity vector. Eleven participants performed these two exercises at a given submaximal load. Motion analysis and musculoskeletal modelling were used to compute joint loads and to simulate a weightless situation. The flywheel load was more than twice as high in LP as in S (p < 0.001). Joint moments and forces were greater during LP than during S in the ankle, hip and lower back (p < 0.01) but were similar in the knee. In the simulated weightless situation, hip and lower-back loadings in S were higher than corresponding values at Earth gravity (p ≤ 0.01), whereas LP joint loads did not increase. The results suggest that LP is a better terrestrial analogue than S for knee-extension exercise in weightlessness and that the magnitude and direction of gravity during resistance exercise should be considered when designing and evaluating countermeasure exercise routines and devices for space.
... This popular exercise has been subject to extensive biomechanical investigations that focus typically on the impact of load, squat depth, stance width and/or shoe design on lower limb mechanics (at the time of submission searches on Web of Science and PubMed using terms such as "Squat", "Kinematics" and "Biomechanics" revealed over relevant 100 manuscripts). However, of this extensive body of literature proportionally less focuses specifically on back squat spinal kinematics and/or kinetics (Charlton et al., 2017;Hartmann et al., 2013;Lee et al., 2019;List et al., 2013;Lorenzetti et al., 2018;McKean et al., 2010;Walsh et al., 2007;Whitting et al., 2016). ...
... However, herein lies a paradox as scientific reports indicate that restricting anterior knee movement results in increased lumbar flexion (List et al., 2013). Importantly, increased lumbar flexion during squatting is also associated with increased spinal loading (Fry et al., 2003;Hartmann et al., 2013;Swinton et al., 2012;Whitting et al., 2016). Additionally, physical limitations in areas such as reduced dorsiflexion and/or hip flexion range of motion (ROM) may limit an individual's ability to achieve the NSCA's "optimal" knee position and spinal posture (Myer et al., 2014;Sato et al., 2012;Whitting et al., 2016). ...
... Our timeseries analyses show that these differences are small (typically <5 deg) and occur only during the first and last 25% of the lifting cycle where the joint moments about L4/L5 were reduced. This ability to maintain spinal curvature during all phases of the squat cycle is a key issue in spinal safety, as previous researchers suggest that back pain and high intervertebral disc pressures are associated with excessive lumbar lordosis and spinal flexion during lifting tasks (Hartmann et al., 2013;Sadler et al., 2017;Schmidt et al., 2007). Our spinal curvature data are similar to earlier research (List et al., 2013), with the small differences between these data due to the normalization adopted by the earlier group (i.e., their data were normalized to static posture). ...
Article
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This research assessed the influence of various heel elevation conditions on spinal kinematic and kinetic data during loaded (25% and 50% of body weight) high-bar back squats. Ten novice (mass 67.6 ± 12.4 kg, height 1.73 ± 0.10 m) and ten regular weight trainers (mass 66.0 ± 10.7 kg, height 1.71 ± 0.09 m) completed eight repetitions at each load wearing conventional training shoes standing on the flat level floor (LF) and on an inclined board (EH). The regular weight training group performed an additional eight repetitions wearing weightlifting shoes (WS). Statistical parametric mapping (SPM1D) and repeated measures analysis of variance were used to assess differences in spinal curvature and kinetics across the shoe/floor conditions and loads. SPM1D analyses indicated that during the LF condition the novice weight trainers had greater moments around L4/L5 than the regular weight trainers during the last 20% of the lift (P < 0.05), with this difference becoming non-significant during the EH condition. This study indicates that from a perspective of spinal safety, it appears advantageous for novice weight trainers to perform back squats with their heels slightly elevated, while regular weight trainers appear to realize only limited benefits performing back squats with either EH or WS.
... The squat process involves more than 200 muscles and demands multi-joint coordination [2,4]. The squat is widely conducted during resistance training, which could increase lower limb strength, prevent sports injuries, and improve sports performance [5][6][7][8][9]. It is also used in rehabilitation therapy to assess physical flexibility and symmetry [6] and postoperative rehabilitation training [1,7]. ...
... Research has revealed that different depths of squats may result in different joint kinematics, dynamics, and muscle activities [6,9]. Full squats (F-SQ) may enhance flexibility and improve athletic performance [12]. ...
... Full squats (F-SQ) may enhance flexibility and improve athletic performance [12]. Squats are usually performed at a shallow depth (knee flexion 0-60 • ) during rehabilitation training, because the injury risk to the soft tissue in the knee joint may increase during high flexion [5,9,18]. In addition, the increase of squat depth will lead to the rise in the moment of the hip joint, knee joint, and ankle joint [12,19,20], which may lead to related sports injuries. ...
Article
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Background: Females with different practice experience may show different body postures and movement patterns while squatting in different depths, which may lead to changes of biomechanical loadings and increase the risks of injuries. Methods: Sixteen novice female participants without squat training experience participated in this study. A 3D motion capture system was used to collect the marker trajectory and ground reaction force data during bodyweight squatting in different depths. The participants' kinematic data and joint moment were calculated using OpenSim's inverse kinematics and inverse dynamics algorithm. In this study, authors adapted a model especially developed for squatting and customized the knee joint with extra Degree-of-Freedom (DoF) in the coronal and horizontal plane with adduction/abduction and internal/external rotation. A paired-sample t-test was used to analyze the difference of joint range of motions (ROM) and peak moments between full-squat (F-SQ) and half-squat (H-SQ). One-Dimensional Statistical Parametric Mapping (SPM1D) is used to analyze the difference of joint angle and moment between the process of squatting F-SQ and H-SQ. Results: (1) Compared with H-SQ, F-SQ showed larger ROM in sagittal, coronal, and transverse planes (p < 0.05). (2) SPM1D found that the difference in joint angles and joint moments between F-SQ and H-SQ was mainly concentrated in the mid-stance during squatting, which suggested the difference is greatly pronounced during deeper squat. (3) Peak hip extension moment, knee extension moment, hip adduction moment, and plantar flexion moment of F-SQ were significantly higher than H-SQ (p < 0.05). (4) Difference of hip and knee extension moments and rotation moments between the F-SQ and H-SQ were exhibited during descending and ascending. Conclusions: The study found that novice women had larger range of joint motion during the F-SQ than H-SQ group, and knee valgus was observed during squatting to the deepest point. Greater joint moment was found during F-SQ and reached a peak during ascending after squatting to the deepest point. Novice women may have better movement control during H-SQ. The findings may provide implications for the selection of lower limb strength training programs, assist the scientific development of training movements, and provide reference for squat movement correction, thus reducing the risk of injury for novice women in squatting practice.
... The key difference between these techniques involves the position of the upper body in relation to the hip and knee joints. During the front squat, it is expected that the vertical projection of the upper body mass and any external load would be closer to the hip than the knee joint [1], assuming that the load lifted is the same between techniques. This is expected to increase the moment-arm for the knee joint and potentially reduce the contribution from the hip joint [2]. ...
... This is expected to increase the moment-arm for the knee joint and potentially reduce the contribution from the hip joint [2]. Conversely, the back squat should require an increased hip contribution than the knee joint [1]. In parallel, increments in external loads during squats have been shown to increase the contribution from the hip compared to the knee joint [3]. ...
... Sahli et al. [10] found that peak compressive and shear force components increased significantly as the external load increased during squats. Hartmann et al. [1] supports these findings by stating that higher loads resulted in increased tibiofemoral and patellofemoral compressive forces when squatting due to an increased knee extensor moment [11]. It was found that joint compressive forces did not differ between the two squat techniques [12]. ...
Article
BACKGROUND: Comparison of knee loads on a Smith machine, which utilised in for maintenance of health and rehabilitation, has not been attempted. OBJECTIVE: This study compared lower limb muscle and knee joint forces during front and back squats performed on a Smith Machine. METHODS: Eleven participants performed front and back squats with loads at 40%, 60% and 80% of their back squat 1-RMs. Ground reaction forces and three-dimensional full body motion were collected and used for modelling lower limb muscle and knee joint forces. RESULTS: Larger loads increased tibiofemoral compressive force during back squat at 80% compared to 40% (p< 0.01; d= 1.58) and to 60% (p< 0.01; d= 1.37). Patellofemoral compressive (p= 0.96) and tibiofemoral shear forces (p= 0.55) were not influenced by external load or type of squat. Gluteus medius and minimus produced more force at 80% compared to 60% (p= 0.01; d= 1.10) and to 40% (p< 0.01; d= 1.87) without differences for other muscles (p= 0.09–0.91). CONCLUSIONS: Greater external load was associated with increase in gluteus medius and minimus force and with increased tibiofemoral compressive force without effects on tibiofemoral shear force, patellofemoral compressive force or other lower limb muscle forces.
... Squat depths and stance widths were reported to present different joint kinematics, kinetics, and muscle activities [8][9][10]. Due to the altered distribution of biomechanical loadings, different squatting movements may be related to several malfunctions in the lower extremity, especially the knee joint. ...
... The practice of the squat can enhance musculature functions and sports performances from the aspect of strength and conditioning [11]. The deep squat with external loading (such as barbell squat) was commonly practiced by professional weightlifting athletes and recreational amateurs [10,26]. Comprehensively revealing the biomechanical characteristics would provide implications to help increase performances and prevent potential injuries [4,11,27]. ...
Article
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Populations of different ethnicities may present different movement capacities and muscular function adaptations. The purpose of this study was to investigate the differences of motion and loading in the lower extremity during dynamic deep squats between Asian and Caucasian individuals using OpenSim modelling technique with a customized squat-specific musculoskeletal model. Twenty-four participants joined the test performing the step-squat test, with right foot stepping side, squatting, and returning. The one-dimensional statistical parametric mapping package was used for statistical analysis. The main findings of the current study were as follows: (1) significant lower squat depth was observed in the Asian individuals, (2) the greater knee range of motion and contact forces were found in the Asian individuals, and (3) the greater ankle contact forces in the Caucasian individuals were notable while performing the deep squat compared to the Asian group. Knowledge found in the current study may provide implication for exercise practitioners and physiotherapists while designing schemes for the prevention of loading accumulation in the lower extremity.
... 6MWT can be the tool to evaluate the improvements in functional exercise capacity of patients of OA. Taping of knee improves pain and disability in patients with knee OA that can benefit after stopping treatment too [1]. ...
... Exercises which allows to strengthen the muscles which can lead to reduction in pain and swelling . here physiotherapy interventions proves beneficial in reducing pain and improve functions of knee joint [1]. ...
Article
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Background: Osteoarthritis is a condition which causes the joint inflammation that results from cartilage degeneration. There are two types of osteoarthritis one primary OA and second secondary OA. The conventional treatment TENS, Ultrasound, IFT, along with knee specific exercises in one group. And the second group focused on the spinal exercises with all these conventional approaches. The purpose of the study was to see the effect of spinal exercises effect on knee OA symptoms and functional ability. The significant difference was found in the pain , range of motion and the timed -up-go test. Methods: Total 30 participants were selected. groups of two were done one experimental given the spinal exercise and conventional treatment second controlled group given the knee exercises and conventional management. The pain, ROM and TUGT were analysed pre and post treatment. Results: According to statistical analysis, the study showed a significant difference in the pain intensity, ROM of knee and TUGT pre and post intervention. The study documented difference in the pain intensity post-intervention (0.0004) at rest and (0.0002) on activity and range of motion of right knee (<0.0001) and of left knee (<0.0001), timed up go test (0.0110) considered significant. Conclusion: The conducted study shows that there was significant difference in values of pain, ROM of knee and timed up go test in experimental group compared to controlled group. So, the spinal exercises have proven beneficial in knee osteoarthritis. KEYWORDS: Osteoarthritis, visual analogue scale, kellgren and Lawrence classification, spinal exercises.
