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Quadriceps and Hamstrings Strength in Athletes
Abstract
Quadriceps and hamstrings strength is usually quantified by the peak torque during maximal voluntary isokinetic contractions. Ratios of peak torque are used to assess limb asymmetry and compare hamstrings strength relative to quadriceps strength. Peak torque is affected by the mode and speed of testing, and it is important to consider whether or not to normalize peak torque (e.g., to body mass). Positive, but moderate correlations were observed between knee strength and triple hop distance and between knee strength and hip strength in a population of collegiate freshmen football players. No significant correlations were observed between knee strength and Functional Movement Screen™ performance, or between limb symmetry indices based on different strength and functional tests. Deficiencies in quadriceps and hamstrings strength may increase the risk of lower extremity injuries, but large prospective studies are needed to determine which measures of strength are the best predictors for specific injuries and to optimize injury prevention strategies.
... Muscle strength in athletes is one of the important determinants of sports performance, where muscle strength loss has been related with an increased risk of injury [1,2]. Muscle strength evaluations are used to determine physical conditioning to define weakness connected with sports injuries and to enhance improvement in exercise/rehabilitation programs [3][4][5]. Knee joint muscle strength is associated with the strength of other muscles of the body and is important for both athletes, trainers and health professionals working in this field since it effects sports performance regardless of sector [5]. For this reason, the strength of the knee flexor and extensor muscles is frequently evaluated both for the preparation and regulation of training programs at the beginning of the season, in the middle of the season, and at the end of the season to determine the amount of training necessary to reach the desired goal [2,5]. ...
... Muscle strength evaluations are used to determine physical conditioning to define weakness connected with sports injuries and to enhance improvement in exercise/rehabilitation programs [3][4][5]. Knee joint muscle strength is associated with the strength of other muscles of the body and is important for both athletes, trainers and health professionals working in this field since it effects sports performance regardless of sector [5]. For this reason, the strength of the knee flexor and extensor muscles is frequently evaluated both for the preparation and regulation of training programs at the beginning of the season, in the middle of the season, and at the end of the season to determine the amount of training necessary to reach the desired goal [2,5]. ...
... Knee joint muscle strength is associated with the strength of other muscles of the body and is important for both athletes, trainers and health professionals working in this field since it effects sports performance regardless of sector [5]. For this reason, the strength of the knee flexor and extensor muscles is frequently evaluated both for the preparation and regulation of training programs at the beginning of the season, in the middle of the season, and at the end of the season to determine the amount of training necessary to reach the desired goal [2,5]. ...
This study aimed to evaluate the intra- and inter-rater reliability of a well-used and a lessused IsoMed-2000 dynamometer for knee flexion and extension peak torque (PT) measurements in a concentric test in athletes. Two IsoMed-2000 isokinetic dynamometers were used, an old one that was well-used and a new one that was less-used. Thirty-seven weight-lifting athletes (12 female, 25 male) were included in this study. Both legs of each athlete were tested twice on each isokinetic dynamometer at 60°/s and 180°/s. The Intraclass Correlation Coefficients (ICC), Standard Error Measurement (SEM), Smallest Detectable Change (SDC), SDC% and 95% limits of agreement were calculated to evaluate the intra- and inter-rater reliability of a well-used and a less-used IsoMed 2000 dynamometer for knee flexion and extension peak torque in athletes. Intra-rater reliability was moderate to excellent (ICCs: 0.516–0.928) for knee muscle strength parameters, and the highest SDC and SEM values were 0.76 N/kg and 0.28 N/kg, respectively. Inter-rater reliability was moderate to excellent (ICCs: 0.519–915) for knee muscle strength parameters, and the highest SDC and SEM values were 0.81 N/kg and 0.29 N/kg, respectively. At least 89.2% of the obtained values of parameters fell within the 95% limits of agreement. Our findings demonstrate the intra and inter-rater reliability of a Well-Used and a Less-Used IsoMed 2000 Dynamometer for Knee Flexion and Extension Peak Torque in Athletes.
Keywords: muscle strength; muscle strength dynamometer; quadriceps muscle; hamstring muscles
... contraction of the quadriceps results in knee extension, while contraction of the hamstrings results in a flexion of the knee joint [9]. As the intermittent nature of the soccer match, the player would be tired when the match goes towards ending. ...
... While the functional H:Q ratio is defined as the ratio between the peak torque of the hamstring during an eccentric contraction and the peak torque of the quadriceps during a concentric contraction [9,14,15]. ...
... Nevertheless, hamstrings and quadriceps muscles are antagonists to one another, simultaneous concentric contraction of both these muscles does not happen. Therefore, it may be preferred to examine eccentric hamstrings peak torque with respect to the concentric quadriceps peak torque when assessing functional strength [9]. A reduced H:Q ratio may be indicative of quadriceps dominance, may put athletes at a greater risk for lower extremity injury [22]. ...
Background:
Soccer players are required to perform explosive and powerful movements as the game is very competitive and intermittent nature. Functional hamstring to quadriceps strength ratio can plays a significant role to perform these movements. The imbalance of this ratio occurs hamstring muscles injury. Current researchers found the clear connection between functional hamstring to quadriceps strength ratio and the non-contact hamstrings injury of soccer players. Objective:
The aim of the review study was to analyze the functional strength ratio between hamstrings and quadriceps as a measure of hamstring injury.
Method:
Researchers collected scientific evidences through electronic online databases; PubMed, Embase, Medline, Google scholar, Web of science, PsycInfo, and critically analyzed the entire relevant article according to the nature of this study.
Findings:
Nordic hamstring strengthening exercise and FIFA 11+ injury prevention programme may reduce the rate and severity of hamstring muscle injuries and also develop the eccentric strength of hamstrings especially on biceps femoris long headmuscle fascicles.
Conclusion:
Hamstring to quadriceps strength ratio need to be maintaining regularly to overcome hamstrings injury. Progressive and systematic nordic hamstring strengthening exercise can decrease hamstring lesions and reduction of re-injury.
Keywords:
Hamstring to quadriceps strength ratio; Biceps femoris long head; Nordic hamstring exercise; Eccentric strength; Muscles injury; Soccer
... Our results of isokinetic knee extension and flexion muscle strength at 60°/s were higher than those of healthy, active individuals reported in another study. 28 In this study, lower knee extension torques (N.m) and similar knee flexion torques (N.m) were seen at a velocity of 120°/s when compared with Aagaard et al. 3 We compared non-normalized values with that study because aerobica moderata e non esiste alcuna differenza fra le classi di regata Laser e 470. Ad ogni modo, poiché si tratta di una squadra olimpica, riteniamo che i velisti turchi debbano migliorare la loro potenza aerobica. ...
... Poiché non abbiamo potuto trovare alcuno studio che riporta valori di forza normalizzati per le velocità di 60°/s e 120°/s dei velisti, i nostri risultati possono costituire una base di partenza per ulteriori studi. I nostri risultati, riguardanti l'estensione isocinetica del ginocchio e la forza muscolare di flessione a 60°/s, sono stati più elevati rispetto a quelli d'individui sani e attivi, riportati in un altro studio 28 . In questo studio, tensioni inferiori dell'estensione del ginocchio e tensioni simili della flessione del ginocchio (dati non riportati) sono state rilevate ad una velocità di 120°/s in confronto a quanto riportato da Aagaard et al. 3 Abbiamo confrontato i valori non normalizzati con quello studio poiché Aagaard et al. 3 hanno riportato valori non normalizzati; comunque, l'utilizzo di dati non normalizzati può causare una variabilità elevata nel caso in cui si confrontino individui con una notevole differenza di corporatura 28 ; pertanto sono necessari ulteriori studi per risalire ad alcuni concetti, inerenti alla forza muscolare dell'estensione del ginocchio dei velisti, a velocità di 120°/s. ...
... I nostri risultati, riguardanti l'estensione isocinetica del ginocchio e la forza muscolare di flessione a 60°/s, sono stati più elevati rispetto a quelli d'individui sani e attivi, riportati in un altro studio 28 . In questo studio, tensioni inferiori dell'estensione del ginocchio e tensioni simili della flessione del ginocchio (dati non riportati) sono state rilevate ad una velocità di 120°/s in confronto a quanto riportato da Aagaard et al. 3 Abbiamo confrontato i valori non normalizzati con quello studio poiché Aagaard et al. 3 hanno riportato valori non normalizzati; comunque, l'utilizzo di dati non normalizzati può causare una variabilità elevata nel caso in cui si confrontino individui con una notevole differenza di corporatura 28 ; pertanto sono necessari ulteriori studi per risalire ad alcuni concetti, inerenti alla forza muscolare dell'estensione del ginocchio dei velisti, a velocità di 120°/s. Uno studio ha riportato una forza di estensione volontaria massima del ginocchio dei velisti Laser (766 N) e 470 (751 N) 29 Aagaard et al. 3 reported non-normalized values; however, using non-normalized data may cause high variability when comparing subjects with a wide range of body sizes; 28 thus, further studies are required to obtain some idea of the knee extension muscle strength of sailors at a velocity of 120°/s. ...
BACKGROUND: Aerobic and anaerobic capacity, muscle strength and balance skills are important parameters in sailors. We aimed to investigate the aerobic and anaerobic capacity, knee muscle strength, hand grip strength and balance of elite Turkish sailors competing in 470 and Laser classes selected for the Olympic team and to establish the differences in physical fitness status between sailors competing in 470 and Laser classes. METHODS: Nine Laser and ten 470 sailors were evaluated. A treadmill VO2max test for aerobic capacity, a Wingate cycle ergometer test for anaerobic power and capacity, an isokinetic knee muscle strength assessment at 60°/s and 120°/s angular velocities (output data were flexor peak torque, extensor peak torque and H/Q strength ratio), an isometric hand grip strength assessment and a star excursion balance test (SEBT) were performed. RESULTS: Laser and 470 sailors showed similar physical fitness values and no difference was found between sailing classes (P>0.05) for all test results. Most of the sailors' H/Q strength ratios were lower than normal values. CONCLUSIONS: This study shows that the physical requirements of Laser and 470 sailors are similar; however, they are both at risk of knee injury because of low H/Q strength ratios. Athletic trainers and physiotherapists working with sailors should also consider the H/Q strength ratio because low values of H/Q strength ratio are seen in this population. The results of this study may constitute a basis for further studies because we have reported the results of several physical fitness tests together and in a detailed manner.
... 18 Each of these aspects can be assessed with an isokinetic dynamometer, which is the current gold standard or measurement, as it is not influenced by evaluator physical attributes and has excellent reliability for measuring torque. 12, 39 Isokinetic devices allow for the characterization of other strength parameters as well as the rate of force development (RFD), and they can be used at various speeds and under multiple contraction modes. 16,27 Isokinetic strength profiles have been published for the knee muscles across different healthy and injured populations. ...
... Knee Assessment Setup Participants were seated on the isokinetic dynamometer (Con-Trex MJ; CMV AG, Dübendorf, Switzerland) with the contralateral knee blocked at 90° of flexion using a static block and cross-chest straps to limit trunk movements (SUPPLEMENTAL FIGURE 1). 39 The ipsilateral thigh was secured with a wide strap and an anti-shear pad was used. The evaluator then placed a range of motion limit for the test to ensure that flexion and extension were performed through 90° of range of motion. ...
OBJECTIVE: To describe knee and shoulder strength characteristics across amateur sports and compare strength across sexes and sports groups.
METHODS: a total of 233 healthy athletes who were competing at national or international levels across 27 different sports (106 males and 127 females) participated in this study. Using a Con-TREX MJ system, we assessed peak and relative torque, and rate of force development (RFD200), in knee and shoulder joint muscles. Differences between sexes were assessed using Student t-tests and Cohen’s d for effect sizes; nonparametric MANOVA compared sports groups. Spearman rank correlations were used to compare average peak torque and RFD200.
RESULTS: Male athletes had greater peak and relative torques than female athletes (p <0.02, d=0.33 to 1.87). Significant differences across torque variables were also observed between combat, team, precision/skill and speed/strength sport groups for the knee (p <0.01, R2=0.15) and the shoulder (p <0.01, R2=0.03) measurements. Mean peak torque and RFD200 were highly correlated for knee flexion and extension (r=0.95 and 0.97, respectively), and for shoulder external and internal rotation (r=0.95 and 0.99, respectively).
CONCLUSIONS: There were sex and group differences in knee flexion and extension and shoulder internal and external rotation. Male participants were stronger, and athletes from the speed/strength groups showed the greatest values for knee strength whereas combat sport athletes demonstrated the greatest shoulder rotation strength.
... Isokinetic dynamometry tests have been widely used and are the most common tools to assess Quadriceps and Hamstring muscle strength both in professional athletic. Isokinetic testing also provides the essential information about the Hamstring to Quadriceps ratio (H/Q) and limb asymmetry index (LSI) which can be Health, sport, rehabilitation Здоров'я, спорт, реабілітація Здоровье, спорт, реабилитация 7(4) used for evaluating lower limb muscle strength and imbalance between the muscles of the lower limb [14,15,16,17]. ...
... Gravitational force correction was Health, sport, rehabilitation Здоров'я, спорт, реабілітація Здоровье, спорт, реабилитация 7(4) performed in order not to help the flexors, that is, to make the activity of the extensor muscles more difficult when performing movements in the knee joint. Measure of the hamstrings to quadriceps ratio (H / Q ratio), calculated as the peak torque of the hamstrings divided by the peak torque of the quadriceps within the same limb (1) [16]: ...
Purpose: The aim of the study was to determine the differences between football players and basketball players in the mean absolute values of maximum torque flexors and extensors, the ratio of maximum hamstring torque to maximum quadriceps torque dominant (DOM) non-dominant (ND) leg, and differences in the bilateral imbalance of
flexor muscles and knee extensors.
Material and methods: The research included a sample of 39 professional athletes. The first subsample included 19 professional basketball players while the second subsample included 20 professional soccer players.
Results: Based on the results of the torques of the extensors in the knee joint of the DOM and ND legs, it was established that there is no statistically significant difference between basketball players and football players. However, a statistically significant difference was found in the torque flexors of the knee joint DOM (p≤0.01) and ND (p≤0.00) of the leg between basketball players and football players. On the other hand, the results of
the research indicate that the difference between basketball players and football players in the ratio of Hamstrings peak torque to Quadriceps peak torque was recorded only in the ND leg (p≤0.02), while the difference in the DOM leg is not statistically significant. The results of our study indicate that basketball players have a higher percentage of imbalances compared to football players, especially in m. hamstrings.
Conclusion: This study provides normative data on populations specific to soccer and basketball, but does not provide evidence of the ability of the isokinetic assessment of lower extremity muscle strength to predict injuries to football players and basketball players.
... The level of maximal strength capacities of the hamstring and quadriceps muscles is one of the crucial factors that should be considered prior returning to play [2]. Specifically, several studies have reported that the ratio between hamstring and quadriceps strength levels (i.e., H/Q ratio) of the injured leg should reach similar values as in non-injured leg [23], [38]. The H/Q ratio have been used for decades for monitoring knee joint stability, and it has been also considered as an important tool for evaluating lower extremity injury risk and rehabilitation process [34]. ...
