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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... Numerous authors indicate that the squat is one of the most important exercises for increasing the strength of the athlete and the overall development for a variety of sports, particularly the lower body (12,29,154,207). Among relatively untrained, welltrained and various athlete groups, improvements in squatting ability and capacity have been shown to result in improvements in lower-body strength, jumping ability (19,88), change of direction ability (19,88), and sprinting performances (34), all of which can be critical components of sporting success. ...
... Numerous authors indicate that the squat is one of the most important exercises for increasing the strength of the athlete and the overall development for a variety of sports, particularly the lower body (12,29,154,207). Among relatively untrained, welltrained and various athlete groups, improvements in squatting ability and capacity have been shown to result in improvements in lower-body strength, jumping ability (19,88), change of direction ability (19,88), and sprinting performances (34), all of which can be critical components of sporting success. ...
... Squat Training and Jumping Performance. In the scientific literature, there are numerous studies ranging from 5 to 24 weeks in duration, which demonstrate that increases in deep or parallel back squat strength (1RM) translate into improvements in countermovement jump and static jump performance (9,19,39,41,85,87,88,94,102,105,109,143,192,197,201,209). Although, the percent gain and magnitude of effect were moderate (as calculated by the authors of this article), studies using short-duration training (,5 weeks), basketball players (93), and American football players (94) have not shown statistically significant improvements in jumping performance. ...
Article
Stone, MH, and Haff, GG. The use of free weight squats in sports: a narrative review-squatting movements, adaptation, and sports performance: physiological. J Strength Cond Res 38(8): 1494-1508, 2024-The squat and its variants can provide numerous benefits including positively affecting sports performance and injury prevention, injury severity reduction, and rehabilitation. The positive benefits of squat are likely the result of training-induced neural alterations and mechanical and morphological adaptations in tendons, skeletal muscles, and bones, resulting in increased tissue stiffness and cross-sectional area (CSA). Although direct evidence is lacking, structural adaptations can also be expected to occur in ligaments. These adaptations are thought to beneficially increase force transmission and mechanical resistance (e.g., resistance to mechanical strain) and reduce the likelihood and severity of injuries. Adaptations such as these, also likely play an important role in rehabilitation, particularly for injuries that require restricted use or immobilization of body parts and thus lead to a consequential reduction in the CSA and alterations in the mechanical properties of tendons, skeletal muscles, and ligaments. Both volume and particularly intensity (e.g., levels of loading used) of training seem to be important for the mechanical and morphological adaptations for at least skeletal muscles, tendons, and bones. Therefore, the training intensity and volume used for the squat and its variations should progressively become greater while adhering to the concept of periodization and recognized training principles.
... [38,58,59] A point of confusion in the literature is how to clearly define joint angles. For example, some authors define squat depth in the context of the external knee angle [17,22,74], while others relate squatting depth to an internal knee angle [27,43,64,66,68,70,75]. In order to clearly present and define the various squatting depths, this review will reference the internal knee angle for the quantification of the various squatting depths that have been reported in the scientific literature or used in practical settings. ...
... Furthermore, it appears that the stimulus increases with movement velocity [75]. In their review, Hartmann et al. [22] indicated that "concerns about degenerative changes of the tendofemoral complex and the apparent higher risk for chondromalacia, osteoarthritis, and osteochondritis in deep squats are unfounded". As a final analysis, correct squatting technique, appropriate progression, and properly periodized/programmed training can minimize the risk of knee injury and may strengthen connective tissue including ligaments. ...
... Excessive force projected through the joint is believed to be a factor related to greater injury potential. However, researchers question the degree to which squat exercises are actually contributing to acute/chronic pain in, and injuries to, the knee and lower back [22,23]. Although some investigators and clinicians believe that injuries in the knee and lower back may result from performing squat exercises, there is little evidence that the exercise itself is the primary cause of the injury [23,160,164]. ...
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Abstract: There is substantial evidence indicating that increased maximum strength as a result of training with squats, particularly full and parallel squats, is associated with superior athletic capabilities, such as sprinting, jumping and agility. Although full and parallel squats have been strongly associated with sport performance, there is also some evidence that the use of partial squats may provide angle specific adaptations that are likely advantageous for specific sporting activities. Partial squats may be particularly advantageous when trained in conjunction with full or parallel squats, as this practice results in a greater training effect. There is a paucity of evidence that squatting is associated with excessive injuries to the knees, lower back, or other structures. Evidence does indicate that squatting, including full squats, can be undertaken safely, provided an appropriate training methodology is applied. Indeed, based on scientific data, the cost/benefit ratio indicates that squats should be recommended and should be a central strength training exercise for the preparation of athletes in most sports, particularly those requiring strong and powerful whole body and lower body movements.
... Therefore, the HBBS is usually the first variation to master after learning the bodyweight squat and before practicing its derivatives [4]. Even though LBBSs typically permit athletes to lift heavier weights, the HBBS remains one of the most essential exercises in athlete training [41], as it is characterized by an increased amount of knee flexion, a decreased amount of hip flexion, a more upright torso, and a deeper squatting position compared to HBBSs [37,44,57]. Moreover, deep HBBSs are an efficient exercise for preventing injuries and strengthening the lower extremities, provided that a proper technique is learned under the supervision of a professional [57]. ...
... Even though LBBSs typically permit athletes to lift heavier weights, the HBBS remains one of the most essential exercises in athlete training [41], as it is characterized by an increased amount of knee flexion, a decreased amount of hip flexion, a more upright torso, and a deeper squatting position compared to HBBSs [37,44,57]. Moreover, deep HBBSs are an efficient exercise for preventing injuries and strengthening the lower extremities, provided that a proper technique is learned under the supervision of a professional [57]. Contrary to widespread belief, deep barbell squats do not increase the risk of injury of passive tissues [57]. ...
... Moreover, deep HBBSs are an efficient exercise for preventing injuries and strengthening the lower extremities, provided that a proper technique is learned under the supervision of a professional [57]. Contrary to widespread belief, deep barbell squats do not increase the risk of injury of passive tissues [57]. Furthermore, recent research suggests that including deep squats to a preventative training program may be advantageous for reducing deficits prevalent among females and lowering the injury incidence [58]. ...
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The three most fundamental variations of the barbell squat with the bar placed on the shoulders are the high-bar back squat (HBBS), the low-bar back squat (LBBS), and the front squat (FS). There are significant kinematic, kinetic, and biomechanical distinctions between these variations that should be considered in the exercise selection. In comparison to the high-bar variations, the LBBS results in a greater hip joint torque and greater activation of the hip extensor muscles. In contrast, during the FS, the m. quadriceps is utilized more compared to the other two variations due to an increased torque in the knee joint. Regarding the relation between hip and knee joint torques, the HBBS is an intermediate and more balanced exercise variation than the LBBS and the FS. The HBBS is a fundamental exercise in athletic conditioning and a suitable starting point for novices, whereas the LBBS is preferred when the primary objective is to maximize weightlifting performance. The FS is crucial for athletes performing the clean and its derivates since it trains the required body position for a successful catch and might be the biomechanically advantageous variation if the goal is to target the knee extensor muscles. However, the differences in terms of knee extensor demands, muscle activation and kinematics between the HBBS and FS seem to be minimal, as the literature indicates similar results when comparing the FS to the HBBS. As far as analysis methods are concerned, even though 3D movement analysis is regarded as the gold standard for motion capture and analyzing kinematics, 2D models seem to serve as a valid initial guide in order to understand the kinematics and biomechanics of different squat variations.
... To avoid AKD, without performing a technically inaccurate barbell squat in which the peak loads shift towards the lumbar spine, reducing the depth of the squat is an applicable strategy. While in clinical settings full knee extension is typically defined as 0 • , the studies discussed here utilize a 180 • knee angle to define full knee extension (i.e., 180 • being equivalent to a straight stance) [41]. Accordingly, in "quarter" high-bar back squats (QHBBSs) and "half" high-bar back squats (HHBBSs, defined by a knee angle of approximately 110-140 • and 80-100 • , respectively), the knees of most athletes are not or only slightly pushed anterior over the toes (see Figure 1, left and center) [13,41,42]. ...
... While in clinical settings full knee extension is typically defined as 0 • , the studies discussed here utilize a 180 • knee angle to define full knee extension (i.e., 180 • being equivalent to a straight stance) [41]. Accordingly, in "quarter" high-bar back squats (QHBBSs) and "half" high-bar back squats (HHBBSs, defined by a knee angle of approximately 110-140 • and 80-100 • , respectively), the knees of most athletes are not or only slightly pushed anterior over the toes (see Figure 1, left and center) [13,41,42]. [33]. ...
... To avoid AKD, without performing a technically inaccurate barbell squat in which the peak loads shift towards the lumbar spine, reducing the depth of the squat is an applicable strategy. While in clinical settings full knee extension is typically defined as 0°, the studies discussed here utilize a 180° knee angle to define full knee extension (i.e., 180° being equivalent to a straight stance) [41]. Accordingly, in "quarter" high-bar back squats (QHBBSs) and "half" high-bar back squats (HHBBSs, defined by a knee angle of approximately 110-140° and 80-100°, respectively), the knees of most athletes are not or only slightly pushed anterior over the toes (see Figure 1, left and center) [13,41,42]. ...
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Based on seminal research from the 1970s and 1980s, the myth that the knees should only move as far anterior during the barbell squat until they vertically align with the tips of the feet in the sagittal plane still exists today. However, the role of both the hip joint and the lumbar spine, which are exposed to high peak torques during this deliberate restriction in range of motion, has remained largely unnoticed in the traditional literature. More recent anthropometric and biomechanical studies have found disparate results regarding anterior knee displacement during barbell squatting. For a large number of athletes, it may be favorable or even necessary to allow a certain degree of anterior knee displacement in order to achieve optimal training outcomes and minimize the biomechanical stress imparted on the lumbar spine and hip. Overall, restricting this natural movement is likely not an effective strategy for healthy trained individuals. With the exception of knee rehabilitation patients, the contemporary literature suggests it should not be practiced on a general basis.
... During bending tasks, a conscious effort to avoid loading the knees through anterior kneeling kinematics ensures persistent activation of the posterior kinetic chain [36]. Comparatively, a kneel versus a squat displays measurable differences in knee joint loading [37]. ...
... This effectively breaks the musculoligamentous tension band and power of the posterior kinetic chain, leading to accumulative deconditioning if this becomes a default movement pattern. In contrast, enhancement of the posterior kinetic chain is asserted by the adoption of unloaded knee positions, with the hips translating posteriorly and thereby activating the posterior kinetic chain during bending tasks [36,37]. ...
