Article

Eccentric Knee Flexor Strength and Risk of Hamstring Injuries in Rugby Union: A Prospective Study

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Abstract

Hamstring strain injuries (HSIs) represent the most common cause of lost playing time in rugby union. Eccentric knee flexor weakness and between-limb imbalance in eccentric knee flexor strength are associated with a heightened risk of HSIs in other sports; however, these variables have not been explored in rugby union. To determine if lower levels of eccentric knee flexor strength or greater between-limb imbalance in this parameter during the Nordic hamstring exercise are risk factors for HSIs in rugby union. Cohort study; Level of evidence, 2. This prospective study was conducted over the 2014 Super Rugby and Queensland Rugby Union seasons. In total, 178 rugby union players (mean age, 22.6 ± 3.8 years; mean height, 185.0 ± 6.8 cm; mean weight, 96.5 ± 13.1 kg) had their eccentric knee flexor strength assessed using a custom-made device during the preseason. Reports of previous hamstring, quadriceps, groin, calf, and anterior cruciate ligament injuries were also obtained. The main outcome measure was the prospective occurrence of HSIs. Twenty players suffered at least 1 HSI during the study period. Players with a history of HSIs had a 4.1-fold (95% CI, 1.9-8.9; P = .001) greater risk of subsequent HSIs than players without such a history. Between-limb imbalance in eccentric knee flexor strength of ≥15% and ≥20% increased the risk of HSIs by 2.4-fold (95% CI, 1.1-5.5; P = .033) and 3.4-fold (95% CI, 1.5-7.6; P = .003), respectively. Lower eccentric knee flexor strength and other prior injuries were not associated with an increased risk of future HSIs. Multivariate logistic regression revealed that the risk of reinjuries was augmented in players with strength imbalances. Previous HSIs and between-limb imbalance in eccentric knee flexor strength were associated with an increased risk of future HSIs in rugby union. These results support the rationale for reducing imbalance, particularly in players who have suffered a prior HSI, to mitigate the risk of future injuries. © 2015 The Author(s).

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... NHEs are typical training content of youth competitive alpine skiers recommend by the national skiing association Swiss-Ski, and participants were additionally familiarized with this type of exercise by social media challenges before the event. Reliability and application of the NordBord test device within different athlete populations has already been investigated and reported by various studies [26][27][28]. According to Opar et al. [27] the NordBord device possesses high to moderate reliability (intraclass correlation coefficient = 0.83-0.90; ...
... To date, no previous studies on MEHS values (measured during NHE) for U10 athletes in sports other than skiing are available. In adult athletes, however, greater MEHS values were observed in alpine skiers compared to soccer, rugby and Australian football athletes [19,26,28,30]. As stated ...
... To date, no previous studies on MEHS values (measured during NHE) for U10 athletes in sports other than skiing are available. In adult athletes, however, greater MEHS values were observed in alpine skiers compared to soccer, rugby and Australian football athletes [19,26,28,30]. As stated by Franchi et al. [19], this is probably due to the high force production of the knee extensors, the antagonists of the hamstring muscles, which is typical for alpine skiing. ...
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Severe knee injuries are common in alpine skiing and the hamstring muscles are known to counteract the anterior tibial displacement that typically accompanies major injury mechanisms. This study aimed to assess the Maximal Eccentric Hamstring Strength (MEHS) of youth competitive alpine skiers during Nordic Hamstring Exercise (NHE) in terms of dependence of sex, age and biological maturation. A total of 246 7-to 15-year-old skiers were tested with respect to their MEHS using an NHE-based measurement device (Vald Performance, Newstead, Australia). Significantly greater absolute MEHS was observed in skiers of the under 15 years (U15) category compared to skiers under 10 years old (U10) (227.9 ± 61.1 N vs. 142.6 ± 28.9 N; p < 0.001), also when grouped by sex. Absolute MEHS was revealed to be lower in U15 females compared to males (213.5 ± 49.0 N vs. 241.9 ± 68.4 N; p = 0.001); in U10 skiers there was no sex difference. For all age groups and sexes, absolute MEHS values were significantly correlated with age and biological maturation (p < 0.001). However, when normalized to body weight such associations disappeared, which is why this is strongly recommended when testing around their growth spurt. Overall, this study established sport-specific normative reference data that may be of interest to researchers and sport practitioners alike.
... A central component of injury prevention models [9,10] is the identification of factors that can provide an indication Meta-analysis of six studies (156 prospective HSIs and 944 uninjured participants) found no difference in preseason eccentric knee flexor strength quantified during performance of the Nordic hamstring exercise (NHE) between prospectively injured and uninjured participants Irrespective of whether pre-season eccentric knee flexor strength quantified during performance of the NHE was expressed in absolute (N) or relative (N kg −1 ) terms or as a between-limb asymmetry (%) there was no difference between prospectively injured and uninjured participants Accounting for potential effect modifiers (sport played, age, height, mass, average cohort NHE strength) did not alter the findings Gaelic Football [21] have been conflicting. Similarly, whilst greater between-limb asymmetry in eccentric strength during NHE has been reported to increase HSI risk previously [19], this is not a consistent finding [16-18, 20, 21]. ...
... An initial prospective cohort study to test this hypothesis, conducted in elite Australian Football, identified a greater risk of future HSI in those who had lower levels of eccentric knee flexor strength during the NHE, compared to stronger athletes [16]. Whilst this initial finding was subsequently confirmed in a cohort of Australian soccer players [17], further studies in Qatari soccer [18], Australian rugby union [19], Australian Football [20], and separately for participants who did and did not sustain a subsequent HSI during a defined follow-up period. Only peer-reviewed publications in English were considered. ...
... Two studies [17,18] investigated elite soccer players (n = 376 participants, n = 55 injured) and another two studies [16,20] investigated elite Australian Football players (n = 362 participants, n = 53 injured). The two remaining studies investigated elite Gaelic Football players [21] (n = 184 participants, n = 28 injured) or elite and sub-elite Rugby Union players [19] (n = 178 participants, n = 20 injured). Participant characteristics are summarised in Supplementary Table S3. ...
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Background Interventions utilising the Nordic hamstring exercise (NHE) have resulted in reductions in the incidence of hamstring strain injury (HSI). Subsequently, quantifying eccentric knee flexor strength during performance of the NHE to identify an association with the occurrence of future HSI has become increasingly common; however, the data to date are equivocal.Objective To systematically review the association between pre-season eccentric knee flexor strength quantified during performance of the NHE and the occurrence of future HSI.DesignSystematic review and meta-analysis.Data sourcesCINAHL, Cochrane Library, Medline Complete, Embase, Web of Science and SPORTDiscus databases were searched from January 2013 to January 10, 2020.Eligibility criteria for selecting studiesProspective cohort studies which assessed the association between pre-season eccentric knee flexor strength quantified during performance of the NHE and the occurrence of future HSI.Methods Following database search, article retrieval and title and abstract screening, articles were assessed for eligibility against pre-defined criteria then assessed for risk of bias. Meta-analysis was used to pool data across studies, with meta-regression utilised where possible.ResultsA total of six articles were included in the meta-analysis, encompassing 1100 participants. Comparison of eccentric knee flexor strength during performance of the NHE in 156 injured participants and the 944 uninjured participants revealed no significant differences, regardless of whether strength was expressed as absolute (N), relative to body mass (N kg−1) or between-limb asymmetry (%). Meta-regression analysis revealed that the observed effect sizes were generally not moderated by age, mass, height, strength, or sport played.Conclusion Eccentric knee flexor strength quantified during performance of the NHE during pre-season provides limited information about the occurrence of a future HSI.
... 13 Low eccentric knee flexor strength is traditionally pointed out as a risk factor for hamstring injuries, 11 which have been supported by prospective studies with soccer players, 12,14-16 as well as with athletes from other sports. [17][18][19] More recently, a prospective study evidenced that players with short fascicles in the biceps femoris long head (BF LH ) are also more likely to sustain hamstring injury. 12 All these studies have only focused on outcomes for male athletes. ...
... 12 All these studies have only focused on outcomes for male athletes. 12,[14][15][16][17][18][19] However, it seems reasonable that prevention programs for both sexes should address strategies to increase the eccentric knee flexor strength and the BF LH fascicle length. ...
... A few years ago, Opar et al. 30 validated a prototype allowing a cheaper and faster assessment of the eccentric knee flexor strength during the NHE execution. While a large cohort study found no clinical value of strength tests with isokinetic dynamometry or the NHE device for predicting risk of hamstring injury, 34 cohort studies with soccer, 12,14-16 Australian football, 19 rugby, 18 and sprinters 17 have demonstrated that athletes with eccentric knee flexor weakness are more susceptible to hamstring injury. For this reason, eccentric strength was selected as the primary out-come of the current study, and findings demonstrated that an 8-week NHE training program improved eccentric strength of the knee flexor muscles of female soccer players. ...
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Background: Training programs that include the Nordic hamstring exercise (NHE) have been shown to increase eccentric knee flexor strength and biceps femoris fascicle length in male athletes. However, the effect of NHE on female athletes remains unknown. Purpose: To investigate the collective and individual responses of professional female soccer players engaged in a preseason training program with the NHE regarding eccentric knee flexor strength and biceps femoris long head fascicle length. Study design: Quasi-experimental study. Methods: Sixteen amateur female soccer players (without a NHE training routine) were evaluated 8-weeks apart to: (1) assess reliability of eccentric knee flexor strength and biceps femoris fascicle length measures; and (2) determine the typical error of measures that would be used to discriminate training responders and non-responders. The NHE training group had 17 professional female soccer players who performed an 8-week training program with the NHE during preseason. Within-group analysis was performed with paired sample t-tests (pre- vs. post-training), and individual responses were determined using the typical error criteria. Results: The non-trained group's data demonstrated that measures of strength (ICC=0.82-0.87, typical error = 12-13 N) and fascicle length (ICC=0.92-0.97; typical error = 0.19-0.38 cm) were reliable. In the NHE training group, both limbs increased the eccentric knee flexor strength (~13%; ES=0.74-0.82) and the biceps femoris fascicle length (~6%; ES=0.44-0.65). Twelve players (~71%) were considered responders to the NHE training program for the eccentric knee flexor strength, while eight athletes (~47%) were responders for the biceps femoris fascicle length. Conclusion: The 8-week preseason training program with the NHE increased both eccentric knee flexor strength and biceps femoris fascicle length in professional female soccer players. More than two-thirds of players demonstrated a meaningful increase in eccentric strength, while nearly half achieved consistent fascicle length increases with the NHE training.
... Testing of physical qualities is commonplace in professional sport to profile individuals against normative data (8,9), assist in the prescription and evaluation of training (27) and to identify individuals who may be at risk of injury (3,17,18,24). These data can then be used to guide individual physical preparation strategies to improve performance and mitigate injury risk. ...
... Hamstring strength and injury risk has been extensively studied (2,10,18,23), with data obtained for eccentric knee flexor peak force when performing the Nordic Hamstring curl (NHC), using the NordBord device, highlighting injury risk thresholds for various sports (3,18,24). Furthermore, the NordBord device has been assessed for between-day reliability and displays acceptable TE when assessing left (27.5 N; 8.5%) and right (21.7 N; 5.8%) leg eccentric knee flexor peak force when performing the NHC; suggesting it can be used to effectively monitor hamstring strength (16). ...
... More recently, a similar device to the NordBord has been made available; the Hamstring Solo, which is also able to measure eccentric knee flexor peak force. The Hamstring Solo has not been validated against the NordBord, therefore it is unknown whether the injury risk thresholds from the previously mentioned studies (3,18,24) can be applied to athletes who are monitored using the Hamstring Solo. Despite this the Hamstring Solo has been adopted by the English Institute of Sport, England Rugby, Scottish Rugby and other professional sports organisations within the United Kingdom & Ireland to monitor hamstring strength. ...