... The LSI refers to the difference in the performance and mechanical outputs between two legs, while low LSI can affect jumping performance, ability to quickly change direction, provoke injuries [5]. Therefore, besides calculating H/Q ratios physicians and coaches usually also consider the differences in mechanical outputs of both injured and non-injured leg (i.e., LSI) when deciding of an appropriate time for their athletes to retake full training process [1], [13], [38]. ...
Purpose:
The aim of this study was to explore the strength capacities of the injured and non-injured leg following a unilateral anterior cruciate ligament reconstruction.
Methods:
Eight elite soccer players (age = 25.5 ± 3.9 years; height = 1.83 ± 0.04 m; body mass = 78.9 ± 4.5 kg) volunteered to participate in this study. Nine months after the anterior cruciate ligament reconstruction and just before initiating the full training process, the maximal peak torque of the quadriceps and hamstring muscles were measured at 60 and 180 degrees/ second using isokinetic dynamometry. Obtained peak torques were used for calculating hamstring-to-quadriceps ratio, limb symmetry index, and to estimate maximal torque capacity using a two-velocity method (i.e., linear torque-velocity relationship modeled considering peak torque obtained at 60 and 180 degrees/second).
Results:
No differences were found between hamstring-to- -quadriceps ratios of the injured and non-injured leg ( p = 0.165), nor between limb symmetry index of the quadriceps and hamstring muscles ( p = 0.985), regardless of the angular velocity applied during tests. The two-point method revealed significant differences between quadriceps and hamstring muscle groups both in the injured and non-injured leg ( p < 0.001; maximal estimated torque was higher for quadriceps compared to hamstring muscles), while the differences between same muscle groups of the different legs were not significant.
Conclusions:
Collectively, these findings indicate that 9 months were enough for reaching a certain strength level of the injured leg that permits a safe return to play.
... Dynamometers are extensively used to assess the function of muscular strength and are widely regarded 23 as the "gold standard" in the examination of concen-24 tric and eccentric actions, providing researchers with 25 a wide-range of valid parameters [6]. A proper func-26 tional hamstring-to-quadriceps strength ratio may be 27 essential for sport performance [48] and may have a 28 significant impact on the injury [2,9,16]. When assess- often calculated in order to determine a possible risk 33 for injuries [1]. ...
... These results are in 239 agreement with other studies which find the correla-240 tion between strength imbalance between their ham-241 strings and quadriceps and injury risk [8]. The data 242 obtained are broadly consistent with the previous ev-243 idence that points out a proper functional hamstring-244 to-quadriceps strength ratio may be essential for sport 245 performance [48]. We have observed that differences in 246 functional hamstring-to-quadriceps strength ratio are 247 significant and athletes with higher degree of LBP have 248 had lower results. ...
Correspondence: [*] Corresponding author: Dragan Marinkovic, Faculty of Sport and Physical Education, University of Novi Sad, Lovćenska 16 21000 Novi Sad, Serbia. Tel.:+381 21 450 188; Fax: +381 21 450 199; E-mail: marinkovic@uns.ac.rs.
Abstract: BACKGROUND: Soccer as a sport has a very high injury rate and low back pain (LBP) is considered to be the most common overuse injury typically occurring in the back and spine in elite soccer players. OBJECTIVE:This study aimed to investigate differences in knee muscle strength and muscle imbalances in soccer players according to lower back pain. METHODS: One hundred and thirty-six male professional soccer players (20.49 ± 3.73 years, 76.57 ± 8.24 kg, 182.63 ± 6.73 cm) volunteered for the study. The isokinetic dynamometer PrimaDOC (EASYTECH, Italy) was used to assess the hamstring and quadriceps strength at the selected speeds of 60∘/s, whereas the Roland-Morris Disability Questionnaire (RDQ) was used as a health status measure to assess physical disability caused by low back pain. RESULTS: A univariate analysis of variance has shown that there is a statistically significant difference among the groups divided into Absolut peak torque right knee flexors, Absolut peak torque left knee flexors, Ratio between hamstrings and quadriceps strength right leg, Ratio between hamstrings and quadriceps strength left leg based on the RDQ scores. On the other hand, no other significant differences among the groups were found in other parameters CONCLUSION: The current study indicates that knee muscle strength variables, resulting from an isokinetic testing, have the potential to discriminate between soccer players with and without a history of low back pain. However, low back pain is a multidimensional phenomenon and knee muscle strength or imbalance alone cannot be expected to explain low back pain.
Keywords: Soccer, assessment, differences, muscle imbalances
... However, at low speeds (i.e., 0-180°s −1 ) peak force reflected pure muscle strength, while neuromuscular control comes into play at higher speeds (>180°s −1 ). 17 In consequence, to evaluate muscle strength, the isokinetic tests were performed at angular speeds of 180°s −1 and 240°s −1 . Participants adopted a seated position with the hips flexed at 90°. ...
... Moreover, knee total work at low speeds such as 180°s −1 reflects pure muscle strength, while neuromuscular control comes into play at higher speeds (>180°s −1 ). 17 This evidence supports the assertion that total work is a good indicator of functional joint capacity. Despite the relevance of this isokinetic measurement, total work is not usually evaluated in population studies assessing knee OA, it being therefore difficult to compare our results with those from other authors. ...
Purpose:
To determine the effects of the intake of low-fat yoghurt supplemented with rooster comb extract (RCE) on muscle strength.
Methods and results:
148 subjects, with mild knee pain, participated in a randomized, placebo-controlled, double-blind, and parallel study. Muscle strength, knee effusion, and pain perception were measured. C2C12 myoblasts were used to elucidate the mechanisms of action involved. RCE improved total work and mean power in men, and also peak torque in extension by 10%. RCE reduced synovial effusion by 11.8% and pain perception by 24.6%. Both RCE and HA increased myoblast proliferation by 29%, while RCE reduced myoblast differentiation by 36.2%, suggesting a beneficial role of RCE in muscle regeneration.
Conclusions:
Low-fat yoghurt supplemented with RCE improved muscle strength. This effect is partially explained by muscle regeneration enhancement, reduced synovial effusion, and reduced pain perception, which could exert a beneficial clinical impact on men affected by mild knee pain.
... Reliable assessment of muscle strength is important in youth football players from a high-level Academy as it can provide objective data which can be used to identify strength deficits or asymmetries as well as muscle strength changes over time. (Willigenburg et al., 2014). Injuries among youth players can include many long-term deleterious outcomes such as complete cessation of sport participation, physical disability, premature onset of degenerative conditions, lost opportunities to succeed in football, as well as potential negative psychological manifestations (Gabbett et al., 2014, Whittaker et al., 2015. ...
... It has been suggested that a number of knee muscle strength characteristics can predispose a player to a greater risk of injury; including a H/Q ratio less than 0.60 and muscle strength asymmetries between limbs (Navarro et al., 2015, Willigenburg et al., 2014, Daneshjoo et al., 2013, Fousekis et al., 2010a. However, this 'normative' H/Q ratio of 0.60 was suggested using muscle strength data derived from isokinetic dynamometry with the testing methodology (including speed and type of muscle contraction) often varying between studies (Navarro et al., 2015, Coombs andGarbutt, 2002). ...
The objective of this study was to investigate knee muscle strength characteristics in players from a high-level youth football Academy. In total, 110 players (aged 8-15 years) underwent muscle strength assessments carried out by a research physiotherapist using a computer-linked hand-held dynamometer. Results indicated that isometric hamstrings and quadriceps strength increased with age, whereas the isometric hamstring to quadriceps (H/Q) ratio decreased with age. A number of youth football players (n=20; 18%; 95% CI: 11-27%) demonstrated isometric H/Q ratios of less than 0.60, as well as muscle strength asymmetries between limbs for the hamstrings (n=40, 36%; 95% CI: 27-46%) and quadriceps (n=51, 46%; 95% CI 37-56%), potentially increasing injury risk. This study provides new evidence that the isometric H/Q ratio reduces with advancing age during adolescence which may have important implications for junior athlete development and long-term injury prevention in football.
... With respect to the kinetic factors, an increased risk of ACL injury was assessed as an increase in the knee abduction moment [10] and anterior tibial shear [91] and increases in vertical ground reaction force [10]. We assessed quadriceps and hamstring strength and activation variables as increasing the risk of ACL injury post-fatigue if the quadriceps to hamstring ratios decreased (i.e., indicating a larger contribution of the quadriceps post-fatigue) [92][93][94]. Finally, the primary variable that was included in the "other category" was related to measures of proprioception. ...
Background/Objectives: One potential risk factor that remains especially contentious in the anterior cruciate ligament (ACL) injury literature is the role of neuromuscular fatigue in ACL injury risk. Therefore, the purposes of this review are (i) to present the research and practical concepts of lower extremity neuromuscular fatigue; and (ii) to review the literature relating to neuromuscular fatigue as an ACL injury risk factor and mechanism. Methods: A structured review was performed in the Medline database using a search strategy that included terms such as “anterior cruciate ligament injury” and “knee injuries” combined with terms such as “injury” and “fatigue”. Articles were included if they included young healthy participants (18–35) and made a comparison between non-fatigued and fatigued states that were assessed with at least one lower extremity biomechanical variable associated with ACL injury risk. Results: Overall, there were 67 studies included, accounting for 1440 participants (627 male and 813 female) across a variety of sports and activities. Of these, 53 (79%) reported a post-fatigue change in the kinematics, kinetics, neuromuscular, and/or other (e.g., proprioceptive) outcomes that indicate that the participants would be at an increased risk of an ACL injury. The most common argument against fatigue as a risk factor is that ACL injuries do not tend to occur later in a game or season, when it is assumed that athletes would be most fatigued. Conclusions: The evidence presented in this review suggests that localized neuromuscular fatigue is a risk factor, among multiple factors, for ACL injuries, providing another modifiable risk factor that should be considered when developing ACL injury risk reduction interventions.
... In concentric isokinetic test, muscular peak torque is assessed in the muscle shortening phase; whereas eccentric analyses estimate this parameter during muscle lengthening [4]. Concentric tests are typically preferred because they are easier to perform and carry a lower risk of injury [5]. ...
Purpose The aims of the study were: comparing the strength of the thigh muscles at 30°/s and 60°/s, comparing the hamstring to quadriceps ratio (H/Q) resulting from the two movement velocities, and calculating an optimum cut-off for H/Q at 30°/s. Methods The study was conducted on 29 healthy non-professional athletes aged from 20 to 30. Both legs of the participants were assessed at angular velocities of 30°/s and 60°/s. Participants underwent a three-phase protocol: 3-minute warm-up on an elliptical machine, 30-second of whole-body vibration and isokinetic test using Technogym’s REV 7000 dynamometer. Maximum concentric torques and H/Q were measured at 30°/s and then at 60°/s, with five repetitions per leg and a 60-second rest between phases. Results At 30°/s, quadriceps and hamstring forces were higher compared to 60°/s, but there was no significant difference in the resulting H/Q. We found a positive correlation between the H/Q ratios at the two speeds (R = 0.796, p < 0.001). Age, sex, BMI, dominant leg, or activity level didn’t influence this ratio at 30°/s and at 60°/s. Receiver Operating Characteristic (ROC) models and agreement tests suggested an optimal cut-off value of 0.57 at 30°/s. Conclusions Operating at the 30°/s velocity generates higher peak torques, while it maintains H/Q comparable to that obtained at the 60°/s velocity. This lower speed may make the isokinetic test more feasible during rehabilitation after ACL-R surgery, especially for patients who struggle with a 60°/s test. However, when using 30°/s, the conventional H/Q cut-off should be set at 0.57.
... The results obtained from these studies indicate that these methods did not improve muscle strength in different populations. Since the knee flexor and extensor muscles are the most important muscle groups that determine the physical performance of athletes among the major muscle groups in the lower extremities, these muscles were focused on in the present study (Willigenburg et al., 2014). The results of the study showed that both VFR and FR improved the dominant extremity knee flexor, non-dominant extremity knee flexor and extensor muscle strength. ...
... In high angular velocity, none of the groups presented ratio imbalances according to Baroni et al. (33). The use of isokinetic dynamometry provides substantial information about the torque profile as asymmetries between limbs or the torque relationship of antagonist muscles, such as conventional H:Q ratio (9,(37)(38). The relative strength difference between limbs is known as "inter-limb strength asymmetry" (39), and the size of those asymmetries may provide useful information about injury risk and performance (19,37). ...
... Athletes with an abnormal Q-angle can stabilize the knee joint by strengthening and stretching the muscles around the knee [68,69]. The quadriceps muscles, comprising the rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius, are crucial for knee stability and function [70,71]. Thus, quadriceps muscle strength is required for a variety of athletic activities, including running, jumping, cutting movements, and landing movements [72,73]. ...
The quadriceps angle, knowns as the Q-angle, is an anatomical feature of the human body that is still largely unknown and unstudied despite its initial discovery in the 1950s. The strength disparities between male and female athletes are largely determined by the Q-angle. In spite of a growing number of women participating in sports such as track, tennis, soccer, gymnastics, basketball, volleyball, swimming, and softball, studies investigating injuries in this group are scanty. Even though the Q-angle has been the subject of many studies carried out all over the world, a review of the literature regarding its effects on health and injury risk in female athletes has not yet been completed. The aim of this review is to examine the crucial role of the Q-angle in the biomechanics of the knee joint and its effect on performance and injury risk, particularly in female athletes. Furthermore, we highlight the greater likelihood of knee-related injuries seen in female athletes being caused by the Q-angle. Athletes, coaches, healthcare professionals, and athletic trainers can better comprehend and prepare for the benefits and drawbacks resulting from the Q-angle by familiarizing themselves with the research presented in this review.
... The H:Q ratio has conventionally been calculated as maximal knee flexion strength divided by maximal knee extension strength obtained at a given knee angular velocity and contraction mode (isometric, concentric, eccentric) (Willigenburg, 2014). It is well known that chronic forceful muscular contractions will result in an increase in muscle contractile protein and fiber area. ...
... As in every sport branch, it is known that in soccer, it is extremely important to have flexible, balanced and strong muscle basic strength levels in the lower extremities in terms of optimal performance and injury prevention. Because Hamstrings and Quadriceps muscle groups, which are among the lower extremity muscle groups, play an important role in acceleration, deceleration, jumping, falling from the air to the ground and other physical activities (Willigenburg et al., 2015). The quadriceps femoris, the only extensor muscle of the knee joint, plays an important role in performing dynamic movements in the lower extremity. ...
The aim of this study was to investigate the relationship between lower extremity flexibility values and vertical jump performance of elite soccer players. Twenty-six young elite male soccer players voluntarily participated in the study. Age, height, and weight of the participants were determined as descriptive statistics. Lower extremity flexibility (.=ROM) test and vertical jump (counter movement jump=CMJ) performance determination test were applied to the participants. A goniometer was used for lower extremity flexibility measurement and My Jump 2 application, which has proven its validity and reliability, was used for CMJ performances. Descriptive characteristics of the participants included in the study were mean age: 16.23 ±.51 years, height: 172.96 ±7.56 cm, body weight: 63,15±7,69 kg. The mean values of CMJ performance of the participants were: 37,54±5,51; the mean value of lower extremity flexibility angles (ROM) was 115±4,99°. According to the data obtained, a statistically significant relationship was observed between ROM and CMJ performance characteristics of elite soccer players (p=.008) (p<0.05). According to the results obtained, a significant relationship was found between ROM and CMJ performances of soccer players. It can be said that teaching the importance of flexibility exercises to soccer players in soccer training programs and including them in training programs will positively affect the sudden power output performances of soccer players such as jumping.