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Movement theory and the study of movement dysfunction mark a paradigm shift in the treatment of low back pain symptoms, the majority of which are mechanical in origin at the outset. Treating movement dysfunction centers around unified and consistent rehabilitation that defines proficient movement for the lumbopelvic spine. The purpose of this study is to document the improvement in pain and disability of 290 patients who underwent NeuroHAB Functional Movement Therapy to reverse their lumbopelvic movement dysfunction attributed to causing their back pain symptoms between 2019 and 2023. Oswestry Disability Index (ODI) scores were collected from each participant on three occasions: the first consultation, after a waiting period/pre-intervention, and after the eight-week intervention. A single-factor ANOVA of all three ODI data sets was conducted, along with supporting descriptive statistics. A post-hoc t-test pairwise comparison was conducted for accuracy. The average ODI 1 score (taken at the first consultation) was 15.26 ± 6.1% (CI: 14.3–16.2); ODI 2 (after a waiting period, before NeuroHAB) was 14.71 ± 6.0% (CI: 13.82–15.59); and ODI 3 (post-intervention) was 9.09 ± 8.6% (CI: 8.305–9.875). There was no significant change from ODI 1 to ODI 2 (between the consultation and waitlist control periods). However, a significant reduction between ODI 2 and ODI 3 was observed (pre- and post-intervention) (mean difference: 5.62, p ≤ 0.001), and a 40.41% reduction was observed between ODI 1 (the ODI score taken at the first consultation) and ODI 3 (the ODI score taken after NeuroHAB, post-intervention) (mean difference: 6.17, p ≤ 0.001). A 50% ODI reduction was reported in the “Crippled” category (mean difference 16.15, p ≤ 0.001). The inclusion of functional movement proficiency and stability in future guidelines is a necessary step towards meaningful improvement in epidemic levels of back pain-related clinical and economic morbidity.
... • Squat: The squat involves substantial compres sive and shear forces on the lumbar spine. Incorrect tech ni que, such as excessive forward lean or insuf ficient hip mobility, can exacerbate these forces, increasing injury risk [14]. • Deadlift: The deadlift is particularly taxing on the lumbar spine due to the high loads lifted and the ne cessity of maintaining a neutral spine position to avoid excessive lumbar flexion. ...
... • Przysiad: Przysiad wiąże się ze znacznymi siłami ściskającymi i ścinającymi na odcinku lędźwiowym kręgosłupa. Nieprawidłowa technika, taka jak nadmierne pochylenie do przodu lub niewystarcza jąca ruchomość bioder, może zwiększać przeciążenia, podnosząc ryzyko kontuzji [14]. • Martwy ciąg: Martwy ciąg jest szczególnie obciążający dla odcinka lędźwiowego kręgosłupa ze względu na podnoszone duże ciężary i koniecz ność utrzymania neutralnej pozycji kręgosłupa w celu unik nięcia nadmiernego zgięcia lędźwiowego. ...
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Key word: lower back injuries, powerlifting, spine injuries Słowa kluczowe: urazy dolnego odcinka pleców, trójbój siłowy, urazy kręgosłupa Summary Background. Powerlifting is a non-Olympic sport consisting of three main lifts: squat, bench press, and deadlift. Powerlifting involves repetitive heavy loading and extreme exertion, which can cause injuries to the spine, especially to the lower back. Such injuries can be anything from minor sprains and strains to more significant problems like fractures or herniated discs. This article reviews the scientific research on back injuries and how po-werlifting is related to them. The aim was to report on the incidence of lower back injuries and their proportion in powerlifting-related injuries among powerlifters. Materials and methods. A thorough search of major electronic databases, such as Embase and MEDLINE/Pubmed, was conducted. The data concerning powerlifting-related injuries, especially those involving lower back, was extracted. Statistical analysis was performed with MetaXL (version 5.3) software. Results. This meta-analysis included 9 studies, comprising a total of 799 patients. 565 injuries were reported, 200 of them involved pain of the lower back. Statistical analysis revealed that lower back pain occurred approximately in every fourth powerlifter (Pooled prevalence estimate (PPE) = 25.6% (95% CI: 15.8%-38.7%)) and over one third of all powerlifting-related injuries entailed pain of the lower back (PPE = 35.4% (95%CI: 26.2%-45.8%)). Conclusions. Lower back injuries are a prevalent and significant issue in powerlifting, affecting a substantial proportion of athletes. For the purpose of creating efficient preventative and management plans, it is imperative to comprehend the biomechanical, training-related, and individual aspects that contribute to these injuries.
... The barbell back squat is considered a safe strength training exercise, provided it is performed and progressed in a controlled manner. [1][2][3] However, the squat appears to be associated with injuries in people participating in powerlifting, weightlifting, bodybuilding, and strongman sports. 4 In Sweden, 70% of sub-elite powerlifters reported a current injury, and 87% had experienced an injury within the prior 12 months. ...
... [6][7][8] With respect to the spine, a correct technique is described as maintaining the spine in an upright position with preservation of its neutral posture while the trunk is held stable without any observation of wavering or displacement in all planes of movement, throughout the entire squat movement 6,8 In a neutral posture, where the spine usually has a gentle "S" shape where the lower back has a slight lordotic curve and the thoracic spine a slight kyphotic curve, it is said that axial load is distributed in a balanced way in all movement segments. 9 It seems, however, that there is an ongoing discussion about what constitutes correct squat technique for different parts of the body, 3,6 though robust evidence in the matter is somewhat lacking. Nevertheless, experts have stated that improper technique in combination with heavy loads may cause back injuries while squatting 10 and that flexion (rounding), twisting (rotating), and side bending of the spine are movements that should be avoided to reduce risk of injury risk and improve performance. ...
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Background Maintaining neutral spinal alignment is considered important when performing the barbell back squat exercise. Since male and female lifters may differ in injury location it is important to examine whether they differ in spinal alignment during the back squat. Objectives The study aimed to quantify the spinal alignment in the upper and lower lumbar spine during the barbell back squat exercise in male and female lifters. Secondary aims were to compare alignment during the back squat to standing habitual lumbar spine alignment and determine whether male and female lifters differ in these aspects. Study Design Observational, Cross-sectional. Methods Competitive power- and weightlifters were recruited and performed three repetitions of the barbell back squat exercise using a load equivalent to 70% of their one-repetition maximum. Spinal alignment and range of motion were measured using inertial measurement units placed on the thoracic, lumbar and sacral spine. Data was presented descriptively and comparisons between men and women as well as spinal alignment in four different positions were done with a factorial repeated measures analysis of variance. Results Twenty-three (14 males, 9 females) were included. During execution of the squat, spinal alignment adjustments in the lumbar spine were made in all three planes of movement, compared to the start position, in both male and female lifters. Compared to their standing habitual posture, all lifters adjusted their upper lumbar spine to a less lordotic position when in the start position of the back squat (standing upright with the barbell on their back). Only male lifters assumed a less lordotic alignment in their lower lumbar spine in the start position compared their habitual posture. Conclusions Adjustments of spinal alignment, predominantly in the sagittal plane, are made during execution of the back squat in both male and female lifters. Further, lifters adopt a less lordotic alignment with a heavy barbell on their upper back, more so in male than female lifters. In conclusion, it seems that spinal alignment changes noticeably during the barbell back squat. Level of Evidence 3 ©The Author(s)
... This activity of weight lifting is not specifically exclusive to weight-lifters only, rather almost all athletes perform weight lifting as a substantial physical exercise to gain strength, power and muscular mass. 6 Bodybuilders also utilize this regime to develop and refine their athletic bodies. Talking about the Olympics, weight lifting is measured as strength power, lifting, balance and coordination between two quick movements, for example, clean and jerk and lifts the snatch. ...
... Talking about the Olympics, weight lifting is measured as strength power, lifting, balance and coordination between two quick movements, for example, clean and jerk and lifts the snatch. 6 Two important proceedings that take place during weight lifting are the snatch and the clean and jerk. The first one is snatching which is probably the most powerful and the most quickest movement an athlete can perform. ...
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Background: Weight lifting is considered as one of the most widely used sport for strength training focusing on lifting maximum weight in a single repetition. Weight lifting is not exclusive to weight lifters only, rather all athletes perform this as a substantial physical exercise to gain power, strength and muscle mass. Although, the research evidences on prevalence of musculoskeletal pain among this population needs more authentic evidences so that this information can add more into preparing more reliable precautionary, preventive and treatment measures for this population. Objective: The aim of this study is to determine the prevalence of musculoskeletal pain among weight- lifters of Lahore, Pakistan. Methods: This current study is a cross- sectional survey. Two- hundred and forty weight lifters were recruited in this study. Data was collected from various health clubs, gyms and universities in Lahore, Pakistan. A self- made customized questionnaire and Nordic Pain Scale was used to gather the data needed for this survey. Prevalence was determined by using descriptive statistics. Results: The prevalence of musculoskeletal pain in shoulders was 88.75%, in elbow was 84.58%, in neck was 84.16%, wrists/ hands 84.16%, upper back and lower back was 92.08%, hips was 93%, knees was 92.9% and ankles/ foot was 22.08% in weight-lifters of Lahore, Pakistan. Conclusion: This study concludes that there is high prevalence of musculoskeletal pain among weight lifters in shoulders, elbows, wrists and hands, upper and lower back, neck, knee and hip joints. Key Words: Prevalence, Musculoskeletal pain, Weight- lifters
... For instance, a functioning ankle with sufficient dorsiflexion is essential to perform a deep squat. Limited ankle dorsiflexion has been found to negatively alter squat mechanics and is associated with increased knee valgus while squatting and aberrant flexion of the hips and lumbar spine, which may result in excessive compressive force on the lumbar discs (12,23,65,79,91). Furthermore, decreased hip ROM may also lead to compensatory movement patterns, which increase the risk of low back injury (50). ...
... Furthermore, decreased hip ROM may also lead to compensatory movement patterns, which increase the risk of low back injury (50). In a deep squat, the hip crease is required to travel below the knee, with similar requirements relating to a successful catch position during a snatch (17,50,65). Improving ankle dorsiflexion may reduce lower limb injury rates with improved joint mobility shown to be beneficial in reducing the risk of sustaining musculoskeletal injury (64,76). ...