... During snatch lifting, carrying enormous weights can produce high joint moments, compressive loads and shearing forces over the knee joint in the deep squat position (5,6). The compressive force and mechanical loading of the knee joint during a 110 kg lift ranges from 6,000 to 7,000 Newtons and exceeds approximately 24 times of the body weight (7). Thus, the mechanical stress can contribute to high local peak forces, microscopic trauma and stiffness in the knee joint which may cause knee pain (7). ...
... The compressive force and mechanical loading of the knee joint during a 110 kg lift ranges from 6,000 to 7,000 Newtons and exceeds approximately 24 times of the body weight (7). Thus, the mechanical stress can contribute to high local peak forces, microscopic trauma and stiffness in the knee joint which may cause knee pain (7). Among the weightlifters who missed the training, approximately 95% reported knee pain lasting for more than a week (8). ...
... A reduction in ankle mobility during a squat increases forward trunk tilt and displaces weight distribution towards the forefoot aids in reducing knee flexion (Biscarini, Botti and Pettorossi, 2013). Avoiding deep flexion (knee angle < 90°) has been recommended to minimise the magnitude of knee-joint forces and reduce injury risk to the lumbar spine and knee (Hartmann, Wirth and Klusemann, 2013). Weight displacement to the forefoot and increased forward trunk tilt can drastically reduce loading occurring at major knee ligamentsnotably the Anterior Cruciate Ligament (ACL) (Biscarini, Botti and Pettorossi, 2013). ...
... Quadriceps loading with the knee in flexion has been found to induce significant anterior tibial translation of the knee joint, and it is suggested that overloading at the quadriceps plays an intrinsic role in non-contact knee injuries (DeMorat et al., 2004). Similarly, as quadricep activation decreases during a squat movement, forces acting across the knee-joint are seen to significantly decrease (Hartmann, Wirth and Klusemann, 2013). This reduction in kneejoint loading is the result of alterations to the stability and postural changes associated when performing squats at an incline (Biscarini, Botti and Pettorossi, 2013). ...
Thesis
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The importance of a squat is widely recognised as the key contributor for lower-body muscle strengthening, however it is also important in a clinical setting. The use of decline squatting is an established exercise for knee rehabilitation due to the increases of ankle and knee range of motion and also progressive knee loading when applied. Due to its effect on postural biomechanics, incline squatting has less use in a clinical setting, however findings suggest an almost total removal in loading at the knee which could see use in a rehabilitation program. Muscular activation of the quadriceps group, as the prime mover of the knee joint, is an essential component when understanding the effect of squatting in a clinical setting. The aim of this study was to compare muscular activation of the quadriceps during a bodyweight squat on a flat surface against a 20 incline and 20 decline protocol. It was hypothesised that muscular activation of the vastus lateralis would increase when squatting at a decline and would decrease when squatting at an incline. Fifteen participants (age 29.9 ± 6.1 years, height 1.7 ± 0.1 m, weight 78.5 ± 22.2 kg) performed bodyweight squats on a flat, 20 decline and 20 incline surface. During each squat, electromyographic activity was obtained in the vastus lateralis. Raw data had a cut off set to 20Hz, underwent full-wave rectification, smoothing and a Butterworth filter was applied. There was a significant increase in muscular activation at a decline compared against flat protocol (+29.2  28.2%, p = 0.003). There was a significant decrease in muscular activation at an incline compared against a flat protocol (- 18.6  18.3%, p = 0.003). Where knee loading should be minimised during early stage rehabilitation, an incline squat is suggested to reduce quadricep activation and knee loading injury risk. Where knee loading should be progressively increased, declining squat protocols are recommended to increase quadricep activation and knee loading exercises. Through alternation of ankle angle and subsequently altered biomechanics of the squat itself, motor recruitment of the quadriceps can be controlled.
... 5,6 The classification of squat positions is commonly seen in studies of weightlifters, which are usually divided into half squats (knee flexion 80-100°), horizontal squats (110-120°) and deep squats (above 135°) according to the depth of the squat. 7 Deep squat requires the knee to flex at least 135°. For Asian people, many movements in daily life require deep squats, such as the Asian squat, the use of squatting stool and kneeling for religious beliefs. ...
... Our criteria for determining whether patients could squat were based on studies of Olympic athletes. 7 In the inability to squat group (Group I), the knee flexion angle or squat position did not exceed the critical value during squatting. In the ability to squat group (Group II), the knee flexion angle was greater than the critical angle and the squatting position was greater than the critical position. ...
Article
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Purpose: Total knee arthroplasty (TKA) is widely used as a treatment for knee osteoarthritis. Few studies have analysed the factors affecting the squatting ability of patients after TKA. The purpose of this study was to comprehensively analyse the factors affecting squatting ability after TKA and to determine which ones are important. Patients and methods: Three hundred primary TKA cases with a minimum 3-year follow-up were retrospectively analysed. All patients received a conventional posterior-stabilized TKA implant and underwent a standard perioperative care pathway. The patients were divided into two groups according to the squatting position and knee flexion angle while weight-bearing (Group I - inability to squat group, Group II - ability to squat group). Demographic, operative, and clinical data were collected. Radiographic assessment included joint line elevation, patellar position, posterior condylar offset (PCO), etc. Statistical analysis of the effect of all the above factors on squatting ability was performed. Results: The preoperative range of motion and joint line of Group I were 82.9±12.6 and 3.24±1.07, respectively, and those of Group II were 107±9.6 and 1.83±0.89 respectively. The univariate analysis showed that age, prosthesis size, preoperative ROM and joint line position were correlated with squatting ability. But in the final multivariate analysis, joint line position and preoperative ROM were independent influencing factors that affected squatting ability after TKA (p value < 0.01). Conclusion: Preoperative ROM and joint line position were independent influencing factors affecting squatting ability after TKA. Patients should be counseled accordingly and be made to understand these factors. To ensure that patients can squat postoperatively, we should improve surgical techniques to control joint line elevation.
... 20 In daily practice, the ROM can be modified by altering the body posture 21 or grip width, 22,23 using external materials like security bars or wood boards 24,25 or by voluntarily reducing the degree of movement at the beginning or end of the execution. 26,27 Thus, resistance training with no restrictions in the degree of movement is commonly defined as "full ROM," while training using any displacement reduction is considered as "partial ROM." 28 On this matter, the specific ROM influences different biomechanical aspects that affect, among others, the development of force, motor units activation, and dynamic joint stability. 25,29 More specifically, the ROM used in each repetition determines the zone of the force-length relationship on which the stimulus is applied. ...
... The choice of the optimal ROM to improve sports performance has been under discussion for decades. 28,[77][78][79] According to our review, most of the research suggests full ROM resistance training as preferable to increase jump ability 53,56,63,67 (Table 2), with only one study supporting the superior effectiveness of partial ROM 61 ( Figure 4). However, although effect sizes favored the full ROM, the meta-analysis was not significant. ...
Article
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Background Nowadays, there is a lack of consensus and high controversy about the most effective range of motion (ROM) to minimize the risk of injury and maximize the resistance training adaptations. Objective To conduct a systematic review and meta-analysis of the scientific evidence examining the effects of full and partial ROM resistance training interventions on neuromuscular, functional, and structural adaptations. Methods The original protocol (CRD42020160976) was prospectively registered in the PROSPERO database. Medline, Scopus, and Web of Science databases were searched to identify relevant articles from the earliest record up to and including August 2020. The RoB 2 and GRADE tools were used to judge the level of bias and quality of evidence. Meta-analyses were performed using robust variance estimation with small-sample corrections. Results Sixteen studies were finally included in the systematic review and meta-analyses. Full ROM training produced significantly greater adaptations than partial ROM on muscle strength (ES=0.56, P=0.004) and lower-limb hypertrophy (ES=0.88, P=0.027). Furthermore, although not statistically significant, changes in functional performance were maximized by the full ROM training (ES=0.44, P=0.186). Finally, no significant superiority of either ROM was found to produce changes in muscle thickness, pennation angle, and fascicle length (ES=0.28, P=0.226). Conclusion Full ROM resistance training is more effective than partial ROM to maximize muscle strength and lower-limb muscle hypertrophy. Likewise, functional performance appears to be favored by the use of full ROM exercises. On the other hand, there are no large differences between the full and partial ROM interventions to generate changes in muscle architecture.
... Additionally, McKean et al 3 reported that the lordotic curvature is prone to collapse in the descent phase of the deep squat, which may elevate the risk of posterior protrusion of the lumbar IVDs. [6][7][8] Thus, lumbar load possibly increases with increasing squat depth, 9,10 but the relationship between the mechanical stress on the lumbar IVDs and squat depth has not been fully elucidated. ...
... Although the detailed reasons why the smaller lumbar lordosis and anterior pelvic tilt were induced during parallel squat exercise are unclear in this study, the lumbar and pelvic movements may be related to individual intrinsic factors such as the muscle strength and joint flexibility in the regions of the trunk and lower extremity, and the interdependent movements of the hip, knee, and ankle joints. [1][2][3][4]9,10,31 Moreover, muscle fatigue of the trunk and/or lower extremity might significantly influence the results. 10,32 In fact, it might have been hard for most participants to complete parallel squat exercise under exercise condition of the present study. ...
Article
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We aimed to evaluate the acute physiological effects of high‐load barbell back squat exercise on each lumbar intervertebral disk with varying squat depths. Thirteen subjects (age, 23.3 ± 3.5 years) performed parallel and half‐squat exercises (80% of one repetition maximum, eight repetitions, five sets) using a Smith machine. Sagittal magnetic resonance diffusion‐weighted and spin‐echo images of lumbar intervertebral disks were obtained by using a 1.5‐Tesla MR system before and after each squat exercise; apparent diffusion coefficient (ADC; an index of water movement) and T2 relaxation time (an index of water content level) of the nucleus pulposus were calculated at all lumbar intervertebral disks. Additionally, we measured the angles of lumbar lordosis and anterior pelvic tilt at the bottom position of each squat using a three‐dimensional motion‐capture system. The nucleus pulposus of L4/5 (−5.0%, P < .01) and L5/S1 (−6.6%, P < .01) intervertebral disks showed decreased ADC values after parallel squat exercise. Moreover, post‐exercise ADC value in parallel squat exercise was lower than that in half‐squat exercise at L5/S1 intervertebral disk (P < .05). In contrast, the nucleus pulposus of all lumbar intervertebral disks had no significant T2 change before and after both squat exercises. The angles of lumbar lordosis (P < .01) and anterior pelvic tilt (P < .01) were smaller in parallel squat than in half‐squat. Lower lumbar intervertebral disks are subject to greater mechanical stress during high‐load parallel back squat exercise, which may result from smaller lumbar lordosis and anterior pelvic tilt angles at the bottom position during parallel squat.