... When the literature was examined, Willigenburg and Hewet (2017) did not find any statistically significant relationship between FMS scores and knee strength in their study on university football players. In a different study conducted by Willigenburg et al. (2014), no statistically significant relationship was found between FMS tests and knee strength of NCAA Division I football players. In another study, İbiş et al. (2023) investigated the relationship between functional movement scores and hamstring muscle strength in professional football players and found that there was no significant relationship between FMS scores and hamstring muscle strength. ...
Objective of the Study: In football, one of the branches with a large audience in the world, it is thought that ever-increasing performance, the strengthening of competition and the desire to succeed as well as technical-tactical, psychological, and psychological needs and the improvement of physical and physiological characteristics at the most appropriate level will contribute positively to the performance of football players. Especially in football competitions, high-intensity actions may cause athletes to spend higher effort. Many qualities of football players should be improved to perform these actions at the most appropriate level and to protect them from injuries. For this purpose, the aim of this study is to investigate the relationship between FMS (Functional Movement Screen) scores and isokinetic lower body strength of football players. Method: The correlational survey model was preferred as the research model of the study. The sample group consisted of a total of 28 volunteer football players competing at the level of amateur league. The maximum strength of the knee extensor and flexor muscles of the participants was measured using an isokinetic dynamometer device (Cybex NORM®, Humac, CA, USA) that allows to record instantaneous isokinetic torque. The FMS test was applied to assess mobilisation and stabilisation of football players. SPSS 25.0 software was used for statistical analysis of the data and Spearman's correlation analysis was used to compare the relationship between isokinetic lower body strength and FMS scores. Findings: When the FMS scores and right and left knee flexion/extension degrees were analysed, no statistically significant correlation was found between the parameters. Conclusion: The results of the statistical analysis revealed no correlation between FMS scores and right-left knee flexion and extension parameters of the amateur football players. Accordingly, it is suggested to include FMS applications in the training programmes of the football players and contribute to their performance by minimising their injuries and providing neuromuscular coordination and thus to make contribution to the related literature and to guide future studies.
... CBA was calculated as the ratio between the peak torque (Nm) of the extensors of the KL and SL in percent, using the formula ((PT of the stronger leg -PT of the weaker leg)/ PT of the stronger leg) *100 (Lockie et al., 2012). Unilateral, flexor/extensor strength asymmetry was calculated as H/Q ratio (percent) according to the formula of Willigenburg et al. (2014): (Hamstring peak torque / Quadriceps peak torque) *100. ...
Football players experience increased risks of lower limb injuries, particularly hamstring strains and knee ligament damage, often attributed to muscle imbalances. This study aimed to conduct a detailed isokinetic assessment of the knee joint, focusing on both kicking and supporting legs, involving 24 football players from the university football team of SWU "Neofit Rilski". The objective was to monitor the physiological and biomechanical characteristics of the thigh musculature. Isokinetic measurements of knee joint extensors (quadriceps) and flexors (hamstrings) strength were conducted bilaterally at angular velocities of 60, 180, and 300 °/s A comparative analysis included traditional parameters-peak torque (PT, Nm), average power (AP, W) and total work (TW, J)-together with additional parameters such as time to peak torque (TPT) and acceleration time (AcT). Conventional H/Q ratios were used for quadriceps and hamstring strength balance evaluation, and potential side-to-side strength deficits were calculated. Results indicated that the kicking leg (KL) demonstrated significant strength superiority (Wilcoxon, p < 0.05) compared to the supporting leg (SL). PT values in both antagonist groups were reduced when compared to those in other studies. Additionally, at low speeds (60 °/s), the time to PT was significantly prolonged, distinguishing these football players from their professional counterparts. Differences in time parameters, work capacity, and power at moderate velocity-180 o/s, were observed in both muscles' groups, with the SL having lower values compared to the KL. At 60o/s and 300o/s the extensors of the SL had a longer time to reach AcT and TPT and a more reduced AP than the KL. The TW of Q and H is greater in the KL compared to the SL. The H/Q ratios between KL and SL, at all three measured speeds, fell below normal balance values, with nearly 75% of players exhibiting unilateral asymmetry in the KL and approximately 85% in the SL. This study provides evidence that a comprehensive isokinetic assessment, considering both traditional and additional parameters, is beneficial for university footballers. The findings revealed potential risks and susceptibility to noncontact knee injuries, offering valuable insights for the development of targeted training and therapy programmes.
... The H:Q ratio has conventionally been calculated as maximal knee flexion strength divided by maximal knee extension strength obtained at a given knee angular velocity and contraction mode (isometric, concentric, eccentric) (Willigenburg, 2014). It is well known that chronic forceful muscular contractions will result in an increase in muscle contractile protein and fiber area. ...
Introduction: Strength of the quadriceps and hamstring of a person is determined by individual gender, age and individuals physical activity. There seems to be a difference in strength of quadriceps and hamstring in male and female but no study has been done to study the same. Hence this study Aims to find out the difference between strength of quadriceps and hamstring Muscle among college students. Methodology: 120 Individuals both male and female between the age group of 18-25 who actively consented to participate and had no history of disease or difficulty with walking or musculoskeletal disorder were taken from Padmashree Institute of Physiotherapy. Quadriceps and Hamstring strength was measured by using FET2 dynamometer. Results: The demographic characteristics were tabulated and the difference between the strength of male and female in hamstrings and quadriceps muscles were calculated in the form of Mean ±SD. Conclusion: From our study we conclude that quadriceps strength was higher than hamstring strength. Also while considering the gender males were seen to have higher quadriceps and hamstring strength compared to female. This could have been because men has more of type II muscle fibers while women has more of type I muscle fibers.
... Anterior and posterior thigh musculature imbalances have previously been quantified using a Hamstring:Quadriceps strength ratio (Aagard et al., 1998;Holcomb et al., 2007) defined as the ratio between peak concentric torque (PT) of hamstring and quadriceps. The functional strength ratio more appropriately considers the eccentric hamstring:concentric quadrideps strength ratio (Willigenburg et al., 2018), with a value closer to 1.0 considered to reduce the risk of hamstring injury (Holcomb et al., 2007;Orchard et al., 1997), but is also quantified using PT. The traditional use of peak torques and control ratios has more recently been usurped by a broader consideration of the strength curve, including angle-specific torque and functional range (Eustace et al., 2017). ...
Isokinetic dynamometry represents the clinical gold standard for strength assessment but testing lack consensus. Elite youth male football players (n = 28) completed 20 repetitions (analysed as four epochs) of eccentric knee flexor (eccKF) and concentric knee extensor (conKE) trials at 60, 180 and 270°∙s⁻¹, quantifying peak torque (PT) and functional range (FR). There was a significant (P < 0.001) main effect for fatigue and angular velocity in conKE PT; eccKF PT was not significant across epoch (P = 0.35) and velocity (P = 0.12) and a velocity x epoch interaction highlighted more repetitions were required to elicit fatigue as velocity increased. FR decreased with fatigue (P < 0.001) and velocity (P < 0.01) in conKE and eccKF, indicative of a narrowing of the strength curve. Clinical interpretation advocates an isokinetic test comprising at least 15 reps at a velocity ≥ 180°∙s⁻¹ and analysis beyond the peak of the strength curve (PT) to inform clinical reasoning and individualized exercise prescription.
... In our study, it has been found that the increase in angular velocity, increases the number of repetitions. While, the peak torque value basically reflects pure muscle strength at low angular velocities, neuromuscular control plays a more active role at high angular velocities (Willigenburg et al., 2014). This is also consisted with the negative relationship between the velocity of contraction and muscle strength (McArdle et al., 2010). ...
Introduction
This study aims to develop a standard number of repetition at angular velocities of 60º/sec and 180º/sec and define the difference of number of repetitions between genders.
Method
One hundred ninety-six athletes (judo, volleyball, Greco-Roman wrestling, runners, and gymnastics) were involved. Concentric-concentric isokinetic muscle strength of the knee flexor-extensor muscles of the athletes were performed with an ISOMED 2000 isokinetic dynamometer. The evaluation test protocol consisted of 10 repetition of knee flexion-extension at 60º/sec and 30 repetitions at 180º/sec.
Results
Athletes performed with maximal knee flexion strength at their second and third trial at 60º/sec and third-forth trial at 180º/sec. It was found that 2 repetitions and 2-3 repetitions were needed for knee extension peak torque at 60º/sec and 180º/sec respectively. The difference between the genders was significant at 60º/sec for knee flexion and extension on the dominant side; at 180º/sec for knee extension on the dominant and non-dominant side. It was determined that 3 repetitions for 60º/sec, 4 repetitions for 180º/sec were enough to determine peak torque values.
Discussion
Optimal number of repetitions is crucial so that athletes could have the opportunity to reach maximal strength without unnecessary workload or waste of time. Conclusions: Protocols involving 3 repetitions for 60º/sec, 4 repetitions for 180º/sec were enough to determine peak torque values. Gender of athletes should be considered when establishing isokinetic knee evaluation protocols.
... Concentric and eccentric quadriceps strength was assessed bilaterally using a isokinetic knee protocol at a low (60°/s) and high speed (120°/s) as per previous research. 21 Individuals were given three practice trials before each condition and for each leg assessed. The testing procedure consisted of five repetitions at each of the given speeds with at least 1 minute of rest between trials. ...
Introduction
To determine whether individuals with a history of anterior cruciate ligament reconstruction (ALCR) exhibit altered neuromotor function compared to healthy controls. It was hypothesized that the ACLR group would have slower postural responses compared to healthy individuals of similar age.
Materials and Methods
Sixteen adults with a unilateral ACLR and 16 matched healthy controls participated. General assessments of neuromotor function were gathered and included measures of reaction time (both seated and postural conditions), walking ability, balance, ankle ROM, proprioception, knee joint laxity, patellar tendon reflex latency, and quadriceps strength. Data were analyzed using mixed generalized linear models with between‐subject (i.e., controls, ACLR) and within‐subject factors (i.e., affected, unaffected limb).
Results
Individuals with an ACLR exhibited a significant slowing of their postural reaction times compared to the control individuals. The ACLR group was slower under both the simple (ACLR: 484±6.17 ms, control: 399±1.95 ms) and choice reaction time conditions (ACLR: 550±43 ms, control: 445±43 ms). No other group differences were found in any of the other measures.
Conclusion
Overall, ACLR individuals had a reduced ability to respond quickly under more challenging postural conditions (i.e., stepping response). This finding would indicate that the impact of an ACLR is not purely mechanical and restricted to the joint. Rather, injury and reconstruction of the ACL impacts neural mechanisms, altering individuals’ ability to respond under challenging balance tasks.
... Es sollte nicht vergessen werden, dass, unabhängig von einem ausgewogenen Hamstrings/Quadriceps-Verhältnis, ein gutes generelles Grundkraftniveau des Quadriceps vonnöten ist, um Belastungen beim Abbremsen und plötzlichen Richtungswechseln sowie beim Landen nach Sprüngen problemlos abfangen zu können. Als Anhaltspunkt können hier Untersuchungen von Willigenburg et al. (2015) angeführt werden. Sie konnten bei gesunden aktiven Frauen eine durchschnittliche relative isokinetische Maximalkraft von 2.4 Nm/kg für den Quadriceps (beidseits) nachweisen. ...
Vor dem theoretischen Hintergrund, dass die große Gruppe der biomechanischen und neuromuskulären Risikofaktoren als modifizierbar gilt, stellt sich die Frage, ob die VKB-Verletzung bzw. das Rupturrisiko durch spezifisches Training tatsächlich verhindert werden kann. Die alarmierenden VKB-Verletzungsraten, insbesondere im Frauensport haben dazu geführt, dass eine Vielzahl verschiedener Präventionsprogramme entwickelt wurde, deren verletzungsprophylaktische Wirkung entweder anhand der tatsächlichen Verletzungshäufigkeit der Athleten/innen oder über die Auswirkung auf die beschriebenen biomechanischen und neuromuskulären Risikofaktoren untersucht wird.
... Es sollte nicht vergessen werden, dass, unabhängig von einem ausgewogenen Hamstrings/Quadriceps-Verhältnis, ein gutes generelles Grundkraftniveau des Quadriceps vonnöten ist, um Belastungen beim Abbremsen und plötzlichen Richtungswechseln sowie beim Landen nach Sprüngen problemlos abfangen zu können. Als Anhaltspunkt können hier Untersuchungen von Willigenburg et al. (2015) angeführt werden. Sie konnten bei gesunden aktiven Frauen eine durchschnittliche relative isokinetische Maximalkraft von 2.4 Nm/kg für den Quadriceps (beidseits) nachweisen. ...
Wie kann man das Risiko einer VKB-Verletzung im weiblichen Leistungshandball bestmöglich reduzieren? Sabrina Erdrichs Studie zeigt: Der innovative modifizierte Heidelberger Sprungkoordinationstest ist geeignet, Trainingseffekte auf biomechanische Risikofaktoren von VKB-Verletzungen zu überprüfen. Die Analyse der Gruppeneffekte ergab eine Überlegenheit des progressiv funktionellen Koordinationstrainingskonzepts gegenüber dem gerätegestützten Hypertrophietraining. Dies zeigt sich in einer verbesserten Rotationsstabilität bei unerwarteten Einbeinlandungen. Fragebögen zu Bewegungsangst sollten stärker in den Fokus VKB-verletzungspräventiver Forschung rücken. Sie haben möglicherweise großes Potential, Risiko-Athletinnen im Vorfeld zu identifizieren.
Der Inhalt
• Zur Wirksamkeit aktueller verletzungspräventiver Trainingsprogramme
• Komplexe Messsysteme/Testverfahren zur Erfassung der biomechanischen Bewegungskontrolle
• Interventionseffekte: Kraft- vs. Koordinationstraining
• Einzelfalldarstellung einer „Risiko-Athletin“
• Bewegungsangst und biomechanische Bewegungspräsentation
Die Zielgruppen
• Dozierende und Studierende der Sportwissenschaft, Sportmedizin, Physiotherapie
• Trainer, Ärzte, Physiotherapeuten, Athleten
Die Autorin
Sabrina Erdrich hat am ISSW der Universität Heidelberg geforscht und gelehrt. Sie arbeitet heute überwiegend im Nachwuchsleistungssport als Sportwissenschaftlerin, Trainerin und Referentin mit den Schwerpunkten Verletzungsprävention, Return to Sports und Leistungsoptimierung.
... The knee flexion angle was set to 25 to be consistent with the knee orientation at initial contact (IC) in young athletes landing from a drop height of 31 cm. 4 Pneumatic pistons (CG5LN40SV-100 and CG5LN50SV-100; SMC) mounted on the mechanical impactor were affixed to the tendon clamps to apply 450-N pretension to the quadriceps tendon and 225-N pretension to both hamstring tendon groups throughout testing. The magnitude of muscle forces was based on a previous report of maximum isometric voluntary contractions, and the force ratio between the quadriceps and hamstring muscles was kept at 1:1. 6 Furthermore, Willigenburg et al 35 reported peak healthy quadriceps torque in female athletes to be approximately 155 NÁm. As 30 to 35 cm is a common range for tibial length on a dynamometer, the estimated force to generate this torque would be calculated as around 442 to 517 N. Similarly, peak hamstring torque was approximately 77 NÁm, which would have estimated a generating force of around 220 to 256 N. ...