Article
Fascial restrictions that occur in response to myofascial trigger points (MTrP), exercise-induced muscle damage (EIMD) and delayed onset of muscle soreness (DOMS) cause soft tissue to lose extensibility which contributes to abnormal muscle mechanics, reduced muscle length and decrements in joint range of motion (ROM) and actively contributes to musculoskeletal pain. Resistance training and in particular, weightlifting movements have unique mobility requirements imperative for movement efficacy and safety with ROM restrictions resulting in ineffective volume and intensity tolerance and dampened force output and power which may lead to a failed lift or injury. Self-massage (SM) provides an expedient method to promote movement efficiency and reduce injury risk by improving ROM, muscular function and reducing pain and allows athletes to continue to train at their desired frequency with minimal disruption from MTrPs associated adverse effects. Thus, the aim of this review was to determine the efficacy of various self-massage tools in managing pain and mobility and to explore the potential benefits of SM on resistance training performance. Many SM devices are available for athletes to manage ROM restrictions and pain including differing densities of foam rollers, roller massagers, tennis balls and vibrating devices. To attenuate adverse training effects, a 10-to-20-minute bout consisting of 2-minute bouts of SM on the affected area may be beneficial. When selecting a SM device, athletes should note that foam rollers appear to be more effective than roller massagers, with vibrating foam rollers eliciting an increased reduction to pain perception and tennis balls and soft massage balls shown to be efficacious in targeting smaller affected areas.
... No further divisions or descriptions of squatting depth have been highlighted in those studies and scales. Even the specially developed questionnaire, "High-flexion Knee Scoring System", or the isolated subdomain "floor life" in the "Korean Knee Score", is inadequate to evaluate squatting ability and completeness in detail [9,10]. ...
... To fill the gap between surgeons and patients in evaluating the outcome of TKA, numerous PROMs have emerged over the years. Most of them incorporated a section devoted to high-flexion or high-level activities[6, 9,10]. Even so, with no further division of squatting positions, respondents might make the wrong tick, which usually causes a ceiling effect along with the questionnaire. ...
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Background: Total knee arthroplasty (TKA) has been shown to improve quality of life and reduce pain. High-flexion activities such as squatting, kneeling, and floor transfers are mainly listed as demanding tasks. Among them, squatting is an important position. Aim: To provide a new squat position classification and evaluate the different squatting positions of a series of patients after primary TKA. Methods: From May 2018 to October 2019, we retrospectively reviewed 154 video recordings of the squatting-related motions of patients after TKA. Among the included patients, 119 were women and 35 were men. Their mean age at the index surgery was 61.4 years (range, 30 to 77). Results: The median follow-up was 12 mo (range, 6 to 156 mo). We classified those squatting-related motions into three major variations according to squatting depth: Half squat, parallel squat, and deep squat. The angles of hip flexion, knee flexion, and ankle dorsiflexion were measured in the screenshots captured from the videos at the moment of squatting nadir. A total of 26 patients were classified as half squats, 75 as parallel squats, and 53 as deep squats. The angles of hip flexion, knee flexion, and ankle dorsiflexion all differed significantly among the three squatting positions (P < 0.001). In the parallel squat group, the mean knee flexion angle (°) was 116.5 (SD, 8.1; range, 97 to 137). In the deep squat group, the mean knee flexion angle (°) was 132.5 (SD, 9.3; range, 116 to 158). Conclusion: Among the three squatting positions, deep squat showed the highest hip, knee, and ankle flexion angles, followed by the parallel squat. With the improvement of squatting ability, the patient's postoperative satisfaction rate was also significantly enhanced. However, the different squatting abilities of the patients cannot be effectively distinguished from the scoring results (P > 0.05). Our squatting position classification offers a pragmatic approach to evaluating patients' squatting ability after TKA.
... 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]. ...
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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.
... This finding is consistent with previous studies by Foch, who also pointed out that simultaneous two-foot landing leads to a significant increase in joint angles and may trigger greater loading and injury risk [15]. Typically, greater joint angles mean that the joints are subjected to greater loads during landing, which may lead to reduced joint stability and increased risk of injury [3,16]. Further analysis showed that the increase in joint angle when landing on both feet at the same time may reflect the failure of individuals to effectively control their center of gravity and path of motion during landing, which may result in uneven forces on the joints [17]. ...
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High-altitude landing maneuvers can pose a significant injury risk, particularly when performed with different landing techniques. This study aims to compare the biomechanical parameters and injury risks associated with two landing positions—staggered foot landing and simultaneous bilateral landing—using Xsens inertial units and electromyography (EMG) sensors. A total of 26 university students (13 males, 13 females) participated in this study. Kinematic data were collected using inertial measurement units (IMUs), muscle activity was recorded with EMG, and ground reaction forces were captured using 3D force plates. The data were processed and analyzed using the AnyBody modeling system to simulate joint forces, moments, and muscle activation. This study found that simultaneous bilateral landing exhibited greater hip flexion-extension, knee flexion-extension, and ankle inversion. Vertical joint forces were also significantly higher in the hip, knee, and ankle during simultaneous bilateral landing. Staggered foot landing showed higher muscle forces in the gluteus maximus, iliopsoas, and quadriceps femoris (p < 0.001). The EMG analysis revealed significant differences in the biceps femoris (p = 0.008) and quadriceps femoris (p < 0.001). These findings suggest that simultaneous bilateral landing increases joint load, while staggered foot landing increases muscle activation, which may lead to different injury risks between the two techniques.
... The range of motion (ROM) refers to the distance in degrees that are covered in a particular joint during the execution of an exercise. If all possible degrees of freedom of that joint are traversed for a given exercise, it is called full ROM, whereas if only part of the possible degrees of movement is performed, it is called partial ROM [110]. ...
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The present chapter delves into the topic of muscle hypertrophy in detail, focusing on defining what muscle hypertrophy is, the types of hypertrophy, the mechanisms, and the relationship with resistance training, as well as the variables affecting hypertrophy such as nutrition, rest, exercise selection, training volume, and training frequency, among others. The importance of mechanical tension, metabolic stress, and muscle damage as triggers for muscle hypertrophy is emphasized. Various types of muscle hypertrophy are explored, including connective tissue hypertrophy and sarcoplasmic and myofibrillar hypertrophy. The text also delves into how hypertrophy mechanisms relate to resistance training, highlighting the significance of mechanical tension and metabolic stress as stimuli for muscle hypertrophy. In a practical point of view, the text also discusses factors like nutrition and recovery, highlighting the importance of maintaining a positive energy balance and adequate protein intake to promote muscle growth optimally. Training variables such as exercise selection, exercise order, intensity, volume, frequency, and tempo of execution are discussed in detail, outlining their impact on muscle hypertrophy. The text provides a comprehensive overview of muscle hypertrophy, analyzing various factors that influence the ability to increase muscle mass. It offers detailed information on the biological mechanisms, types of hypertrophy, training strategies, and nutritional and recovery considerations necessary to achieve optimal results in terms of muscle hypertrophy.
... Apart from the squat, current literature suggests more exercises leading to similar activation of the lower extremity muscles such as step-ups, lunges and deadlifts (21, 22). Both, the squat and the deadlift permit the use of high loads (23)(24)(25) with a high relationship between those two exercises (11). Accordingly, comparable to the squat, evidence underlines the potential of using the deadlift to improve jumping performance (11,26), however, while direct evidence calculating correlations is scarce. ...
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Introduction: Based on the assumption of maximal strength as a basic ability,several studies show a high influence of maximum strength on jumping performance in several sport athletes. However, there is a wide range ofcorrelations from r = 0.17–0.9 between squat 1RM and jumping performancein different sports. Additionally, there are only a few studies investigating the influence of deadlift one repetition maximum (1RM) on jumping performance.Thus, this study aimed to investigate the correlations between 1RM in thedeadlift on jumping performance using the countermovement jump height(CMJ) and squat jump height (SJ) considering different sports. Methods: 103 athletes with experience in the deadlift from soccer, basketball,American football, powerlifting as well as participants from different sports without any deadlift experience (control group) were included to this study. Results: Overall statistics showed a significant moderate influence of deadlift 1RM (r = 0.301–0.472) on jumping performance. However, subgroup analysisshowed no significant correlation between deadlift 1RM and jumping performance in control participants, while moderate correlations could bedetected in powerlifters (r = 0.34–0.39), soccer players (r = 0.437–0.46),American football players (0.584–0.62) and high correlations in basketball players (r = 0.809–0.848) showing significant influence of type of sport on correlations between deadlift maximum strength and jumping performance. Discussion: Presented results underline movement velocity- and taskspecificity of strength training routines which is discussed in the light of the respective sports
... This study considered 3 practical factors: (a) BS exercise, (b) WR, and (c) RR. First, the BS exercise is a widely used closed kinetic chain and multijoint lower-body exercise that has a great potential to confer desired alterations (13). Second, WR involve relatively low budget and spatial requirements in prescribing AEL (20,40). ...
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Chae, S, Long, SA, Lis, RP, McDowell, KW, Wagle, JP, Carroll, KM, Mizuguchi, S, and Stone, MH. Combined accentuated eccentric loading and rest redistribution in high-volume back squat: Acute kinetics and kinematics. J Strength Cond Res 38(4): 640–647, 2024—The purpose of this study was to explore acute kinetic and kinematic responses to combined accentuated eccentric loading and rest redistribution (AEL + RR). Resistance-trained men (n = 12, 25.6 ± 4.4 years, 1.77 ± 0.06 m, and 81.7 ± 11.4 kg) completed a back squat (BS) 1 repetition maximum (1RM) and weight releaser familiarization session. Three BS exercise conditions (sets × repetitions × eccentric/concentric loading) consisted of (a) 3 × (5 × 2) × 110/60% (AEL + RR 5), (b) 3 × (2 × 5) × 110/60% (AEL + RR 2), and (c) 3 × 10 × 60/60% 1RM (traditional sets [TS]). Weight releasers (50% 1RM) were attached to every first repetition of each cluster set (every first, third, fifth, seventh, and ninth repetition in AEL + RR 5 and every first and sixth repetition in AEL + RR 2). The AEL + RR 5 resulted in significantly (p < 0.05) greater concentric peak velocity (PV) (1.18 ± 0.17 m·s−1) and peak power (PP) (2,304 ± 499 W) compared with AEL + RR 2 (1.11 ± 0.19 m·s−1 and 2,148 ± 512 W) and TS (1.10 ± 0.14 m·s−1 and 2,079 ± 388 W). Furthermore, AEL + RR 5 resulted in significantly greater PV and PP across all 10 repetitions compared with TS. Although AEL + RR 5 resulted in significantly greater concentric mean force (MF) (1,706 ± 224 N) compared with AEL + RR 2 (1,697 ± 209 N) and TS (1,685 ± 211 N), no condition by set or repetition interactions existed. In conclusion, AEL + RR 5 increases PV and PP but has little effect on MF. Coaches might consider prescribing AEL + RR 5 to increase especially peak aspects of velocity and power outcomes.