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The purpose of this study was to determine the between-day reliability of the Hamstring Solo for measuring peak eccentric knee flexor force (EKF) during the Nordic hamstring curl. Data were collected on 18 male Professional rugby union players across two testing sessions separated by 7 days. There was no between-session difference in EKF force for left (p = 0.440 – 0.580) or right (p = 0.477 – 0.656) leg when using the best of 1 (left = 405.3±88.2 N vs. 412.8±92.7 N; right = 408.0±88.1 N vs. 416.7±85.2 N), 2 (left = 409.9±87.6 N vs. 415.0±96.2 N; right = 413.0±87.5 N vs. 418.3±86.2 N), or 3 repetitions (left = 411.2±88.2 N vs. 417.3±92.7 N; right = 417.7±87.4 N vs. 417.7±87.4 N). The between-day reliability of EKF peak force was acceptable for left (7.2 to 8.3%) and right (8.3 to 9.8%) leg, with the typical error lowest when using the best of three repetitions. The smallest worthwhile change (SWC) was similar for left (4.2 – 4.3%) and right (3.6 – 3.7%) when using the best of 3 repetitions. As the typical error was greater than the SWC for both the left (1.71 x the SWC) and right (2.24 x the SWC) legs, changes of 2.71 (∆ 41 N; 11%) and 3.24 (∆ 47 N; 12%) xSWC are required to detect a small change in EKF peak force, taking into account the typical error. Practitioners can use the reliability statistics from this study to monitor EKF peak force in professional rugby union players, when using the Hamstring Solo device. It is recommended that when monitoring EKF peak force with the Hamstring Solo, practitioners use the best of 3 repetitions.
... Index-12 similarly avoids the limitations associated with normalisation to a reference limb or value. Referred to as the Bilateral Limb Imbalance in the included articles Bourne et al., 2015), the index is based upon the method proposed by Impellizzeri et al., (2008) which involves log-transformation of the ratio between two limbs. The log-transformed ratio can then be converted to a percentage by multiplying by 100. ...
... As such, the authors concluded that 85% symmetry was sufficient to identify abnormal symmetry based on normative data in knee-healthy controls and functional outcomes in patients and controls. More recent evidence supports the use of this threshold, reporting increased risk of injury with asymmetries greater than or equal to 15% (Bourne et al., 2015). However, contradictory findings using the same index (Index-12) demonstrated no increase in hamstring strain injury risk for asymmetries of 10%, 15% or 20% . ...
... Investigation into the effects of strength asymmetry on injury risk in athletes has become a well-researched topic as it is advocated that better competitive performance comes from minimising the time an athlete spends away from training through injury. One study assessed eccentric hamstring strength in 194 rugby players using the Nordic hamstring exercise and reported that between limb force asymmetries of ≥15% and ≥20% increased the risk of prospective hamstring strain injury by 2.4-fold and 3.4-fold, respectively (Bourne et al., 2015). However, a similar study observed contradictory findings, reporting no statistically significant increase in relative risk of future hamstring strain injuries in professional Australian rules footballer's with Nordic strength imbalances of 10%, 15% or 20%. ...
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The prevalence of inter-limb strength differences is well documented in the literature however, there are inconsistencies related to measurement and reporting, and the normative values and effects associated with inter-limb asymmetry. Therefore, the aims of this systematic review were to: 1) assess the appropriateness of existing indices for the calculation of asymmetry, 2) interrogate the evidence basis for literature reported thresholds used to define asymmetry and 3) summarise normative levels of inter-limb strength asymmetry and their effects on injury and performance. To conduct this systematic review, scientific databases (PubMed, Scopus, SPORTDiscus and Web of Science) were searched and a total of 3,594 articles were retrieved and assessed for eligibility and article quality. The robustness of each identified asymmetry index was assessed, and the evidence-basis of the identified asymmetry thresholds was appraised retrospectively using the references provided. Fifty-three articles were included in this review. Only four of the twelve identified indices were unaffected by the limitations associated with selecting a reference limb. Eighteen articles applied a threshold to original research to identify “abnormal” asymmetry, fifteen of which utilised a threshold between 10-15%, yet this threshold was not always supported by appropriate evidence. Asymmetry scores ranged between and within populations from approximate symmetry to asymmetries larger than 15%. When reporting the effects of strength asymmetries, increased injury risk and detriments to performance were often associated with larger asymmetry, however the evidence was inconsistent. Limitations of asymmetry indices should be recognised, particularly those that require selection of a reference limb. Failure to reference the origin of the evidence for an asymmetry threshold reinforces doubt over the use of arbitrary thresholds, such as 10-15%. Therefore, an individual approach to defining asymmetry may be necessary to refine robust calculation methods and to establish appropriate thresholds across various samples and methodologies that enable appropriate conclusions to be drawn.
... (8)(9)(10) Thus, quantifying eccentric hamstring strength to assess an individual's risk of HSI is common practice, (11,12) with more strength or less between-limb asymmetry in eccentric hamstring strength theoretically reducing HSI risk. Although recent reviews suggest assessment of preseason eccentric hamstring strength provides limited information about the occurrence of a future HSI, (7,13) findings reported thus far involve males only and are limited to sports such as rugby, (14) soccer, (12,15) and Australian (11,16) and Gaelic football. (17) Prospective studies assessing this association and inclusive of females and other sports in which HSI are common, such as track and American football, have not yet been investigated. ...
... An overwhelming majority of known evidence supporting HSI risk factors is based on study samples of exclusively male athletes. (11,12,(14)(15)(16) Despite female participants in collegiate sports being at an all-time high (47% of Division I athletes in 2019-2020; NCAA database), a known underrepresentation of female athletes in the sports medicine literature continues to exist. (25)(26)(27) To the best of our knowledge, this study is the first to include female athletes when determining the association between eccentric hamstring strength and subsequent HSI. ...
... Our study expanded on prior work in Australian Football, (11,16) soccer, (12,15) rugby, (14) and Gaelic Football(17) by involving a more diverse sample of American collegiate athletes (American football, soccer, track, and basketball). This allowed us to preliminarily explore A C C E P T E D whether sport confounds or mediates the relationship between eccentric hamstring strength and HSI. ...
Article
Introduction: Established risk factors for hamstring strain injuries (HSI) include older age and prior HSI. However, these are non-modifiable and have a limited role in injury prevention. Eccentric hamstring strength is a common component of HSI prevention programs but its association with injury is less clear. Purpose: To determine if eccentric hamstring strength was prospectively associated with HSI among collegiate athletes, while controlling for sex, age, and prior HSI. We hypothesized that athletes with lower eccentric hamstring strength or greater between-limb strength asymmetry at preseason would have an increased risk of HSI. Methods: Hamstring eccentric strength measures, maximum total force (FTotal) and between-limb asymmetry in maximum force (FAsym), were measured at preseason on male and female athletes. HSIs were tracked over the subsequent 12-months. Generalized estimating equations were used to identify univariable and multivariable associations between athlete demographics, eccentric hamstring strength, and HSI risk. Results: Data for 326 athletes (85 female; 30 track, 43 basketball, 160 American football, 93 soccer) were included and 64 HSIs were observed. Univariable associations between eccentric hamstring strength and subsequent HSI were non-significant (FTotal OR = 0.99 [95% CI 0.93, 1.05], p = 0.74; FAsym OR = 1.35 [95% CI 0.87, 2.09], p = 0.23). No relationship between eccentric hamstring strength and HSI (FAsym OR = 1.32 [95% CI: 0.84, 2.08], p = 0.23) was identified after adjusting for confounders including sex, age, and prior HSI. Conclusions: No association between preseason eccentric hamstring strength and risk of subsequent HSI was identified after controlling for known risk factors and sex among collegiate athletes. Eccentric hamstring strengthening may continue to serve as a preventative approach to HSI, but it does not provide additional insight into HSI risk beyond factors such as age and prior HSI.
... Preseason deficits in eccentric knee flexor strength during the Nordic hamstring exercise (NHE) have been associated with an increased risk of future hamstring injury in elite Australian rules footballers [11] and Australian soccer players [12], although no such relationship was noted for rugby players [13], Gaelic football players [14] or Qatari soccer players [15]. However, interactions between previous HSI history and eccentric strength have been reported, with weakness appearing to have a more significant effect on future injury rates in previously injured than uninjured athletes [11,12]. ...
... This study involved a secondary analysis of data collected between 2013 and 2015 for three previously published prospective studies [11][12][13]. Ethics approval for these studies was granted by the Queensland University of Technology Human Research Ethics Committee and the Australian Catholic University Human Research Ethics Committee. From these combined studies, a total of 535 male athletes, including 210 elite Australian Football League (AFL) players, 147 elite A-League soccer players (goalkeepers included), and 75 elite and 103 sub-elite rugby union players, were included for observation (see Fig. 1). ...
... For athletes with no history of lower limb injury, a betweenlimb imbalance in peak eccentric knee flexor force was calculated as a right: left limb ratio and, for athletes with a prior ACLR or HSI, as an uninjured: injured limb ratio. The between-limb imbalance ratio was converted to a percentage difference as per previous work [11,13] using log-transformed raw data, followed by back transformation. Negative percentage imbalances specify that the left limb was stronger than the right limb in athletes with no history of lower limb injury, or that the previously injured limb was stronger than the uninjured limb in athletes with a prior ACLR or HSI. ...
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Objective: To determine the impacts of anterior cruciate ligament reconstruction (ACLR) and recent (< 12 months) hamstring strain injury (HSI) on 1) future HSI risk ; and 2) eccentric knee flexor strength and between-limb imbalance during the Nordic hamstring exercise (NHE). A secondary goal was to examine whether eccentric knee flexor strength was a risk factor for future HSI in athletes with prior ACLR and/or HSI. Methods: In this prospective cohort study, 531 male athletes had preseason eccentric knee flexor strength tests. Injury history was also collected. The main outcome was HSI occurrence in the subsequent competitive season. Results: 74 athletes suffered at least one prospective HSI. Compared to control athletes, those with a life-time history of ACLR and no recent HSI had 2.2 (95%CI=1.1-4.4; p = 0.029) times greater odds of subsequent HSI while those with at least one HSI in the previous 12 months and no history of ACLR had 3.1 (95%CI=1.8-5.4; p < 0.001) times greater odds for subsequent HSI. Only athletes with a combined history of ACLR and recent HSI had weaker injured limbs (p = 0.001) and larger between-limb imbalances (p < 0.001) than uninjured players. An exploratory decision tree analysis suggested eccentric strength may protect against HSI after ACLR. Conclusion: ACLR and recent HSI were similarly predictive of future HSI. Lower levels of eccentric knee flexor strength and larger between-limb imbalances were found in athletes with combined histories of ACLR and recent HSI. These findings may have implications for injury rehabilitation.
... Rightward-shifts in the torque-angle relationship could be of critical importance for athletes that require high eccentric hamstring force application at specific knee angles, such as those seen in high-speed running (Figure 1). Where the torque is being produced in the muscle is of importance as current research suggests having "strong and long" hamstring muscles is effectual for injury prevention (Bourne et al., 2015;Timmins et al., 2015) with lengthening hamstring exercises showing the fastest return-to-play and a lower reinjury rate compared with conventional hamstring exercises (Ishøi et al., 2020). ...
... The HALHAM • uses strain gauge load cells (Omega, Engineering Inc. Norwalk, USA) attached at the rear in a fixed position within a moveable tray parallel to the shank, with the platform tray free to rotate (Figure 3). The load cells measure both individual right and left limb, and combined limb total forces producing force-time traces in line graph format, useful for determining individual leg strength and any bilateral force asymmetries during the NHE, as a >15% difference between limbs has been cited as a risk factor for HSI (Bourne et al., 2015). Torque is calculated for each NHE trial across all three inclinations from the force measured by the load cells and the distance measured from the set pivot point (0.6 m). ...