... The benefits of squat exercises have been reported in athletic training [1,2], rehabilitation [3,4], and locomotive syndrome in elderly people [5]. Squats can refer to a wide variety of exercises, comprising partial squat [6], half squat [7], parallel squat [8,9], full squat [8,9], and deep squat [7]. Furthermore, there are front [9][10][11], back [10][11][12], and overhead squats [12] with various bar positionings. ...
... The benefits of squat exercises have been reported in athletic training [1,2], rehabilitation [3,4], and locomotive syndrome in elderly people [5]. Squats can refer to a wide variety of exercises, comprising partial squat [6], half squat [7], parallel squat [8,9], full squat [8,9], and deep squat [7]. Furthermore, there are front [9][10][11], back [10][11][12], and overhead squats [12] with various bar positionings. ...
Article
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Isometric bodyweight squats are fundamental exercises in athletic training and rehabilitation. Previously, we measured muscle activity in a normal squat posture (NSP) and a squat posture with the center of foot pressure (COP) intentionally shifted forward as far as possible (forward-shifted posture: FSP), and the muscle activity patterns varied significantly according to the COP location. This study focused on stepwise loading as a training strategy. Ten healthy male participants performed isometric bodyweight squats in a previous study, adopting the NSP and FSP, with three knee flexion angles (30°, 60°, and 90°). The muscle activities of the vastus medialis (VM), semitendinosus, tibialis anterior (TA), and gastrocnemius muscle lateral head were measured using surface electromyogram. This study further explored the relationship between COP shifting and knee flexion angles on electromyogram changes using three-dimensional diagrams. In one-way repeated measures analysis of variance by ranks, knee flexion angles affected the muscle activities of the VM and TA in the NSP and muscle activities of the VM in the FSP. Combining these findings, stepwise loading tasks were created to train individual target muscles. The ten male participants examined all the tasks, and the feasibility was confirmed accordingly.
... Among the resistance exercises that trigger muscle groups of the lower limbs, the squatting is considered one of the main movements [20][21][22] . Squatting is a natural movement of the human being who is directly related to the important task of everyday life: sit-and-stand, in addition to recruiting several muscle groups during its implementation 20.21 . ...
Article
Resistance exercise has been widely recommended for elderly population, since this type of exercise induces important health benefits, especially to improve functional capacity and preserve muscle mass, thus reflecting on the quality of life of older individuals. Among the several components of the resistance exercises the selection of movements to be performed is one of the most important and must be carefully analyzed. Although there may be a wide range of options, the most important recommendations do not specifically indicate the movements that should be included and muscle groups that should be prioritized when prescribing resistance exercise for the elderly. Therefore, considering that there is a lack of information for the Physical Education professional about the topic, this study was developed to support the choices of the movements that will compose the resistance exercise program for the elderly. The study was carried out by compiling and analyzing assumptions and scientific evidences related to resistance exercises and needs of elderly individuals. In conclusion, the choice of movements should be based on the principles of kinesiology, the needs of the elderly, muscle action and exercise safety in order to obtain beneficial results for general health and attenuate possible risks.Keywords: Exercise. Aging. Physical Exertion.ResumoO exercício resistido vem sendo amplamente recomendado para população idosa, uma vez que esse tipo de exercício físico induz a importantes benefícios para saúde; sobretudo, no aprimoramento da capacidade funcional e na preservação da massa muscular, refletindo, desse modo, na qualidade de vida do indivíduo idoso. Dentre os diversos componentes dos exercícios resistidos, a seleção dos movimentos a serem executados é um dos mais importantes e deve ser cuidadosamente analisado. Embora possa existir vasta gama de opções, as principais recomendações não indicam especificamente os movimentos que devem ser incluídos e os grupos musculares que devem ser priorizados nos programas de exercícios resistidos. Portanto, considerando haver uma lacuna de informações sobre o tema, o estudo foi realizado com intuito de subsidiar a seleção dos movimentos que deverão compor os programas de exercícios resistidos para idosos. O estudo foi realizado mediante compilação e análise de pressupostos e evidências científicas referentes aos exercícios resistidos e as necessidades dos idosos. Concluiu-se que a seleção dos movimentos deve ser baseada nos princípios da cinesiologia, nas necessidades dos idosos, na ação muscular e na segurança de execução para se alcançar resultados benéficos para saúde em geral e atenuar possíveis riscos.Palavras-chave: Exercício. Envelhecimento. Esforço Físico.
... Similar results have been obtained in a large epidemiological study on several sport disciplines, with 80% of the knee injuries resulting in surgery [44]. In order to reducing knee injuries associated with powerlifting movements, a well-learned correct technique under expert supervision and with progressive loads seems to enough to protect knee structures [45]. Additionally, it has been concluded that quadriceps fatigue is an important factor to consider during the execution of a squat exercise. ...
Article
Objective To review the characteristics of the injuries among CrossFit® practitioners, including prevalence and incidence, nature, location and risk factors. Methods PubMed/MEDLINE, EMBASE, Web of Science, Scopus, and SPORTDiscus databases were searched from inception through August 2020, and English-language articles reporting on CrossFit®-related injuries were included. Data including sample (sex, age and demographics) and injuries’ characteristics (prevalence, incidence rate, nature, location, percentage of injuries requiring surgery andrisk factors) were extracted. Results Overall, twenty-five studies involving a total of 12,079 CrossFit® practitioners met the inclusion criteria. The mean prevalence of injuries among the included studies was 35.3%, with an incidence rate varying between 0.2 and 18.9 per 1000 hours of training. The most injured areas were shoulder (26%), spine (24%) and knee (18%). Among the studies that reported the injuries requiring surgery, the mean percentage was 8.7%. Regarding the risk factors associated with injuries, older age, male sex, a greater body mass index, the existence of previous injuries, the lack of coach supervision, the experience on CrossFit® and the participation in competitions were reported by the studies. Conclusions CrossFit® training has an injury incidence rate similar to weightlifting and powerlifting. Findings from the studies suggest that the most affected areas are shoulder, spine and knee. The limited quality of the studies prevents us from draw solid conclusions about injury risk factors. Level of Evidence of the Included Studies III
... Squats are convenient and allow an effective transfer of strength gain to activities with similar neuromuscular demands (Wilson et al., 1996;Wirth et al., 2016). Previous studies have extensively examined the effects of load magnitudes, squat depths, and squat techniques on low-back and lower extremity loading to identify optimal training strategies and minimise injury risk (Hartmann et al., 2013). While greater loads and depths generally increase lower extremity joint moments and muscle activities (Bryanton et al., 2012;Cotter et al., 2013), greater trunk flexion could decrease knee moments but increase low-back and hip moments in back squats (Fry et al., 2003). ...
Article
The purpose was to quantify trunk and lower extremity biomechanics among back and front squats with a straight bar and four squats with different anterior-posterior load placements imposed by a transformer bar. Ten males and eight females performed six squat conditions: back and front squats with a straight bar, back and front squats with a transformer bar, and squats with more posteriorly or anteriorly placed loads with a transformer bar. A constant load of 70% of the participant’s one-repetition maximum in the straight-bar front squat was used. Kinematic and kinetic data were collected to quantify joint biomechanics at an estimated parallel squat position in the descending and ascending phases. Squats with more anteriorly placed load significantly decreased trunk flexion and pelvis anterior tilt angles with large effect sizes but increased low-back extension moments with medium to large effect sizes. Hip, knee, and ankle extension moments were generally similar among most conditions. Participants adjusted their trunk and pelvis to mediate the effects of load placements on low-back and lower extremity moments. While lower extremity loading was similar among different squats, the different trunk and pelvis angles and low-back moments should be taken into consideration for people with low-back impairment. KEYWORDS: Low back, hip, knee, squatting, load placement
... The results of this study might aid clinicians' understanding of the relationship between the level of articular surfaces compressive loads and qualitative aspects of arthrokinematics considered as friction-reducing properties of diarthrosis. Furthermore, these results could broaden knowledge related to the joint biotribology, and might bene t clinicians, because the squat has long been a basic element of strength training among athletes, as well as is various rehabilitative protocols [31][32][33][34]. Because PFJ disorders are commonly encountered in sports and rehabilitation, better recognition of biomechanical behavior of the PFJ during loaded and unloaded movements is essential in order to treat it effectively [4]. ...
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Background: The patellofemoral joint (PFJ) provides extremely low kinetic friction, which results in optimal arthrokinematic motion quality. Previous research showed that these friction-reducing properties may be diminished due to the increase in articular contact forces. However, this phenomenon has not been analyzed in vivo during functional daily-living activities. The aim of this study was the vibroarthrographic assessment of changes in PFJ arthrokinematics during squats with variated loads. Methods: 114 knees from 57 asymptomatic subjects (23 females and 34 males) whose ages ranged from 19 to 26 years were enrolled in this study. Participants were asked to perform 3 trials: 4 repetitions of bodyweight squats (L0), 4 repetitions of 10 kg barbell back loaded squats (L10), 4 repetitions of 20 kg barbell back loaded squats (L20). During the unloaded and loaded (L10, L20) squats, vibroarthrographic signals were collected using an accelerometer placed on the patella and were described by the following parameters: variation of mean square (VMS), mean range (R4), and power spectral density for frequency of 50-250 Hz (P1) and 250-450 Hz (P2). Results: Obtained results showed that the lowest values were noted in the unloaded condition and that the increased applied loads had a significant concomitant increase in all the aforementioned parameters bilaterally (p<0.05). Conclusion: This phenomenon indicates that the application of increasing knee loads during squats corresponds to higher intensity of vibroacoustic emission, which might be related to higher contact stress and kinetic friction as well as diminished arthrokinematic motion quality.
... The results of this study might aid clinicians' understanding of the relationship between the level of articular surfaces compressive loads and qualitative aspects of arthrokinematics considered as friction-reducing properties of diarthrosis. Furthermore, these results could broaden knowledge related to the joint biotribology, and might benefit clinicians, because the squat has long been a basic element of strength training among athletes, as well as is various rehabilitative protocols [31][32][33][34]. Because PFJ disorders are commonly encountered in sports and rehabilitation, better recognition of biomechanical behavior of the PFJ during loaded and unloaded movements is essential in order to treat it effectively [4]. ...
Article
Full-text available
Background: The patellofemoral joint (PFJ) provides extremely low kinetic friction, which results in optimal arthrokinematic motion quality. Previous research showed that these friction-reducing properties may be diminished due to the increase in articular contact forces. However, this phenomenon has not been analyzed in vivo during functional daily-living activities. The aim of this study was the vibroarthrographic assessment of changes in PFJ arthrokinematics during squats with variated loads. Methods: 114 knees from 57 asymptomatic subjects (23 females and 34 males) whose ages ranged from 19 to 26 years were enrolled in this study. Participants were asked to perform 3 trials: 4 repetitions of bodyweight squats (L0), 4 repetitions of 10 kg barbell back loaded squats (L10), 4 repetitions of 20 kg barbell back loaded squats (L20). During the unloaded and loaded (L10, L20) squats, vibroarthrographic signals were collected using an accelerometer placed on the patella and were described by the following parameters: variation of mean square (VMS), mean range (R4), and power spectral density for frequency of 50-250 Hz (P1) and 250-450 Hz (P2). Results: Obtained results showed that the lowest values were noted in the unloaded condition and that the increased applied loads had a significant concomitant increase in all the aforementioned parameters bilaterally (p < 0.05). Conclusion: This phenomenon indicates that the application of increasing knee loads during squats corresponds to higher intensity of vibroacoustic emission, which might be related to higher contact stress and kinetic friction as well as diminished arthrokinematic motion quality.