Background
A recently developed mechanical impact simulator induced an anterior cruciate ligament (ACL) rupture via the application of a combination of inverse dynamics–based knee abduction moment (KAM), anterior tibial shear force (ATS), and internal tibial rotation moment with impulsive compression in a cohort of cadaveric limbs. However, there remains an opportunity to further define the interaction of internal forces and moments at the knee and their respective influence on injury events.
Purpose
To identify the influence of internal knee loads on an ACL injury event using a cadaveric impact simulator.
Study Design
Controlled laboratory study.
Methods
Drop-landing simulations were performed and analyzed on 30 fresh-frozen cadaveric knees with a validated mechanical impact simulator. Internal forces and moments at the knee joint center were calculated using data from a 6-axis load cell recorded on the femur during testing. Kinetic data from a total of 1083 trials that included 30 ACL injury trials were used as inputs for principal component (PC) analysis to identify the most critical features of loading waveforms. Logistic regression analysis with a stepwise selection was used to select the PCs that predicted an ACL injury. Injurious waveforms were reconstructed with selected PCs in logistic regression analysis.
Results
A total of 3 PCs were selected in logistic regression analysis that developed a significant model ( P < .001). The external loading of KAM was highly correlated with PC1 (ρ < –0.8; P < .001), which explained the majority (>69%) of the injurious waveforms reconstructed with the 3 selected PCs. The injurious waveforms demonstrated a larger internal knee adduction moment and lateral tibial force. After the ACL was ruptured, decreased posterior tibial force was observed in injury trials.
Conclusion
These findings give us a better understanding of ACL injury mechanisms using 6-axis kinetics from an in vitro simulator. An ACL rupture was correlated with an internal knee adduction moment (external KAM) and was augmented by ATS and lateral tibial force induced by an impact, which distorted the ACL insertion orientation.
Clinical Relevance
The ACL injury mechanism explained in this study may help target injury prevention programs to decrease injurious knee loading (KAM, ATS, and lateral tibial force) during landing tasks.
... Isokinetic dynamometry tests have been widely used and are the most common tools to assess Quadriceps and Hamstring muscle strength both in athletic and the non-athletic populations 8) . Isokinetic testing also provides the essential information about the Hamstring to Quadriceps ratio (H:Q) and limb asymmetry index (LSI) which can be used for evaluating lower limb muscle strength and imbalance between the muscles of the lower limb [9][10][11][12] . Although some researchers argued that LSI and H:Q are not good indicators of evaluating lower extremity performance and injury risk estimation factor [13][14][15] , there have been several studies reporting different results 8,11,12) . ...
Purpose] The present study aimed to investigate the lower limbs injury risk factors that are based on conventional Hamstring to Quadriceps ratio and limb asymmetry index in varsity American football players. [Par-ticipants and Methods] Twenty-six varsity American football players aged 19-27 years and with 2.31 ± 1.29 years of American football experience from Dogu Akdeniz University volunteered to undergo measurements of average peak torque for isokinetic flexion and extension of dominant limb and non-dominant limb at 60°·s −1 and 300°·s −1. Hamstring to Quadriceps ratio and limb asymmetry index were also calculated for Hamstring and Quadriceps muscles. [Results] Statistical analysis revealed that dominant Quadriceps is stronger than non-dominant Quadri-ceps at 60°·s −1 speed. No statistical difference was found between dominant and non-dominant Hamstring peak torque at 60°·s −1. Hamstring to Quadriceps ratio determined as normal both for 60°·s −1 and 300°·s −1 according to the currently reported cut off value (H:Q ratio >60). Hamstring and Quadriceps limb asymmetry index also determined as normal (cut off value for LSI 10%) at 60°·s −1. However, for both Hamstring and Quadriceps, side-to-side strength asymmetry at 300°·s −1 was observed. [Conclusion] To prevent possible lower limb injury and to increase performance, varsity American football players who are actively training and competing might consider taking strength asymmetry into account to tailor their strength training program accordingly.
... The participants started when the knee joint was in 90° flexion. Then, the movement of the dominant leg in the range of 90°-180° in the range of motion of the limbs was followed [12][13][14]. ...
Purpose
Polycystic ovary syndrome (PCOS) is the most common endocrine disorder of women of reproductive age. The aim of the current study was to assess muscle mechanical function in PCOS and its relationship with hormonal and metabolic features of the syndrome.
Methods
The study included 44 women with PCOS, all having clinical or biochemical hyperandrogenism, chronic oligo-anovulation and PCOM, and 32 age- and BMI-matched healthy women. Anthropometric, hormonal and biochemical measurements were performed. Muscle mechanical function including lower limb explosive strength and average power (AvP) was measured using isokinetic dynamometry, a valid and reliable instrument for measuring muscle strength.
Results
The mean age and BMI of the women with PCOS and controls were 21.8 ± 3.2 versus 22.8 ± 3 years and 26.1 ± 5.4 versus 25.5 ± 5.7 kg/m², respectively (p = NS for both). PCOS patients had higher androgen levels, whereas total and regional fat and lean body mass and insulin resistance parameters were similar between the groups. The peak muscle force output defined as the peak torque of knee extensor and flexor muscles was higher in normal weight women compared to overweight and obese (p < 0.05 for both) but did not differ in patients and controls. AvP determined by the time-averaged integrated area under the curve at 60°/s angular velocity was higher in the PCOS group for extension and flexion (50.3 ± 21.2 vs 42.1 ± 11.6 and 35.3 ± 27 vs 22.2 ± 11.1, respectively, p < 0.05 for both). These measurements were correlated with bioavailable testosterone (r = 0.29, p = 0.012, r = 0.36, p = 0.001, respectively).
Conclusion
Muscle mechanical function is altered in PCOS. Women with PCOS have increased average lower limb power that is associated with hyperandrogenism.
... As in every sports branch, it is known that the basic muscle strength of the lower extremities in the balanced and strong levels in the parkour sport is extremely important for optimal performance and prevention of the injuries. Hamstrings and Quadriceps muscle groups, which are the lower extremity muscle groups, play an important role in acceleration, deceleration, jumping, falling from height to ground and other physical activities (Willigenburg, McNally, & Hewett, 2015;Zorba, et al., 2010). The quadriceps femoris, the single extensor muscle of the knee joint, plays an important role in the dynamic movements of the lower extremity. ...
The parkour is a physical activity that contains special technique applications and requires a great number of jumps.The purpose of this study was to investigate the effects of 8-week strength training on the jump heights of thetraceurs (parkour practitioners). A total of 12 traceurs, including 6 individuals as the control group and 6 individualsas the strength group, were included in the study. The control group was provided with parkour training sessionstwice a week, and the other group provided with both strength and parkour training sessions twice a week. Eachparticipant's vertical jumps were recorded with the high-speed camera in the validated My Jump 2 application. Themean age of the traceurs control group was 19±.89 years, 173.67±4.63 cm, body mass 66.5±5.32 kg; experimentalgroup was 19.5±1.05 years, 175.83±8.86 cm, and body mass 67.67±7.20 kg. Also according to the results, it can besaid that a significant increase was observed in countermovement jump (CMJ) vertical jump heights (p=0.028) of thestudy group at the end of the 8-week strength trainings compared to the control group and that the strength trainingprovided a positive contribution to vertical jump heights. On the other hand, there was no significant difference(p=0.075) in the control group. At the same time, the CMJ height values of the participants who performed strengthtraining increased 4.97±0.09%. Learning of the vertical jump heights, which is an important parameter for successfulperformance in traceurs, can enable the coaches and athletes to prepare a better training program.
... There were two velocities involved which were 60°/s and 300°/s. Velocity at 60°/s was used to assess strength while velocity at 300°/s was used to assess power of the knee flexors and extensors (Willigenburg, McNally & Hewett, 2014). Results showed there were no statistically significant differences of knee PT/BW of the dominant and non-dominant leg at 60°/s and 300°/s (Table 5 and 6) at sagittal plane between collegiate and club groups. ...
This study was conducted to compare the futsal-specific skills and biomechanical characteristics of futsal female players at collegiate and club levels. Ten collegiate and ten club level female futsal players were voluntarily participated in the study. Four futsal-specific skills tests (i.e., Massey Futsal Shooting Test, Illinois Agility Test, 20m sprint test and Futsal Intermittent Endurance Test) and four lower limb biomechanical tests (i.e., Drop Vertical Jump, Counter Movement Jump, Star Excursion Balance Test and isokinetic strength and power at 60°/s and 300°/s of knee flexors and extensors) were completed by the participants. Anthropometric parameters such as body weight, standing height and body fat composition were collected. Independent T-test was used to to determine the mean differences across groups in all variables. Results showed that there were no statistically significant differences between both groups except for MFST (p value = 0.00). The shot speed for club group was statistically faster (52.16 km.h-1) than collegiate group (43.44 km.h-1). The duration to complete the shots for club group was statistically shorter (4.35s) than collegiate group (4.43s). More total scores were obtained by collegiate group (4.43 point) than club group (4.35 point). These results conclude that both groups had similar level of strength and power for the lower limb, except for shooting skill. Training should focus on strength development for hamstring and quadriceps muscles because these muscles may affect shooting speed in both collegiate and club players.
... In contrast to sprint fatigue, the decline in knee extensor strength and increases in knee flexor strength were positively associated with jump fatigue during simulated basketball activity. The significant influence of the knee extensors might be explained by the strong, concentric, contractile recruitment of this muscle group during the takeoff jumping phase (Willigenburg, McNally, & Hewett, 2014). The recruitment of the knee flexors may be related to their role in maintaining pelvic stability, aiding power transfer between hip and knee joints, controlling rotation and translation mechanisms, and assisting extension at the hip joint during jump tasks (Brughelli, Cronin, & Nosaka, 2010;Jacobs, Bobbert, & Van Ingen Schenau, 1996). ...
This study quantified lower-limb strength decrements and assessed the relationships between strength decrements and performance fatigue during simulated basketball. Ten adolescent, male basketball players completed a circuit-based, basketball simulation. Sprint and jump performance were assessed during each circuit, with knee flexion and extension peak concentric torques measured at baseline, half-time, and full-time. Decrement scores were calculated for all measures. Mean knee flexor strength decrement was significantly (P < 0.05) related to sprint fatigue in the first half (R = 0.65), with dominant knee flexor strength (R = 0.67) and dominant flexor:extensor strength ratio (R = 0.77) decrement significantly (P < 0.05) associated with sprint decrement across the entire game. Mean knee extensor strength (R = 0.71), dominant knee flexor strength (R = 0.80), non-dominant knee flexor strength (R = 0.75), mean knee flexor strength (R = 0.81), non-dominant flexor:extensor strength ratio (R = 0.71), and mean flexor:extensor strength ratio (R = 0.70) decrement measures significantly (P < 0.05) influenced jump fatigue during the entire game. Lower-limb strength decrements may exert an important influence on performance fatigue during basketball activity in adolescent, male players. Consequently, training plans should aim to mitigate lower-limb fatigue to optimise sprint and jump performance during game-play.
... In contrast to sprint fatigue, the decline in knee extensor strength and increases in knee flexor strength were positively associated with jump fatigue during simulated basketball activity. The significant influence of the knee extensors might be explained by the strong, concentric, contractile recruitment of this muscle group during the takeoff jumping phase (Willigenburg, McNally, & Hewett, 2014). The recruitment of the knee flexors may be related to their role in maintaining pelvic stability, aiding power transfer between hip and knee joints, controlling rotation and translation mechanisms, and assisting extension at the hip joint during jump tasks (Brughelli, Cronin, & Nosaka, 2010;Jacobs, Bobbert, & Van Ingen Schenau, 1996). ...
... Common quadriceps strength measures are peak knee extensor torque normalized to body weight or a quadriceps symmetry index. 54 The association of peak knee extensor torque or quadriceps symmetry index with singleleg hop performance is inconclusive. k Rate of torque development is another measure of quadriceps strength. ...
Background
Clinicians use the single-leg hop test to assess readiness for return to sports after knee injury. Few studies have reported the results of single-leg hop testing after meniscectomy. Additionally, the contributions of impairments in quadriceps strength and psychosocial factors to single-leg hop performance are unknown.
Purpose
To compare single-leg hop performance (distance and landing mechanics) between limbs and to examine the association of single-leg hop performance with quadriceps strength and psychosocial factors in patients with meniscectomy.
Study Design
Descriptive laboratory study.
Methods
A total of 22 subjects who underwent meniscectomy for traumatic meniscal tears received either standard rehabilitation alone or with additional quadriceps strengthening. Testing was conducted immediately postrehabilitation and at 1 year postsurgery. A single-leg hop test was performed bilaterally, and hop distance was used to create a hop symmetry index. Landing mechanics (peak knee flexion angle, knee extension moment, and peak vertical ground-reaction force) were analyzed with a motion-capture system and a force plate. An isokinetic dynamometer (60 deg/s) assessed knee extensor peak torque and rate of torque development (RTD0-200ms and RTD0–peak torque). Questionnaires assessed fear of reinjury (Tampa Scale for Kinesiophobia [TSK-11]) and self-efficacy (Knee Activity Self-Efficacy [KASE]).
Results
Rehabilitation groups did not significantly differ in single-leg hop performance; therefore, groups were combined for further analyses. The mean hop symmetry index was 88.6% and 98.9% at postrehabilitation and 1 year postsurgery, respectively. Compared with the nonsurgical limb, the surgical limb showed decreased peak knee flexion angle at postrehabilitation and decreased knee extension moment at 1 year postsurgery. The hop symmetry index was positively associated with peak torque, RTD0-200ms, and the KASE score at postrehabilitation. Moreover, at postrehabilitation, the peak knee flexion angle was positively associated with peak torque and RTD0-200ms, and the knee extension moment was positively associated with RTD0-200ms. At 1 year postsurgery, peak knee flexion angle and knee extension moment were both positively associated with peak torque, RTD0-200ms, and RTD0–peak torque.
Conclusion
Although the hop symmetry index could be considered satisfactory for returning to sports, asymmetries in landing mechanics still exist in the first year postmeniscectomy. Greater quadriceps strength was associated with greater single-leg hop distance and better landing mechanics at both postrehabilitation and 1 year postsurgery. Knee activity self-efficacy was the only psychosocial factor associated with single-leg hop performance and isolated to a positive association with single-leg hop distance at postrehabilitation.
Clinical Relevance
Rate of development is not typically measured in the clinic but can be an additional quadriceps measure to monitor for single-leg hop performance. Quadriceps strength and psychosocial factors appear to have separate influence on single-leg hop performance after meniscectomy, which has implications for developing appropriate interventions for optimal single-leg hop performance.
... A threshold for isometric quadriceps strength after ACLR has been recommended as >3.0 Nm/kg [23]. Although isokinetic strength was tested, the aforementioned threshold is almost identical to the 2.8 Nm/kg obtained during isokinetic tests in patients who were cleared to RTS after ACLR [42]. In addition, the hamstrings/quadriceps ratio was determined at 300°/s, as high knee flexion/extension angular velocities reveal significant gender differences, whereas low speeds do not [18]. ...