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The Nordic hamstring exercise (NHE) has been shown to reduce hamstring injury risk when employed in training programs. This study investigates a novel device to modify the NHE torque-length relationship of the knee flexors, as targeting the hamstrings at a more extended length may have benefits for hamstring strain injury prevention and rehabilitation. Eighteen recreational male participants completed three bilateral NHE repetitions at a conventional 0° flat position, a 10° incline, and a 10° decline slope on a novel device (HALHAM°). Measures of peak torque and break-torque angle explored the effect of inclination on the knee flexors' length-tension relationship. Relative thigh-to-trunk angle and angular velocity of the knee joint were used to assess influence of inclination on technique and exercise quality. Break-torque angle increased when performed at an incline (134.1 ± 8.6°) compared to both the decline (112.1 ± 8.3°, p <0.0001, g = 2.599) and standard flat NHE positions (126.0 ± 9.8°, p = 0.0002, g = 0.885). Despite this, altering inclination did not affect eccentric knee flexor peak torque (decline = 132.0 ± 63.1 Nm, flat = 149.7 ± 70.1 Nm, incline = 148.9 ± 64.9 Nm, F = 0.952, p = 0.389), angular velocity of the knee joint at break-torque angle (decline = 23.8 ± 14.4°, flat = 29.2 ± 22.6°, incline = 24.5 ± 22.6°, F = 0.880, p = 0.418) or relative thigh-to-trunk angle at break-torque angle (decline = 20.4 ± 10.4°, flat = 16.7 ± 10.8°, incline = 20.2 ± 11.2°, F = 1.597, p = 0.207). The report recommends the use of arbitrary metrics such as break-torque angle that can be replicated practically in the field by practitioners to assess proxy muscle length changes i.e., the angular range over which the torque can be produced. Inclination of the Nordic hamstring exercise leads to hamstring muscle failure at longer muscle lengths without reductions in the maximal force exuded by the muscle. Therefore, the NHE performed on an incline may be a more effective training intervention, specific to the proposed mechanism of hamstring strain injury during sprinting that occurs whilst the muscle is rapidly lengthening. Using a graded training intervention through the inclinations could aid gradual return-to-play rehabilitation.
... Knee position on the pad was standardised for each individual's leg-length based for consistency in each assessment. Participants were instructed to place their hands crossed on their chest and gradually lean forward whilst keeping their trunk and hips neutral, until they were unable to sustain the position and fell to the padded mat (Bourne et al. 2015). Players completed two partial warm-up repetitions followed by a single set of three maximal repetitions for strength assessment, with the peak force in absolute newtons (N) and relative terms (N/kg-1 ) used for analysis (Bourne et al. 2015). ...
... Participants were instructed to place their hands crossed on their chest and gradually lean forward whilst keeping their trunk and hips neutral, until they were unable to sustain the position and fell to the padded mat (Bourne et al. 2015). Players completed two partial warm-up repetitions followed by a single set of three maximal repetitions for strength assessment, with the peak force in absolute newtons (N) and relative terms (N/kg-1 ) used for analysis (Bourne et al. 2015). Each protocol was repeated at the half time (HT) interval and immediately post SAFT 90 (termed full-time; FT) to assess strength differences. ...
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Together, the burden of hamstring and hip and groin injuries in soccer is substantial and the risk of re-injury in these areas is high. Reduced muscle strength has been identified as an important modifiable intrinsic risk factor of injury. However, little is known regarding the within-match changes in hip and hamstring muscle strength in order to inform early detection and management strategies. Seventy-one male soccer players (age, 19.2 ± 0.9 yrs; height, 175.9 ± 5.8 cm; weight, 73 ±8.2 kg) from an international academy completed a fixed soccer specific activity profile (SAFT⁹⁰). Isometric hip and eccentric hamstring strength were measured after a standardised 5-min warm-up and repeated at half time and full time. Repeated-measures ANOVA were used to determine changes in muscle strength with magnitude-based decisions used to express probabilistic uncertainty. Findings indicate that i) there was likely to very likely substantial changes in isometric hip strength (-9.9-15.7%) and ii) no substantial changes in eccentric hamstring strength (-2.6-5.1%). By extrapolating these findings, it can be inferred that reduced isometric hip strength during match play may be one risk factor for injury, especially during periods of fixture congestion and practitioners should routinely assess muscle strength to inform training and match exposure based on player readiness. In doing so, it is likely that practitioners may enhance player availability and minimise injury incidence.
... Eccentric knee flexor strength. The assessment of eccentric knee flexor strength during the NHE has been reported previously (4,6,9,10). Players knelt on an instrumented device (NordBord, Vald Performance, Queensland, Australia), with their ankles secured immediately superior to the lateral malleolus by individual ankle hooks attached to uniaxial load cells. ...
... When tested at multiple time points, relative BFlh fascicle length was inversely associated with the probability of HSI, particularly in previously hamstring strain injured athletes and those with between-limb imbalances in eccentric knee flexor strength (Fig. 5). A previous study observed a similar relationship between eccentric knee flexor strength imbalances and prior HSI, whereby the probability of HSI was aug-mented in rugby players with a history of HSI and larger imbalances (9). In the present study, relative fascicle length was able to offset the increased risk associated with greater between-limb strength imbalances (or vice-versa), particularly in players with a history of HSI. ...
Article
Purpose: To determine if eccentric knee flexor strength and biceps femoris long head (BFlh) fascicle length were associated with prospective HSI in professional Australian Football players, and if more frequent assessments of these variables altered the association with injury risk. Methods: Across two competitive seasons, 311 Australian Football players (455 player seasons) had their eccentric knee flexor strength during the Nordic hamstring exercise and BFlh architecture assessed at the start and end of preseason and in the middle of the competitive season. Player age and injury history were also collected in preseason. Prospective HSIs were recorded by team medical staff. Results: Seventy-four player seasons (16%) sustained an index HSI. Shorter BFlh fascicles (<10.42 cm) increased HSI risk when assessed at multiple time points only (RR = 1.9; 95%CI = 1.2 to 3.0). Neither absolute (N) or relative (N.kg-1) eccentric knee flexor strength were associated with HSI risk, regardless of measurement frequency (RR range = 1.0 to 1.1), however between-limb imbalance (>9%) when measured at multiple time points was (RR = 1.8, 95%CI = 1.1 to 3.1). Prior HSI had the strongest univariable association with prospective HSI (RR = 2.9; 95%CI = 1.9 to 4.3). Multivariable logistic regression models identified a combination of prior HSI, BFlh architectural variables and between-limb imbalance in eccentric knee flexor strength as optimal input variables, however, their predictive performance did not improve with increased measurement frequency (Area under the curve = 0.681 to 0.726). Conclusions: More frequent measures of eccentric knee flexor strength and BFlh architecture across a season did not improve the ability to identify which players would sustain a HSI.
... Practitioners and scientists should use foam pads, towel rolls, or related tools to place the knee joint on an edge and to provide appropriate cushioning to the shins [12,[59][60][61]93]. The shanks should be placed at least 15 cm above the level that chest and/or hands touch at full knee extension [8,23,38,61,102,103] to accentuate the eccentric stimulus at extended muscle lengths. The particular knee flexion angles of~30 • to 0 • mirror the critical ROM of hamstring injuries [35,104] and have the potential for biggest NHE-induced strength gains [56]. ...
... Although the great benefits of NHE testing and regular NHE training are wellknown [2,3,83,103,104], the present scoping review revealed a 'below average' and 'poor' quality of published NHE assessments and interventions. These findings confirmed the current scoping review of Breed et al. [85], who demonstrated a predominantly low exercise intervention reporting quality of hamstring-related research. ...
Article
Full-text available
The objective of this scoping review is to assess Nordic Hamstring Exercise quality (ANHEQ) of assessments and interventions according to the ANHEQ rating scales and to present practical recommendations for the expedient design and reporting of future studies. A total of 71 Nordic Hamstring Exercise (NHE) assessments and 83 NHE interventions were selected from the data sources PubMed, Scopus, and SPORTDiscus. Research studies which were presented in peer-reviewed academic journals and implemented the NHE during laboratory-based assessments or multi-week interventions met the eligibility criteria. NHE assessments analyzed force (51%), muscle activation (41%), knee angle kinematics (38%), and bilateral symmetry (37%). NHE interventions lasted 4–8 weeks (56%) and implied an exercise volume of two sessions per week (66%) with two sets per session (41%) and ≥8 repetitions per set (39%). The total ANHEQ scores of the included NHE assessments and interventions were 5.0 ± 2.0 and 2.0 ± 2.0 (median ± interquartile range), respectively. The largest deficits became apparent for consequences of impaired technique (87% 0-point-scores for assessments) and kneeling height (94% 0-point-scores for interventions). The 0-point-scores were generally higher for interventions compared to assessments for rigid fixation (87% vs. 34%), knee position (83% vs. 48%), kneeling height (94% vs. 63%), and separate familiarization (75% vs. 61%). The single ANHEQ criteria, which received the highest score most frequently, were rigid fixation (66% of assessments) and compliance (33% of interventions). The quality of NHE assessments and interventions was generally ‘below average’ or rather ‘poor’. Both NHE assessments and interventions suffered from imprecise reporting or lacking information regarding NHE execution modalities and subsequent analyses. Based on the findings, this scoping review aggregates practical guidelines how to improve the design and reporting of future NHE-related research.
... Furthermore, HADD:HABD ratio of~103% from bilateral measurement and HFLX:HEXT ratio of~75% from unilateral measurement is in agreement with previous studies using the GroinBar device on football players [13,15], while measured HIR:HER ratio of~96% from unilateral and 124% from bilateral measurement in our study is comparable to bilaterally measured the HIR:HER ratio of 108% from the study by Desmyttere et al. (2019) [15]. In addition, peak torques during the NHE showed high intra-session reliability, which is comparable to other similar devices for measuring forces during the NHE-namely, Opar et al. (2015) [19], who tested the NordBord device, and Lodge et al. (2020) [20], who recently tested the Hamstring Solo Elite device. This is a particularly important measurement characteristic of dynamometers since eccentric strength of the hamstrings (measured during the NHE but not on the isokinetic dynamometer) [21,22] is a significant risk factor for the occurrence of hamstring strain injuries [23]. ...
... This is a particularly important measurement characteristic of dynamometers since eccentric strength of the hamstrings (measured during the NHE but not on the isokinetic dynamometer) [21,22] is a significant risk factor for the occurrence of hamstring strain injuries [23]. Another important measurement characteristic of the device in the context of prevention/rehabilitation of hamstring injuries is the ability to measure forces for each limb separately since inter-limb strength asymmetry during the NHE is another risk factor for hamstring injuries [24]. ...
Article
Full-text available
The purpose of this study was to evaluate intra- and inter-session reliability of the new, portable, and externally fixated dynamometer called MuscleBoard® for assessing the strength of hip and lower limb muscles. Hip abduction, adduction, flexion, extension, internal and external rotation, knee extension, ankle plantarflexion, and Nordic hamstring exercise strength were measured in three sessions (three sets of three repetitions for each test) on 24 healthy and recreationally active participants. Average and maximal value of normalized peak torque (Nm/kg) from three repetitions in each set and agonist:antagonist ratios (%) were statistically analyzed; the coefficient of variation and intra-class correlation coefficient (ICC2,k) were calculated to assess absolute and relative reliability, respectively. Overall, the results display high to excellent intra- and inter-session reliability with low to acceptable within-individual variation for average and maximal peak torques in all bilateral strength tests, while the reliability of unilateral strength tests was moderate to good. Our findings indicate that using the MuscleBoard® dynamometer can be a reliable device for assessing and monitoring bilateral and certain unilateral hip and lower limb muscle strength, while some unilateral strength tests require some refinement and more extensive familiarization.
... Practitioners and scientists should use foam pads, towel rolls, or related tools to place the knee joint on an edge and to provide appropriate cushioning to the shins [12,[59][60][61]93]. The shanks should be placed at least 15 cm above the level that chest and/or hands touch at full knee extension [8,23,38,61,102,103] to accentuate the eccentric stimulus at extended muscle lengths. The particular knee flexion angles of~30 • to 0 • mirror the critical ROM of hamstring injuries [35,104] and have the potential for biggest NHE-induced strength gains [56]. ...
... Although the great benefits of NHE testing and regular NHE training are wellknown [2,3,83,103,104], the present scoping review revealed a 'below average' and 'poor' quality of published NHE assessments and interventions. These findings confirmed the current scoping review of Breed et al. [85], who demonstrated a predominantly low exercise intervention reporting quality of hamstring-related research. ...