... Participants descended in a controlled manner at an average velocity of~0.70-0.50 m·s −1 until reaching a fibula-femoral flexion angle of 35-40 • along the sagittal plane [38] to achieve a full squat [40]. This was measured with a goniometer (Nexgen Ergonomics, Point Claire, QC, Canada). ...
Article
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The purpose of this study was to determine the mean propulsive velocity (MVP) at various percentages of one repetition maximum (1RM) in the full squat and chest press exercises. A total of 96 young women and 256 young men (recreational athletes) performed an incremental test (50–60–70–80% 1RM) comprising the bench press and full squat exercises in two different sessions. The individual load and velocity ratios were established through the MPV. Data were analyzed using SPSS software version 25.0, with the significance level set at 5%. The following findings were revealed: highly linear load-velocity relationships in the group of women (r = 0.806 in the squat, and r = 0.872 in the bench press) and in the group of men (r = 0.832 and r = 0.880, respectively); significant differences (p < 0.001) in the MPV at 50–70–80% 1RM between the bench press and the full squat in men and at 70–80% 1RM in women; and a high variability in the MPV (11.49% to 22.63) in the bench press and full squat (11.58% to 25.15%) was observed in women and men (11.31% to 21.06%, and 9.26% to 24.2%) at the different percentages of 1RM evaluated. These results suggest that the load-velocity ratio in non-strength-trained subjects should be determined individually to more precisely establish the relative load to be used in a full squat and bench press training program.
... In rehabilitation settings, squats are often limited to less than 90°of knee flexion in order to minimize tibiofemoral compressive and shear forces, strain in the cruciate ligaments, and patellofemoral compressive forces (Escamilla, Fleisig, Zheng, et al., 2001). In powerlifting competitions, legal squat depth requires the inguinal crease to be below the base of the patella, resulting in approximately 110°of knee flexion and the thigh being parallel to the ground (Hartmann, Wirth, & Klusemann, 2013;Wretenberg, Feng, Lindberg, & Arboreilus, 1993). Lastly, full depth squats to 120-130°of knee flexion are commonly prescribed for athletic performance or Olympic weightlifting (Escamilla, Fleisig, Lowry, Barrentine, & Andrews, 2001). ...
Article
Full-text available
Back squats are a common strengthening exercise for knee and hip musculature. However, repetitive loaded movements like backs squats result in high patellofemoral joint loading and therefore may contribute to the development of common overuse injuries. Thus, it is important to understand how changing parameters such as squat depth or load influences patellofemoral loading. This study investigated differences in patellofemoral loading when experienced female lifters squatted to three depths (above parallel, parallel, and below parallel) and with three loads (unloaded, 50%, and 85% of depth-specific one repetition maximums). Patellofemoral joint reaction forces (pfJRF) and stresses (pfJS) were calculated from biomechanical models incorporating knee extensor moments (KEM) and joint angles. Peak KEMs displayed a depth-by-load interaction such that within each depth, as load increased so did peak KEM. However, within each load, the effects of depth were different. Peak pfJRF also increased with load and was higher at below parallel than above or parallel depths. Peak pfJS also displayed a depth by load interaction, increasing with load within a given depth, and being greatest at the below parallel depths within a given load. If patellofemoral joint loading is a concern clinicians or coaches should carefully monitor the depth and load combinations being used.
... The results of this study might aid clinicians' understanding of the relationship between the level of articular surfaces compressive loads and qualitative aspects of arthrokinematics considered as friction-reducing properties of diarthrosis. Furthermore, these results could broaden knowledge related to the joint biotribology, and might bene t clinicians, because the squat has long been a basic element of strength training among athletes, as well as is various rehabilitative protocols [31][32][33][34]. Because PFJ disorders are commonly encountered in sports and rehabilitation, better recognition of biomechanical behavior of the PFJ during loaded and unloaded movements is essential in order to treat it effectively [4]. ...
Preprint
Full-text available
Background: The patellofemoral joint (PFJ) provides extremely low kinetic friction, which results in optimal arthrokinematic motion quality. Previous research showed that these friction-reducing properties may be diminished due to the increase in articular contact forces. However, this phenomenon has not been analyzed in vivo during functional daily-living activities. The aim of this study was the vibroarthrographic assessment of changes in PFJ arthrokinematics during squats with variated loads. Methods: 114 knees from 57 asymptomatic subjects (23 females and 34 males) whose ages ranged from 19 to 26 years were enrolled in this study. Participants were asked to perform 3 trials: 4 repetitions of bodyweight squats (L0), 4 repetitions of 10 kg barbell back loaded squats (L10), 4 repetitions of 20 kg barbell back loaded squats (L20). During the unloaded and loaded (L10, L20) squats, vibroarthrographic signals were collected using an accelerometer placed on the patella and were described by the following parameters: variation of mean square (VMS), mean range (R4), and power spectral density for frequency of 50-250 Hz (P1) and 250-450 Hz (P2). Results: Obtained results showed that the lowest values were noted in the unloaded condition and that the increased applied loads had a significant concomitant increase in all the aforementioned parameters bilaterally (p<0.05). Conclusion: This phenomenon indicates that the application of increasing knee loads during squats corresponds to higher intensity of vibroacoustic emission, which might be related to higher contact stress and kinetic friction as well as diminished arthrokinematic motion quality.
... After 5 min rest from HST 1-RM the runners performed three repetitions at maximal speed for a load of 70% of their 1-RM in this half-squad exercise, with 1-min rest between repetitions to determinate the concentric movement speed of half-squad test (HST Speed ). During half squat test the athletes performed a knee flexion until the thigh was parallel to the ground (90 • knee angle) and, following a command, moved the bar up as fast as possible, without their shoulder losing contact with the bar [47]. They then had to wait 3 s to remove the elastic component, after which they were given an external signal to perform a concentric extension of the lower limbs until reaching 180 • at the highest ...
Article
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Background: Current carbohydrate (CHO) intake recommendations for ultra-trail activities lasting more than 2.5 h is 90 g/h. However, the benefits of ingesting 120 g/h during a mountain marathon in terms of post-exercise muscle damage have been recently demonstrated. Therefore, the aim of this study was to analyze and compare the effects of 120 g/h CHO intake with the recommendations (90 g/h) and the usual intake for ultra-endurance athletes (60 g/h) during a mountain marathon on internal exercise load, and post-exercise neuromuscular function and recovery of high intensity run capacity. Methods: Twenty-six elite trail-runners were randomly distributed into three groups: LOW (60 g/h), MED (90 g/h) and HIGH (120 g/h), according to CHO intake during a 4000-m cumulative slope mountain marathon. Runners were measured using the Abalakov Jump test, a maximum a half-squat test and an aerobic power-capacity test at baseline (T1) and 24 h after completing the race (T2). Results: Changes in Abalakov jump time (ABKJT), Abalakov jump height (ABKH), half-squat test 1 repetition maximum (HST1RM) between T1 and T2 showed significant differences by Wilcoxon signed rank test only in LOW and MED (p < 0.05), but not in the HIGH group (p > 0.05). Internal load was significantly lower in the HIGH group (p = 0.017) regarding LOW and MED by Mann Whitney u test. A significantly lower change during the study in ABKJT (p = 0.038), ABKH (p = 0.038) HST1RM (p = 0.041) and in terms of fatigue (p = 0.018) and lactate (p = 0.012) within the aerobic power-capacity test was presented in HIGH relative to LOW and MED. Conclusions: 120 g/h CHO intake during a mountain marathon might limit neuromuscular fatigue and improve recovery of high intensity run capacity 24 h after a physiologically challenging event when compared to 90 g/h and 60 g/h.
... The results of this study may aide clinicians' understanding of the relationship between the level of articular surfaces compressive loads and qualitative aspects of arthrokinematics considered as friction-reducing properties of diarthrosis. Furthermore, these results could broaden knowledge related to the joint biotribology, and may benefit clinicians, because the squat has long been a basic element of strength training among athletes, as well as is various rehabilitative protocols [31][32][33][34]. Because PFJ disorders are commonly encountered in sports and rehabilitation, better recognition of biomechanical behavior of joints during loaded and unloaded movements is essential in order to treat it effectively [4]. ...
Preprint
Full-text available
Background: The patellofemoral joint (PFJ) provides extremely low kinetic friction, which results in optimal arthrokinematic motion quality. Previous research showed that these friction-reducing properties may be diminished due to the increase in articular contact forces. However, this phenomenon has been not analyzed in vivo during functional daily-living activities. The aim of this study was the vibroarthrographic assessment of changes in PFJ arthrokinematics during squats with variated loads. Methods: Fifty-seven asymptomatic subjects were enrolled in this study. Participants were asked to perform 3 trials: 4 repetitions of bodyweight squats (L0), 4 repetitions of 10 kg barbell back loaded squats (L10), 4 repetitions of 20 kg barbell back loaded squats (L20). During the unloaded and loaded (L10, L20) squats, vibroarthrographic signals were collected using an accelerometer placed on the patella and were described by the following parameters: variation of mean square (VMS), mean range (R4), and power spectral density for frequency of 50-250 Hz (P1) and 250-450 Hz (P2). Results: Obtained results showed that the lowest values were noted in the unloaded condition and that the increased applied loads had a significant concomitant increase in all the aforementioned parameters bilaterally (p<0.05). Conclusion: This phenomenon indicates that the application of increasing knee loads during squats corresponds to higher intensity of vibroacoustic emission, which may result in higher contact stress and kinetic friction as well as diminished arthrokinematic motion quality.
... During the deadlift, in elite powerlifters, the average compression force in the spine is > 17,000 N [10]. Likewise, the knees are exposed to high forces when performing deep squats [11]. Shoulder injuries are more commonly classified as overuse injuries, probably due to years of repeated shoulder strain during the bench press [12]. ...
Article
Objective While powerlifting is a popular sport, there may be some safety concerns due to the repeated high loads. This literature review focuses on injury rates, areas of injury and biomechanical movement analysis. Method “Powerlifting” and “injury” were used in the most relevant databases. Inclusion and exclusion criteria were applied and 11 studies were included separated in three different categories. Results Based on 11 studies with a total of 763 lifters, the injury incidence in powerlifting is low; between 1.0–4.4 per 1000 hours, with the low back, shoulders and knees being the most affected areas. Lifting biomechanics were different between novice and elite lifters. Conclusion Evaluation of lifting technique and athlete characteristics may be a viable strategy to prevent acute or overuse pain and injury. During the main lifts, compressive/supportive apparel could be protective for lifters on this risk areas.
... The back-squat is one of the most effective exercises to strengthen the lower limbs and prevent injuries [16]. Additionally, lower-body strength gains following back-squat training have been shown to positively transfer to athletic performance during short duration high-intensity actions such as jumping and sprinting [17,18]. ...