Purpose:
There is a lack of consensus regarding the appropriate criteria for releasing patients to return to sports (RTS) after anterior cruciate ligament reconstruction (ACLR). A test battery was developed to support decision-making.
Methods:
Twenty-eight patients (22 males and 6 females) with a mean age of 25.4 ± 8.2 years participated and were 6.5 ± 1.0 months post-ACLR. All patients followed the same rehabilitation protocol. The test battery used consisted of the following: isokinetic test, 3 hop tests and the jump-landing task assessed with the LESS. The isokinetic tests and single-leg hop tests were expressed as a LSI (involved limb/uninvolved limb × 100 %). In addition, patients filled out the IKDC and ACL-Return to Sport after Injury (ACL-RSI) scale. RTS criteria to pass were defined as a LSI > 90 % on isokinetic and hop tests, LESS < 5, ACL-RSI > 56 and a IKDC within 15th percentile of healthy subjects.
Results:
Two out of 28 patients passed all criteria of the test protocol. The pass criterion for the LESS < 5 was reached by 67.9 % of all patients. For the hop tests, 78.5 % of patients passed LSI > 90 % for SLH, 85.7 % for TLH and 50 % for the SH. For the isokinetic test, 39.3 % of patients passed criteria for LSI peak torque quadriceps at 60°/s, 46.4 % at 180°/s and 42.9 at 300°/s. In total, 35.7 % of the patients passed criterion for the peak torque at 60°/s normalized to BW (>3.0 Nm) for the involved limb. The H/Q ratio at 300°/s > 55 % for females was achieved by 4 out of 6 female patients, and the >62.5 % criterion for males was achieved by 75 %. At 6 months post-ACLR, 85.7 % of the patients passed the IKDC score and 75 % the ACL-RSI score >56 criteria.
Conclusion:
The evidence emerging from this study suggests that the majority of patients who are 6 months after ACLR require additional rehabilitation to pass RTS criteria. The RTS battery described in this study may serve as a framework for future studies to implement multivariate models in order to optimize the decision-making regarding RTS after ACLR with the aim to reduce incidence of second ACL injuries.
Level of evidence:
III.
... A threshold for isometric quadriceps strength after ACLR has been recommended as >3.0 Nm/kg [23]. Although isokinetic strength was tested, the aforementioned threshold is almost identical to the 2.8 Nm/kg obtained during isokinetic tests in patients who were cleared to RTS after ACLR [42]. In addition, the hamstrings/quadriceps ratio was determined at 300°/s, as high knee flexion/extension angular velocities reveal significant gender differences, whereas low speeds do not [18]. ...
Context:
Injury-related fear and quadriceps strength are independently associated with secondary anterior cruciate ligament (ACL) injury risk. It is not known whether injury-related fear and quadriceps strength are associated, despite their individual predictive capabilities of secondary ACL injury. The purpose of this study was to examine the association between injury-related fear and quadriceps strength in individuals at least 1 year after ACL reconstruction (ACLR).
Design:
Cross-sectional study.
Methods:
Forty participants between the ages of 18 and 35 years at least 1 year post unilateral primary ACLR. Participants completed the Tampa Scale of Kinesiophobia-11 (TSK-11) and a standard isokinetic quadriceps strength assessment using the Biodex Isokinetic Dynamometer. Pearson Product-Moment correlations were used to examine the linear association between the TSK-11 scores and peak torque (in nanometers per kilogram) for each limb and between the TSK-11 scores and limb symmetry indices for each limb. Pearson Product-Moment correlation coefficients (r) were interpreted as very high (.90-1.00), high (.70-.90), moderate (.50-.70), low (.30-.50), and no correlation (.00-.30).
Results:
The average TSK-11 score was 18.2 (5.3), average ACLR peak quadriceps torque was 1.9 (0.50) N·m/kg, average contralateral peak quadriceps torque was 2.3 (0.48) N·m/kg, and average limb symmetry index was 85.3% (12.6%). There was no statistically significant correlation between the TSK-11 and peak quadriceps torque on the ACLR limb (r = .12, P = .46), the TSK-11 and contralateral limb (r = .29, P = .07), or the TSK-11 and limb symmetry index (r = -.18, P = .27).
Conclusions:
There was no association between kinesiophobia and peak isokinetic quadriceps strength in individuals at least 1 year post-ACLR. Both factors, independently, have been shown to influence risk of secondary injury in patients after ACLR.
Objectif : Proposer une alternative fiable, et plus proche de la réalité fonctionnelle, en utilisant une approche isocinétique sectorielle représentée par le calcul de ratios agonistes/antagonistes par plage angulaire de 10°. Matériel et Méthode : Trois études ont été menées, chaque étude portant sur des sites articulaires particulièrement impliqués dans la motricité humaine, et également très concernés par la survenue de blessure en lien avec la balance musculaire des principaux groupes stabilisateurs. Il s'agit respectivement de l'articulation scapulo-humérale (muscles rotateurs interne/externe), de l'articulation fémoro-tibiale (muscles fléchisseurs/extenseurs), et du rachis lombaire (muscles fléchisseurs/extenseurs). Les sujets étaient des volontaires sains, non spécialistes d'une pratique sportive. Les ratios par plage angulaire de 10° étaient comparés entre les plages angulaires et également par rapport aux ratios classiques associés aux valeurs "pic". La reproductibilité était évaluée pour l'ensemble des ratios. Résultats : Nos études ont montré que les ratios par plage angulaire étaient évolutifs au cours du mouvement et significativement différents des ratios classiques. De plus, nos résultats ont mis en exergue une bonne reproductibilité absolue des ratios associés aux plages angulaires de 10°. Conclusion : La méthode sectorielle associée aux plages angulaires de 10° permet une évaluation fiable et pertinente de la balance musculaire
Bu çalışmanın amacı Türkiye Futbol Federasyonu Spor Toto Süper Liginde mücadele eden profesyonel bir takımının alt yapısında (U16 liginde) mücadele eden futbolcuların 5m, 10m ve 30m sürat performansları ile dikey sıçrama performansları ve kuvvet değerleri arasındaki ilişkiyi belirlemektir. Katılımcıların yaşları, boy uzunlukları, ağırlıkları, belirlenen 1RM (1 tekrar maksimum kuvvet) ile kuvvet performansları, 5m,10m,30m sürat performans verileri, sıçrama performansları countermovement jump (CMJ) ve squat jump(SJ) ile belirlendi. Çalışmaya katılan toplam 23 futbolcunun tanımlayıcı özellikleri olarak yaş ortalaması: 15,78 ±,42 yıl, boy uzunluğu: 172,43±7,89 cm, vücut kütlesi: 62,04±7,61 kg olarak tespit edildi. Çalışmadan elde edilen bulgular doğrultusunda 0-5m koşu performansı ile back squat 1RM performansı (0,57) arasında anlamlı bir ilişki olduğu görüldü (p<0.001). Diğer bir yandan süratin diğer kompanentleri olan maksimum hıza ulaşma-yavaşlama (10m, 30m) ile sıçrama performanslarının kuvvet performansları ile anlamlı bir ilişki göstermediği tespit edildi. Sonuç olarak, antrenörlerin başarılı bir performans için sporculara vertical güç üretimini artıracak squat, deadlift gibi büyük kas gruplarına yönelik antrenmanları uygulanması, futbolcularının oyun sırasında kaslarının çok kısa sürede ve etkili şekilde kasılması ile çok daha başarılı başlangıç koşuları yapmalarına imkan sağlayabilir.
The aim of this study was to examine the validity and reliability of Turkish version of the Athlete Burnout Questionnaire (ABQ) which has been developed by Raedeke and Smith (2001). Scale was completed by 207 athletes (79 female, 128 male) with a mean of age 20.57 3.62 years. ABQ consists of 15 items assigned to 3 subscales (Reduces Sense of Accomplishment, Emotional/Physical Exhaustion and Devaluation). Construct validity was evaluated by confirmatory factor analysis. The Internal consistency of the scale was determined by Cronbach alpha. Beside, Sport Motivation Scale and Physical Self Perception Profile were administered for testing convergent validity; Maslach Burnout Questionnaire was used to test concurrent validity. Findings of final Turkish version of ABQ (13 items) regarding the construct validity of the scale were rather consistent with the original scale’s three-factor structure [SB-2 (df = 66) = 185.70, RMSEA = .06, SRMR = .05, NFI = .92, NNFI= .94, CFI = .96, GFI = .92]. Internal consistency coefficients were ranged between 0.75 and 0.87. Results
on concurrent validity revealed a significant correlation found between Athlete Burnout Questionnaire and Maslach Burnout Questionnaire (p<.01). Furthermore, the convergent validity results indicated a significant relationship found between subscales of Athlete Burnout Questionnaire and intrinsic motivation, amotivation and sport competence subscales (p<.01); but no significant relationship was found between ABQ and extrinsic motivation (p>.01). The psychometric properties of the Turkish version of Athlete Burnout Questionnaire showed that the instrument is a valuable additional measure for the determination of athletes’ burnout levels in Turkey.
The main aim of this study was to characterize the muscle strength profile the shoulder external and internal
rotators and the knee flexors and extensors in elite Serbian male Karate athletes. The second aim was to
compare the muscle strength between the hamstrings and quadriceps in male karate athletes of different age
groups.The sample was composed of three groups of male karate athletes. First group included seniors
(24.1±3.72), the second-juniors (17.6±0.84) and the third group was composed of cadets (15.85±0.69).The
following isokinetic parameters were used in the research: Maximal force of right leg extensors (Right_Ext),
Maximal force of left leg extensors (Left_Ext), Maximal force of right leg flexors (Right_Flx), Maximal force of
left leg flexors (Left_Flx), Maximal force of external rotation of the right arm (Right_Ext_Rot), Maximal force
of external rotation of the left arm (Left_Ext_Rot), Maximal force of internal rotation of the right arm
(Right_Int_Rot), Maximal force of internal rotation of the left arm (Left_Int_Rot). Based on the discriminant
analysis, all variables significantly contribute to the difference between the groups, except maximal force of
internal rotation of the right arm. We found that the seniors significantly differ from the cadets in all
parameters, and the difference is in favour of seniors (p≤0.05). Seniors and juniors differ in maximal force of
left leg extensors, maximal force of right leg flexors, maximal force of internal rotation of the left arm and
maximal force of external rotation of the left arm. Juniors and cadets differ in maximal force of left leg
flexors and maximal force of internal rotation of the left arm, the difference is in favour of juniors. To
conclude, the lower and upper limbs’ isokinetic parameters were significantly higher in the senior compared
junior and cadet group. Since only elite competitors were tested, the findings could be of importance for both
the selection and training design of karate athletes.
Hamstring strains are one of most common sports injuries. The purpose of this literature review is to summarize studies on hamstring strain injury rate, mechanism, and risk factors in the last several decades with a focus on the prevention and rehabilitation of this injury. Hamstring injury commonly occurs in sporting events in which high speed sprinting and kicking are frequently performed, such as Australian football, English rugby, American football, and soccer. Basic science studies have demonstrated that a muscle strain injury occurs due to excessive strain in eccentric contraction instead of force, and that elongation speed and duration of activation before eccentric contraction affect the severity of the injury. Hamstring strain injury is likely to occur during the late swing phase and late stance phase of sprint running. Shortened optimum muscle length, lack of muscle flexibility, strength imbalance, insufficient warm-up, fatigue, lower back injury, poor lumbar posture, and increased muscle neural tension have been identified as modifiable risk factors while muscle compositions, age, race, and previous injuries are non-modifiable risk factors. The theoretical basis of some of these risk factors, however, is lacking, and the results of clinical studies on these risk factors are inconsistent. Future studies are needed to establish the cause-and-effect relationships between those proposed risk factors and the injury.
Objectives. To investigate motor control as a possible contributing factor in hamstring injuries using a test movement similar to the injury-critical phase during running. Leg swing movement discrimination (MD), thigh muscle strength as tested by Cybex isokinetic dynamometry and previous hamstring injury history were all assessed to determine any association with subsequent hamstring injury.Design. Prospective and retrospective observational and analytical cohort study.Setting. A professional football club and a university laboratory.Participants. Twenty elite level players of Australian football.Results. In the 2 years prior to testing, 7 subjects had sustained a hamstring injury. At the time of testing, there were no significant differences between subjects never injured and those previously injured. In the two years following testing, 6 players sustained a hamstring injury. Mean MD score and concentric hamstring-to-quadriceps strength ratio of subsequently injured subjects were significantly worse than those uninjured (p
Cross-sectional study.
To investigate the impact of quadriceps femoris (QF) muscle strength asymmetry at the time of return to sport on self-reported function and functional performance of individuals following anterior cruciate ligament reconstruction (ACLR).
Evidence-based QF strength guidelines for return-to-sport decision making are lacking. Objective guidelines necessitate understanding the impact of QF strength deficits at the time of return to sport on function and performance.
Fifty-five individuals (mean age, 17.3 years) who were cleared for return to sport following primary ACLR (ACLR group) and 35 uninjured individuals (mean age, 17.0 years) in a control group participated in the study. QF strength (maximum voluntary isometric contraction) was assessed, and the quadriceps index (QI) was calculated [(involved strength/uninvolved strength) × 100%]. The ACLR group was further subdivided into 2 groups, based on the QI: high quadriceps (QI of 90% or greater) and low quadriceps (QI of less than 85%). The International Knee Documentation Committee Subjective Knee Evaluation Form score was used to assess self-reported function, and hop tests were used to assess functional performance. Multivariate analysis of variance and hierarchical regression analyses were performed.
The individuals in the ACLR group were weaker, reported worse function, and performed worse on hop tests compared to those in the control group (P<.05). The low-quadriceps group demonstrated worse performance on the hop tests compared to the high-quadriceps group and the control group (P≤.016). Hop test performance did not differ between the high-quadriceps and control groups (P≥.14). QF strength predicted performance on the hop tests beyond graft type, presence of meniscus injury, knee pain, and knee symptoms.
At the time of return to sport, individuals post-ACLR who had weaker QF (QI of less than 85%) demonstrated decreased function, whereas those with minimal QF strength deficits (QI of 90% or greater) demonstrated functional performance similar to uninjured individuals. QF strength deficits predicted hop test performance beyond the influences of graft type, presence of meniscus injury, knee pain, and knee symptoms.J Orthop Sports Phys Ther 2012;42(9):750-759, Epub 19 July 2012. doi:10.2519/jospt.2012.4194.
The main objective of this study was to establish normative values for maximal concentric isokinetic strength and maximal isometric strength of all major muscle groups in healthy subjects applying sex, age, height, and body mass-adjusted statistical models. One hundred and seventy-eight (178) (93 male and 85 female) healthy non-athletic Danish volunteers aged 15-83 years were recruited. Eighteen test protocols for each sex were applied to determine isokinetic and isometric muscle strength at knee, ankle, hip, shoulder, elbow, and wrist using a dynamometer (Biodex System 3 PRO). Multiple linear regressions were performed with maximal muscle strength (peak torque) as dependent variable and age, height, and body mass as independent variables. Muscle strength significantly related to age in 24, to height in 13 and to body mass in 27 out of the 36 models. In gender-specific analyses, the variables age, height and body mass accounted for 25% (20-29) (95% confidence interval) of the variation (r (2)) in strength for men and 31% (25-38) for women. The r (2) was similar for the isokinetic models and the isometric models [31% (22-40) vs. 28% (23-34)]. Age, height, and body mass related to strength in most muscle groups and gender-specific models with estimated prediction intervals were established for maximal strength of major muscle groups.