Preprint
OBJECTIVE: Assessing Nordic Hamstring Exercise quality (ANHEQ) of assessments and interventions according to the ANHEQ rating scales and to present practical recommendations for the expedient design and reporting of future studies. DESIGN: Scoping review of 71 NHE assessments and 83 NHE interventions (12 of 131 full-text articles were applicable to both categories). DATA SOURCES: PubMed, MEDLINE and SPORTDiscus. ELIGIBILITY CRITERIA FOR SELECTING STUDIES: Research studies which were presented in peer-reviewed academic journals and implemented the NHE during laboratory-based assessments or multi-week interventions. RESULTS: The total ANHEQ scores of the analysed NHE assessments and interventions were 5.0±2.0 and 2.0±2.0 (median±IQR), respectively. Largest deficits became apparent for consequences of impaired technique (87% 0-point-scores for assessments) and kneeling height (94% 0-point-scores for interventions). The single ANHEQ criteria which received the highest score most frequently were rigid fixation (66% of assessments) and compliance (33% of interventions). CONCLUSIONS: The quality of NHE assessments and interventions was generally ‘below average’ or rather ‘poor’. Practitioners and scientists are encouraged to provide detailed information about their NHE modalities and about how their participants performed the exercise. The appropriate setup is suggested to be essential for best possible NHE performance and neuromuscular adaptations. NHE assessments should present comprehensive kinematic and kinetic data of supramaximal NHE performance, whereas NHE interventions should focus on exercise intensity and the implementation of facilitations. This scoping review aggregates practical guidelines how to improve the design and reporting of future NHE assessments and interventions to overcome the revealed limitations of current NHE-related evidences.
... During all attempts, force data of each load cell (sample rate = 10 Hz) were simultaneously transferred via Bluetooth to a mobile smartphone. Both the peak force value obtained in each limb (Bourne et al., 2015;Buchheit et al., 2016;Opar et al., 2015;Ribeiro-Alvares et al., 2020) and the between-limb average peak force value (Bourne et al., 2015;Ribeiro-Alvares et al., 2021;Roe et al., 2018;Timmins et al., 2016) were considered for statistical analysis. The participants' age and anthropometric data (body mass and height) were provided by the respective clubs. ...
... During all attempts, force data of each load cell (sample rate = 10 Hz) were simultaneously transferred via Bluetooth to a mobile smartphone. Both the peak force value obtained in each limb (Bourne et al., 2015;Buchheit et al., 2016;Opar et al., 2015;Ribeiro-Alvares et al., 2020) and the between-limb average peak force value (Bourne et al., 2015;Ribeiro-Alvares et al., 2021;Roe et al., 2018;Timmins et al., 2016) were considered for statistical analysis. The participants' age and anthropometric data (body mass and height) were provided by the respective clubs. ...
Article
The study aimed to verify how age, height, body mass and body mass index affects the eccentric knee flexor strength during the Nordic hamstring exercise (NHE) in male soccer players. Ten professional soccer clubs were included in this cross-sectional trial. Three hundred and eleven soccer players (192 from senior and 119 from under-20 teams) were assessed using a load-cell based device. Pearson’s correlation tests were performed between peak force values (measured in Newtons) and age, height, body mass and body mass index. The individual-limb strength (n = 622 limbs) and the between-limb average strength (n = 322 players) presented no correlation with age (r = 0.12 for both) and height (r = 0.13; r = 0,15), and fair correlations with body mass (r = 0.37; r = 0,41) and body mass index (r = 0.40; r = 0,43). In conclusion, the male soccer players’ eccentric knee flexor strength measured during the NHE execution is not affected by age or height. Body mass and body mass index play somewhat effect on strength, thus normalising absolute strength measures by body mass or body mass index can provide more accurate analysis in some contexts.
... 22 Similar to the present study, data from other sports involving high-speed running and change-of-direction activities (Gaelic soccer, cricket, and rugby) have indicated that youth players show similar or higher normalized knee flexor strength compared with senior players when measured in the Nordbord during the Nordic Hamstring exercise. [22][23][24] Collectively, these observations indicate that maximal hamstring strength capacity is lower at the senior level compared with youth level, which may lead to an increased susceptibility of sustaining hamstring muscle strain injury. 2,4 Several studies have highlighted the increased risk of sustaining a hamstring strain injury with increasing age. ...
... Notwithstanding these factors, the present findings appears to closely resemble previous reports obtained in elite soccer players 10,19 and athletes from other sports. [22][23][24] ...
Purpose: Increasing age, high quadriceps strength, and low hamstring muscle strength are associated with hamstring strain injury in soccer. The authors investigated the age-related variation in maximal hamstring and quadriceps strength in male elite soccer players from under-13 (U-13) to the senior level. Methods: A total of 125 elite soccer players were included from a Danish professional soccer club and associated youth academy (first tier; U-13, n = 19; U-14, n = 16; U-15, n = 19; U-17, n = 24; U-19, n = 17; and senior, n = 30). Maximal voluntary isometric force was assessed for the hamstrings at 15° knee joint angle and for the quadriceps at 60° knee joint angle (0° = full extension) using an external-fixated handheld dynamometer. Hamstring-to-quadriceps strength (H:Q) ratio and hamstring and quadriceps maximal voluntary isometric force levels were compared across age groups (U-13 to senior). Results: Senior players showed 18% to 26% lower H:Q ratio compared with all younger age groups (P ≤ .026). Specific H:Q ratios (mean [95% confidence interval]) were as follows: senior, 0.45 (0.42-0.48); U-19, 0.61 (0.55-0.66); U-17, 0.56 (0.51-0.60); U-15, 0.59 (0.54-0.64); U-14, 0.54 (0.50-0.59); and U-13, 0.57 (0.51-0.62). Hamstring strength increased from U-13 to U-19 with a significant drop from U-19 to the senior level (P = .048), whereas quadriceps strength increased gradually from U-13 to senior level. Conclusion: Elite senior soccer players demonstrate lower H:Q ratio compared with youth players, which is driven by lower hamstring strength at the senior level compared with the U-19 level combined with a higher quadriceps strength. This discrepancy in hamstring and quadriceps strength capacity may place senior-level players at increased risk of hamstring muscle strain injuries.
... HKY'ye neden olan faktörler arasında; ileri yaş (Henderson, 2010), hamstring yaralanma öyküsü (Engebretsen, 2010), eksantrik diz hamstring kas kuvvetindeki azalma Timmins, 2016), hamstring kas kuvvetinin kuadriseps kas kuvvetine oranındaki dengesizlik, kas yorgunluğuna sebep olan hamstring reaksiyon zamanındaki gecikme ve hamstringlerin aşırı aktif olması, zayıf lumbopelvik stabilite (Shield, 2018), kognitif fonksiyon (Buckthorpe, 2019) ve bozulmuş hamstring kas mimarisi (Timmins, 2016) yer almaktadır. Literatürde birçok prospektif çalışmada, eksantrik ve konsantrik diz fleksör kas kuvvetinin hamstring yaralanma oranları üzerine etkileri incelenmiştir (Bourne, 2015;Croisier, 2008;Timmins, 2016;van Dyk, 2016;Yeung, 2009). Bu çalışmalarda hem düşük konsantrik kuadriseps kuvveti hem de düşük eksantrik hamstring kas kuvvetinin artan HKY riski ile ilişkili olduğu ifade edilmiştir (Bourne, 2015;Croisier, 2008;Timmins, 2016;van Dyk, 2016;Yeung, 2009). ...
... Literatürde birçok prospektif çalışmada, eksantrik ve konsantrik diz fleksör kas kuvvetinin hamstring yaralanma oranları üzerine etkileri incelenmiştir (Bourne, 2015;Croisier, 2008;Timmins, 2016;van Dyk, 2016;Yeung, 2009). Bu çalışmalarda hem düşük konsantrik kuadriseps kuvveti hem de düşük eksantrik hamstring kas kuvvetinin artan HKY riski ile ilişkili olduğu ifade edilmiştir (Bourne, 2015;Croisier, 2008;Timmins, 2016;van Dyk, 2016;Yeung, 2009). ...
Conference Paper
Full-text available
İnsanlar, sağlık sorunlarının giderilebilmesi, sağlıklı yaşam, yaşam kalitesinin artırılması, vücut kütlesinin ve yağ dokusunun azaltılması, fiziksel görünüm ve estetik kaygısı gibi birçok sebep ve hedefle özel diyet uygulamalarına yönelmektedir. Günümüzde, daha olumlu yanıtlar alınabileceği düşünülerek modern diyetlere yönelim giderek artmıştır. Bu diyet uygulamaları zamanla sporda ve sporcularda da ilgi görmeye başlamış ve yerini almıştır. Sporcuların, bireysel amaç ve hedefleri, inançları, beslenme kültürleri ve yaşam koşulları da dikkate alınarak bu tip diyetlere yönelimleri değişiklik arz etmektedir. Bu çalışma, aralıklı açlık, İslami oruç ve ketojenik diyet uygulamalarının sporcu performansına etkisi, tercih nedenleri, diğer klasik ve modern diyet uygulamalarına göre değerlendirilmesi, yağ kütlesi üzerindeki etkilerinin belirlenebilmesi amacıyla yapılmıştır. Çalışma, mikro-analiz biçiminde bir derleme örneği olarak sunulmuştur. Konu ile ilgili literatür taraması yapılarak, sonuçlar ışığında tartışılmış ve genelleme önerilere yer verilmiştir. İnanç temelli olarak sürdürülen İslami oruç, sporcular tarafından kısa süreli olarak yaşama dahil edilmekte ve ötelenmemektedir. Müslüman sporcular, oruç tutarak antrenman yaşamlarına devam edebilmektedirler. Fakat araştırma sonuçları, orucun performansa etkisi konusunda kararlılık göstermemektedir. Aralıklı açlık diyetinin daha çok yağ kütlesinde azalma istemi ile tercih edildiği, fakat dikkatli uygulanmadığında performansı olumsuz etkilediği, ek takviyelere ve gerekli hidrasyonun sağlanmasına ihtiyaç olduğu belirlenmiştir. Ketojenik diyet uygulamasının ise, glikojen depolarının korunması, yağ oksidasyonunun artması, yağ kütlesinde azalma, daha uzun süreli dayanıklılık gerektiren durumlarda performansa olumlu etkilerinin olduğu belirlenmiştir. Yine de bu tip özel diyetlerde genel sağlık ve performansa dayalı olarak, organizmada kısa ve uzun süreli etkilerinin takip edilerek, dikkatli bir şekilde uygulama yapılması gerekliliği düşünülmektedir.
... Accordingly, it has been suggested that the level of strain experienced by the hamstring muscles is at least partially determined by the ratio of hamstring-to-quadriceps strength, given that the quadriceps muscles are responsible for knee extension motion (41,58). Indeed, a growing body of literature now supports these suggested associations because hamstring strength (8,64,79,81), BFlh fascicle length (63,81), APT (12), and low H:Q strength imbalances (14,20,24,65) have been correlated with future HSIs. However, despite the ever-growing interest in HSIs in soccer among sport scientists, the incidence in soccer has increased over the past few years (30). ...
... The most uniform improvements across hamstring strength variables (concentric, eccentric, and isometric) were observed following combined low-and high-velocity eccentric and concentric training (56). Poor eccentric hamstring strength has been associated with increased risk for HSIs on a more frequent basis than both concentric and isometric strength (8,64,65,79,81); based on the findings of this systematic review, eccentric hamstring strength increased most after combined lowand high-velocity eccentric and concentric training (56) and low-velocity concentric training (3). The results seen in the latter subgroup are rather surprising given that concentric training is often thought to be less effective than eccentric training when it comes to improving eccentric strength (70). ...