... Squatting may also increase the risk of osteoarthritis, according to Kujala et al. [8]. This could be because squats put significant strain on the knee joint [9]. Weightlifters' unique equipment, such as their suits, elbow and knee sleeves, hook straps and bandages, lumber or back belts, and shoes, could also cause harm [10]. ...
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Background The prevalence and pattern of injury among weightlifters are insufficiently documented despite these research works. Understanding the injury pattern is crucial for minimizing side effects and maximizing the advantages of weight training. Therefore, the purpose of this study is to determine the frequency and pattern of musculoskeletal injury among weightlifters and to investigate the associations between the prevalence of injury and sociodemographic and training characteristics variables. Methods A descriptive cross-sectional, questionnaire-based study was conducted. An online questionnaire was designed by Google Forms to collect the data by using a self-administered questionnaire. From all health clubs in Taif city, Saudi Arabia, one club was chosen by simple random sampling methodology, where all attendant weightlifters during the study period were contacted to participate in the study. Data was entered on the computer using Microsoft Office Excel 2016 for Windows. Qualitative data was expressed as numbers and percentages, and the Chi-squared test (χ²) was used to assess the relationship between variables. A p-value < 0.05 was considered statistically significant. Results The study included 393 participants, and most respondents fall within the age range of 18-29, accounting for 60.1% of the total. About 27% of participants had a weightlift injury during the last six months. The body parts most injured during weightlifting include the shoulder (7.4%), knee (4.6%), and wrist (3.6%). In terms of the type of injuries sustained, inflammation and pain in the bending of the body (5.9%), torsion (3.6%), ligament tear/muscle tear (3.8%), and stripped-off injuries (2.3%) were reported. Conclusion Musculoskeletal injuries are prevalent among weightlifters due to the nature of the sport and the demands it places on the body. There was no significant association between the injury occurrence with gender, age, or body mass index. However, there was a significant association between the occurrence of injury and weight carried while lifting weights.
... s load time estimated to occur during each stance phase of running [84]. Weightbearing femoral cartilage contact with the patella can occur during the maximum compressive force of a knee bend at 90° flexion [85] which has been estimated to be high (up to 18 times body weight) and associated with activities requiring greater knee flexion [43,83]. We also identified a dose-response to loading in patellar cartilage where every increase of 10 knee bend repetitions resulted in decreases in cartilage thickness and volume by 2%. ...
... Identifying key musculoskeletal and biomechanical criteria that impact squatting performance is essential to avoiding injuries while ensuring maximum training efficiency and has generated a great deal of interest in researchers in recent years [3][4][5][6]. Here, squat depth has played a crucial role in defining different technical recommendations for athlete performance and rehabilitation programs [2,3,7]. In particular, a significant correlation has been shown between squat depth, the lifted load, and the relative muscular effort in the ankle plantar flexors and hip and knee extensors [8]; similar average joint ranges of motion in the lower limbs and pelvis were found during the full back squat in healthy, recreationally active, college-aged volunteers (twenty female, four male) [3]. ...
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Identifying key criteria of squat performance is essential to avoiding injuries and optimizing strength training outcomes. To work towards this goal, this study aimed to assess the correlation between lower limb anatomy and back squat performance during a set-to-exhaustion in resistance-trained males and females. Optical motion captures of squat performance and data from magnetic resonance imaging (MRI) of the lower limbs were acquired in eight healthy participants (average: 28.4 years, four men, four women). It was hypothesized that there is a correlation between subject-specific musculoskeletal and squat-specific parameters. The results of our study indicate a high correlation between the summed volume of the hamstrings and quadriceps and squat depth normalized to thigh length (r = −0.86), and a high correlation between leg size and one-repetition maximum load (r = 0.81), respectively. Thereby, a marked difference was found in muscle volume and one-repetition maximum load between males and females, with a trend of females squatting deeper. The present study offers new insights for trainers and athletes for targeted musculoskeletal conditioning using the squat exercise. It can be inferred that greater muscle volume is essential to achieving enhanced power potential, and, consequently, a higher 1RM value, especially for female athletes that tend to squat deeper than their male counterparts.
... s load time estimated to occur during each stance phase of running [84]. Weightbearing femoral cartilage contact with the patella can occur during the maximum compressive force of a knee bend at 90° flexion [85] which has been estimated to be high (up to 18 times body weight) and associated with activities requiring greater knee flexion [43,83]. We also identified a dose-response to loading in patellar cartilage where every increase of 10 knee bend repetitions resulted in decreases in cartilage thickness and volume by 2%. ...
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Background The impact of activity-related joint loading on cartilage is not clear. Abnormal loading is considered to be a mechanical driver of osteoarthritis (OA), yet moderate amounts of physical activity and rehabilitation exercise can have positive effects on articular cartilage. Our aim was to investigate the immediate effects of joint loading activities on knee and hip cartilage in healthy adults, as assessed using magnetic resonance imaging. We also investigated delayed effects of activities on healthy cartilage and the effects of activities on cartilage in adults with, or at risk of, OA. We explored the association of sex, age and loading duration with cartilage changes. Methods A systematic review of six databases identified studies assessing change in adult hip and knee cartilage using MRI within 48 h before and after application of a joint loading intervention/activity. Studies included adults with healthy cartilage or those with, or at risk of, OA. Joint loading activities included walking, hopping, cycling, weightbearing knee bends and simulated standing within the scanner. Risk of bias was assessed using the Newcastle–Ottawa Scale. Random-effects meta-analysis estimated the percentage change in compartment-specific cartilage thickness or volume and composition (T2 relaxation time) outcomes. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) system evaluated certainty of evidence. Results Forty studies of 653 participants were included after screening 5159 retrieved studies. Knee cartilage thickness or volume decreased immediately following all loading activities investigating healthy adults; however, GRADE assessment indicated very low certainty evidence. Patellar cartilage thickness and volume reduced 5.0% (95% CI 3.5, 6.4, I² = 89.3%) after body weight knee bends, and tibial cartilage composition (T2 relaxation time) decreased 5.1% (95% CI 3.7, 6.5, I² = 0.0%) after simulated standing within the scanner. Hip cartilage data were insufficient for pooling. Secondary outcomes synthesised narratively suggest knee cartilage recovers within 30 min of walking and 90 min of 100 knee bends. We found contrasting effects of simulated standing and walking in adults with, or at risk of, OA. An increase of 10 knee bend repetitions was associated with 2% greater reduction in patellar thickness or volume. Conclusion There is very low certainty evidence that minimal knee cartilage thickness and volume and composition (T2 relaxation time) reductions (0–5%) occur after weightbearing knee bends, simulated standing, walking, hopping/jumping and cycling, and the impact of knee bends may be dose dependent. Our findings provide a framework of cartilage responses to loading in healthy adults which may have utility for clinicians when designing and prescribing rehabilitation programs and providing exercise advice.
... Wang et al. (2022) found that when going downhill the probability of knee joint injury was higher than when walking flat because of the knee extension torque increased significantly. Hartmann et al. (2013) found that the angle of knee flexion in weight-bearing squats is an important influencing factor of knee joint injury. Tsarbou et al. (2021) found that jumping and landing after human fatigue can also cause knee joint injuries. ...
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In this paper, the numerical study focuses on the stress field of the knee meniscus in the two gaits of the jumping motion, and the knee injury and its knee protection effect are studied based on the stress field distribution characteristics of the knee meniscus. The jumping gait simulation was carried out by using a more detailed healthy knee model including bone, articular cartilage, meniscus, ligaments and peripheral soft tissues constructed by combining CT and MRI tomography, and the peak stress and its distribution area were analyzed based on the stress field characteristics of the meniscus, and the knee meniscus and its injury and protection under different knee pads were discussed. The results showed that the anterior angle of the meniscus on the medial knee joint was an area prone to injury in the take-off and landing gait. Under the knee pads, the peak stress of the meniscus decreases, and its distribution area gradually shifts from the anterior angle to the middle, and the functional knee pads with the optimized force load significantly alleviate the stress concentration of the meniscus. Therefore, the numerical study of the stress field of the knee meniscus provides theoretical support and optimization guidance for the design of functional knee pads.
... Knee injury ranges were mostly lower than those reported in other sports, which might indicate that training CrossFit ® has some degree of protection against knee injuries. As indicated by previous studies [41], moves such as squat (performed as back squat and in other forms) was considered harmful but do not result in a higher level of knee injuries. ...
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CrossFit® Training is a physical and sports-conditioning system based on constantly varied functional movements performed at high intensity. CrossFit® has been shown to significantly improve general physical performance and body composition. Although there seems to be an association between the practice of CrossFit® and musculoskeletal injuries, the relationship between CrossFit® and injury risks has been poorly studied. The main objective of this study was to establish the relationship between CrossFit® and musculoskeletal injuries. Secondary objectives were the analysis of various risk factors and injury and the comparison of the incidence of CrossFit® injuries to that of other sports. An online questionnaire was distributed to gyms affiliated with CrossFit®, Inc. in the Principality of Asturias, Spain in order to carry out a retrospective transversal descriptive study. The frequency of injuries in CrossFit® is similar to most sports. Injuries are often minor and of short duration, with the shoulder being the most affected joint complex.
... Scientific research in the field of traumatism in weightlifting shows that most of the injuries in this sport appear in the locations of the knee, lumbar spine, and shoulder [2][3][4][5][6][7] . Deep squats performed in training and competitions lead to overloading the knee joints which are subjected to great pressure and influenced by great forces 8 . The movements in Olympic weightlifting require high levels of development of dynamic force of the upper and lower limbs. ...
Article
Olympic weightlifting is a sport in which athletes compete to lift the greatest amount of weight overhead within an athlete's weight category. The competition lifts are the Snatch and the Clean and Jerk. The purpose of the study was to analyse the incidence, localisation, injury rate and reasons for injuries in elite Olympic weightlifters in Bulgaria. The research was conducted among 21 elite Olympic weightlifters -- the Bulgarian National Team. In order to assess the level of injuries in the previous year (12 months), we had the participants fill out a questionnaire, which included open and closed questions about type, severity, location, and the reasons for the appearance of injuries. The injury rate of the national team of Olympic weightlifters in Bulgaria was 1.98/1000 h of training and 2 injuries per weightlifter for a year. The most often injured locations are the lumbar spine -- 31.7{\%}, knee -- 24.4{\%} and shoulder -- 24.4{\%}. The most common injuries are strain -- 36.6{\%} and sprain -- 17.07{\%}. Acute injuries dominate with 68.29{\%}. The most often reported exercises which resulted in injuries are squat and clean and jerk. The most common reasons for injuries are excessive overload and fatigue. It was concluded that although the training of the Bulgarian national weightlifting team is characterised by high volume and intensity, the injury rate is lower than described in the literature for elite weightlifters and other strength sports.