Unlabelled:
Part 1 of this two-part series (presented in the June issue of IJSPT) provided an introduction to functional movement screening, as well as the history, background, and a summary of the evidence regarding the reliability of the Functional Movement Screen (FMS™). Part 1 presented three of the seven fundamental movement patterns that comprise the FMS™, and the specific ordinal grading system from 0-3, used in the their scoring. Specifics for scoring each test are presented. Part 2 of this series provides a review of the concepts associated with the analysis of fundamental movement as a screening system for functional movement competency. In addition, the four remaining movements of the FMS™, which complement those described in Part 1, will be presented (to complete the total of seven fundamental movements): Shoulder Mobility, the Active Straight Leg Raise, the Trunk Stability Push-up, and Rotary Stability. The final four patterns are described in detail, and the specifics for scoring each test are presented, as well as the proposed clinical implications for receiving a grade less than a perfect "3". The intent of this two part series is to present the concepts associated with screening of fundamental movements, whether it is the FMS™ system or a different system devised by another clinician. Such a fundamental screen of the movement system should be incorporated into pre-participation screening and return to sport testing in order to determine whether an athlete has the essential movements needed to participate in sports activities at a level of minimum competency. Part 2 concludes with a discussion of the evidence related to functional movement screening, myths related to the FMS™, the future of functional movement screening, and the concept of movement as a system.
Level of evidence:
5.
Unlabelled:
To prepare an athlete for the wide variety of activities needed to participate in or return to their sport, the analysis of fundamental movements should be incorporated into screening in order to determine who possesses, or lacks, the ability to perform certain essential movements. In a series of two articles, the background and rationale for the analysis of fundamental movement will be provided. The Functional Movement Screen (FMS™) will be described, and any evidence related to its use will be presented. Three of the seven fundamental movement patterns that comprise the FMS™ are described in detail in Part I: the Deep Squat, Hurdle Step, and In-Line Lunge. Part II of this series which will be provided in the August issue of IJSPT, will provide a detailed description of the four additional patterns that complement those presented in Part I (to complete the seven total fundamental movements): Shoulder Mobility, the Active Straight Leg Raise, the Trunk Stability Push-up, and Rotary Stability, as well as a discussion about the utility of functional movement screening, and the future of functional movement. The intent of this two part series is to present the concepts associated with screening of fundamental movements, whether it is the FMS™ system or a different system devised by another clinician. Such a functional assessment should be incorporated into pre-participation screening and return to sport testing in order to determine whether the athlete has the essential movements needed to participate in sports activities at a level of minimum competency.
Level of evidence:
5.
Strain injuries of the posterior thigh are common in soccer. It seems that previous injury and age are important risk factors, but the literature is limited. This study was conducted to see if we could identify intrinsic risk factors for hamstring injuries among male soccer players.
We hypothesized that previous hamstring injuries, reduced function scores, abnormalities on a clinical examination, high maximum sprint speed, poor hamstring strength, or low hamstring/quadriceps ratio can predict increased risk of new hamstring injuries.
Cohort study; Level of evidence, 2.
A total of 508 players representing 31 amateur teams were tested during the 2004 preseason for potential risk factors for hamstring injury through a questionnaire on previous injury and function score (Hamstring Outcome Score [HaOS]), a clinical examination of the hamstring, and specific hamstring relevant tests. Generalized estimating equations were used in univariate analyses to identify candidate risk factors, and factors with a P value of <.10 were then examined in a multivariate model.
During the soccer season, 76 hamstring injuries, affecting 65 legs (61 players), were registered. Univariate analyses revealed previous acute hamstring injury (yes/no) (odds ratio [OR], 2.62; 95% confidence interval [CI], 1.54-4.45), HaOS function score with all subscores except "Soreness" (OR for a 10-point difference in total score, 1.29; 95% CI, 1.08-1.54), age (OR, 1.25; 95% CI, 0.96-1.63), and player position (P = .09) as candidate predictors of high injury risk. In a multivariate analysis, the most important risk factor for injuries to the hamstring was previous acute hamstring injury (yes/no) (adjusted OR, 2.19; 95% CI, 1.19-4.03; P = .01).
In a multivariate analysis, previous acute hamstring injury was found to be a significant risk factor for new hamstring injuries. Previously injured players have more than twice as high a risk of sustaining a new hamstring injury.
The purpose of this study was to test the effect of a jump-training program on landing mechanics and lower extremity strength in female athletes involved in jumping sports. These parameters were compared before and after training with those of male athletes. The program was designed to decrease landing forces by teaching neuromuscular control of the lower limb during landing and to increase vertical jump height. After training, peak landing forces from a volleyball block jump decreased 22%, and knee adduction and abduction moments (medially and laterally directed torques) decreased approximately 50%. Multiple regression analysis revealed that these moments were significant predictors of peak landing forces. Female athletes demonstrated lower landing forces than male athletes and lower adduction and abduction moments after training. External knee extension moments (hamstring muscle-dominant) of male athletes were threefold higher than those of female athletes. Hamstring-to-quadriceps muscle peak torque ratios increased 26% on the nondominant side and 13% on the dominant side, correcting side-to-side imbalances. Hamstring muscle power increased 44% with training on the dominant side and 21% on the nondominant. Peak torque ratios of male athletes were significantly greater than those of untrained female athletes, but similar to those of trained females. Mean vertical jump height increased approximately 10%. This training may have a significant effect on knee stabilization and prevention of serious knee injury among female athletes.
To determine the relation of hamstring and quadriceps muscle strength and imbalance to hamstring injury using a prospective observational cohort study
A total of 102 senior male Australian Rules footballers aged 22.2 (3.6) years were tested at the start of a football season. Maximum voluntary concentric and eccentric torque of the hamstring and quadriceps muscles of both legs was assessed using a Kin-Com isokinetic dynamometer at angular velocities of 60 and 180 degrees/second. Twelve (11.8%) players sustained clinically diagnosed hamstring strains which caused them to miss one or more matches over the ensuing season.
There were no significant differences for any of the isokinetic variables comparing the injured and non-injured legs in players with unilateral hamstring strains (n=9). Neither the injured nor the non-injured leg of injured players differed from the mean of left and right legs in non-injured players for any isokinetic variable. The hamstring to opposite hamstring ratios also did not differ between injured and non-injured players. A hamstring to opposite hamstring ratio of less than 0.90 and a hamstring to quadriceps ratio of less than 0.60 were not associated with an increased risk of hamstring injury. A significantly greater percentage of players who sustained a hamstring strain reported a history of hamstring strain compared with non-injured players (p=0.02). However, this was not related to muscle weakness or imbalance.
Isokinetic muscle strength testing was not able to directly discriminate Australian Rules football players at risk for a hamstring injury.
To prospectively evaluate the effect of neuromuscular training on the incidence of knee injury in female athletes, we monitored two groups of female athletes, one trained before sports participation and the other not trained, and a group of untrained male athletes throughout the high school soccer, volleyball, and basketball seasons. Weekly reports included the number of practice and competition exposures and mechanism of injury. There were 14 serious knee injuries in the 1263 athletes tracked through the study. Ten of 463 untrained female athletes sustained serious knee injuries (8 noncontact), 2 of 366 trained female athletes sustained serious knee injuries (0 noncontact), and 2 of 434 male athletes sustained serious knee injuries (1 noncontact). The knee injury incidence per 1000 athlete-exposures was 0.43 in untrained female athletes, 0.12 in trained female athletes, and 0.09 in male athletes (P = 0.02, chi-square analysis). Untrained female athletes had a 3.6 times higher incidence of knee injury than trained female athletes (P = 0.05) and 4.8 times higher than male athletes (P = 0.03). The incidence of knee injury in trained female athletes was not significantly different from that in untrained male athletes (P = 0.86). The difference in the incidence of noncontact injuries between the female groups was also significant (P = 0.01). This prospective study demonstrated a decreased incidence of knee injury in female athletes after a specific plyometric training program.
Strengthening of the hamstrings is often recommended following injury and reconstruction of the anterior cruciate ligament. It has been suggested that hamstrings activity stabilizes the knee and reduces anterior cruciate ligament load during weight-bearing flexion; however, the effects of hamstrings cocontraction on the kinematics and mechanics of the normal knee have not been assessed at physiological load levels. The aim of this study was to determine whether the addition of hamstrings force affects knee rotations, translations, and joint and quadriceps force during flexion with loads at physiological levels applied to the muscles and joints. Eight cadaveric knee specimens were tested with a servohydraulic mechanism capable of applying controlled dynamic loads to simulate quadriceps and hamstrings muscle forces throughout a physiological range of motion. A constant vertical load of physiologic magnitude was applied to the hip, and quadriceps force was varied to maintain equilibrium throughout flexion. Two conditions were tested: no hamstrings force and a constant hamstrings force equivalent to the vertical load. Hamstrings force significantly reduced internal rotation (p<0.0001) and anterior translation (p<0.0001), increased quadriceps force (p<0.0001) and normal resultant force on the tibia (p<0.0001), and reversed the direction of the shear force on the tibia (p<0.0001). These results suggest that hamstrings strengthening following anterior cruciate ligament injury may benefit anterior cruciate ligament-deficient and reconstructed knees by reducing the load in the ligament; however, they also imply that this comes at the expense of efficiency and higher patellofemoral and joint forces.
Background: Injuries to lower extremities are common in team sports such as soccer, basketball, volleyball, football and field hockey. Considering personal grief, disabling consequences and high costs caused by injuries to lower extremities, the importance for the prevention of these injuries is evident. From this point of view it is important to know which screening tools can identify athletes who are at risk of injury to their lower extremities. Objective: The aim of this article is to determine the predictive values of anthropometric and/or physical screening tests for injuries to the leg, anterior cruciate ligament (ACL), knee, hamstring, groin and ankle in team sports. Methods: A systematic review was conducted in MEDLINE (1966 to September 2011), EMBASE (1989 to September 2011) and CINAHL (1982 to September 2011). Based on inclusion criteria defined a priori, titles, abstracts and full texts were analysed to find relevant studies. Results: The analysis showed that different screening tools can be predictive for injuries to the knee, ACL, hamstring, groin and ankle. For injuries in general there is some support in the literature to suggest that general joint laxity is a predictive measure for leg injuries. The anterior right/left reach distance >4 cm and the composite reach distance <4.0% of limb length in girls measured with the star excursion balance test (SEBT) may predict leg injuries. Furthermore, an increasing age, a lower hamstring/quadriceps (H : Q) ratio and a decreased range of motion (ROM) of hip abduction may predict the occurrence of leg injuries. Hyperextension of the knee, side-to-side differences in anterior-posterior knee laxity and differences in knee abduction moment between both legs are suggested to be predictive tests for sustaining an ACL injury and height was a predictive screening tool for knee ligament injuries. There is some evidence that when age increases, the probability of sustaining a hamstring injury increases. Debate exists in the analysed literature regarding measurement of the flexibility of the hamstring as a predictive screening tool, as well as using the H : Q ratio. Hip-adduction-to-abduction strength is a predictive test for hip adductor muscle strain. Studies do not agree on whether ROM of the hamstring is a predictive screening tool for groin injury. Body mass index and the age of an athlete could contribute to an ankle sprain. There is support in the literature to suggest that greater strength of the plantar flexors may be a predictive measure for sustaining an ankle injury. Furthermore, there is some agreement that the measurement of postural sway is a predictive test for an ankle injury. Conclusions: The screening tools mentioned above can be recommended to medical staff and coaches for screening their athletes. Future research should focus on prospective studies in larger groups and should follow athletes over several seasons.
Synopsis:
Successful return to previous level of activity following anterior cruciate ligament (ACL) reconstruction is not guaranteed, and the prevalence of second ACL injury may be as high as 30%. In particular, younger athletes who return to sports activities within the first several months after ACL reconstruction may be at significantly greater risk of a second ACL rupture compared to older, less active individuals. Significant neuromuscular deficits and functional limitations are commonly identified in athletes following ACL reconstruction, and these abnormal movement and neuromuscular control profiles may be both residual of deficits existing prior to the initial injury and exacerbated by the injury and subsequent ACL reconstruction surgery. Following ACL reconstruction, neuromuscular deficits are present in both the surgical and nonsurgical limbs, and accurately predict second-ACL injury risk in adolescent athletes. While second ACL injury in highly active individuals may be predicated on a number of modifiable and nonmodifiable factors, clinicians have the greatest potential to address the modifiable postsurgical risk factors through targeted neuromuscular interventions. This manuscript will (1) summarize the neuromuscular deficits commonly identified at medical discharge to return to sport, (2) provide the evidence underlying second-ACL injury risk factors, (3) propose a method to assess the modifiable deficits related to second-ACL injury risk, and (4) outline a method of intervention to prevent second ACL injury. The program described in this clinical commentary was developed with consideration for the modifiable factors related to second-injury risk, the principles of motor learning, and careful selection of the exercises that may most effectively modify aberrant neuromuscular patterns. Future validation of this evidence-based, late-phase rehabilitation program may be a critical factor in maximizing return-to-activity success and reduction of second-injury risk in highly active individuals.
Level of evidence:
Therapy, level 5.
Isokinetic concentric quadriceps and hamstring strength data using a Cybex dynamometer are collected for elite collegiate American football players invited to the annual National Football League (NFL) Scouting Combine. We constructed a normative (reference) database of the Cybex strength data for the purpose of allowing comparison of an individual's values to his peers. Data reduction was performed to construct frequency distributions of hamstring/quadriceps (H/Q) ratios and side-to-side strength differences. For the cohort (n = 1252 players), a statistically significant but very small (1.9%) mean quadriceps strength preference existed for dominant side vs. nondominant side. Peak torque (Newton meters, best repetition) for quadriceps and hamstrings was significantly correlated to player body mass (weight) (the same relationship was found for other variables using peak torque in the calculation). Peak torque varied by player position, being greatest for offensive linemen and lowest for kickers (P < 0.0001). Adjusting for body weight overcorrected these differences. H/Q ratios and frequency distributions were similar across positions, with a mean of 0.6837 ± 0.137 for the cohort dominant side vs. 0.6940 ± 0.145 for the nondominant side (P = 0.021, n = 1252). There was a wide range of values for dominant-to-nondominant side differences. For quadriceps, 47.2% of players had differences between -10% to +10%, 21.1% < -10% (i.e., a deficit of 10% or greater on dominant side compared to nondominant side), and 31.8% > +10%. For hamstrings, 57.0% of players had differences between -10% to +10%, 19.6% < -10%, and 23.4% > +10%. We observed that isokinetic absolute strength variables are dependent on body weight and vary across player position. H/Q ratios vary only within a relatively narrow range. Side-to-side differences in strength variables > 10% are common, not the exception.
Background:
There are conflicting reports regarding the association between isokinetic concentric quadriceps and hamstring strength deficits and ratios and risk for hamstring injuries in athletes.
Purpose:
To determine if isokinetic concentric Cybex data collected during the annual National Football League (NFL) Scouting Combine are predictive of hamstring injury in professional American football players during their first season.