... HKY'ye neden olan faktörler arasında; ileri yaş (Henderson, 2010), hamstring yaralanma öyküsü (Engebretsen, 2010), eksantrik diz hamstring kas kuvvetindeki azalma Timmins, 2016), hamstring kas kuvvetinin kuadriseps kas kuvvetine oranındaki dengesizlik, kas yorgunluğuna sebep olan hamstring reaksiyon zamanındaki gecikme ve hamstringlerin aşırı aktif olması, zayıf lumbopelvik stabilite (Shield, 2018), kognitif fonksiyon (Buckthorpe, 2019) ve bozulmuş hamstring kas mimarisi (Timmins, 2016) yer almaktadır. Literatürde birçok prospektif çalışmada, eksantrik ve konsantrik diz fleksör kas kuvvetinin hamstring yaralanma oranları üzerine etkileri incelenmiştir (Bourne, 2015;Croisier, 2008;Timmins, 2016;van Dyk, 2016;Yeung, 2009). Bu çalışmalarda hem düşük konsantrik kuadriseps kuvveti hem de düşük eksantrik hamstring kas kuvvetinin artan HKY riski ile ilişkili olduğu ifade edilmiştir (Bourne, 2015;Croisier, 2008;Timmins, 2016;van Dyk, 2016;Yeung, 2009). ...
... Literatürde birçok prospektif çalışmada, eksantrik ve konsantrik diz fleksör kas kuvvetinin hamstring yaralanma oranları üzerine etkileri incelenmiştir (Bourne, 2015;Croisier, 2008;Timmins, 2016;van Dyk, 2016;Yeung, 2009). Bu çalışmalarda hem düşük konsantrik kuadriseps kuvveti hem de düşük eksantrik hamstring kas kuvvetinin artan HKY riski ile ilişkili olduğu ifade edilmiştir (Bourne, 2015;Croisier, 2008;Timmins, 2016;van Dyk, 2016;Yeung, 2009). ...
Conference Paper
Full-text available
İskelet kasları; istemli kasılmayı, duruşun korunmasını, kas aktivitesinden ısı üretilmesini ve hareket oluşumunu sağlar. Kaslar, aynı zamanda vücudun ana protein deposu ve metabolizmanın önemli bir oyuncusu olarak hizmet eder. Protein homeostazını (iç denge) koruyarak bireyin sağlığına önemli ölçüde katkıda bulunur. Bu fonksiyonun değişmesi, kas atrofisi ya da sarkopeni olarak da adlandırılan kas kütlesi kaybına yol açar. Bu çalışma, kas distrofisi ve Miyostatin arasındaki ilişkinin, yapılan araştırma sonuçlarına dayalı olarak ifade edilmesi ve yorumlanabilmesi amacıyla yapılmıştır. Çalışma, derleme örneği olarak sunulmuştur. Konu ile ilgili literatür taraması yapılarak, sonuçlar ışığında tartışılmış ve genelleme önerilere yer verilmiştir. Kas distrofisinde, kas kütlesi ve fonksiyonunun yeniden kazandırılması, insan sağlığı için önemlidir. İskelet kaslarının gelişimi ve büyümesi Miyostatin tarafından düzenlenir. Embriyogenez sırasında somitlerden iskelet kasları oluşur. Miyostatin başlangıçta iskelet kasını oluşturan somitlerin (embriyoda doku kümesi) myotom tabakasında eksprese edilir ve bu ekspresyon kas büyümesini kısıtlar. Miyostatin, yetişkinlerde esas olarak iskelet kası tarafından üretilir. Endokrin hormonlar gibi, Miyostatin de serumda yüksek miktarlarda dolaşır ve kas lifi büyümesini sınırlar. Sonuç olarak, Miyostatin iskelet kasının aşırı büyümesini kontrol eden negatif yönlü bir düzenleyici olması nedeniyle, kas distrofi yaşayan bireylerde Miyostatin ekspresyonunun yüksek düzeyde olacağı düşünülmektedir. Bu tip kas hastalıklarının varlığı ve düzeyi arttıkça, Miyostatin düzeyinin de artacağı tahmin edilmektedir. Yapılan araştırmalarda, Miyostatin ve kas atrofisi arasındaki ilişki açıklanmış olmasına karşın, kas distrofisi ile Miyostatin ilişkisi açıklanmamıştır. Bu nedenle, yeni ve farklı bir araştırma konusu olmakla birlikte, laboratuvar sonuçları ile desteklenerek, özgünlüğünün ifade edilmesi gereken bir konu olduğu düşünülmektedir.
... Hamstring injuries have been postulated as a pandemic in sports and occur most commonly in sports involving frequent intense acceleration and deceleration actions, such as soccer or track and field (Junge & Dvořák, 2015;Valle et al., 2017). Modifiable risk factors for hamstring injuries encompass short biceps femoris fascicles (Bourne et al., 2015), low levels of strength (Ribeiro-Alvares et al., 2021; and several other factors such as poor sprinting mechanics (Goode et al., 2015;Schuermans et al., 2017). ...
Article
Full-text available
One of the main benefits of the Nordic Hamstring Exercise (NHE) is that it can be performed without the need of any extra material. However, numerous technical execution variables such as the ankle and pelvis position can influence the performance. The primary aims of this study were to investigate the effects of ankle position (i.e., plantar or dorsal flexion) on Nordic Hamstring Break Point (NHBP), repetition time and heel contact force. A secondary aim was to investigate differences in biceps femoris long head and semitendi- nosus muscle activation. Male professional field hockey players (n = 12) volunteered for the study. Paired t-tests were used to analyse the effect of ankle position on muscle NHBP, eccentric peak torque and repetition time. Ankle dorsal flexion resulted in a higher NHBP (p = 0.002, effect size [ES] = 1.48 [0.57 to 2.38]), repetition time (p = 0.004, ES = 0.98 [0.24 to 1.72]) and both absolute and relative heel contact force (p = 0.028, ES = 0.67 [0.01 to 1.34], p = 0.017, ES = 0.76 [0.07 to 1.44], respectively) compared to plantar flexion. Muscle activation was not significant different. This study showed a higher NHBP, absolute and relative heel contact force and repetition time with a dorsal flexed ankle vs. a plantar flexed ankle in the NHE, without changes in hamstrings muscle activation.
... Moreover, studies have investigated interventions aimed to reduce between-limb asymmetries, which have been reported to increase the likelihood of sustaining hamstring injury by 2.4 to 3.8. 24,36 This review determined that strength asymmetry was reduced with eccentric training, and imbalances in H/Q ratio and flexibility were normalized via resistance training and static stretching. ...
Article
Background: Hamstring injuries are common among athletes. Considering the potentially prolonged recovery and high rate of recurrence, effective methods of prevention and risk factor management are of great interest to athletes, trainers, coaches, and therapists, with substantial competitive and financial implications. Purpose: To systematically review the literature concerning evidence-based hamstring training and quantitatively assess the effectiveness of training programs in (1) reducing injury incidence and (2) managing injury risk factors. Study design: Systematic review and meta-analysis; Level of evidence, 1. Methods: A computerized search of MEDLINE, CINAHL, Cochrane Central Register of Controlled Trials, and SPORTDiscus with manual screening of selected reference lists was performed in October 2020. Randomized controlled trials investigating methods of hamstring injury prevention and risk factor management in recreational, semiprofessional, and professional adult athletes were included. Results: Of 2602 articles identified, 108 were included. Eccentric training reduced the incidence of hamstring injury by 56.8% to 70.0%. Concentric hamstring strength increased with eccentric (mean difference [MD], 14.29 N·m; 95% CI, 8.53-20.05 N·m), concentric, blood flow-restricted, whole-body vibration, heavy back squat, FIFA 11+ (Fédération Internationale de Football Association), and plyometric training methods, whereas eccentric strength benefited from eccentric (MD, 26.94 N·m; 95% CI, 15.59-38.30 N·m), concentric, and plyometric training. Static stretching produced greater flexibility gains (MD, 10.89°; 95% CI, 8.92°-12.86°) than proprioceptive neuromuscular facilitation (MD, 9.73°; 95% CI, 6.53°-12.93°) and dynamic stretching (MD, 6.25°; 95% CI, 2.84°-9.66°), although the effects of static techniques were more transient. Fascicle length increased with eccentric (MD, 0.90 cm; 95% CI, 0.53-1.27 cm) and sprint training and decreased with concentric training. Although the conventional hamstring/quadriceps (H/Q) ratio was unchanged (MD, 0.03; 95% CI, -0.01 to 0.06), the functional H/Q ratio significantly improved with eccentric training (MD, 0.10; 95% CI, 0.03-0.16). In addition, eccentric training reduced limb strength asymmetry, while H/Q ratio and flexibility imbalances were normalized via resistance training and static stretching. Conclusion: Several strategies exist to prevent hamstring injury and address known risk factors. Eccentric strengthening reduces injury incidence and improves hamstring strength, fascicle length, H/Q ratio, and limb asymmetry, while stretching-based interventions can be implemented to improve flexibility. These results provide valuable insights to athletes, trainers, coaches, and therapists seeking to optimize hamstring training and prevent injury. Keywords: hamstring flexibility; hamstring injury; hamstring strength; prevention; risk factor.
... Long-term participation in football also leads to the development of various degrees and modes of functional asymmetries (Fousekis et al.). MS deficiency and strength asymmetry has been proposed as one of the several risk factors for injury in football Xaverova et al., 2015) andit is documented that greater MS reduces this potential injury risk (Bourne et al., 2015;Suchomel et al.). ...
Article
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The purpose of this study was to investigate the effect of age on peak torque (PT) relative strength measures of knee extensors (KE) and knee flexors (KF), bilateral strength ratio (Q:Q, H:H), and ipsilateral strength ratio (H:Q) in youth elite male football players.Elite male players (n = 70) from four age categories (U16: n = 20, U17: n = 20, U19: n = 15, U21: n = 15) performed isokinetic strength tests using a Cybex dynamometer. Results show a significant effect of age on PTKE (F3,142 = 4.54, p = 0.005, = 0.09) and PTKF (age: F3,142 = 3.07, p = 0.030, = 0.06). No significant effect of age on unilateral (F3,142 = 1.05, p = 0.375, = 0.02) or ipsilateral strength ratio (F3,142 = 2.63, p = 0.053, = 0.06) was found. Results revealed significant differences in PTKE for nondominant limbs between U16 and U21. Higher bilateral differences were detected for flexors (H:H = 7.94-11.47 %, Q:Q = 7.97-9.29 %) compared to extensors. Our study showed that 17-year-old players have levels of strength similar to U19 players. A higher bilateral difference of knee flexors than extensors was found, suggesting that more attention should be paid to knee flexors. No effect of laterality was found for strength and strength asymmetries. Future research should also focus on ipsilateral strength ratio in late stage of maturation.
... Hamstring strain injury (HSI) is one of the most common injuries in team sports. 1 Cohort studies have supported that athletes with low eccentric knee flexor strength are more prone to sustain an HSI. [2][3][4][5][6] In addition, although restoring strength is a widely used criterion for discharge from rehabilitation, 7 it is not uncommon for players to return to play with residual strength deficits following an HSI. 8 Therefore, eccentric knee flexor strength assessments have a key role in both prevention and rehabilitation of HSI. ...
Article
Context: Eccentric knee flexor strength assessments have a key role in both prevention and rehabilitation of hamstring strain injuries. Objective: To verify the reliability of a clinical test for measuring eccentric knee flexor strength during the Nordic hamstring exercise using a commercially available handheld dynamometer. Design: Reliability study. Setting: Physical Therapy Laboratory, Federal University of Health Sciences of Porto Alegre (Brazil). Participants: Fifty male amateur athletes (soccer or rugby players; 24 [3] y). Main outcome measures: Eccentric knee flexor strength. Results: When compared with a load cell-based device, the clinical test using a handheld dynamometer provided smaller force values (P < .05) with large effect sizes (.92-1.21), moderate intraclass correlation (.60-.62), typical error of 30 to 31 N, and coefficient of variation of 10% to 11%. Regarding the test-retest reproducibility (2 sessions separated by 1 week), the clinical test provided similar force values (P > .05) with only small effect sizes (.20-.27), moderate to good correlation (.67-.76), typical error of 23 to 24 N, and coefficient of variation of 9% to 10%. Conclusion: The clinical test with handheld dynamometer proposed by this study can be considered an affordable and relatively reliable tool for eccentric knee flexor strength assessment in the clinical setting, but results should not be directly compared with those provided by load cell-based devices.