... s load time estimated to occur during each stance phase of running [84]. Weightbearing femoral cartilage contact with the patella can occur during the maximum compressive force of a knee bend at 90° flexion [85] which has been estimated to be high (up to 18 times body weight) and associated with activities requiring greater knee flexion [43,83]. We also identified a dose-response to loading in patellar cartilage where every increase of 10 knee bend repetitions resulted in decreases in cartilage thickness and volume by 2%. ...
... The human knee joint evolved to adapt to bipedalism more than 300 million years ago (Dye, 2003). The continuous and repetitive stress from everyday activities, such as jogging, playing sports, working, standing, or sitting, makes the knee joints susceptible to problems such as injury or even osteoarthritis (Hartmann et al., 2013). Accordingly, the knee joint is the site at which the "wear-and-tear" type of arthritis occurs most commonly (Darlow et al., 2018), and knee-joint pain has a 22.9% global prevalence in individuals aged 40 and over (Cui et al., 2020). ...
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Objectives: This study aimed to evaluate the clinical efficacy and safety of PE extracts developed for the purpose of relieving pain and improving knee joint function on semi-healthy people with mild knee joint pain. Methods: A randomized, double-blind, two-arm, single-center, placebo-controlled clinical trial was conducted. Individuals with knee joint pain and a visual analogue scale (VAS) score < 50 mm were included in the study, and participants with radiological arthritis were excluded. Participants were administered either PFE or a placebo capsule (700 mg, twice a day) orally for eight weeks. The comparisons of the changed VAS score and Western Ontario and McMaster Universities Osteoarthritis (WOMAC) scores between the PFE and placebo groups were primary outcomes, while the five inflammation-related laboratory tests including cartilage oligomeric matrix protein, cyclooxygenase-2, neutrophil and lymphocyte ratio, high sensitive C-reactive protein, and erythrocyte sedimentation rate were secondary outcomes. Also, a safety assessment was done. Results: Eighty participants (mean age, 38.4 ± 14.0, male: female, 28:52) were enrolled; 75 completed the trial (PFE 36 and placebo 39). After eight weeks, both VAS and WOMAC scores were reduced in the PFE and placebo groups. The changed scores were significantly higher in the PFE group compared to the placebo group: 19.6 ± 10.9 vs. 6.8 ± 10.5; VAS scores (p < 0.001), and 20.5 ± 14.7 vs. 9.3 ± 16.5; total WOMAC scores (p < 0.01) including the sub-scores for pain, stiffness, and functions. No significant changes were reported in the five inflammation-related laboratory parameters. All adverse events were considered minor and unlikely to result from the intervention. Conclusion: Eight weeks of PFE intake was more effective than placebo in reducing knee joint pain and improving knee joint function in sub-healthy people with mild knee joint pain, and there were no major safety concerns. Clinical Trial Registration: https://cris.nih.go.kr/cris/search/detailSearch.do?search_lang=E&focus=reset_12&search_page=M&pageSize=10&page=undefined&seq=23101&status=5&seq_group=19745, identifier CRIS: KCT0007219
... DS attempts to assess the quality of movement patterns that depends on the control of muscle tension in the back and lower limbs, including the hamstrings muscles. The same neuromuscular mechanism is used in activities requiring active mobility in the flexion and hyperextension of the hips [50,51]. Such actions are illustrated by the ASLR test which is closely related to the previous tests. ...
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Functional Movement Screen (FMS) is a tool used to assess fundamental movement patterns. There are relationships between musculoskeletal fitness (MSF) and a FMS. However, there is limited data regarding the multidimensional associations between these two constructs. This study is aimed at investigating the associations and detailed structures of FMS components and MSF components and identifying a deeper detailed structure of their relations to physical fitness. The study sample included 114 physically active men with an average body height of 1.81 ± 0.07 (cm), body weight of 80.61 ± 9.49 (kg), and a BMI of 24.65 ± 2.46 (kg/m2). Each participant performed a FMS test, sit-and-reach (S&R) test, sit-ups (ABS) evaluation, balance evaluation on an AMTI platform, handgrip strength (HG) testing, and standing broad jump (SBJ) ability. The Kendall’s Tau correlation was performed to identify simple associations between FMS and MSF. Cluster analysis was used to determine the multidimensional nature of the relationships. In the vast majority, a positive correlation was observed suggesting that a high level of MSF improved FMS test results. A cluster analysis revealed 4 separate clusters. Shoulder mobility (SM) was identified as a single cluster. A strong similarity was observed between SBJ and trunk stability push-up (TSPU) forming a second cluster. This cluster joined to another consisting of the S&R test and active straight leg raise (ASLR) test. The last cluster consisted of HG and hurdle step (HS). These results confirmed that FMS and MSF tests measure the same constructs—a foundation for an individual’s motor coordination, muscle strength, postural stability, and dynamic balance. This knowledge could be helpful in effectively enhancing physical performance based on combining similar constructs to accelerate the achievement of established goals.
... If a cadaveric knee specimen is flexed at 90°, compressive forces and stresses occur within the patellofemoral joint. As the knee flexion angle increases, the wrapping effect contributes to enhanced load distribution and enhanced force transfer (23). The results of this study are consistent with the findings of this paper, where high-density areas of varying size were observed on the patellofemoral joint surface of the knee in judo athletes (region 4; approximately 12 individuals; 24 knees), while some control subjects (region 4; approximately 6 individuals; 12 knees) showed a distribution of high-density areas on the patellofemoral joint surface. ...
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Objective To investigate the distribution of bone density in the subchondral bone tissue of the knee joint due to the mechanical stress load generated by judo, the bone tissue volume of different densities and the bone remodeling characteristics of the subchondral bone of the knee joint. Methods CT imaging data of the knee joint were collected from 15 healthy individuals as controls and 15 elite judo athletes. Firstly, they were processed by the CTOAM technique, and secondly, the distribution pattern of high-density areas of the knee joint was localized using nine anatomical regions. In addition, three tomographic images were selected in the sagittal, coronal, and axial 2D image windows to observe the distribution of different densities of bone tissue. Finally, the percentage of bone tissue volume (%BTV) and bone remodeling trend of bone tissues with different densities were determined. Results In this study, high-density areas were found in the 4th, 5th, and 6th regions of the articular surface of the distal femur and the 1st, 2nd, 3rd, 4th, 5th, 6th, 7th and 8th regions of the tibial plateau in judo athletes; the distribution of high-density areas on the articular surface of the distal femur in control subjects was similar with judo athletes, and high-density areas were mainly found in the 4th and 5th regions of the tibial plateau. The %BTV of low (401-500HU in the distal femur; 301-400 HU and 401-500HU in the tibial plateau), moderate, and high bone density was higher in judo athletes than in controls in the subchondral bone of the distal femur and tibial plateau (P< 0.05). Conclusion The history of compressive stresses, struck stresses, soft tissue tension and pull, self-gravity and intra-articular stress loading generated by the lower limb exercise technique of judo leads to specific forms of stress distribution and bone tissue remodeling in the subchondral bone tissue within the distal femur and tibia plateau.
... The stance was approximately shoulder-width apart, parallel feet flat on the floor or externally rotated to a maximum of 15°. From this position, participants descended in a controlled motion until the inguinal crease reached (point B) the same horizontal plane as the superior border of the patella [10,22]. After a momentary pause (~1.5 s), they ascended back to the upright position while keeping an upright straight trunk posture [23]. ...
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Objectives: The purposes of this investigation were: 1) to compare the load-velocity relationship estimated by the two-point method between untrained men and women during the parallel back squat exercise (BS) and 2) to compare the load-velocity profile found in our study with the load-velocity profiles reported in the scientific literature for trained individuals. Beyond, we aimed to compare the measured 1RM velocity with predicted 1RM velocity by the two-point method in the BS exercise in untrained individuals. Methods: Seventy-six untrained individuals (38 men (22.7 ± 4.4 years; 174.9 ± 6.8 cm; 76.1 ± 14.9 kg) and 38 women (24.7 ± 4.3 years; 159.1 ± 6.0 cm; 64.7 ± 13.3 kg) performed a one-repetition maximum test and a progressive two-load test with 20% 1RM and 70% 1RM to estimate their load-velocity relationships. Results: The main results revealed that 1) mean propulsive velocity and mean velocity attained at each relative load were different between men and women (p < 0.05). However, the measured 1RM velocity was not significantly different between them. Untrained men provided a steeper load-velocity relationship than women. We found that 2) untrained individuals of our study showed a different load-velocity profile than trained individuals from scientific literature studies. Furthermore, 3) the measured 1RM velocity was lower than the predicted 1RM velocity (p < 0.05). Conclusion: These results suggest that the load-velocity relationship is dependent on sex and training background, and the two-point method using 20% and 70% 1RM might not be reliable to estimate the load-velocity relationship in the BS exercise for untrained men and women.
... The primary function of quadriceps heads is to extend the knee, while the expression of neural, biological, physiological, anatomical, and mechanical properties of quadriceps depend on the mechanical conditions of the movement that this muscle needs to perform [16,17]. Therefore, choosing the correct knee angle may often have a crucial role in effective movement performance with a lower risk of injury as knee angle affects the force and power outputs [18][19][20], as well as musculoskeletal loading and loading of cruciate ligaments [21][22][23][24]. ...
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This study investigated the effects of knee joint angle on muscle activation, exerted torque, and whether the knee angle affects the muscle activation–torque ratio. Nine healthy adult male participants participated in the study. They performed maximal voluntary isometric contraction (MVIC) at six (80°, 90°, 100°, 110°, 120°, and 130°) different knee joint angles (i.e., angles between the thigh and shin bones). Their maximal torque was assessed utilizing an isokinetic chair, while their muscle activation (root mean square [RMS]) was assessed using an eight-channel single differential surface EMG sensor. For the purposes of the torque–knee angle relationship and muscle activation–knee angle relationship, the torque and RMS were normalized relative to the maximal value obtained by each participant. To evaluate the muscle activation–torque ratio in function of knee angle, RMS was normalized relative to the corresponding torque obtained at each knee angle. Repeated measure analysis of variance was used to investigate the effects of knee angle on muscle activation, torque, and muscle activation–torque ratio. There was a significant effect of knee joint angle on normalized torque (F = 27.521, p < 0.001), while the activation of vastus lateralis and vastus medialis remained unchanged. The changes in knee angle affected the muscle activation–torque ratio of vastus lateralis (Chi-square = 16.246, p = 0.006) but not the vastus medialis. These results suggest that knee joint angles from 80° to 130° provide a stable milieu for muscle electrification, while mechanical factor such as knee joint angle (i.e., lever arm length) affect the torque output when one needs to contract quadriceps maximally during the isometric contraction.