Study design:
Case-control study; Level of evidence, 3.
Methods:
All 32 NFL teams identified players selected during the first 5 rounds of the NFL annual draft who had hamstring injuries during their first professional season. Of these, 164 players with 172 injuries also had Cybex data from the previous year's Combine. Analyses compared injured legs with contralateral uninjured legs and also injured players with uninjured controls using a database of Cybex data from all players who participated in the NFL Scouting Combine from 2006 to 2011.
Results:
No Cybex strength variable differentiated the injured legs from the contralateral uninjured legs or injured players from uninjured controls, even after taking into account days lost from activity. Mean ± SD peak torque for the injured and contralateral uninjured sides was as follows: 315.7 ± 70.0 and 313.5 ± 68.3 N · m, respectively (P = .773, paired t test), for quadriceps and 203.0 ± 42.4 and 205.3 ± 42.5 N · m, respectively (P = .608, paired t test), for hamstrings. The sensitivity and specificity for the hamstrings-to-quadriceps ratio predicting hamstring injury were 0.513 (95% confidence interval, 0.419-0.607) and 0.524 (0.495-0.554), indicating that the hamstrings-to-quadriceps ratio was not a useful predictor of injury (calculation used the mean ± SD ratio for injured legs, 0.656 ± 0.133). Side-to-side peak torque differences were also not predictive of injury, with more than a 10% difference (plus or minus) occurring commonly in both injured and uninjured players for quadriceps (53% prevalence for both injured and uninjured) and hamstrings (injured, 41% prevalence; uninjured, 43% prevalence).
Conclusion:
Isokinetic strength data collected from collegiate players at the NFL Scouting Combine were not useful for predicting risk of hamstring injury in subsequent professional NFL competition. These data call into question commonly accepted assumptions about risk factors for hamstring injury, at least for elite collegiate American football players, when the temporal relationship between Cybex testing and actual injury is several months.
Purpose:
Women sustain more anterior cruciate ligament (ACL) ruptures than men, and this gender disparity is apparent from pubertal onset. Although the hamstring muscles play a vital role in ACL protection during landing by restraining anterior tibial motion relative to the femur, it is unknown whether hamstring strength affects landing biomechanics during a functional movement. This study aimed to determine whether pubescent girls with lower hamstring strength displayed different lower limb biomechanics when landing from a leap compared with girls with higher hamstring strength.
Methods:
Thirty-three healthy girls, age 10-13 yr, in Tanner stage II (pubertal onset) and 4-6 months from their peak height velocity were recruited. The concentric and the eccentric isokinetic strength of the hamstring and quadriceps muscles were assessed. On the basis of peak concentric hamstrings torque, participants were divided into a lower (peak torque < 45 N·m) and higher (peak torque > 60 N·m) strength group. Participants performed a functional landing movement, during which ground reaction forces (1000 Hz), lower limb electromyography (1000 Hz), and kinematic data (100 Hz) were collected.
Results:
Girls with lower hamstring strength displayed significantly (P < 0.05) greater knee abduction alignment, reduced hip abduction moments, and greater ACL loading at the time of the peak anteroposterior ground reaction forces compared with their stronger counterparts.
Conclusions:
Girls with reduced hamstring strength appear to have a decreased capacity to control lower limb frontal plane alignment. This reduced capacity appears to contribute to increased ACL loading and, in turn, increased potential for injury.
Hamstring muscle strain-type injuries are common in sports that involve sprinting,1 acceleration, deceleration, rapid change in direction and jumping.2 ,3 Occurring in both recreational and professional sports, these injuries can result in substantial time lost from sport and commonly recur.4 ,5
In the Australian Football League (AFL), hamstring muscle strain-type injuries have displayed a high incidence rate, with a 10 year mean of 6.1 new injuries per club each year and a 23% average recurrence rate.6 A recurrence rate of 17% has been reported in elite soccer players7 with hamstring injuries also recorded as the most common injury accounting for 12% of all injuries and resulting in an average of four missed games per injury.8
The high incidence of hamstring muscle strain-type injuries and potential associated costs has resulted in a substantial amount of research into the factors related to such injuries. Two recent systematic reviews have been completed in an attempt to collate the evidence around risk factors for hamstring injuries.9 ,10 Both reviews identified hamstring muscle weakness and thigh muscle imbalance, muscle flexibility, previous hamstring injury, other previous injury and age as potential risk factors; however, these reviews concluded that single variables were inconsistently identified as associated factors. Both reviews provided a qualitative synthesis of the literature and included risk factor studies as well as intervention studies, where a potential risk factor was modified with a training programme. The inclusion of intervention studies may potentially complicate risk factor analyses, as such studies assume that the factor being modified is associated with the injury and that the factor can be modified by the treatment programme.
The aim of the current review was to assemble all available knowledge and data to identify the intrinsic and extrinsic risk factors associated with …
The Functional Movement Screen (FMS™) is an easily administered and non-invasive tool for identifying weaknesses and asymmetry during exercises and daily activity. The clinical utility of FMS™ is currently limited by its lack of normative reference values. This study aimed to fill this void by providing normative reference values for healthy, middle aged adults. Furthermore, we hypothesized that FMS would be affected by other factors such as age, BMI, exercise participation, and BESS (Balance Error Scoring System) scores. 622 healthy adults were assessed based on their performance on the 7-Point Functional Movement Screen™. A higher level of exercise participation was associated with higher FMS scores, while higher BMI and age were associated with lower FMS™ scores. There was a significant difference between individuals with high (>30) and moderate BMIs (F (621) = 33.98, p < .0001). The normative reference values presented can be used in clinical practice to identify abnormal scores across a broad age spectrum.
Hamstring strain injuries (HSIs) are common in a number of sports and incidence rates have not declined in recent times. Additionally, the high rate of recurrent injuries suggests that our current understanding of HSI and re-injury risk is incomplete. Whilst the multifactoral nature of HSIs is agreed upon by many, often individual risk factors and/or causes of injury are examined in isolation. This review aims to bring together the causes, risk factors and interventions associated with HSIs to better understand why HSIs are so prevalent. Running is often identified as the primary activity type for HSIs and given the high eccentric forces and moderate muscle strain placed on the hamstrings during running these factors are considered to be part of the aetiology of HSIs. However, the exact causes of HSIs remain unknown and whilst eccentric contraction and muscle strain purportedly play a role, accumulated muscle damage and/or a single injurious event may also contribute. Potentially, all of these factors interact to varying degrees depending on the injurious activity type (i.e. running, kicking). Furthermore, anatomical factors, such as the biarticular organization, the dual innervations of biceps femoris (BF), fibre type distribution, muscle architecture and the degree of anterior pelvic tilt, have all been implicated. Each of these variables impact upon HSI risk via a number of different mechanisms that include increasing hamstring muscle strain and altering the susceptibility of the hamstrings to muscle damage. Reported risk factors for HSIs include age, previous injury, ethnicity, strength imbalances, flexibility and fatigue. Of these, little is known, definitively, about why previous injury increases the risk of future HSIs. Nevertheless, interventions put in place to reduce the incidence of HSIs by addressing modifiable risk factors have focused primarily on increasing eccentric strength, correcting strength imbalances and improving flexibility. The response to these intervention programmes has been mixed with varied levels of success reported. A conceptual framework is presented suggesting that neuromuscular inhibition following HSIs may impede the rehabilitation process and subsequently lead to maladaptation of hamstring muscle structure and function, including preferentially eccentric weakness, atrophy of the previously injured muscles and alterations in the angle of peak knee flexor torque. This remains an area for future research and practitioners need to remain aware of the multifactoral nature of HSIs if injury rates are to decline.
Unlabelled:
The management of patients after anterior cruciate ligament reconstruction should be evidence based. Since our original published guidelines in 1996, successful outcomes have been consistently achieved with the rehabilitation principles of early weight bearing, using a combination of weight-bearing and non-weight-bearing exercise focused on quadriceps and lower extremity strength, and meeting specific objective requirements for return to activity. As rehabilitative evidence and surgical technology and procedures have progressed, the original guidelines should be revisited to ensure that the most up-to-date evidence is guiding rehabilitative care. Emerging evidence on rehabilitative interventions and advancements in concomitant surgeries, including those addressing chondral and meniscal injuries, continues to grow and greatly affect the rehabilitative care of patients with anterior cruciate ligament reconstruction. The aim of this article is to update previously published rehabilitation guidelines, using the most recent research to reflect the most current evidence for management of patients after anterior cruciate ligament reconstruction. The focus will be on current concepts in rehabilitation interventions and modifications needed for concomitant surgery and pathology.
Level of evidence:
Therapy, level 5.
HEWETT, T.E. and G.D. MYER. The mechanistic connection between the trunk, hip, knee, and anterior cruciate ligament injury. Exerc. Sport Sci. Rev., Vol. 39, No. 4, pp. 161-166, 2011. Neuromuscular control of the trunk and knee predicts anterior cruciate ligament injury risk with high sensitivity and specificity. These predictors are linked, as lateral trunk positioning creates high knee abduction torque (load). The hypotheses explored are that lateral trunk motion increases load and that neuromuscular training that enhance trunk control will decrease load.
To determine the association of quadriceps and hamstrings strength to anterior cruciate ligament (ACL) injury risk in female athletes. The primary hypothesis was that there would be decreased knee flexor and increased knee extensor strength in female athletes who went on to ACL injured status (FACL) compared to uninjured female (FC) and male (MC) control subjects.
Matched case control.
Institutional Biomechanics Laboratory.
Prospectively measured FACL (n = 22) female athletes who subsequently suffered confirmed noncontact ACL ruptures (16 during soccer and 6 during basketball play) were matched (1:4 ratio) to female controls (FC; n = 88) using limb (dominant or nondominant), pubertal status, sport, and nearest height and mass. In addition, male controls (MC) were matched (1:1 ratio) to FACL to serve as a secondary comparative control.
Isokinetic (concentric) knee extension/flexion strength (300 degrees/s).
FACL subjects had decreased hamstrings strength compared to MC (15%; 95% CI, 1 to 27%; P = 0.04). FC were not different from MC in hamstrings strength. Conversely, FACL subjects did not differ compared to the MC in quadriceps strength, and the FC demonstrated decreased quadriceps strength relative to MC (10%; 95% CI, 3 to 18%; P = 0.01).
The results of this investigation indicate that female athletes who suffered ACL injury subsequent to strength testing had a combination of decreased hamstrings strength but not quadriceps strength compared to males. In direct contrast, female athletes who did not go on to ACL injury had decreased quadriceps strength and similar hamstrings strength compared to matched male athletes.
One hundred thirty-eight female collegiate athletes, participating in eight weightbearing varsity sports, were administered preseason strength and flexibility tests and followed for injuries during their sports seasons. Strength was measured as the maximal isokinetic torque of the right and left knee flexors and knee extensors at 30 and 180 deg/sec. Flexibility was measured as the active range of motion of several lower body joints. An athletic trainer evaluated and recorded injuries occurring to the athletes in practice or competition. Forty percent of the women suffered one or more injuries. Athletes experienced more lower extremity injuries if they had: 1) a right knee flexor 15% stronger than the left knee flexor at 180 deg/sec; 2) a right hip extensor 15% more flexible than the left hip extensor; 3) a knee flexor/knee extensor ratio of less than 0.75 at 180 deg/sec. There was a trend for higher injury rates to be associated with knee flexor or hip extensor imbalances of 15% or more on either side of the body. These data demonstrate that specific strength and flexibility imbalances are associated with lower extremity injuries in female collegiate athletes.
Strain in the anteromedial fibers of the anterior cruciate ligament [ACL(am)] was studied in six cadaver knees. ACL(am) strain was measured in five knees during the application of isometric quadriceps forces alone and simultaneously applied isometric quadriceps and hamstrings forces at 10 degrees increments from 0 degrees to 90 degrees of knee flexion. ACL(am) strain during muscle loading was measured with respect to the ACL(am) strain measured with the knee in its resting position (neutral or near neutral position). A sixth knee was used to investigate the reproducibility of the resting position and quadriceps-induced ACL(am) strains. The strains induced in the ACL(am) by the quadriceps were significantly greater than 0 at knee flexion angles from 0 to 40 degrees and not significantly different from 0 for 50 to 90 degrees. The ACL(am) strains induced by simultaneously applied hamstrings and quadriceps forces were not significantly different from 0 at any of the knee flexion angles tested. Simultaneously applied hamstrings and quadriceps forces significantly reduced ACL(am) strain at 10, 20, and 90 degrees of knee flexion compared to the ACL(am) strain induced by quadriceps forces alone. The hamstrings are potentially capable of both significantly reducing and negating quadriceps-induced ACL(am) strain at 10 and 20 degrees of knee flexion.
The purpose of our investigation was to compare, for the hamstring and quadriceps femoris muscles, peak torque values uncorrected for gravity with the peak torque values corrected for gravity and to determine the effect of making this correction on the hamstring to quadriceps femoris muscle peak torque ratio at slow and fast isokinetic speeds. We measured peak torques isokinetically at 60 degrees/sec (slow) and 240 degrees/sec (fast) in 25 female university soccer players. The gravity effect torque (GET) is the torque resulting from the effect of gravity on the combined weight of the leg and dynamometer arm at the precise angle of extension and flexion peak torque. The GET was added to the measured quadriceps femoris muscle peak torque and subtracted from the hamstring muscle peak torque to yield gravity corrected values. Failure to consider GET greatly underestimated quadriceps femoris muscle torque and overestimated hamstring muscle torque and the ratio between these torques at both speeds. Whereas the uncorrected hamstring to quadriceps femoris muscle peak torque ratio increased as speeds went from 60 degrees/sec to 240 degrees/sec, the gravity corrected ratio significantly decreased. Clinicians must remember the importance of making the gravity correction in patients with reduced torque output where the gravitational torque is a greater percentage of the measured torque to ascertain correctly the relative strength of antagonists inversely affected by gravity.
The purpose of this study was to compare the normalization methods of ratio standards, allometry, and ANCOVA with knee extensor strength of older adults. The apparently healthy older volunteers were 71 men (mean +/- SD; age, 71 +/- 4 yr; body mass, 81 +/- 10 kg; height, 174 +/- 7 cm) and 77 women (71 +/- 4 yr, 65 +/- 8 kg, 160 +/- 5 cm. respectively). Strength was defined as peak torque (N.m-1) and measured with a Cybex II isokinetic dynamometer. Body composition was estimated with dual energy x-ray absorptiometry. With allometry, the body mass exponent (0.74) was not statistically different from theory (0.67). Body mass adjusted strengths were 34.7% (allometry), 32.0% (ANCOVA), and 29.4% (ratio standards) greater in older men than women. Allometry revealed that the bone-free lean tissue mass exponent was not different from ratio standard exponent of 1.0. After adjustment by bone-free lean tissue mass, strength in men remained 16.0% (allometry and ratio standards) higher than in women, but, strength differences between genders were eliminated with ANCOVA. The methods used to normalize strength yielded similar results with body mass but conflicting results with bone-free lean tissue mass.