... It was found in this study that the players had an overall average eccentric hamstring force output of 427.47 ± 57.98 N and an average imbalance of 8.2 ± 6.65%. These findings exceed the recommended level, which suggest that strength greater than 337 N and a between limb imbalance less than 15% can reduce the risk of hamstring injury risk [52,78]. Hamstring strength, more so than limb imbalance, has been shown to have a greater influence on injury risk [20]. ...
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Background: Hamstring strains are the most common moderate-major severity injuries in football. The majority of hamstring injuries occur during sprinting, with low eccentric hamstring strength being associated with an elevated risk. Objective: To examine the relationship between sprinting and eccentric hamstring strength by monitoring total weekly sprint distance and weekly efforts > 90% and >95% of maximum velocity. Methods: Fifty-eight professional male footballers were observed over one-and-a-half seasons. Players' running was monitored during training and matches using GPS, and eccentric hamstring strength was measured weekly. Results: Weekly sprint distance (ρ = -0.13, p < 0.01) and weekly efforts >90% of maximum velocity (ρ = -0.08, p = 0.01) both displayed significant inverse relationships with the percentage change in eccentric hamstring strength; weekly efforts >95% of maximum velocity showed no relationship with hamstring strength (ρ = -0.02, p = 0.45). Only weekly efforts >90% of maximum velocity significantly influenced the mean percentage change in eccentric hamstring force, F(3,58) = 3.71, p = 0.01, with significant differences occurring when comparing 7-8 sprint efforts with 0-2 efforts (0.11%, p = 0.03) and 5-6 efforts (0.12%, p = 0.03). Conclusions: Eccentric hamstring strength levels significantly decrease when 7-8 weekly sprint efforts are completed at >90% of maximum velocity. Monitoring weekly sprint loading at velocities > 90% of maximum velocity may be valuable to help to reduce the risk of hamstring injuries in professional football.
... Delahunt et al., 2016). Although the participant group was previously unfamiliar with performing the NHE, the level of NHE strength (429 ± 47 N) was higher compared with that of elite Australian footballers (301 ± 84 N) , professional soccer players (310 ± 73 N) (Timmins et al., 2016), and elite (367 ± 77 N) and sub-elite (388 ± 96 N) Rugby Union players (Bourne et al., 2015). Initially, it was expected that this might be because the participants in this study were more familiarized with the NHE as they performed six to nine maximal-effort trials and most frequently attained their highest peak NHE force in the sixth trial, whereas the previous studies had athletes perform only three maximal-effort repetitions. ...
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Current debate exists around whether a presumed eccentric exercise, the Nordic hamstring exercise (NHE), actually causes active hamstring muscle lengthening. This is because of the decoupling that can occur between the muscle fascicle and muscle-tendon unit (MTU) length changes in relatively compliant human lower-limb MTUs, which results in MTU lengthening not necessarily causing muscle fascicle lengthening. This missing knowledge complicates the interpretation of why the NHE is effective at reducing running-related hamstring muscle injury risk in athletes previously unfamiliar with performing this exercise. The purpose of the study was therefore to investigate if the most-commonly injured hamstring muscle, the biceps femoris long head (BF), exhibits active muscle lengthening (i.e. an eccentric muscle action) during the NHE up until peak force in Nordic novices. External reaction force at the ankle, knee flexion angle, and BF and semitendinosus muscle activities were recorded from the left leg of 14 participants during the NHE. Simultaneously, BF muscle architecture was imaged using B-mode ultrasound imaging, and muscle architecture changes were tracked using two different tracking algorithms. From ~85 to 100% of peak NHE force, both tracking algorithms detected that BF muscle fascicles (n = 10) significantly lengthened (p < 0.01) and had a mean positive lengthening velocity (p ≤ 0.02), while knee extension velocity remained positive (17°·s−1) over knee flexion angles from 53 to 37° and a duration of 1.6 s. Despite some individual cases of brief isometric fascicle behavior and brief fascicle shortening during BF MTU lengthening, the predominant muscle action was eccentric under a relatively high muscle activity level (59% of maximum). Eccentric hamstring muscle action therefore does occur during the NHE in relatively strong (429 N) Nordic novices, which might contribute to the increase in resting BF muscle fascicle length and reduction in running-related injury risk, which have previously been reported following NHE training. Whether an eccentric BF muscle action occurs in individuals accustomed to the NHE remains to be tested.
... Of interest, recent literature found an increased hamstring-to-quadriceps ratio with an increasing amount of skill level and professional training in football players (Fousekis, Tsepis, & Vagenas, 2010). Additionally, low hamstring-to-quadriceps strength ratios of 0.61 or less have been found to substantially increase the risk of a muscle injury and may increase the risk of concomitant injuries such as anterior cruciate ligament (ACL) (re-) injuries (Bourne, Opar, Williams, & Shield, 2015;Croisier et al., 2008;Fousekis et al., 2010;Kellis, Galanis, & Kofotolis, 2019;Liu et al., 2012;Orchard et al., 1997;Steffen et al., 2016;Waldén, Hägglund, Werner, & Ekstrand, 2011). However, these findings have only been made in studies addressing strength ratios, not volume ratios and remain controversial (Evangelidis, Pain, & Folland, 2015;van Dyk et al., 2017). ...
Article
Muscle injuries of the hamstrings are among the most frequent in football and a main cause for significant time away from training and competition. The purpose of this study was to prospectively evaluate the loss of muscle volume in recreational football players three and six weeks after initial trauma. We hypothesized that significant muscle volume loss occurs within 6 weeks after the initial injury event. Twenty recreational football players (mean-age=25 ± 4years; mean-height=181 ± 8cm; mean-weight=81 ± 10kg) with type3a (minor partial muscle tear) and type3b (moderate partial muscle tear) injuries were included. Muscle volume was determined using established methods for the hamstrings and the quadriceps femoris muscle within 3 days and after 3 and 6 weeks following the initial injury. The injured hamstrings lost 6.5% (mean=64cm³(95%CI=31-98cm³),p<0.001), the healthy hamstrings lost 2.1% (mean=21cm³(3-44cm³),p=0.096) of muscle volume after six weeks. The quadriceps in the injured leg lost 3.8% (mean=78cm³(51-104cm³),p<0.001) and 4.5% (83cm³(45-121cm³),p<0.001) in the healthy leg. Muscle volume loss inversely correlated with activity levels in the healthy leg for the quadriceps (r=0.96(0.90-0.98);R²=0.92;p<0.001) and the hamstrings (r=0.72(0.40-0.88);R²=0.51;p<0.001), as well as the quadriceps in the injured leg (r=0.70(0.37-0.87);R²=0.49;p<0.001), but not the injured hamstrings. Muscle volume ratio of hamstrings to quadriceps in the control limb was 0.52 ± 0.06 and 0.53 ± 0.06 in the injured leg. The rehabilitation period of six weeks did not have a relevant negative or a positive effect on ratios. Significant muscle volume loss in the upper thigh occurs in recreational soccer players within three, and within six weeks after a hamstring injury and lies between 2 and 7%.
... A recent systematic review (21) reported significantly higher fat-free mass (FFM) and less fat mass (FM) in senior elite-level male RL forwards compared with their senior subelite or junior elite-level counterparts. In addition to these physical and physiological characteristics, eccentric knee-flexor strength and hip-abductor/ adductor strength have received recent attention as potential determinants of lower-limb injury risk in football players of all codes (6,7,29,43). Indeed, low levels of eccentric knee-flexor strength has been reported to increase the risk of future hamstring injury in male players (36,44) and low levels of isometric hipabduction/adduction strength have been associated with an increased risk of hip and groin injuries (8). ...
Article
Minahan, C, Newans, T, Quinn, K, Parsonage, J, Buxton, S, and Bellinger, P. Strong, Fast, Fit, Lean, and Safe: A positional comparison of physical and physiological qualities within the 2020 Australian Women's Rugby League team. J Strength Cond Res XX(X): 000-000, 2021-The purpose of the present study was to report the physical and physiological characteristics of elite women Rugby League (RL) players. Thirty-nine women (25.6 ± 4.3 years, 171.3 ± 7.7 cm, 83.5 ± 13.9 kg) from the 2020 Australian women's RL squad were recruited for this study. Players were categorized as adjustables (n = 7), backs (n = 15), or forwards (n = 17) for analysis. Each player was assessed for anthropometry, body composition (dual-energy X-ray absorptiometry), speed (5, 10 and 20 m sprint times), lower-body power (countermovement jump), upper-body power (medicine ball throw and explosive push up force), estimated one repetition maximum (e1RM) bench press, squat and bench pull, isometric mid-thigh pull strength, eccentric knee flexor strength, isometric hip abduction and adduction, and intermittent endurance performance (30-15 intermittent fitness test; 30-15 IFT). Linear mixed models were performed to compare positional groups. Forwards were significantly heavier and had greater fat mass, fat-free mass, and body fat percentage compared with backs and adjustables (P < 0.01). Backs were faster over 20 m compared with forwards (P = 0.025), whereas forwards had a lower 30-15 IFT peak velocity and estimated V[Combining Dot Above]O2peak compared with backs and adjustables. Nonetheless, when including body mass in the model, there were no differences between groups in 30-15 IFT peak velocity. There were no significant differences in other variables. These results provide contemporary benchmark physical, physiological, and anthropometric data for elite women RL players, which can inform recruitment, selection, training, and testing.
... Musculoskeletal injuries are common in sports, and thus International Journal of Human Movement and Sports Sciences 10(2): 294-302, 2022 295 injury prevention is becoming increasingly important. Leg dominance or musculoskeletal asymmetry has been reported to be a risk factor for lower extremity injuries, including anterior cruciate ligament injuries, stress fractures, and muscle strain [1][2][3][4][5][6][7]. For example, Brophy et al. reported that when limited to a non-contact injury mechanism, females are more likely to injure the anterior cruciate ligament in their supporting leg, whereas males tend to injure their kicking leg in soccer players [2]. ...
... This has been termed the, "break-point angle" in earlier literature (Sconce et al., 2015). It is well documented in the research that eccentric strength is an important concept of NHE performance (Bourne et al., 2015;Opar et al., 2015), with a "loss of control" indicating that torque has exceeded the capability of the knee flexor muscles, causing the participant to "break" and fall to the floor. Sconce et al., (2015) demonstrated that the BPA, determined by video analysis software to be a valid field-based measure of eccentric knee flexor torque when measured by isokinetic dynamometry. ...
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The Nordic hamstring exercise (NHE) is employed as a component of preventative training programmes to minimise hamstring strain injury risk. Variation in the methods and terminology used to assess the NHE makes comparison between studies difficult. We aimed to compare the utility of kinetic and kinematic metrics by comparing several collected concurrently. 18 male recreational rugby union participants completed 3 bilateral NHE repetitions on a hamstring device equipped with in-line strain gauge load cells, integrated with a 3-dimensional motion tracking system. Mean break-point angle occurred after the angle at first acceleration (121.5 ± 10.4° vs. 119.2 ± 7.1°) whereas break-torque angle (BTA) occurred later in the NHE action (126.0 ± 9.8°) showing highest correlation to the angle at greatest acceleration (123.9 ± 7.9°, r = 0.85). Future research should consider movement quality as the angular velocity of the knee joint at BTA demonstrated large variation (range = 3.6–93.4 deg·s¹), with high intrasubject variability of relative trunk-to-thigh angle at peak-torque (range = 0.4–44.7°). This study proposes standardisation of methods and terminology used to define the NHE. Measuring BTA is recommended to represent the point at which hamstring muscle failure occurs, specific to the proposed injury mechanism during high-speed running.
... To implement preventive strategies, the identification of risk factors, both intrinsic and extrinsic, associated with hamstring injury occurrence is crucial. These include: age [15], previous injury [16], hamstring strength [17][18][19], decreased range of knee extension [20,21], and ankle dorsiflexion [22,23]. Specifically, in the case of an intermittent sport such as field hockey, fatigue has been linked to a decrease in hamstring strength values, and this is an important risk factor for a hamstring injury [24]. ...