Article
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This study aimed to compare the between-session reliability of different performance variables during 2 variants of the Smith machine back-squat exercise. Twenty-six male wrestlers performed 5 testing sessions (a 1-repetition maximum [1RM] session, and 4 experimental sessions [2 with the pause and 2 with the rebound technique]). Each experimental session consisted of per-forming 3 repetitions against 5 loads (45-55-65-75-85% of the 1RM). Mean velocity (MV), mean power (MP), peak velocity (PV), and peak power (PP) variables were recorded by a linear position transducer (GymAware PowerTool). The best and average scores of the 3 repetitions were con-sidered for statistical analyses. The coefficient of variation (CV) ranged from 3.89% (best PV score at 55%1RM using the pause technique) to 10.29% (average PP score at 85%1RM using the rebound technique). PP showed a lower reliability than MV, MP, and PV (CVratio≥1.26). The relia-bility was comparable between the exercise techniques (CVratio=1.08) and between the best and av-erage scores (CVratio=1.04). These results discourage the use of PP to assess back-squat performance at submaximal loads. The remaining variables (MV, MP, or PV), exercise techniques (pause or rebound), and repetition criteria (best score or average score) can be indistinctly used due to their acceptable and comparable reliability.
... The back squat (SQ) is one of the most commonly used and effective resistance training exercises for strengthening the lower limbs, protecting against injuries and enhancing athletic performance. 1,2 Numerous studies have demonstrated that increases in lower-limb strength after SQ training transfer positively to functional athletic performance in both short-duration actions, such as sprints and vertical jumps 2,3 and long-duration movements (eg, rowing, cross-country, or cycling). 4,5 During traditional SQ, the subject starts from an upright position and descends (eccentric phase) to a specific depth (half, parallel, or full SQ), and then immediately reverses the motion and ascends back to the starting position (concentric phase). ...
Article
Purpose: A variation of the traditional squat (SQ) rebound technique (REBOUND) including a momentary pause ∼2 seconds (PAUSE) between eccentric and concentric phases has been proposed. Although there is a consensus about the lower acute effects on performance of this PAUSE variant compared with traditional REBOUND technique, no information exists about the differences in longitudinal adaptations of these SQ executions. Methods: A total of 26 men were randomly assigned into the PAUSE (n = 13) or REBOUND (n = 13) groups and completed a 10-week velocity-based training using the SQ exercise, only differing in the technique. Neuromuscular adaptations were assessed by the changes in the 1-repetition maximum strength and mean propulsive velocity achieved against the absolute loads (in kilograms) common to pretest and posttest. Functional performance was evaluated by the following tests: countermovement jump, Wingate, and sprint time at 0 to 10, 10 to 20, and 0 to 20 m. Results: Whereas both groups showed significant increases in most of the neuromuscular tests (P < .05), the PAUSE (effect size [ES] = 0.76-1.12) presented greater enhancements than REBOUND (ES = 0.45-0.92). Although not significant, improvements in Wingate and sprint time at 0 to 10 and 0 to 20 m were higher for PAUSE (ES = 0.31-0.46) compared with REBOUND (ES = 0.10-0.29). Conversely, changes on countermovement jump and sprint time at 10 to 20 m were superior for REBOUND (ES = 0.17-0.88) than for PAUSE (ES = 0.09-0.75). Conclusion: Imposing a pause between eccentric and concentric phases in the SQ exercise could be an interesting strategy to increase neuromuscular and functional adaptations in sport actions that mainly depend on concentric contractions. Moreover, sport abilities highly dependent on the stretch-shortening cycle could benefit from the REBOUND or a combination of the 2 techniques.
... According to this definition, the participants in the present study, adopted a stiffer landing strategy with increasing barbell load. Due to the stiff landing technique the lever arm of the GRF around the knee and the hip joint were reduced, which mainly determine the magnitude of the joint moments (Hartmann et al., 2013). ...
Article
Loaded jumps are commonly used to improve leg muscle power. However, the additional load during jump-landing might increase the potential for overuse injury. Therefore, the aims of this study were to evaluate the effect that barbell load has on lower limb joint kinematics and kinetics during jump-landing and to evaluate the effect of arresting the barbell load at flight apex prior to landing on joint kinematic and kinetic variables. Barbell-loaded squat jumps (20, 40, and 60 kg) were investigated during two jump-landing conditions: 1) barbell-loaded (landing with barbell load) and 2) barbell-arrested (barbell load arrested at flight apex prior to jump-landing). Lower body kinematics and joint kinetics were assessed during jump-landing. In the barbell-loaded jump-landing condition, joint angles at initial contact decreased with increasing barbell load. Knee and hip peak power decreased (knee: -38%; hip: -46%), while ankle joint work increased with increasing barbell load. Joint moments, powers and work were decreased in the barbell-arrested condition compared to the barbell-loaded condition. Barbell-loaded jump-landings do not pose increased demands on the knee and the hip joint compared to bodyweight only jump-landings, due to the load-based reductions in jump height and joint kinematic adaptions. However, ankle joint contribution in energy dissipation is increased, possibly resulting in an increased overuse injury risk at this joint. Arresting the barbell load at flight apex prior to jump-landing substantially reduces the joint kinetics, hence serving as valuable training tool for athletes returning to sport after injuries.
... These results supported our first hypothesis that at loads heavier than the optimal loads reported in previous studies (65%-80% 1RM), peak power would decrease significantly due to decreases in velocity relative to decreases in bar displacement. When the criterion for a quarter squat was set at a knee joint angle of 110°to 140°, consistent with the criterion used by Hartmann et al 17 and Schoenfeld,18 loads where the subjects received the bar at the quarter-squat position or higher were 40% to 70% 1RM (Figure 3). In the present study, peak power increased with increment in relative load from 40% to 80% 1RM. ...
Article
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Purpose: The optimal load for maximal power output during hang power cleans (HPCs) from a mechanical perspective is the 1-repetition-maximum (1RM) load; however, previous research has reported otherwise. The present study thus aimed to investigate the underlying factors that determine optimal load during HPCs. Methods: Eight competitive Olympic weight lifters performed HPCs at 40%, 60%, 70%, 80%, 90%, 95%, and 100% of their 1RM while the ground-reaction force and bar/body kinematics were simultaneously recorded. The success criterion during HPC was set above parallel squat at the receiving position. Results: Both peak power and relative peak power were maximized at 80% 1RM (3975.7 [439.1] W, 50.4 [6.6] W/kg, respectively). Peak force, force at peak power, and relative values tended to increase with heavier loads (P < .001), while peak system velocity and system velocity at peak power decreased significantly above 80% 1RM (P = .005 and .011, respectively). There were also significant decreases in peak bar velocity (P < .001) and bar displacement (P < .001) toward heavier loads. There was a strong positive correlation between peak bar velocity and bar displacement in 7 of 8 subjects (r > .90, P < .01). The knee joint angle at the receiving position fell below the quarter-squat position above 70% 1RM. Conclusions: Submaximal loads were indeed optimal for maximal power output for HPC when the success criterion was set above the parallel-squat position. However, when the success criterion was defined as the quarter-squat position, the optimal load became the 1RM load.
... A final component with leg press MST, as performed in the current study, is that the repetitions involves a knee joint range of motion from ~ 180° to an angle not lower than 90° in the lowest position, reducing the stress on the hip (Wretenberg et al. 1993) and knee (Cotter et al. 2013) joints that occur below 90° of knee flexion. However, it is uncertain if this reduces the risk of injuries (Hartmann et al. 2013) or pain. ...
Article
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Purpose Patients with inflammatory rheumatic disease (IRD) have attenuated muscle strength in the lower extremities, resulting in impaired physical function and quality of life. Although maximal strength training (MST), applying heavy resistance, is documented to be a potent countermeasure for such attenuation, it is uncertain if it is feasible in IRD given the pain, stiffness, and joint swelling that characterize the population. Methods 23 patients with IRD (49 ± 13 years; 20 females/3 males), diagnosed with spondyloarthritis, rheumatoid arthritis, or systemic lupus erythematosus, were randomized to MST or a control group (CG). The MST group performed four × four repetitions dynamic leg press two times per week for 10 weeks at ~ 90% of one repetition maximum (1RM). Before and after training 1RM, rate of force development (RFD), and health-related quality of life (HRQoL) were measured. Results Session attendance in the MST group was 95%, of which 95% conducted according to MST protocol. Furthermore, MST increased 1RM (29 ± 12%, p = 0.001) and early and late phase RFD (33–76%, p < 0.05). All improvements were different from the CG ( p < 0.05). MST also resulted in HRQoL improvements in the dimensions; physical functioning, general health, and vitality ( p < 0.05). Physical functioning was associated with 1RM (rho = 0.55, p < 0.01) and early phase RFD (rho = 0.53–0.71, p < 0.01; different from CG p < 0.05). Conclusions Despite being characterized by pain, stiffness, and joint swelling, patients with IRD appear to tolerate MST well. Given the improvements in 1RM, RFD, and HRQoL MST should be considered as a treatment strategy to counteract attenuated muscle strength, physical function, and HRQoL. Trial registration: ClinicalTrials.gov, NCT04998955, retrospectively registered.
... Por razones de estandarización y seguridad, las participantes descienden de forma controlada a una velocidad media de ~ 0.50-0.60m s − 1 hasta llegar a una flexion que condujera a un ángulo tibiofemoral de 35-40 ° en el plano sagital, el cual fue medido con un goniómetro (Nexgen Ergonomics, Point Claire, Quebec, Canadá) para lograr una sentadilla profunda (Hartmann, Wirth, & Klusemann, 2013). En esta posición se efectuaba una pausa de 1.5 s. y ante la orden del evaludor realizaban una extensión a maxima velocidad. ...
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Objetivo: Comparar la tasa de fuerza relativa (TFR) con distintos indicadores de fuerza en mujeres jóvenes. Métodos: Se evaluaron a 146 mujeres que se distribuyeron en tres grupos de acuerdo con los resultados de la TFR obtenida en el ejercicio de sentadilla y se compararon los resultados obtenidos en las pruebas de Fuerza prensil de la mano derecha e izquierda (FPMD- FPMI), Fuerza isométrica miembros inferiores (FIMI), Fuerza máxima de pecho (FMP), Fuerza máxima en sentadilla (FMS) Velocidad de desplazamiento sobre treinta metros (V30), altura del salto en (CMJ), potencia de pedaleo (PP) y la velocidad media propulsiva de miembros superiores e inferiores (VMPMS-VMPMI) obtenida al 50%, 60%, 70% y 80% de una repetición máxima en sentadilla. Resultados: Se observaron diferencias significativas (p?0,01) entre los grupos en la FMS, CMJ, V30, VMP y PP, y la mayoría de las variables presentaban la diferencia entre el G1 y G3 (p?0,01).
... In many respects, back squat strength training may impose similar physiologic demands on the body as anaerobic sprint cycle training, especially from a metabolic perspective (6). Further, back squats have been shown to be safe as well as effective in preventing against lower body injury and significantly increasing lower body strength (14,24,36). Programs designed to improve endurance performance often center on increases in training load, and subsequently expose athletes to an increased risk of injury (12,45). ...