... This position was carefully checked so that it could be reproduced in each series. For reasons of standardization and safety, the participants descend in a controlled manner at an average velocity of~0.50-0.60 m·s −1 , until they reach a flexion that leads to a tibiofemoral angle of 35-40 • in the sagittal plane, measured with a goniometer (Nexgen Ergonomics, Point Claire, QC, Canada) to achieve a deep squat [21]. In this position, there was a pause of 2 s, and at the order of the evaluator, they carried out an extension at maximum velocity. ...
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The purpose of this study was to examine the type of relationship between measures of maximal force (dynamic and isometric), maximal power, and mean propulsive velocity. In total, 355 recreational athletes, 96 women (age 20.5 ± 2.5 years; height 158.2 ± 17.3 cm; weight 61.8 ± 48.4 kg) and 259 men (age 21.0 ± 2.6 years; height 170.5 ± 12.6 cm; weight 65.9 ± 9.2 kg) were evaluated in three sessions separated by 72 h each in isometric midthigh pull exercise (ISOS) (kg), bench press maximum strength (1RM MSBP) (kg), jump height (CMJ) (m), and maximum pedaling power (WT) the maximum squat strength (1RM MSS) (kg), the mean propulsive velocity in the bench press (MPVBP) (m·s−1), and the peak power (PPBP) (w), mean propulsive squat velocity (MPVS) (m·s−1), peak power (PP) (w), maximum handgrip force (ISOHG) (kg), and 30 m movement speed (V30) (s). Significant correlations (p ≤ 0.01) were identified between 95% of the various manifestations of force, and only 5% presented a significance of p ≤ 0.05; however, when the magnitude of these correlations is observed, there is great heterogeneity. In this sense, the dynamic strength tests present the best correlations with the other strength and power tests used in the present study, followed by PPBP and PP. The results of this study complement what is reported in the literature regarding the correlation between different types of force manifestations being heterogeneous and contradictory.
... The range of motion of the FS was defined as the beginning of the movement in an upright posture, with hips and knees fully extended, barbell resting on the shoulders and feet flat on the floor, spaced approximately shoulder-width apart, parallel or externally rotated to a maximum of 15° (point A). Participants descended in controlled motion from this position until the back of the thigh touched the calf (point B; Hartmann et al., 2013;Martínez-Cava et al., 2019). After that phase (with a brief pause during the incremental testing), they returned to point A (Pallarés et al., 2014). ...
Article
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.
... Il reclutamento dei muscoli addominali è simile durante gli squat che durante un plank prono, a eccezione dell'EO. 1 Inoltre, è stato notato l'impegno dei muscoli del tronco per controllare la flessione del tronco durante lo squat. 2 La combinazione del movimento degli arti inferiori e del tronco osservata durante uno squat riflette ampiamente azioni tipiche della vita quotidiana, come il sedersi e lo stare in piedi, 3 osservazione che fornisce un ulteriore supporto riguardo l'importanza di migliorare la funzione mentre si effettua lo squat. La lombalgia colpisce gran parte della popolazione attraverso un incremento del carico trasferito attraverso la colonna vertebrale quando il tronco si flette in avanti, 4 In addition, engagement of trunk muscles has been observed in order to control trunk flexion whilst squatting. 2 The combination of lower limb and trunk movement observed in a squat largely reflects daily living actions such as sitting and standing, 3 and rectus abdominis). ...
... The squatting motion has been considered as an efficient exercise to improve the strength of the lowerlimb muscle system and torso for the human motor activation and coordination for balance and stability. Squat also induced high joint loads and increased the risk of spine and knee joint injuries [21]. Hence, it has been extensively utilized in clinical evaluations [22] and in microgravity environments [23]. ...
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— Unicompartmental knee arthroplasty (UKA) is a surgical method used to treat osteoarthritis in one portion of the knee, most often the medial compartment. UKA supporters argued that the procedure more closely replicates natural knee kinematics, results in reduced perioperative morbidity and intraoperative blood loss, and allows for quicker mobility and rehabilitation than traditional bicondylar knee arthroplasty. The goal of this study is to look at the impact of implant design on the mechanics of unicompartmental knee arthroplasty (UKA). 3D models of the UKA implant were modified from three different design of off-the-shelf total knee arthroplasty (TKA) implants. Then, finite element analysis was performed to investigate the influence of implant geometrical design on stress distribution and deformation in polyethylene (PE) inserts. This study revealed that the implant design significantly affects the stress distribution and deformation of tibial insert and varies with the joint angle. Keywords—Deformation, polyethylene (PE) insert, stress distribution, Unicompartmental knee arthroplasty
... 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). ...
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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.
... 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. ...
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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.
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PURPOSE This study analyzed the effect of dynamic lumbar kyphosis on the biomechnical factors affecting the lumbar joints during deep squats.METHODS Thirty adults in their 20s who had experienced weight training for more than one year participated in this study (age: 23.4±3.5years old, height: 175.3±4.3cm, weight: 75.8±6.5kg, squat single repetition maximum (1RM) weight: 115.3±19.5kg). Under both restricted dynamic lumbar kyphosis (RDLK) and dynamic lumbar kyphosis (DLK), subjects completed one repetition of deep squats at a load of 70% of their 1-RM weight. To verify the consistency of deep squat movements performed under DLK and RDLK conditions, intra-rater reliability was analyzed using intra-class correlation . The biomechnical variables of the lumbar joint were calculated during DLK and RDLK deep squats. Paired sample t-tests (IBM SPSS 27.0, Armonk, New York, USA) were used for statistical verification.RESULTS During the deep squat movement performed in DLK and RDLK conditions, the peak angles of the ankle, knee, and hip joints, the minimum height of the pelvis, and the time and tempo showed statistically high reliability, confirming the accuracy of the movement. The peak flexion angle and moment, left flexion moment, left rotation moment, and compression force factors of the lumbar joint during deep squat were significantly lower in RDLK than in DLK.CONCLUSIONS Restricting lumbar dynamic kyphosis during deep squats is essential for decreasing the risk of lumbar joint injury.
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Background This study aimed to use vibroarthrography to evaluate the effect of different external loads on the arthrokinematics of the patellofemoral joint during the back squat motion in vivo. The level of vibroarthrographic signal was expected to increase with the level of applied load; however, the trend of increase was unknown. Methods Participants, who were recruited from team sport athletes, were requested to perform eight trials: four bodyweight squats and four back-loaded barbell squats of 10–70 kg, with 1 min rest between tests. Finally, 38 male volunteers (age: 22.0 ± 1.1 years, body mass: 82.8 ± 10.1 kg, height: 186,7 ± 7.9 cm) were included in the study. All participants described their health condition as “very good.” An average physical activity of moderate-to-vigorous intensity, mostly aerobic, was considered as 12,47 ± 3,37 hours across the week. The arthrokinematic quality of movement of the PFJ was assessed using an accelerometer sensor placed 1 cm above the apex of the patella. Results The experimental results revealed that the vibroarthrographic signal level steadily increased with an increasing knee load during squatting, which could be attributed to higher contact stress and kinetic friction of the joint surfaces. The phenomenon was analyzed throughout the range of loads applied, which followed a linear pattern. Conclusions The proposed method is a promising tool for monitoring the effects of external loads on the knee joint mechanics and adaptive changes that occur during training. Moreover athletes and coaches should take into account that increased loads can result in accelerated joint wear and tear.
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In this review, we discuss the interaction of mechanical factors influencing knee osteoarthritis (KOA) and post-traumatic osteoarthritis (PTOA) pathogenesis. Emphasizing the importance of mechanotransduction within inflammatory responses, we discuss its capacity for being utilized and harnessed within the context of prevention and rehabilitation of osteoarthritis (OA). Additionally, we introduce a discussion on the Goldilocks zone, which describes the necessity of maintaining a balance of adequate, but not excessive mechanical loading to maintain proper knee joint health. Expanding beyond these, we synthesize findings from current literature that explore the biomechanical loading of various rehabilitation exercises, in hopes of aiding future recommendations for physicians managing KOA and PTOA and athletic training staff strategically planning athlete loads to mitigate the risk of joint injury. The integration of these concepts provides a multifactorial analysis of the contributing factors of KOA and PTOA, in order to spur further research and illuminate the potential of utilizing the body’s own physiological responses to mechanical stimuli in the management of OA.
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Maintenance of mitochondrial homeostasis is crucial for ensuring healthy mitochondria and normal cellular function. This process is primarily responsible for regulating processes that include mitochondrial OXPHOS, which generates ATP, as well as mitochondrial oxidative stress, apoptosis, calcium homeostasis, and mitophagy. Bone mesenchymal stem cells express factors that aid in bone formation and vascular growth. Positive regulation of hematopoietic stem cells in the bone marrow affects the differentiation of osteoclasts. Furthermore, the metabolic regulation of cells that play fundamental roles in various regions of the bone, as well as interactions within the bone microenvironment, actively participates in regulating bone integrity and aging. The maintenance of cellular homeostasis is dependent on the regulation of intracellular organelles, thus understanding the impact of mitochondrial functional changes on overall bone metabolism is crucially important. Recent studies have revealed that mitochondrial homeostasis can lead to morphological and functional abnormalities in senescent cells, particularly in the context of bone diseases. Mitochondrial dysfunction in skeletal diseases results in abnormal metabolism of bone-associated cells and a secondary dysregulated microenvironment within bone tissue. This imbalance in the oxidative system and immune disruption in the bone microenvironment ultimately leads to bone dysplasia. In this review, we examine the latest developments in mitochondrial respiratory chain regulation and its impacts on maintenance of bone health. Specifically, we explored whether enhancing mitochondrial function can reduce the occurrence of bone cell deterioration and improve bone metabolism. These findings offer prospects for developing bone remodeling biology strategies to treat age-related degenerative diseases.
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This study aimed to investigate the relationship between different foot stances during weight squats and knee injuries resulting from repetitive movement, specifically focusing on repetitive stress injuries (RSIs). An integrative approach combining computational simulations with experimental data was used to analyse the biomechanical behaviour of the knee joint and surrounding structures. The results demonstrated that foot placement significantly affected knee alignment, and deviations from optimal alignment increased the risk of proximal tibial stress fracture and hip dysplasia.