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This study aimed to analyze the effects of match congestion in a short period on isometric hamstring strength and hip/ankle range of motion in female field hockey players. Fourteen professional female field hockey players (age: 20.0 � 5.4 years) played two consecutive hockey matches in 24 h and maximal isometric hamstring strength and hip and ankle range of motion were obtained before and after the first match, after the second match, and 48 h after the second match. Furthermore, locomotion patterns and ratings of perceived exertion were recorded during hockey competitions. Isometric knee flexion strength showed significantly higher values 48 h after the second match for the non-dominant limb (p � 0.005, �p2 = 0.19), while no differences were reported in the dominant limb (p = 0.370, �p2 = 0.05). In addition, no differences were reported in the range-of-motion (ROM) variables such as the straight leg raise test or ankle dorsiflexion test (p = 0.075–0.217, �p2 = 0.01–0.03). The countermovement jump height steadily increased over the matches except between post-match 2 and 48 h after post-match 2 (p < 0.001, �2 = 0.382). Two consecutive official league field hockey matches played within 24 h did not have a negative effect on lower-limb risk factors (strength, hip and ankle ranges of motion, and ratings of perceived exertion) in female field hockey players directly, but they improved 48 h after the matches. This could indicate that 48 h recovery period following matches might be ideal for female field hockey players.
... Eccentric hamstring strength and inter-limb asymmetries have more recently been described as possible modifiable risk factors for HSI [11], with several studies publicizing that ECC hamstring training can reduce the incidence of HSI [12][13][14]. There is also a growing body of evidence [15,16] to suggest that inter-limb imbalances in hamstring strength increase the risk factor of HSI. Fousekis et al. [17] found that elite soccer players with imbalances in eccentric hamstring strength ≥ of 15% in the pre-season were at a greater risk (OR = 3.88; 95% CI 1.13 to 13.23, p = 0.03) of HSIs. ...
... [13][14][15][16] A lack of flexibility of the hip flexors discerned using the Modified Thomas test and of the hamstring using the straight-leg raise (SLR) test was identified prospectively to increase injury risk of hamstring strains among older (≥25 years old) Australian football athletes 17 and among male professional soccer athletes, 18 respectively. Contrarily, several studies did not find these neuromuscular characteristics such as weaker eccentric hamstring strength 19,20 and poor hamstring flexibility 21 as prospective risk factors of hamstring strains. A systematic review has reported that concentric and eccentric hamstring muscular strength was not a strong prospective risk factor. ...
Article
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Background: Eccentric hamstring strength and hamstring/quadriceps strength ratios have been identified as modifiable risk factors of hamstring strains. Additionally, those strength and flexibility characteristics are commonly used as clinical tests to monitor progress of athletes with acute or chronic hamstring strains. Although hamstring strains are common among basketball athletes, normative values of knee strength and flexibility characteristics are scarce. Normative values for these athletes would be important in prevention and management of hamstring strains. Purpose: To establish quadriceps and hamstring isokinetic strength and flexibility values among high school basketball athletes and examine the effects of sex and age. Study design: Cross-sectional research. Methods: Isokinetic knee muscular strength (concentric quadriceps [QuadC], concentric hamstring [HamC], eccentric hamstring [HamE], and strength ratios ([HamC/QuadC and HamE/Quad]), flexibility of hip flexors and quadriceps during a Modified Thomas test, and flexibility of hip extensors and hamstring during passive straight leg raise (SLR) and passive knee extension (PKE) tests were measured. Effects of sex and age were analyzed using t-tests and analysis of variance, respectively with Bonferroni corrected post hoc tests (p≤0.01). Results: A total of 172 high school basketball athletes (64 males/108 females; mean age (range): 15.7 (14-18) years old) participated in the study. Male athletes were significantly stronger than female athletes (QuadC: p<0.001; HamC: p<0.001) while no differences were observed in strength ratio (HamC/QuadC: p=0.759-0.816; HamE/QuadC: p=0.022-0.061). Among male athletes, a significant effect of age on quadriceps and hamstring strength was observed: older male athletes were stronger than younger male athletes. Contrarily, there were no effects of age on strength among female athletes. There were significant sex differences in quadriceps flexibility, SLR, and PKE (female athletes were more flexible; p=0.001-0.005) while no sex differences were found in hip flexor flexibility (p=0.105-0.164). There were no effects of age for any flexibility variables within male and female athletes (p=0.151-0.984). Conclusion: The current results provide normative values for hamstring strength and flexibility in high school basketball athletes. These normative values may further assist sports medicine specialists to develop screening tests, interventions, and return-to-sport criteria in this population. Level of evidence: 3B.
... To the best of our knowledge, this is the first study suggesting that contralateral deficits among hamstring and quadriceps muscle groups may be influenced by the variable used to analyze it (e.g., PT or TW). Since this variable can be an important predictor of injuries in sports, understanding aspects related to different methods of assessment and possible outcomes is essential for properly monitoring injury risk factors [29,30]. Isokinetic dynamometry outcomes are within the five most common tests used as part of a periodic assessment for identifying injury risk in sports [24]. ...
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Background: Running is a very popular activity and muscle strength imbalance has been treated with caution to prevent injuries. Aims: The present study aimed to compare and correlate knee flexion and extension strength imbalance based on Peak Torque (PT) and total work (TW) in running athletes. Methods: Thirty-eight male amateur running athletes (38±6 years; 80.6±8.3 kg; 177±7 cm; 7.8±8.4 years of training; 3.5±0.9 training sessions a week; 33.5±13.4 kilometers of training per week) took part in the present study. Knee flexion eccentric and concentric PT and TW, as well as concentric knee extension PT and TW were assessed. PT- and TW-based hamstring-to-quadriceps ratios (H:Q), as well as PT and TW contralateral imbalance were quantified. Results: A significant correlation was observed between TW and PT concentric knee flexion contralateral deficits (r=0.52, p<0.001). No further correlations were found among TW- and PT-based muscle strength imbalance variables (p>0.05). All mean comparisons of H:Q and contralateral imbalances using TW or PT were significantly different (p<0.05). Conclusions: Our results showed that TW and PT muscle strength imbalance were unrelated, and the H:Q and contralateral imbalance profile of endurance runners may differ based on the isokinetic variable analyzed.
... Among the HS muscles, the majority of muscle injuries and reinjuries generally involve the biceps femoris long head (BFlh), in particular in its proximal region (1,26). Between-limb imbalance (27) and low levels (28,29) of eccentric HS strength have been associated with an increased risk of HS muscle injury. Moreover, short absolute values of BFlh fascicle length (Lf ), potentially reflecting fewer sarcomeres placed in series, have been proposed as a risk factor for HS muscle injury because the fascicles may then be more susceptible to rapid overstretching experienced during powerful eccentric actions, such as sprinting (29). ...
Article
Purpose: The hamstrings (HS) muscle group plays a fundamental role in maintaining knee stability, thus contributing to the prevention and rehabilitation of lower limb musculoskeletal injuries. However, little is known about HS structural and functional adaptations after periods of prolonged inactivity. Our purpose was to investigate the HS morphological and contractile properties changes during 10 days of bed rest (BR). Methods: Ten young healthy males underwent a 10-day BR. HS cross-sectional area (CSA) (at 30%, 50%, and 70% of femur length), biceps femoris long head (BFlh) architecture were assessed by ultrasound imaging after 0 (BR0), 2 (BR2), 4 (BR4), 6 (BR6) and 10 (BR10) days of BR, while BFlh contractile properties (radial twitch displacement (Dm); contraction time (Tc)) were evaluated at the same time points by tensiomyography. HS muscle volume was assessed by magnetic resonance imaging at BR0 and BR10. Results: A reduction in muscle volume was observed in BFlh (p = 0.002; Δ = -3.53%), biceps femoris short head (p = 0.002; Δ = -3.54%), semitendinosus (p = 0.002; Δ = -2.63%), semimembranosus (p = 0.002; Δ = -2.01%) and HS pooled together (p < 0.001; Δ = -2.78%). Early changes in CSA were detected at 30% femur length already at BR6 for BFlh (p = 0.009; Δ = -2.66%) and BFsh (p = 0.049; Δ = -1.96%). We also found a reduction in fascicle length (Lf) at BR6 (p = 0.035; Δ = -2.44%) and BR10 (p < 0.001; Δ = -2.84%). Dm and Tc increased at BR2 (p = 0.010; Δ = 30.0%) and B10 (p = 0.019; Δ = 19.7%), respectively. Conclusions: Despite being a non-postural muscle group, HS exhibited a moderate reduction in muscle dimensions in response to a short unloading period. Small changes in BFlh Lf were also observed, accompanied by alterations in BFLh contractile properties. These HS modifications should not be ignored from a clinical perspective.
... Hamstring injuries are one of the most common and severe non-contact injury in sports involving high-speed running such as soccer, rugby, baseball, [3][4][5][6][7] with the biceps femoris long head being the most commonly affected muscle. 3,5,[8][9][10] Modifiable risk factors for hamstring injuries include low levels of (eccentric) hamstring strength, 8,11 shorter biceps femoris long head fascicle length, 3 higher levels of eccentric strength asymmetries, 12 and poorer fatigue-resistance as well as lumbo-pelvic control. 13 A training program that includes the Nordic hamstring exercise (NH E ) can effectively modify several of these risk factors. ...
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Objective The primary aim of this study was to investigate the effects of the Nordic Hamstring Exercise (NHE) on sprint performance (i.e., 5, 10 and 20 m) and explore associations between study characteristics and sprint outcomes in team sport players. Secondary aims were to 1) investigate the effects of the NHE on eccentric strength of knee flexors (ESKF) with categorical subgroup analysis to determine differences between recreationally, well-trained individuals and young athletes, 2) determine the relation between ESKF and sprint performance in team sport players, and (3) explore the effect of study characteristics (i.e., weekly volume, time duration and body mass) on ESKF. Methods Electronic databases were searched until the 20th of June 2020. 17 studies met the inclusion criteria. Random-effects meta-analyses were used to determine the mean difference (MD) or standardized change of mean difference (SCMD) between NHE and control group for sprint time and ESKF, respectively. Results NHE interventions showed a positive effect on sprint performance (-0.04 sec [-0.08, -0.01]). Sub-group meta-analyses indicated no significant differences in 5 and 20 m sprint performance (MDsprint(5m)= -0.02 sec [-0.10, 0.06]) and (MD sprint(20m)= -0.05 sec [-0.30, 0.19]), respectively. A significant difference was however found for 10 m sprint performance (MDsprint(10m)= -0.06 sec [-0.10, -0.01]). Meta-analysis on the effects of the NHE on ESKF showed a significant benefit of 0.83 SCMD [0.55, 1.12] in favour of the intervention group. Conclusions Studies with some concerns or high risk of bias show that training programs involving the NHE can have small beneficial effects on sprint performance in team sport players. Studies with some concerns or high risk of bias showed moderate beneficial effects on ESKF among a sample of relatively untrained individuals. However, for well-trained team sport players, the improvements in ESKF were less consistent, suggesting a higher training intensity during the NHE may be required to induce adaptations.
... However, male athletes with a history of unilateral hamstring strain injury display lower eccentric knee flexor strength during the Nordic hamstring exercise in their previously injured leg compared to their uninjured contralateral leg (Maniar, Shield, Williams, Timmins, & Opar, 2016). Nordic eccentric knee flexor weakness and between-leg asymmetry (Bourne, Opar, Williams, & Shield, 2015) has also been associated with an increased risk of future hamstring strain injury in elite male footballers. Further, male footballers with current hip/groin pain display reduced isometric (Nevin & Delahunt, 2014) and eccentric adductor strength (Thorborg, Branci, Nielsen, et al., 2014), and lower Copenhagen Hip and Groin Outcome Scores (HAGOS) (Thorborg, Branci, Stensbirk, Jensen, & H€ olmich, 2014), all of which have been associated with the development of future hip/groin injury . ...