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International Journal of Exercise Science 13(7): 1770-1782, 2020. The purpose of this study was to evaluate the hypothesis that a novel high-repetition, low-resistance back squat training protocol, designed to stimulate high-intensity interval training, improves 5-km run performance. Fifteen runners [4 male, 11 female; 150 + minutes of endurance exercise/week; age = 22.7 ± 2.0 y; 21.5 ± 2.2 kg/m2 BMI] in this single-group test-retest design completed two weeks of back squats consisting of three sets of 15-24 repetitions at 60% of estimated one-repetition max (1RM), three times per week (1-2 days of rest between sessions). Outcome tests included a 5-km outdoor timed run, laboratory indirect calorimetry to quantify substrate oxidation rates during steady-state submaximal exercise (60% and 70% heart rate max (HRmax)), and estimated 1RM for back squats. Back squat estimated 1RM increased by 20% (58.3 ± 18.5 to 70.2 ± 16.7 kg, P < 0.001). However, 5-km run times due to the back squat protocol did not significantly change (Pre-Squats: 23.9 ± 5.0 vs. Post-Squats: 23.7 ± 4.3 minutes, P = 0.71). Likewise, the squat training program did not significantly alter carbohydrate or lipid oxidation rates during steady-state submaximal exercise at 60% or 70% of HRmax (P values ranged from 0.36 - 0.99). Short term high-repetition back squat training does not appear to impact 5-km run performance or substrate utilization during submaximal exercise.
... A lack of ergonomics or improper use of weight training machines during training can be detrimental to the health of the person performing the exercise, and can also cause changes in the maximum strength-producing capacity of the user by modifying biomechanics. More specifically, the execution of exercises with an excessive range of motion and the adoption of inadequate postures, especially with regard to the spine, or an incorrect execution of the exercise performed (Chow, 2013;Rodriguez-Ridao et al., 2020), together with an increase in the loads during execution can lead to multiple injuries of different kinds (Hartmann, Wirth & Klusemann, 2013;McGill, Cannon & Andersen, 2014;Sayers et al., 2020). Among the most frequent injuries that could result from overloading caused by incorrect use of this type of machinery we find herniated discs, spondylolysis, and spondylolisthesis (Harrison et al., 2005). ...
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Background: Outdoor fitness training has become popular as a tool for improving the health, especially middle-aged and older adults. For this purpose, outdoor fitness equipment (OFE) have been installed in public areas. However, their safety and effectiveness are still unknown. The aim of the present research was to analyze the sagittal disposition of the spine and pelvic tilt during the use of OFE, and to determine the influence of anthropometric variables on these factors in middle-aged and older adults. Methods: Seventy healthy volunteers, 56 women and 14 men (age: 63.14 ± 8.19 years) participated in the study. Sagittal spine disposition and pelvic tilt were measured using a Spinal Mouse®, in the relaxed standing position, and during the use of the OFE. In addition, kinanthropometry variables were also measured according to the guidelines of the International Society for the Advancement of Kinanthropometry. Results: Regarding thoracic kyphosis, a significant decrease was found in thoracic kyphosis in the initial position (IP) in single bonny rider (SBR) (p = 0.006) and row (p = 0.046), and a significant increase in the final position (FP) in the row (p = 0.011), surfboard (p < 0.001) and air walker (p = 0.027) machines. In relation to the lumbar curvature and pelvic tilt, a significant decrease in lumbar lordosis and a decrease in pelvic anteversion were observed in the IP and FP in SBR and row; and in the bike (p < 0.001) machine. In the surfboard machine, a significant decrease in lumbar lordosis was found (p = 0.002), with no changes in pelvic tilt. According to the multiple linear regression analysis, the subjects with a higher cormic index and height were more at risk of increasing their thoracic kyphosis, decreasing lumbar lordosis and/or decreasing pelvic anteversion towards pelvic retroversion. Conclusions: Middle-aged and older adults show spinal misalignments when using the OFE with respect to the standing position, showing a decrease in the thoracic kyphosis in IP of SBR and ROW, and a significant increase in the surfboard and air walker, and in the FP of Row, in the lumbar lordosis in all the OFE in sitting and some in standing, and in the pelvic anteversion in all the OFE in sitting. The variables height and the cormic index explained most of the changes in sagittal spine disposition.
... The particularly high frequency of PFJ cartilage damage among athletes participating in Beach Volleyball and Volleyball, as well as weightlifting was previously reported in the same cohort [9]. In weightlifting, it has been suggested that cartilage damage risk increases with exposure to high loading forces while performing squats [11]. Regarding Beach Volleyball and Volleyball, we found higher frequency of PFJ cartilage damage/BML in comparison with a recent study including adolescents and adults volleyball players, which showed frequency of cartilage damage not exceeding 38 % [12]. ...
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Background Patellofemoral joint (PFJ) disease is a common ailment in elite athletes. Our aim is to report the frequency of superolateral Hoffa’s fat pad (SHFP) edema, and PFJ cartilage damage and bone marrow lesions (BML), among Olympian athletes, and to study the association between measurements of trochlear morphology and vertical patellar position and a) PFJ cartilage damage or BML, and b) SHFP edema. Methods All knee MRI, performed in the Olympic Village and polyclinics, of participating athletes in the 2016 Olympic Games of Rio de Janeiro were included. MRI were scored for PFJ cartilage damage and BML, and SHFP edema. Trochlear morphology measurements included sulcus angle, trochlear angle, lateral trochlear inclination, and medial trochlear inclination. Insall-Salvati ratio was also assessed. Results One hundred twenty-one knee MRIs were included (62 female, 51.2 %). The highest frequencies of PFJ cartilage damage, combination of PFJ cartilage damage and BML, and SHFP edema were found among Beach Volleyball and Volleyball athletes. SHFP edema was more common among female compared to male Olympian athletes. We found no statistically significant associations between different measurements of trochlear morphology/vertical patellar position, and 1. SHFP edema, and 2. PFJ cartilage damage/BML. Conclusion SHFP edema and the combination of PFJ cartilage damage and BML are highly frequent among Olympic athletes especially those competing in Beach volleyball and Volleyball. SHFP edema is more common among female athletes. Further studies are needed to determine whether PFJ cartilage damage has a stronger association to sports disciplines rather than trochlear morphology.
... All participants carried out an 8-week velocity-based RT program involving 2 sessions per week (16 total sessions), using only the SQ exercise. The full-squat exercise was chosen as training exercise because this type of exercise induce greater neuromuscular and functional adaptations and lower pain than half-or quarter-squat after prolonged RT period (Hartmann et al. 2013;Pallares et al. 2019). Training variables such as relative intensity (70%-85% 1RM), number of sets (three), recovery time between sets (4 min) and recovery time between sessions (72 hours) were the same for both experimental groups. ...
Article
This study aimed to compare the effects of 2 resistance training (RT) programs with different velocity losses (VLs) allowed in each set: 10% (VL10%) versus 30% (VL30%) on neuromuscular performance and hormonal response. Twenty-five young healthy males were randomly assigned into 2 groups: VL10% (n = 12) or VL30% (n = 13). Subjects followed a velocity-based RT program for 8 weeks (2 sessions per week) using only the full-squat (SQ) exercise at 70%–85% 1-repetition maximum (1RM). Repetition velocity was recorded in all training sessions. A 20-m running sprint, countermovement jump (CMJ), 1RM, muscle endurance, and electromyogram (EMG) during SQ exercise and resting hormonal concentrations were assessed before and after the RT program. Both groups showed similar improvements in muscle strength and endurance variables (VL10%: 7.0%–74.8%; VL30%: 4.2%–73.2%). The VL10% resulted in greater percentage increments in CMJ (9.2% vs. 5.4%) and sprint performance (–1.5% vs. 0.4%) than VL30%, despite VL10% performing less than half of the repetitions than VL30% during RT. In addition, only VL10% showed slight increments in EMG variables, whereas no significant changes in resting hormonal concentrations were observed. Therefore, our results suggest that velocity losses in the set as low as 10% are enough to achieve significant improvements in neuromuscular performance, which means greater efficiency during RT. Novelty The VL10% group showed similar or even greater percentage of changes in physical performance compared with VL30%. No significant changes in resting hormonal concentrations were observed for any training group. Curvilinear relationships between percentage VL in the set and changes in strength and CMJ performance were observed.
... Increasing squat depth after PPT has been initiated causes the lumbar spine to flex and decreases the moment arm of the lumbar erector spinae. This minimizes the muscles' ability to withstand shear and compressive forces, potentially causing a greater risk for spinal injury (4,6,17). In addition, it is important to consider the implications that squat depth may have on the hip. ...
Article
During the lowering phase of a squat, it has been observed that a posterior pelvic tilt (PPT) may occur when squatting to full depth. Research suggests that defaulting to compensatory movement strategies, such as PPT, during the squat may correlate with risk of lower extremity and trunk pathology. The purpose of this study was to examine hip flexion (HF) angles at the point when PPT occurs among three conditions: standard squats, heel raise squats, and supine passive HF; analyzing the differences in depth between standard and heel raise squats; and calculating differences in knee angles and ankle excursion between standard and heel raise squats. 28 participants performed bodyweight squats and underwent supine passive HF while outfitted with 32 retroreflective motion capture markers. Hip, knee, and ankle joint angles were extracted at the point of PPT. A one-way repeated measures ANOVA was used to determine differences in hip joint angles between conditions, and a paired sample t-test was used to compare knee angles, ankle excursion, and squat depth between standard and heel raise squats. HF angles at PPT remained unchanged across all conditions. However, significantly greater knee flexion, ankle excursion, and squat depth were observed in the heel raise squats compared to the standard squats. Results suggest that PPT is a compensatory movement that occurs as the femur compresses into the acetabulum once hip flexion has been exhausted.
... A articulação do tornozelo com sua adequada ADM é essencial para um agachamento profundo adequado, pois se um agachamento profundo for realizado sem a adequada dorsiflexão, podem resultar compensações, incluindo aumento da flexão nos quadris, lombar e tronco [25][26][27] . Sendo que neste estudo, mais de 20% dos praticantes avaliados não apresentaram adequado valores para o tornozelo. ...
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RESUMO: O objetivo desse estudo foi avaliar a amplitude de movimento articular de praticantes de um programa de condicionamento extremo. O estudo transversal, descritivo, caracteriza-se por uma pesquisa quanti-qualitativa. Os praticantes responderam perguntas sociodemográficas, relacionadas à prática da modalidade, se possuía alguma dor/desconforto articular e realizaram testes para a avaliação da amplitude articular de ombro, punho, quadril e tornozelo. Os testes realizados foram: Reverse Wall Slide para o ombro, Weight-Bearing Box Test para o punho, Supine Kness-To-Chest para o quadril e Weight-Bearing Lunge Test para a articulação do tornozelo. Foram avaliados 46 praticantes, sendo 26 mulheres e 20 homens. Os resultados foram analisados e apresentados de forma descritiva com cálculo da média e desvio padrão. Nos praticantes avaliados cerca de 30,43%; 80,45%; 58,69% e 60,28% apresentaram avaliação positiva para a amplitude de movimento de ombro, punho, quadril e tornozelo, respectivamente. Foi encontrado correlação positiva e fraca somente entre o resultado do teste de mobilidade do tornozelo e dor/desconforto Palavras-chave: Amplitude de Movimento; Exercício; Treinamento de Resistência. Limitação da Mobilidade. Neto, A.R., Magalhães, L.F., Bertoncello, D. AVALIAÇÃO DA AMPLITUDE DE MOVIMENTO EM PRATICANTES DE UM PROGRAMA DE CONDICIONAMENTO EXTREMO. R. bras. Ci. e Mov 2020;28(4):63-69. Abstract: The objective of this study was to evaluate the range of articular movement of practitioners of an extreme conditioning program. The cross-sectional, descriptive study is characterized by quantitative and qualitative research. The practitioners answered sociodemographic questions, related to the practice of the sport, if they had any joint pain / discomfort and performed tests to assess the shoulder, wrist, hip and ankle joint amplitude. The tests performed were: Reverse Wall Slide for the shoulder mobility, Weight-Bearing Box Test for the wrist mobility, Supine Kness-To-Chest for the hip mobility and Weight-Bearing Lunge Test for the ankle mobility. Was evaluated 46 practitioners, 26 women and 20 men. The results were analyzed and presented descriptively with calculation of the mean and standard deviation. In the evaluated practitioners about 30.43%; 80.45%; 58.69% and 60.28% had a positive evaluation for the range of motion of the shoulder, wrist, hip and ankle, respectively. A positive and weak correlation was found only between the result of the ankle mobility test and pain / discomfort.