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EntryThe squat pattern is present in the life of every human being from his earliest years. In sports, the squat is one of the most popular exercises, used in almost every discipline in countless variations by both professionals and amateurs. Due to its biomechanics and the degree of involvement of the nervous system and the musculoskeletal system, its use is an essential training link in any plan aimed at developing muscle mass, strength and endurance. The squat pattern is also used in medicine, rehabilitation and improving people suffering from all kinds of injuries and dysfunctions of the locomotor system. Material and methodsThe study used the diagnostic survey method, with the use of a proprietary questionnaire consisting of 37 questions. The study was conducted among a group of 250 men aged 20-50 practicing amateur strength sports. Conclusions The current state of knowledge about the squat technique (high bar, low bar, front squat) among men practicing strength sports as amateurs is at an insufficient level. Respondents did not show sufficient knowledge about the impact of squats on the human body.
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» Chronic lower back pain (LBP) is common in both nonathletes and weight lifters, but the diagnosis and treatment should be approached differently in these 2 populations based on the unique movement patterns causing the pain. » Injury rates of weight lifters are far less than those of contact sports, ranging from 1.0 to 4.4 injuries per 1,000 workout hours. However, the lower back was consistently one of the top 2 injury sites for weight lifters, accounting for anywhere from 23% to 59% of all injuries. LBP was most often associated with the squat or deadlift. » Guidelines for evaluating general LBP are applicable to weight lifters, including a thorough history and physical examination. However, the differential diagnosis will change based on the patient's lifting history. Of the many etiologies of back pain, weight lifters are most likely to be diagnosed with muscle strain or ligamentous sprain, degenerative disk disease, disk herniation, spondylolysis, spondylolisthesis, or lumbar facet syndrome. » Traditional recommended therapies include nonsteroidal anti-inflammatory drugs, physical therapy, and activity modification, which are often insufficient to resolve pain and prevent injury recurrence. Because most athletes will want to continue to lift weights, lifting-specific behavior modifications focused on improved technique and correcting mobility and muscular imbalances are important aspects of management in this patient population.
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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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This study evaluates the predictive ability of the skeletal muscle force model derived previously within the ankle joint complex. The model is founded in dimensional analysis, using electromyography and the muscle force-length, force-velocity, and force-frequency curves as inputs. Seventeen subjects (8 males, 9 females) performed five different exercises that activated the primary muscles crossing the ankle joint. Motion capture, force plate, and electromyography data were collected during these exercises. A constant, Km, was calculated for each muscle of each subject using four of the five exercises. The fifth exercise was used to validate the results by treating the moments due to muscle forces as known and all other components in Euler's second law as unknown. While muscle forces cannot be directly validated in vivo, methods can be developed to test these values with reasonable confidence. This study compared moments about the ankle joint due to the calculated muscle forces to the sum of the moments due to all other sources and the kinematic terms in the second Newton-Euler equation of rigid body motion. Average percent errors for each subject ranged from 4.2% to 15.5% with an average percent error across all subjects of 8.2% while maximum percent errors for each subject ranged from 33.3% to 78.0% with an overall average maximum of 52.4%. Future work will examine sensitivity analyses to identify potential simplifications to the model and solution process and will validate the model on a more complex joint.
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This study evaluated the effects of four different weekly stretching protocols on the rate of gain and decline in hamstring flexibility over an 8-week period, across sex. Using a randomized single-blind design, 53 healthy subjects aged 18–46 years were assigned to 1 of 4 stretching protocols or a control group. The stretching protocols consisted of either daily or 3 times per week stretching and performed once or twice each day. These protocols differed in terms of frequency and total weekly stretching time. All the subjects stretched their hamstring muscles for 4 weeks and were measured weekly for their hip range of motion (ROM). Stretching ceased the final 4 weeks as the weekly measurements continued. The results revealed no significant differences in the rate of gain or the rate of loss between the different stretching protocols (2-way analysis of variance, F = 2.60, p > 0.05). All the stretching groups gained in hip ROM from pre to week 4 (F = 269.24, p < 0.001). After cessation, the rate of loss was similar for all the 4 stretching groups (F = 102.86, p < 0.001); all the groups retained significant gains at the end of the study (p < 0.001). The control group did not change over time. Those who stretched at least 6 times per week gained more than those who stretched 3 times per week (24 and 16.8%, respectively, F = 5.20, p < 0.05). Subject sex did not influence ROM changes (p > 0.05). Stretching appears to be equally effective, whether performed daily or 3 times per week, provided individuals stretch at least 2 times each day. Moreover, although women are more flexible than men are, there was no sex difference in terms of stretching response.
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The aim of this research was to investigate if perennial, professional weightlifting training, started at puberty, leads to hypertrophy of the patellar ligament (PL). The knee examinations were performed with a 1.5 T magnetic resonance imaging system. The area of the cross-sectional area (CSA) of the PL midsubstance was evaluated in T1-weighted images. A control group of 19 participants was also examined with the same protocol. A significant increase of the PL midregion CSA was observed in a group of weightlifters. The area of the PL midsubstance and the onset of training were very strongly, reversely correlated. This paper presents the first description of PL midregion hypertrophy due to professional weightlifting training initialised and continued from a pubertal spurt. The described overgrowth is more intensified than has been reported for other parts of the PL. Moreover, it has been observed in the region that is the least susceptible for injuries, which in another situation could also have led to increased volume of the PL. The described phenomenon should be considered by orthopaedic surgeons because it can influence the choice of the surgical technique for cruciate ligament reconstruction as the PL is one of the structures for harvesting autografts.
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Objective: To determine if differences in biomechanical properties and biochemical composition exist between human patellar articular cartilage and the opposing femoral articular cartilage. Design: The biomechanical properties and biochemical composition of the articular cartilage of 17 knees from 13 donors were determined for four sites on the patella and three sites on the femur representing regions of contact at 30 degrees and 90 degrees of flexion. The material properties were determined by biphasic indentation testing, yielding the compressive aggregate modulus, HA, permeability, k, and Poisson's ratio, vs. The thickness of the cartilage at the indentation site, h, was also measured using a needle probe. Full-thickness samples of cartilage adjacent to each indentation site were used for wet weight, sulfated glycosaminoglycan content and hydroxyproline content determinations. Results: The patellar cartilage was found to have a lower compressive aggregate modulus by 30% (P < 0.001), higher permeability to fluid flow by 66% (P < 0.001) and greater thickness by 23% (P = 0.017) than that of the opposing femoral cartilage. The Poisson's ratios for both surfaces were found to be nearly zero. The water content of the patella was higher by 5% (P = 0.031) and the proteoglycan content lower by 19% (P = 0.030) than that of the femur. However, no differences were found between the collagen contents of the cartilages. Conclusions: Significant differences were found between the intrinsic material properties of the patellar cartilage and those of the femoral-trochlear cartilage. This variability of cartilage material properties with the patellofemoral joint may help explain why patellar cartilage has been frequently observed clinically to exhibit earlier and more severe fibrillation changes than the opposing femoral cartilage.
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In a group of high performance weightlifters increased values of the cruciate ligaments (CLs) cross-sectional areas were observed. The purpose of this research was to investigate if repeated heavy workouts increase the volume of those structures. The knee examinations were performed with an 1,5T MRI system. The area of the anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL) midsubstance cross-section were evaluated in T1-weighted images with administration of contrast medium in a group of nine athletes. A control group of 19 participants was also examined using the same protocol. Significant differences of the ACL and the PCL midsubstance cross-sectional areas were observed between groups. The area of the CLs' midsubstance and the onset of training were strongly negatively correlated and the PCL cross-sectional area was strongly positively correlated with the duration of training. This research is the first description of the CLs hypertrophy, which is probably caused by heavy training that was started about the age of puberty. The age of training onset seems to have a greater impact on the hypertrophy process than the training duration. Knowledge of the phenomenon of cruciate ligament overgrowth is vital for orthopaedics because, possible changes of the CLs mechanical properties and three-dimensional orientation, may affect the incidence of trauma and reconstruction procedures technique.
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This study investigated the hypothesis that timing and duration of dynamic compression are integral to regulating extracellular matrix (ECM) assembly of tissue-engineered (TE) menisci. The goal of this study was to examine the effects of varying load and static culture duration on structure, composition, and mechanical properties of TE menisci. We accomplished this by varying the duration of dynamic loading over 4 weeks of culture, and by examining increasing periods of static culture after 2 weeks of dynamic loading. Bovine meniscal fibrochondrocytes were seeded into 2% w/v alginate, crosslinked with CaSO(4), injected into anatomical micro-computed tomography-based molds, and post-crosslinked with CaCl(2). Meniscal constructs were dynamically compressed three times a week via a custom bioreactor for a total of 2 h, with an hour of rest between loading cycles, for 1, 2, or 4 weeks. They were then placed in static culture. After 4 weeks of culture, increased load duration was found to be beneficial to matrix formation and mechanical properties, with superior mechanical and biochemical properties in samples loaded for 2 or 4 weeks. Further, the mechanical properties of these constructs were similar, suggesting that the additional 2 weeks of loading may not be necessary. Samples loaded for 2 weeks followed by a 4-week static culture period yielded the most mature matrix with significant improvements in collagen bundle formation, 2.8-fold increase in the glycosaminoglycan content, 2-fold increase in the collagen content, and 4.3-fold increase in the compressive equilibrium modulus. Overall, this study demonstrated the importance of timing and duration of loading. By switching to prolonged static culture after 2 weeks of loading, we decreased the amount of ECM lost to the media, while significantly increasing biochemical and mechanical properties of TE menisci.
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Tendons transmit skeletal muscle forces to bone and are essential in all voluntary movement. In turn, movement appears to affect tendon properties, and in recent years considerable effort has been put into discovering how tendon tissue responds to mechanical stimuli in vivo. Months and years of mechanical loading can influence the gross morphology of tendon, seen as an increase tendon cross sectional area (CSA). Similarly, tendon stiffness appears to be affected by weeks to months of loading. Increased stiffness can relate to changes in CSA and/or tendon material properties (modulus), though the relative contribution of these parameters is largely unclear. The possible mechanisms behind alterations in tendon material properties include changes in collagen fibril morphology and levels of cross-linking between collagen molecules. Furthermore, increased levels of collagen synthesis and expression are seen as a response to acute exercise and training, and may be a central parameter in tendon adaptation to loading. There are indications that this collagen-induction relates to the auto-/paracrine action of collagen-stimulating growth factors, such as TGFβ-1 and IGF-I, which are expressed in response to mechanical stimuli.