Disruption of the anterior cruciate ligament (ACL), a primary stabilizer of the knee, can produce disability. The purpose of our work has been to study the normal ACL in humans, in the presence of normal muscle function and body weight, and develop clinical criteria for reconstruction, establish a basis for rehabilitation programs, and evaluate how knee braces protect this important ligament. The strain behavior of the ACL has been measured by arthroscopic implantation of the Differential Variable Reluctance Transducer while subjects are under local anesthesia. Movement of the knee from a flexed to an extended position, either passively or through contraction of the leg muscles, produces an increase in ACL strain values. Isolated contraction of the dominant quadriceps with the knee between 50 degrees and extension creates substantial increases in strain. In contrast, isolated contraction of the hamstrings at any knee position does not increase strain. With the knee un-weighted, the protective strain shielding effect of a functional knee brace decreases as the magnitude of anterior shear load applied to the tibia increases. A different behavior occurs during weight bearing, the strain shielding effect of the brace remains constant as the magnitude of anterior load increases. Our approach is novel in that it can be used to measure on important portion of the ACLs strain distribution while clinically relevant loads are applied to the knee, subjects perform rehabilitation exercises, or in the presence of different orthoses such as functional knee braces.
This study investigated the effect of hamstring co-contraction with quadriceps on the kinematics of the human knee joint and the in-situ forces in the anterior cruciate ligament (ACL) during a simulated isometric extension motion of the knee. Cadaveric human knee specimens (n = 10) were tested using the robotic universal force moment sensor (UFS) system and measurements of knee kinematics and in-situ forces in the ACL were based on reference positions on the path of passive flexion/extension motion of the knee. With an isolated 200 N quadriceps load, the knee underwent anterior and lateral tibial translation as well as internal tibial rotation with respect to the femur. Both translation and rotation increased when the knee was flexed from full extension to 30 of flexion; with further flexion, these motion decreased. The addition of 80 N antagonistic hamstrings load significantly reduced both anterior and lateral tibial translation as well as internal tibial rotation at knee flexion angles tested except at full extension. At 30 of flexion, the anterior tibial translation, lateral tibial translation, and internal tibial rotation were significantly reduced by 18, 46, and 30%, respectively (p<0.05). The in-situ forces in the ACL under the quadriceps load were found to increase from 27.8+/-9.3 N at full extension to a maximum of 44.9+/-13.8 N at 15 of flexion and then decrease to 10 N beyond 60 of flexion. The in-situ force at 15 was significantly higher than that at other flexion angles (p<0.05). The addition of the hamstring load of 80 N significantly reduced the in-situ forces in the ACL at 15, 30 and 60 of flexion by 30, 43, and 44%, respectively (p<0.05). These data demonstrate that maximum knee motion may not necessarily correspond to the highest in-situ forces in the ACL. The data also suggest that hamstring co-contraction with quadriceps is effective in reducing excessive forces in the ACL particularly between 15 and 60 of knee flexion.
To prospectively evaluate the effect of neuromuscular training on the incidence of knee injury in female athletes, we monitored two groups of female athletes, one trained before sports participation and the other not trained, and a group of untrained male athletes throughout the high school soccer, volleyball, and basketball seasons. Weekly reports included the number of practice and competition exposures and mechanism of injury. There were 14 serious knee injuries in the 1263 athletes tracked through the study. Ten of 463 untrained female athletes sustained serious knee injuries (8 noncontact), 2 of 366 trained female athletes sustained serious knee injuries (0 noncontact), and 2 of 434 male athletes sustained serious knee injuries (1 noncontact). The knee injury incidence per 1000 athlete-exposures was 0.43 in untrained female athletes, 0.12 in trained female athletes, and 0.09 in male athletes (P 0.02, chi-square analysis). Untrained female athletes had a 3.6 times higher incidence of knee injury than trained female athletes (P 0.05) and 4.8 times higher than male athletes (P 0.03). The incidence of knee injury in trained female athletes was not significantly different from that in untrained male athletes (P 0.86). The difference in the incidence of noncontact injuries between the female groups was also significant (P 0.01). This prospective study demonstrated a decreased incidence of knee injury in female athletes after a specific plyometric training program.
Many factors such as anthropometric variables influence strength performance. This study is to determine the relationship between knee isokinetic strength and body composition, and to compare the gender differences. Test-retest reliability had been performed within one week for all measurement methods before the formal study. Fifty-eight 20-25 year-old university students, 32 females and 26 males, participated in this study. Isokinetic strength of the knee flexion and extension was measured at two angular velocities of 60 degrees/sec and 120 degrees/sec. Body composition was measured by bioelectrical impedance analysis (BIA) and skinfold caliper. The others variables including height, body weight, body mass index (BMI), and waist to hip ratio were measured or calculated. The results showed that the intra-class correlation coefficients for isokinetic knee strength were between 0.83 and 0.93, and body composition and anthropometric variables were between 0.83 and 0.98. Isokinetic knee strength was significantly correlated with body height, body weight, BMI, waist and hip ratio and percent of body fat estimated by skinfold caliper (r = -0.56 to 0.64). The correlation between isokinetic strength with percent of body fat estimated by BIA (r = -0.60 to -0.74; p < 0.001) and with fat free mass (r = 0.64 to 0.78; p < 0.001) was even higher. Although male subjects had significantly greater mean values in body height, body weight, waist to hip ratio and isokinetic strength than female subjects, the MANCOVA showed that the effect of gender on knee isokinetic strength would be eliminated when the covariant variable, the percent of body fat measured by BIA and BMI was controlled in the analysis model. In conclusion, knee isokinetic strength was significantly negatively correlated with proportion of fat and positively correlated with fat free mass. The magnitude of strength difference between males and females could be explained by differences in body fat proportion and BMI in this study. Therapist would take the body fat composition, fat free mass, and BMI into consideration in knee muscle strength measurement. Less body fat and higher BMI will contain more fat free mass that produces more muscle strength.
The following possible risk factors for leg injuries in female soccer players were studied: age, anatomical alignment, generalized joint laxity, thigh muscle torque, muscle flexibility, ligamentous laxity of the knee and ankle joints, recent injuries, and duration of soccer exposure. A total of 146 players from 13 teams in the second and third Swedish divisions underwent clinical examination, isokinetic measurements of quadriceps and hamstring torques, and testing of postural sway of the legs. All soccer-related leg injuries resulting in absence from at least one scheduled practice session or game were recorded during one outdoor season (April-October). In 50 players there were 61 traumatic injuries, and 17 players sustained 19 overuse injuries. The overall injury incidence rate (traumatic and overuse) was 5.49/1000 h of soccer. Variables significantly increasing the risk of traumatic leg injuries included generalized joint laxity, low postural sway of the legs, hyperextension of the knee joint, and a low hamstring-to-quadriceps ratio during concentric action. Multivariate logistic regression showed hyperextension of the knee joint, a low postural sway, reduced H/Q ratio during concentric action, and a higher exposure to soccer to significantly increase the risk of traumatic leg injury. All five players who suffered an anterior cruciate ligament injury during the study period had a lower hamstring-to-quadriceps ratio during concentric action on the injured side than on their noninjured side.
The aim of this study was to examine the learning effect during a set of isokinetic measurements, to evaluate the reliability of the Biodex System 3 PRO dynamometer, and to compare the Biodex System 3 PRO and the Lido Active dynamometers on both extension and flexion over the elbow and the knee at 60 degrees s(-1). Thirteen (nine women, four men) healthy participants were measured five times using the Biodex and once using the Lido dynamometer. The intervals between the first four tests were 20 min, and 1 week between tests 4 and 5. Between Biodex and Lido measurements there was a 20 min time interval. When comparing the first five measurements (Biodex), no systematic effect over time and an excellent reliability were found with respect to elbow and knee flexion and extension. No difference in muscle strength (Nm) between the Biodex and Lido was observed for knee flexion (P = 0.59), knee extension (P = 0.18) and elbow extension (P = 0.63). However, elbow flexion showed a 14.8% (95% CI: 11.2-18.4%; P = 0.0001) higher peak torque on Biodex. In conclusion, no learning effect was observed and the Biodex proved to be a highly reliable isokinetic dynamometer. A difference was observed when comparing Biodex and Lido on elbow flexion, but the difference did not outrange the expected variation found with a typical isokinetic measurement, which is why both sets of equipment seem applicable in clinical practice.
The aim of this study was to examine joint power generation during a concentric knee extension isokinetic test and a squat vertical jump. The isokinetic test joint power was calculated using four different methods. Five participants performed concentric knee extensions at 0.52, 1.57, 3.14 and 5.23 rad x s(-1) on a Lido isokinetic dynamometer. The squat vertical jump was performed on a Kistler force plate. Kinematic data from both tests were collected and analysed using an ELITE optoelectronic system. An inverse dynamics model was applied to measure knee joint moment in the vertical jump. Knee angular position data from the kinematic analysis in the isokinetic test were used to derive the actual knee angular velocity and acceleration, which, in turn, was used to correct the dynamometer moment for inertial effects. Power was measured as the product of angular velocity and moment at the knee joint in both tests. Significant differences (P < 0.05) were found between mean (+/- s) peak knee joint power in the two tests (squat vertical jump: 2255 +/- 434 W; isokinetic knee extension: 771 +/- 81 W). Correlation analysis revealed that there is no relationship between the peak knee joint power during the vertical jump and the slow velocity isokinetic tests. Higher isokinetic velocity tests show better relationships with the vertical jump but only if the correct method for joint power calculation is used in the isokinetic test. These findings suggest that there are important differences in muscle activation and knee joint power development that must be taken into consideration when isokinetic tests are used to predict jumping performance.
Our purpose was to determine if females demonstrate decreased hamstrings to quadriceps peak torque (H/Q) ratios compared to males and if H/Q ratios increase with increased isokinetic velocity in both sexes. Maturation disproportionately increases hamstrings peak torque at high velocity in males, but not females. Therefore, we hypothesised that mature females would demonstrate decreased H/Q ratios compared to males and the difference in H/Q ratio between sexes would increase as isokinetic velocity increased. Studies that analysed the H/Q ratio with gravity corrected isokinetic strength testing reported between 1967 and 2004 were included in our review and analysis. Keywords were hamstrings/quadriceps, isokinetics, peak torque and gravity corrected. Medline and Smart databases were searched combined with cross-checked bibliographic reference lists of the publications to determine studies to be included. Twenty-two studies were included with a total of 1568 subjects (1145 male, 423 female). Males demonstrated a significant correlation between H/Q ratio and isokinetic velocity (R=0.634, p<0.0001), and a significant difference in the isokinetic H/Q ratio at the lowest angular velocity (47.8+/-2.2% at 30 degrees /s) compared to the highest velocity (81.4+/-1.1% at 360 degrees /s, p<0.001). In contrast, females did not demonstrate a significant relationship between H/Q ratio and isokinetic velocity (R=0.065, p=0.77) or a change in relative hamstrings strength as the speed increased (49.5+/-8.8% at 30 degrees /s; 51.0+/-5.7% at 360 degrees /s, p=0.84). Gender differences in isokinetic H/Q ratios were not observed at slower angular velocities. However, at high knee flexion/extension angular velocities, approaching those that occur during sports activities, significant gender differences were observed in the H/Q ratio. Females, unlike males, do not increase hamstrings to quadriceps torque ratios at velocities that approach those of functional activities.
Researchers have postulated that coactivation of the hamstrings during active knee extension assists the anterior cruciate ligament in maintaining knee joint stability by exerting an opposing force to anterior tibial translation.
To compare the reciprocal coactivation of the hamstrings while performing low and high velocity isokinetic movements and two closed chain movements.
Within subject's comparison of isokinetic and closed chain exercises.
Biomechanics laboratory utilizing a Cybex norm isokinetic dynamometer and Biopac Data Collection system.
12 healthy women.
The root mean square of the Electromyogram (rmsEMG) was used as a measure of overall muscle activity.
The rmsEMG for hamstring coactivation during knee extension showed significant differences between the isokinetic movements and the closed chain exercises with greater coactivation when performing the isokinetic movements. In addition, greater activity was seen at the higher isokinetic velocity and during the one legged squat.
These results suggest isokinetic movements, particularly at high speed, can more effectively increase the coactivation activity of the hamstrings when compared to two closed chain activities.
The hamstring muscles are well positioned to limit both anterior tibial translation and anterior cruciate ligament strain during the knee flexion phase of a jump landing. We hypothesized that systematically increasing or decreasing hamstring tension during the knee flexion phase of a simulated jump landing would significantly affect peak relative strain in the anterior cruciate ligament.
Ten cadaveric knees from four male and six female donors (mean age [and standard deviation] at the time of death, 60.3 +/- 23.6 years) were mounted in a custom fixture to initially position the specimen in 25 degrees of knee flexion and simulate axial impulsive loading averaging 1700 N to cause an increase in knee flexion. Quadriceps, hamstring, and gastrocnemius muscle forces were simulated with use of pretensioned linear springs, with the tension in the hamstrings arranged to be increased, held constant, decreased, at "baseline," or absent during knee flexion. Impulsive loading applied along the tibia and femur was monitored with use of triaxial load transducers, while uniaxial load cells monitored quadriceps and medial and lateral hamstring forces. Relative strain in the anterior cruciate ligament was measured with use of a differential variable reluctance transducer, and tibiofemoral kinematics were measured optoelectronically. For each specimen, anterior cruciate ligament strains were recorded over eighty impact trials: ten preconditioning trials, ten "baseline" trials involving decreasing hamstring tension performed before and after three sets of ten trials conducted with increasing hamstring tension, constant hamstring tension, or no hamstring tension. Peak relative strains in the anterior cruciate ligament were normalized for comparison across specimens.
Increasing hamstring force during the knee flexion landing phase decreased the peak relative strain in the anterior cruciate ligament by >70% compared with the baseline condition (p = 0.005). Neither a constant hamstring muscle force nor the absence of a hamstring force significantly changed the peak strain in the anterior cruciate ligament relative to the baseline condition.
Increasing hamstring muscle force during the knee flexion phase of a simulated jump landing significantly reduces the peak relative strain in the anterior cruciate ligament in vitro.
The relationship between muscle injury and strength disorders remains a matter of controversy.
Professional soccer players performed a preseason isokinetic testing aimed at determining whether (1) strength variables could be predictors of subsequent hamstring strain and (2) normalization of strength imbalances could reduce the incidence of hamstring injury.
Cohort study (prognosis); Level of evidence, 1.
A standardized concentric and eccentric isokinetic assessment was used to identify soccer players with strength imbalances. Subjects were classified among 4 subsets according to the imbalance management content. Recording subsequent hamstring injuries allowed us to define injury frequencies and relative risks between groups.
Of 687 players isokinetically tested in preseason, a complete follow-up was obtained in 462 players, for whom 35 hamstring injuries were recorded. The rate of muscle injury was significantly increased in subjects with untreated strength imbalances in comparison with players showing no imbalance in preseason (relative risk = 4.66; 95% confidence interval: 2.01-10.8). The risk of injury remained significantly higher in players with strength imbalances who had subsequent compensating training but no final isokinetic control test than in players without imbalances (relative risk = 2.89; 95% confidence interval: 1.00-8.32). Conversely, normalizing the isokinetic parameters reduced the risk factor for injury to that observed in players without imbalances (relative risk = 1.43; 95% confidence interval: 0.44-4.71).
The outcomes showed that isokinetic intervention gives rise to the preseason detection of strength imbalances, a factor that increases the risk of hamstring injury. Restoring a normal strength profile decreases the muscle injury incidence.