... A postura era afastada aproximadamente na largura dos ombros, pés paralelos apoiados no chão ou rodados externamente a um máximo de 15°. A partir dessa posição, os participantes desceram em movimento controlado até que a prega inguinal atingisse (ponto B) o mesmo plano horizontal da borda superior da patela [10,22]. Após uma pausa momentânea (~1,5 s), eles subiram de volta à posição ereta, mantendo uma postura de tronco ereta [23]. ...
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Objetivos: Os objetivos deste estudo foram: 1) comparar a relação carga-velocidade estimada pelo método de dois pontos entre homens e mulheres destreinados durante o exercício agachamento paralelo (BS) e 2) comparar o perfil carga-velocidade encontrado em nosso estudo com os perfis de carga-velocidade relatados na literatura científica para indivíduos treinados. Além disso, comparar a velocidade de 1RM medida com a velocidade de 1RM predita pelo método de dois pontos no exercício BS em indivíduos destreinados. Métodos: Setenta e seis indivíduos destreinados (38 homens (22,7 ± 4,4 anos; 174,9 ± 6,8 cm; 76,1 ± 14,9 kg) e 38 mulheres (24,7 ± 4,3 anos; 159,1 ± 6,0 cm; 64,7 ± 13,3 kg) realizaram um teste de uma repetição máxima e um teste progressivo de duas cargas com 20% e 70% 1RM para estimar suas relações carga-velocidade. Resultados: Os principais resultados revelaram que 1) a velocidade média propulsiva e a velocidade média atingida em cada carga relativa foram diferentes entre homens e mulheres (p < 0,05). No entanto, a velocidade de 1RM medida não foi significativamente diferente entre eles. Homens destreinados forneceram uma relação carga-velocidade mais acentuada do que as mulheres. Descobrimos que 2) os indivíduos destreinados de nosso estudo apresentaram um perfil carga-velocidade diferente dos indivíduos treinados dos estudos da literatura científica. Além disso, 3) a velocidade de 1RM medida foi menor do que a velocidade de 1RM predita (p < 0,05). Conclusão: Esses resultados sugerem que a relação carga-velocidade é dependente do sexo e treinamento, e que o método de dois pontos usando 20% e 70% 1RM não seria confiável para estimar a relação carga-velocidade no exercício agachamento paralelo em homens e mulheres destreinados. Palavras-chave: exercício; mensuração da velocidade; força muscular.
... Therefore, information about the acute effects of set configuration in strength training protocols used in practice on muscle contractile properties is lacking in the literature. In this regard, the SQ is one of the most widely used and effective RT exercises for strengthening the lower limbs and improving athletic performance (12). In addition, TMG measurements should be accompanied by postexercise mechanical performance tests to better comprehend how these outcomes interact. ...
... Dynamic squat is a closed dynamic chain exercise (Escamilla, Fleisig, Zheng, Barrentine, Wilk & Andrews, 1998). It is one of the most widely used and effective resistance training to strengthen the lower limbs, preventing injuries and improving athletic performance (Hartmann, Wirth & Klusemann, 2013) involved the body's largest and strongest muscles (quadriceps, gluteus maximus, and erector spinae, etc.), requiring coordinated movements of the spine, hips, knees, and ankles. It is beneficial to many functional activities and sports, often used in rehabilitation treatment of many chronic diseases (Schoenfeld, 2010), such as chronic obstructive pulmonary disease, stroke, and cerebral palsy (Garvey et al., 2016;Gray, Ivanova & Garland, 2012;Eken, Harlaar, Dallmeijer, de Waard, van Bennekom, & Houdijk, 2017). ...
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Background: The Prevalence of metabolic syndrome is increasing in perimenopausal women. BMI, waist-hip ratio (WHR) and lipids are important factors for controlling metabolic syndrome. The Baduanjin exercise is a traditional Chinese exercise that promotes the integration of physical and mental health, and it is easy to practice at home and fit for busy perimenopausal women. However, the health effects needed to be evaluated.Aim: The purpose of this quasi-experimental research was to evaluate the effects, after twelve weeks of practicing Baduanjin exercise.Methods: This study was conducted at two Buddhism painting clubs, using a parallel-design, control trial recruiting perimenopausal women. There were three instruments: (1) BMI, (2) Waist-Hip Ratio, (3) Lipids—HDL and LDL. The intervention effects from the study baseline to a twelve weeks follow-up were estimated using T-test to evaluate the effectiveness of Baduanjin exercise. The Baduanjin exercise intervention included one-on-one teaching and telephone follow-up to help women practice Baduanjin exercise of 10-15 minutes twice per day for twelve weeks at home. Result: A total of 54 women aged 40 to 60 were recruited from two Buddhism painting clubs. Twenty-seven women were in the experimental group, while 27 women were in the control group. Positive effects were found after 12 weeks doing Baduanjin exercise of 10-15 minutes twice per day at home. In the experimental group, women improved their health by significantly decreasing BMI, increasing HDL, decreasing LDL and more slowly increasing WHR compared with the control group. Conclusion: Baduanjin exercise is a good home exercise to suggest perimenopausal women to improve their BMI, waist-hip ratio and lipid
... While the gait cycle has been the most researched activity in the current literature, it is not particularly demanding for the lower limb joints. For the purpose of implant wear testing, implant fixation, and joint stability analysis, there are other more challenging activities commonly performed in daily living that might be of particular interest (Hartmann et al., 2013). Clinical, experimental, and computational studies have clearly reported increased complication risk and wear rate under high contact stress conditions (Kang et al., 2008;O'Brien et al., 2015;de Ruiter et al., 2017). ...
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PurposeModern statistics and higher computational power have opened novel possibilities to complex data analysis. While gait has been the utmost described motion in quantitative human motion analysis, descriptions of more challenging movements like the squat or lunge are currently lacking in the literature. The hip and knee joints are exposed to high forces and cause high morbidity and costs. Pre-surgical kinetic data acquisition on a patient-specific anatomy is also scarce in the literature. Studying the normal inter-patient kinetic variability may lead to other comparable studies to initiate more personalized therapies within the orthopedics.Methods Trials are performed by 50 healthy young males who were not overweight and approximately of the same age and activity level. Spatial marker trajectories and ground reaction force registrations are imported into the Anybody Modeling System based on subject-specific geometry and the state-of-the-art TLEM 2.0 dataset. Hip and knee joint reaction forces were obtained by a simulation with an inverse dynamics approach. With these forces, a statistical model that accounts for inter-subject variability was created. For this, we applied a principal component analysis in order to enable variance decomposition. This way, noise can be rejected and we still contemplate all waveform data, instead of using deduced spatiotemporal parameters like peak flexion or stride length as done in many gait analyses. In addition, this current paper is, to the authors’ knowledge, the first to investigate the generalization of a kinetic model data toward the population.ResultsAverage knee reaction forces range up to 7.16 times body weight for the forwarded leg during lunge. Conversely, during squat, the load is evenly distributed. For both motions, a reliable and compact statistical model was created. In the lunge model, the first 12 modes accounts for 95.26% of inter-individual population variance. For the maximal-depth squat, this was 95.69% for the first 14 modes. Model accuracies will increase when including more principal components.Conclusion Our model design was proved to be compact, accurate, and reliable. For models aimed at populations covering descriptive studies, the sample size must be at least 50.
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The aim of this study was to compare the effects of two resistance training programs including either a deadlift or a parallel squat on lower body maximal strength and power in resistance trained males. Twentyfive resistance trained men were randomly assigned to a deadlift group (DE; n = 14; age = 24.3 ± 4.1 y; body mass = 84.8 ± 14.2 kg; body height = 180.3 ± 6.8 cm) or to a squat group (SQ; n = 11; age = 22.3 ± 1.6 y; body mass = 83.0 ± 13.6 kg; body height 179.9 ± 6.1 cm). Both groups trained 3 times per week for 6 weeks. The deadlift and the squat were the only lower body maximal strength exercises performed by DE and SQ groups, respectively, while both training programs included jumps. A significantly (p = 0.017) greater increase in deadlift 1RM was observed in the DE compared to the SQ group, while the SQ group obtained a significantly (p = 0.049) greater increase in squat 1RM. A significant increase in jump performance (p = 0.010), without significant interactions between groups (p = 0.552), was observed in both groups. Three participants of the DE group developed lower back pain and were excluded from the study. Results indicate that both the squat and the deadlift can result in similar improvement in lower body maximal strength and jump performance and can be successfully included in strength training programs. The incidence of back pain in the DE group may suggest a marked stress of this exercise on the lower back. Proper technique should be used to minimize the risk of injury, especially when the deadlift is performed. Keywords: resistance training, jump performance, strength exercises.
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Resistance training has been widely recommended as a strategy to enhance the functional autonomy and quality of life in older individuals. Among the variables that comprise a training session, the selection of exercises stands out as an important consideration for the elderly. Although a wide range of resistance exercise options exists, current guidelines generally do not indicate which exercises should be included and which muscles should be prioritized when prescribing training for older individuals. Therefore, given the lack of evidence-based information on the topic, this paper endeavors to establish recommendations to help guide the prescription of resistance exercises for older adults.
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This study analyzed the acute mechanical response to three workouts of the day (WOD) protocols in as many repetitions as possible (AMRAP), every minute on the minute (EMOM), and for time (FT) models by quantifying the degree of mechanical fatigue induced by popular resistance exercises in the Cross modalities, front squat (FS), and shoulder press (SP). Besides, we analyzed whether the exercises’ fastest velocity (Vfastest) could be an objective indicator of relative intensity (%1RM). Nine trained men performed three FS and SP exercises protocols. The degree of fatigue was quantified by the velocity loss (VL) achieved in both exercises and the velocity loss achieved in the WOD (VLWOD). The VLWOD in the AMRAP, EMOM, and FT protocols was 73.2 ± 10.9%, 61.6 ± 15.1%, and 76.1 ± 8.8%, respectively. In the AMRAP and FT protocol, the Vfastest showed very strong relationships with the %1RM for FS and SP (r = -0.83, -0.75, respectively, p<0.01); while in the EMOM protocol, there was a strong relationship between these variables, only for the SP (r = -0.61, p<0.05). In the FT protocol, we observed an extremely strong relationship for FS (r = -0.91, p<0.001) and very strong (r = -0.71, p<0.05) for SP between these variables. Therefore, the AMRAP and FT training models induce the highest degrees of mechanical fatigue in the FS and SP exercises, and the Vfastest is a reliable tool for estimating relative intensity in resistance exercises of Cross modalities.