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Although several studies have examined the relationship between physical activity and knee osteoarthritis, the effect of physical activity on knee joint health is unclear. The aim of this systematic review was to examine the relationships between physical activity and individual joint structures at the knee. Computer-aided searches were conducted up until November 2008, and the reference lists of key articles were examined. The methodological quality of selected studies was assessed based on established criteria, and a best-evidence synthesis was used to summarize the results. We found that the relationships between physical activity and individual joint structures at the knee differ. There was strong evidence for a positive association between physical activity and tibiofemoral osteophytes. However, we also found strong evidence for the absence of a relationship between physical activity and joint space narrowing, a surrogate method of assessing cartilage. Moreover, there was limited evidence from magnetic resonance imaging studies for a positive relationship between physical activity and cartilage volume and strong evidence for an inverse relationship between physical activity and cartilage defects. This systematic review found that knee structures are affected differently by physical activity. Although physical activity is associated with an increase in radiographic osteophytes, there was no related increase in joint space narrowing, rather emerging evidence of an associated increase in cartilage volume and decrease in cartilage defects on magnetic resonance imaging. Given that optimizing cartilage health is important in preventing osteoarthritis, these findings indicate that physical activity is beneficial, rather than detrimental, to joint health.
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Finite element analysis results will show significant differences if the model used is performed under various material properties, geometries, loading modes or other conditions. This study adopted an FE model, taking into account the possible asymmetry inherently existing in the spine with respect to the sagittal plane, with a more geometrically realistic outline to analyze and compare the biomechanical behaviour of the lumbar spine with regard to the facet force and intradiscal pressure, which are associated with low back pain symptoms and other spinal disorders. Dealing carefully with the contact surfaces of the facet joints at various levels of the lumbar spine can potentially help us further ascertain physiological behaviour concerning the frictional effects of facet joints under separate loadings or the responses to the compressive loads in the discs. A lumbar spine model was constructed from processes including smoothing the bony outline of each scan image, stacking the boundary lines into a smooth surface model, and subsequent further processing in order to conform with the purpose of effective finite element analysis performance. For simplicity, most spinal components were modelled as isotropic and linear materials with the exception of spinal ligaments (bilinear). The contact behaviour of the facet joints and changes of the intradiscal pressure with different postures were analyzed. The results revealed that asymmetric responses of the facet joint forces exist in various postures and that such effect is amplified with larger loadings. In axial rotation, the facet joint forces were relatively larger in the contralateral facet joints than in the ipsilateral ones at the same level. Although the effect of the preloads on facet joint forces was not apparent, intradiscal pressure did increase with preload, and its magnitude increased more markedly in flexion than in extension and axial rotation. Disc pressures showed a significant increase with preload and changed more noticeably in flexion than in extension or in axial rotation. Compared with the applied preloads, the postures played a more important role, especially in axial rotation; the facet joint forces were increased in the contralateral facet joints as compared to the ipsilateral ones at the same level of the lumbar spine.
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The squat is one of the most frequently used exercises in the field of strength and conditioning. Considering the complexity of the exercise and the many variables related to performance, understanding squat biomechanics is of great importance for both achieving optimal muscular development as well as reducing the prospect of a training-related injury. Therefore, the purpose of this article is 2-fold: first, to examine kinematics and kinetics of the dynamic squat with respect to the ankle, knee, hip and spinal joints and, second, to provide recommendations based on these biomechanical factors for optimizing exercise performance.
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Careful review of published evidence has led to the postulate that the degree of lumbar lordosis may possibly influence the development and progression of spinal osteoarthritis, just as misalignment does in other joints. Spinal degeneration can ensue from the asymmetrical distribution of loads. The resultant lesions lead to a domino- like breakdown of the normal morphology, degenerative instability and deviation from the correct configuration. The aim of this study is to investigate whether a relationship exists between the sagittal alignment of the lumbar spine, as it is expressed by lordosis, and the presence of radiographic osteoarthritis. 112 female subjects, aged 40-72 years, were examined in the Outpatients Department of the Orthopedics' Clinic, University Hospital of Heraklion, Crete. Lumbar radiographs were examined on two separate occasions, independently, by two of the authors for the presence of osteoarthritis. Lordosis was measured from the top of L1 to the bottom of L5 as well as from the top of L1 to the top of S1. Furthermore, the angle between the bottom of L5 to the top of S1 was also measured. 49 women were diagnosed with radiographic osteoarthritis of the lumbar spine, while 63 women had no evidence of osteoarthritis and served as controls. The two groups were matched for age and body build, as it is expressed by BMI. No statistically significant differences were found in the lordotic angles between the two groups There is no difference in lordosis between those affected with lumbar spine osteoarthritis and those who are disease free. It appears that osteoarthritis is not associated with the degree of lumbar lordosis.
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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.
Chapter
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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Most injuries can be prevented by following safe procedures. A coach or fellow lifter should be present during workouts, and proper breathing is important for preventing blackouts during lifts. Lifting platforms, shoes with good counters and support around the midfoot, and wraps to prevent skin-to-skin sticking also help to prevent injuries. Finally, because inflexibility and improper technique cause most lifting injuries, the lifter should concentrate on developing these abilities.
Article
here are common symptoms that are associated with “Jumper’s Knee”, such as pain, aching, and swelling on the lower side of the Patella on the anterior surface of the knee. Addition symptoms may include weakness and cramping of the knee joint. There are common remedies to treat "Jumper’s Knee”, such as rest, ice, compression, and elevation. Anti-inflammatory medicine, such as Aleve, Advil, or Motrin, may be appropriate in the early stages of injury. If the symptoms are left untreated, the final result may be knee surgery. A patient returning to play after diagnoses and treatment for “Jumpers Knee” should apply heat to the knee for 10 or 15 minutes before starting physical activity. Following physical activity, apply ice for 10 to 15 minutes (Donohue, 2008). Conservative treatments assist the healing process and keep Patellar Tendinopathy at bay for more than 90% of cases (Vulpiani, 2007). Along with becoming knowledgeable regarding remedies to relieve symptoms of minor “Jumper’s Knee”, it is important to know the stages of Patellar Tendinopathy. Knowledge of the warning signs and stages may assist in the avoidance of advancing the condition of Patellar Tendinopathy. Knowing the cause of Patellar Tendinopathy, the five stages, warning signs, and risk factors may assist in the process of diagnosing the injury for faster and more effective treatment. Being able to utilize the correct treatment for a particular stage of “Jumpers Knee” reduces downtime and assists the athletic trainers and doctors in the process of prescribing levels of physical activity.
Article
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.
Article
Three high-skilled powerlifters performed parallel squats with different burden weights. Using a sagittal plane biomechanical model, the moments of force about the bilateral axes of the lumbo-sacral, hip, knee, and ankle joints were determined. A local biomechanical model of the knee was used in order to calculate the knee joint forces induced. The greatest moments were found in the lumbo-sacral joint. The maximum hip moment was greater than that of the knee moment which was greater than the ankle moment. The knee moment had a flexing direction and reached its maximum at the deepest position of the squat, while the lumbo-sacral and hip moments were found to reach their maxima during the first half second of the ascent. One lift that caused a bilateral quadriceps tendon rupture was stimulated and was found to give a maximum knee flexing moment ranging between 335 Nm and 550 Nm. This moment induced a force in each quadriceps tendon of between 10.9 kN and 18.3 kN at the occasion of rupture.
Article
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.
Article
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.
Article
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.
Article
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.
Article
An 13 Leichenkniegelenken wurde die femoropatellare Kongruenz unter verschiedenen Funktionsgraden unter Berucksichtigung der Chondromalazielokalisation uberpruft. Es zeigte sich, das die Chondromalazielokalisation in 50% der Falle nicht mit der Kontaktzone ubereinstimmte. Mogliche weitere Ursachen der Chondromalazie werden diskutiert. At 13 post-mortem-knees we investigated the patellofemoral contact area in different degrees of function, referring to the localization of chondromalacia. We found that the localization of chondromalacia didn't accord to the contact area in 50% of all cases. Possible other causes are discussed.
Article
A problem for some novice trainees in a strength program is the inability to maintain complete foot contact with the ground during the parallel squat weight training exercise. The purpose of this study was to determine the relative contribution of selected physical characteristics in discriminating between subjects who were able to maintain complete foot contact ivith the floor during this exercise and those who could not. Fifty males ((formula presented) age = 21.1 ± 2.67 years) in beginning weight training classes were measured for height (HT), torso length (TL), femur length (FL), mean of right and left ankle dorsi-flexion (AF), and sit and reach flexibility (SR). Each subject performed three parallel squats with a 20 kg barbell across the top of the trapezius, and with feet shoulder- width apart. Those able to maintain complete foot contact with the ground were classified as Group 1 (n=42) and all others as Group 2 (n=8). A correlation matrix revealed that none of the five measured variables shared more than 18 percent common zero-order variance. A full-model multiple discriminant analysis correctly classified 94 percent of the subjects. The relative contribution of each variable to the explained variance from the discriminant function included HT (36.0 percent), TL (33.0 percent), SR (9-3 percent), FL (8.8 percent), and AF (6.9 percent). These data indicate that physical stature and body segment dimensions are more potent discriminators than flexibility measures for the ability to maintain complete foot contact during the parallel squat exercise. Furthermore, tall subjects with relatively short torsos appear to have greater difficulty maintaining foot contact during this exercise than do shorter subjects with relatively long torsos. © 1988 Journal of Applied Sport Science Research. All rights reserved.
Article
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. (C) 1994 National Strength and Conditioning Association
Article
Squatting is a common strength-training exercise used for rehabilitation, fitness training and in preparation for competition. Knowledge about the loading and the motion of the back during the squat exercise is crucial to avoid overuse or injury. The aim of this study was the measurement and comparison of the kinematics of the lower leg, trunk and spine during unrestricted and restricted (knees are not allowed beyond toes) squats.A total of 30 subjects performed unrestricted and restricted barbell squats with an extra load of 0%, 25% and 50% bodyweight. Motion was tracked using a 12-camera Vicon system. A newly developed marker set with 24 trunk and 7 pelvic markers allowed us to measure 3D segmental kinematics between the pelvic and the lumbar regions, between the lumbar and the thoracic segments and between the sagittal curvatures of the lumbar and the thoracic spine.In an unrestricted squat, the angle of the knee is larger and the range of motion (ROM) between the lumbar and the thoracic segments is significantly smaller compared with a restricted squat (p<0.05). The studied subjects showed significantly increased ROM for thoracic curvature during restricted squats.The unrestricted execution of a squat leads to a larger ROM in the knee and smaller changes in the curvature of the thoracic spine and the range of smaller segmental motions within the trunk. This execution in turn leads to lower stresses in the back. To strengthen the muscles of the leg, the unrestricted squat may be the best option for most people. Thus, practitioners should not be overly strict in coaching against anterior knee displacement during performance of the squat.