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The aim of this study was to analyze the relationship of range of motion (ROM) in the sagittal plane and timing parameters during a bodyweight squat to the depth of the squat. Sixty participants (20 females and 40 males) took part in this study. They were instructed to perform a bodyweight squat to the maximal depth position. Kinematic data were obtained using the optical motion capture system. The time for the descent phase of squatting was normalized from 0% (initial position, start of movement) to 100% (squat position-stop of movement). The ROM of ankle, knee, hip, pelvis and spine in the sagittal plane and the normalized time when the maximum joint angles occurred during the descent were analyzed to investigate the relationship between them and the squat depth in males and females. The knee ROM contributed most significantly, from all joints to squatting depth in both females and males (r = 0.92, p < 0.001). The squat depth was related to lumbar, hip and knee motion in females and to all kinematics parameters in males. Maximal ankle dorsiflexion and pelvis anterior tilt were reached earlier than the maximal angles of knee, hip and spine during squatting. Pelvis and ankle timing was negatively correlated with the squat depth (rs =-0.64, p < 0.001 and rs =-0.29, p = 0.02, respectively). This suggests that pelvis and ankle timing can be important to keeping balance during squatting and can lead to achieving the desired depth.
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Objectives To investigate the accuracy of visual assessments made by physical therapists of lumbo-pelvic movements during the squat and deadlift and how much movement is considered injurious. Design Quantitative Cross-sectional. Participants 14 powerlifters, 10 Olympic weightlifters and six physical therapists. Setting The lifters were recorded simultaneously by video and an inertial measurement unit (IMU) system while performing squats and deadlifts. The physical therapists assessed the videos and rated whether specific lumbo-pelvic movements were visible during the lifts and whether the movement amplitude was considered injurious. Main outcome measures The nominal visual assessments, if there was a movement and if it was considered injurious, were compared to the degrees of movement attained from the IMU system. Results During the squat, a posterior pelvic tilt of ≥34° was required to visually detect the movement. For other lumbo-pelvic movements, there was no significant difference in the amount of movement between those who were assessed as moving or not moving their lumbo-pelvic area, nor was there a difference in movement amplitude between those who were assessed as having an increased risk of injury or not. Conclusions Physical therapists did not consistently detect lumbo-pelvic movements during squats and deadlifts when performed by competitive lifters.
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In Ausdauersportarten muss eine muskuläre Leistung über wiederholte Muskelaktionen erbracht werden. Eine Steigerung der Leistung ist deshalb sowohl über verbesserte energetische als auch neuromuskuläre Voraussetzungen möglich. Letzteres kann über ein grundlegendes oder spezifisches Krafttraining (z. B. Fahrten mit erhöhtem Bootswiderstand) verbessert werden. Im Gegensatz zum spezifischen Krafttraining war der Nutzen eines grundlegenden Krafttrainings zur Steigerung der ausdauerorientierten muskulären Leistung in Ausdauersportarten lange Zeit unklar. Wird Ausdauertraining mit einem grundlegenden Krafttraining kombiniert, ist oftmals trotz gleichem Ausdauertrainingseffekt im Vergleich zum isolierten Training der Krafttrainingseffekt reduziert . Trotz dieser Interferenz kann ein grundlegendes Krafttraining auch bei Eliteathleten die komplexe Ausdauerleistung steigern . Die positive Wirkung ist dabei weniger auf eine Muskelhypertrophie, sondern auf Veränderungen der Faserstruktur, des Muskel-Sehnen-Komplexes sowie der neuromuskulären Ansteuerung zurückzuführen. Dadurch verbessert sich die Bewegungsökonomie, die maximale Leistung, der Kraftanstieg oder auch der anaerobe Energiestoffwechsel und infolgedessen die komplexe Ausdauerleistung . Allerdings sind auch negative Auswirkungen eines grundlegenden Krafttrainings bekannt. Es stellt sich also weniger die Frage, ob ein grundlegendes Krafttraining für Ausdauerathleten sinnvoll ist. Entscheidend für den positiven Effekt ist das „Wie?“.
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Resumen. Objetivo: Realizar una revisión sistemática de literatura que evalúa la activación muscular por electromiografía (EMG) en sentadilla libre con barra (SLB), así como cambios producidos por factores cinéticos y cinemáticos. Métodos: Se utilizaron los lineamientos de la declaración PRISMA y de calidad metodológica de la declaración STROBE. Se incluyeron artículos originales encontrados en bases de datos Scopus, PubMed, Scielo y Cochrane Central Register of Controlled Trials (CENTRAL). Se encontraron 1889 artículos de los cuales debido a los criterios: sujetos con experiencia previa en entrenamiento resistido que midieran la ejecución de la SLB y utilización de EMG. Finalmente se utilizaron 18 artículos para el análisis. Resultados: La evidencia posiciona al cuádriceps femoral y el vasto medial como el grupo muscular y el músculo con mayor participación en la SLB. La actividad muscular en la SLB puede ser afectada por la carga de trabajo, la velocidad de ejecución, el tipo de resistencia y el rango de movimiento. Existe una tendencia a mayor compromiso muscular en la medida que aumenta la carga o la velocidad de ascenso, sin embargo, el aumento de la carga tiende a afectar de forma negativa a la velocidad. Conclusiones: Las cargas submáximas parecen generar activaciones musculares similares al 1RM, con el aliciente de menor riesgo de lesión que las cargas máximas. Mayores estudios con criterios metodológicos unificados son requeridos para identificar el punto óptimo de activación muscular en base a la carga de trabajo. Palabras clave: Entrenamiento deportivo, fuerza muscular, ejercicio físico, biomecánica, contracción muscular, 1RM. Abstract. Purpose: To conduct a systematic review of studies that evaluate electromyography muscle activation in the free barbell back squat (BS), and the changes produced by the effect of kinetic and kinematic factors. Methods: This study was conducted according to The PRISMA declaration and the STROBE guidelines to assess the methodological quality. Databases included were Scopus, PubMed, Scielo y Cochrane Central Register of Controlled Trials (CENTRAL). A total of 1889 original articles were selected using the inclusion criteria as follows: subjects previously experienced in resistance training including EMG assesment during the execution of the BS. The final selection consisted of 18 articles. Results: The evidence suggest to the quadriceps femoris and vastus medialis as the muscle group and the muscle with the greatest participation in BS. Muscle activity in BS can be affected by load, speed of execution, resistance type, and range of motion. There is a relationship between high muscle activity and increased load or velocity in the lift back up phase, however, increased load tends to negatively affect velocity in squat performance. Conclusions: Submaximal loads seem to produce similar muscle activation to the 1RM, with the incentive of a lower risk of injury compared to the maximum loads. More studies with unified methodological criteria are required to identify the optimal muscle activation based on the load.
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The first biomechanical analysis of a human patellar-tendon rupture during actual sports competition is reported. Cinematographic data for analysis were collected at a national weight-lifting championship. Dynamic equations to mathematically model the lifter were developed to compute time course and magnitudes of hip, knee and ankle-joint moments of force and of tensile loading of the patellar tendon before and during tendon trauma. Results provided evidence that the range of maximum tensile stress of the tendon may be considerably greater during rapid dynamic loading conditions, as in many sports situations, than maximum tensile stress obtained during static test conditions.
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The knee joint, the largest and most complex synovial joint in the human body, is an anatomical region subject to injuries from activities in various fields including athletics, industry, and recreation. Because this joint is between the longest bones in the body, the femur and the tibia, the forces and moments of force around this joint produce torques of such magnitude that injuries ensue. In athletics, various injuries may occur by overloading the knee joint (Nicholas, 1970; Peterson, 1970). In several studies (Kennedy and Fowler, 1971; Marshall and Olsson, 1971; Newman, 1969; Slocum and Larson, 1968), it was found that the instability of the knee joint was the result of the application of excessive external rotation and abduction forces to a flexed, weight-bearing knee.
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Mechanical stimulation has been implicated as an important regulatory factor in tendon homeostasis. In this study, a custom-designed tensile loading system was used to apply controlled mechanical stimulation to isolated tendon fascicles, in order to examine the effects of 5% cyclic tensile strain at 1 Hz on cell proliferation and matrix synthesis. Sample viability and gross structural composition were maintained over a 24 It loading period. Data demonstrated no statistically significant differences in cell proliferation or glycosaminoglycan production, however, collagen synthesis was upregulated with the application of cyclic tensile strain over the 24 h period. Moreover, a greater proportion of the newly synthesised matrix was retained within the sample after loading. These data provide evidence of altered anabolic activity within tendon in response to mechanical stimuli, and suggest the importance of cyclic tensile loading for the maintenance of the collagen hierarchy within tendon. (c) 2005 Elsevier Inc. All rights reserved.
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We investigated age-related changes in the mechanical properties of rabbit Achilles tendon. The animals used were immature (age 3 weeks, body mass 380 g), young adult (age 8-10 months, body mass 4.1 kg) and old (age 4-5 years, body mass 5.1 kg) rabbits. The cross-sectional area of the tendon increased with growth and the tensile strength of the young adult [67.3 (SEM 4.2) MPa] and old [66.7 (SEM 3.8) MPa] tendon was significantly higher than that of the immature tendon [23.9 (SEM 3.8) MPa]. However, there was no statistically significant difference in tensile strength between mature and old tendons. These differences may be attributable to the change in body mass. The gradient of the stress-strain curves, that is, the tangent modulus of the mature tendon [618.0 (SEM 87.0) MPa], was higher than that of the immature [281.0 (SEM 104.6) MPa] and old [530.5 (SEM 91.0) MPa] tendon, although the difference was not significant. The elongation at failure was approximately 16 percent for all age groups. These results would suggest that rabbit Achilles tendon is highly compliant during growth.
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Living tissues and organs are dynamic and change their mechanical properties and structure in response to stress alteration as a phenomenon of functional adaptation and optimal operation. This phenomenon is called 'Tissue Remodeling', and Wolff's law on bone remodeling is widely known. Several recent studies have shown that fibrous connective tissues such as tendons and ligaments also have the ability of remodeling. However, relatively little is known about the stress and motion effects on tissue homeostasis in biological soft tissues. This article primarily deals with changes of the biomechanical properties of knee joint tendons and ligaments through a wide variety of treatment modalities, including stress deprivation, recovery after stress deprivation, and stress enhancement. The experimental results indicate that tendons and ligaments have an ability to adapt in response to the change of stress if the extent of stress alteration is within allowable ranges.
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This paper discusses statistics derived from surveys and competitions. Analyses of previous publications and comparative data from other studies appear to contradict a general view that weight training is safer than weightlifting, when the latter is defined according to the International Weightlifting Federation's rulebook. Both activities appear to be safer than many other sports. The age group considered is largely school age. © 1994 Journal of Applied Sport Science Research. All rights reserved.
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This second part of a two-part paper is concerned with the measurement of static pressure distribution on the retropatellar surface. The study has been performed in a loading apparatus designed to simulate individually the lines of action and the magnitudes of the tensions in the components of the quadriceps femoris muscle group. Results have been obtained using 24 specimens in the knee flexion range 0 to 130 deg and employing a net quadriceps tension of 734 N. Particular emphasis has been placed on the evaluation of the sensitivity of the results to variations in the characteristics of the simulated quadriceps tension. The pressure distribution results have been interpreted in terms of variation of the normal force and the average contact stress on the retropatellar surface as a function of flexion angle. It has been shown that the “pulley” model of the patella consistently overestimates the actual patellofemoral joint reaction force throughout the range of flexion. Clinical implications of the results, in terms of etiology of degeneration of patellar cartilage, have been discussed.