Article
Objective To compare lower limb strength and countermovement jump (CMJ) kinetics between elite female footballers with and without a history of anterior cruciate ligament reconstruction (ACLR), hamstring strain, or hip/groin injury. Design Cross-sectional. Setting Field-based. Participants 369 elite female Australian football, soccer and rugby league players aged 15–35. Main outcome measures Isometric hip adductor and abductor strength, eccentric knee flexor strength, and CMJ vertical ground reaction forces, including between-leg asymmetry. Players reported their lifetime history of ACLR, and whether they had sustained a hamstring strain, or hip/groin injury in the previous 12-months. Result s: Players with a unilateral history of ACLR (n = 24) had significant between-leg differences and asymmetry in eccentric knee flexor strength (mean = −6.3%, 95%CI = −8.7 to −3.9%, P < .001), isometric hip abductor strength (mean = −2.5%, 95%CI = −4.3 to −0.7%, P = .008), and between-leg asymmetry in CMJ peak landing force (mean = −5.5%, 95%CI = −10.9 to −0.1%, P = .046). Together, between-leg asymmetry in eccentric knee flexor strength, isometric hip abductor strength, and CMJ peak landing force distinguished between players with and without prior ACLR with 93% accuracy. Conclusion Elite female footballers with a history of ACLR, but not hamstring or hip/groin injury, exhibit persistent between-leg asymmetries in lower limb strength and jump kinetics following a return to sport.
... However, male athletes with a history of unilateral hamstring strain injury display lower eccentric knee flexor strength during the Nordic hamstring exercise in their previously injured leg compared to their uninjured contralateral leg (Maniar, Shield, Williams, Timmins, & Opar, 2016). Nordic eccentric knee flexor weakness and between-leg asymmetry (Bourne, Opar, Williams, & Shield, 2015) has also been associated with an increased risk of future hamstring strain injury in elite male footballers. Further, male footballers with current hip/groin pain display reduced isometric (Nevin & Delahunt, 2014) and eccentric adductor strength (Thorborg, Branci, Nielsen, et al., 2014), and lower Copenhagen Hip and Groin Outcome Scores (HAGOS) (Thorborg, Branci, Stensbirk, Jensen, & H€ olmich, 2014), all of which have been associated with the development of future hip/groin injury . ...
... Shooting a ball mainly engages the quadriceps, the glutes and hamstrings (Figure 4) [21]. This high involvement of the thigh explains why it is the most prone to injury in football, as well as in other similar sports like baseball, basketball, American football, and rugby [21][22][23][24]. ...
Article
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Background: Lower limb injuries constitute a problem in the sport of football. Our aim is to explore patterns and trends of lower limb injuries in an English professional football club. Methods: This is a descriptive epidemiological study. Reports provided by the club's physical therapy team were screened for injuries among professional football players sustained over four seasons, from 2015/2016 to 2018/2019. Data included setting of injury (in-match or training), anatomical location of injury, type of injury, number of days off and month of injury. Results: A total of 296 lower limb injuries were recorded in our study, with a rate of 11.14 per 1000 football hours. Injury rate during games was 51.38 per 1000 football hours, significantly greater than that during training at 3.81 per 1000 football hours (p=0.021). The thigh was significantly the most commonly injured location at 4.67 per 1000 football hours (p<0.001). Grade I tears were the most common injury type at 1.73 per 1000 football hours, significantly greater than grade III tears (p=0.027), contusions (p=0.043), fractures (p=0.02), and lacerations (p=0.019). Injury rates were found to be greatest during preseason and declined as season progressed. On average, an injury sidelined the affected footballer for a total of 20 days. Conclusion: Lower limb injuries were more common during matches than training. The thigh is the most common injury location, and grade I muscle tear was the most common type of injury. Injury rates were higher early on in the season. Potential prevention strategies include spacing out competition, adopting training and exercise regimens that cater for recovery, and increasing research regarding injury mechanisms.
... The measured values in the present study are similar to the results reported by Franchi et al. [21], which were 210 N (±44) for the right leg and 207 N (±46) for the left leg in youth female ski racers and 259 N (±51) for the right leg and 258 N (±57) for the left leg in youth male ski racers (U15). Studies by other authors showed higher measured values of the absolute MBEHS (300-370 N) [38][39][40] than those reported in the present study. However, the study populations in all three studies included older and thus more advanced athletes (professional football players or rugby players; aged 22.6 ± 3.8 years). ...
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Background: Physical fitness is an important component in the development of youth alpine ski racers. To write systematically planned and age-appropriate fitness programs athletes need to be physically tested at regular intervals at an early age. Although well-developed hamstring muscle strength is important for alpine ski racing performance and the prevention of serious knee injuries, it has not been well investigated, especially in youth athletes. Accordingly, the first aim of the present study was to assess the test-retest reliability of the maximum bilateral eccentric (MBEHS) and unilateral isometric (MUIHS) hamstring tests. The second aim of the present study was to assess whether the results of these two methods correlate and if it is possible to commit to one of the two methods to provide an economic test procedure. Methods: The first study included 26 (14 females/12 males) youth alpine ski racers aged between 12 and 13 years. All athletes performed two MBEHS and two MUIHS tests, 7 days apart. The intraclass correlation coefficient (ICC 3,1) and their 95% confidence intervals based on a consistency two-way mixed model were used to estimate the reliability of the two different test modalities. The second study included 61 (27 females/34 males) youth alpine ski racers aged between 10 and 13 years. All athletes performed one MBEHS and one MUIHS test. Bland-Altman plots and the 95% limits of agreement as well as correlations by Pearson (r) between the different test modalities were assessed. Results: In study 1 “poor” to “moderate” (MBEHS right leg 0.79 (0.58–0.90); left leg 0.83 (0.66–0.92); MUIHS right leg 0.78 (0.56–0.89); left leg 0.66 (0.37–0.83)) ICC values and 95% confident intervals were obtained. Standard error of measurement (SEM) between trails was between 18.3 and 25.1 N. Smallest detectable difference (SDD) was between 50.8 and 69.5 N. In study 2 mean differences between MBEHS and MUIHS was around 20 N with higher values for MBEHS. Significant moderate-to-strong correlations were found between the test modalities (r = 0.74–0.84, p <0.001). Conclusions: The MBEHS test has higher ICC values, lower CV values, higher SEM values and lower SDD values than the MUIHS test. All this suggests that the MBEHS test is more suitable than the MUIHS test to determine the maximum hamstring force in young alpine ski racers.
... The sample size ranged from 6 [35] to 80 participants [19] with an age range from 19.25 ± 2.40 to 28.6 ± 5.2 years. Eleven studies on muscle architecture compared the injured with the uninjured limb [6,[18][19][20][21][22][23][24][33][34][35] while five studies compared the injured individuals with controls [18][19][20][21]24]. ...
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Hamstring strains are a frequent injury in sports and are characterized by a high recurrence rate. The aim of this review was to examine the muscle and tendon architecture in individuals with hamstring injury. A systematic literature search in four databases yielded eleven studies on architecture following injury. Differences in the fascicle length (FL), pennation angle (PA) and muscle size measures (volume, thickness and physiological cross-sectional area) at rest were not significantly different between the previously injured limb and the contralateral limb (p > 0.05). There was moderate evidence that biceps femoris long head (BFlh) FL shortening was greater during contraction in the injured compared to the contralateral limb. The BFlh FL was smaller in athletes with a previous injury compared to uninjured individuals (p = 0.0015) but no differences in the FL and PA of other muscles as well as in the aponeurosis/tendon size were observed (p > 0.05). An examination of the FL of both leg muscles in individuals with a previous hamstring strain may be necessary before and after return to sport. Exercises that promote fascicle lengthening of both injured and uninjured leg muscles may be beneficial for athletes who recover from a hamstring injury.
... Hamstring strength has been shown to play a major role in increasing or decreasing the risk of hamstring strain injury (Bourne, Opar, Williams, & Shield, 2015;Opar et al., 2015;Timmins et al., 2016). Various contraction methods are necessary to increase hamstring strength. ...
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The purpose of this study was to examine the effect of 6-week eccentric hamstring strength training on vertical jump and sprint performance. There were 19 male active participants in the study, of which 10 were in the experimental group and 9 in the control group. Pre-test and post-test measurements of the participants in the study were taken. Participants' 5-m, 10-m and 30-meter sprint, vertical jump were measured. The SPSS 17.0 package program was used in the analysis of the data, and the test values of the participants were analyzed with the Wilcoxon Signed Ranks test. According to the findings obtained from the research results, in the statistical comparison of the 5-m, 10-m and 30-meter sprint test results of the experimental group participants before and after the training, there was no significant difference between the 5-m sprint pre-test and post-test values of the participants in the research (p> 0.05), there was a significant difference between the 10m and 30m sprint test pre-test and post-test values (p< 0.05). As a result, Nordic hamstring training small to moderately improved both sprint and vertical jump performance.
... As the medial hamstrings are the primary dynamic restraint against tibial external rotation [37], these findings are particularly concerning and may indicate that hamstrings muscle impairments are overlooked in rehabilitation. These results suggest that clinicians should devote more attention to hamstrings hypertrophy exercise to specifically target ST and gracilis, such as eccentric training [38,39]. Selected eccentric hip and knee dominant exercises have been shown to selectively activate the medial hamstrings [40,41]. ...
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Background Hamstrings muscle morphology is determinant of muscle function (i.e. strength). Among individuals with ACL reconstruction (ACLR), less cross-sectional area (CSA) and volume in the ACLR-limb are associated with muscle weakness, and may contribute to lower rates of return to preinjury activity level and an increased risk for long-term sequelae.Objectives To effectively treat muscular impairments, an accurate understanding of differences in hamstrings morphology following ACLR is needed. A systematic review and meta-analysis were undertaken to describe the morphology of the hamstring muscle complex after ACLR.Methods We searched five databases for studies evaluating the difference between hamstrings size and architecture in individuals with ACLR. Two independent reviewers assessed each paper for inclusion and quality. Means and standard deviations were extracted from each included study to allow fixed-effect size meta-analysis calculations for comparison of results.ResultsTwenty-four studies were included for final review. Eight categories of morphological outcomes were identified, and studies were grouped accordingly: (1) volume, (2) cross-sectional area (CSA), (3) muscle length, (4) muscle thickness, (5) fascicle length, (6) pennation angle, (7) fiber area, and (8) fiber type. Meta-analysis demonstrated lower hamstrings volume in the ACLR-limb in both contralateral and control group comparisons, and lower CSA, length, and thickness in the ACLR-limb in contralateral comparisons. The semitendinosus and gracilis were most profoundly impacted. Limited moderate evidence demonstrated greater biceps femoris pennation angle in the ACLR-limb.Conclusions Individuals with ACLR demonstrated large deficits in semitendinosus and gracilis muscle CSA and volume in the ACLR-limb compared contralaterally, with no differences observed in the biceps femoris or semimembranosus. Clinical implications regarding assessment and treatment of individuals with ACLR are discussed.
... To date, the assessment of isometric and eccentric force production has been popular in sporting contexts, with significant relationships with athletic performance observed with the isometric mid-thigh pull (IMTP) and isometric squat (ISQ) (Kawamori et al., 2006;Stone et al., 2003;Thomas, Jones, Rothwell, Chiang, & Comfort, 2015;Wang et al., 2016), while an eccentric assessment of the hamstrings has also been identified as having some potential benefit in hamstring strain injury risk assessment (Bourne, Opar, Williams, & Shield, 2015;Green, Bourne, van Dyk, & Pizzari, 2020;Opar et al., 2015;Roe et al., 2020;Timmins et al., 2016), in addition to relationships to sprinting performance (Markovic et al., 2018). Therefore, the identification of accurate and meaningful methods of force-based assessment using strain gauges can be considered essential to be able to infer training status and the training needs of athletes. ...
Conference Paper
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The purpose of this study was to identify the content validity and accuracy of a commercially available strain gauge (GSTRENGTH (Exsurgo Technologies, Virginia, USA), aimed at use within athletic populations. Six standardised IWF (International Weightlifting Federation) calibrated weights (5-, 25-, 50-, 100-, 200-, 250-kg) were hung from the strain gauge and raw data was collected over a five-second period and exported to a computer. A perfect relationship between the known loads and the strain gauge (r = 1.00, p<0.001) was identified, although the strain gauge was found to have a small overestimation error with no fixed or proportional bias. During data collection there were non-significant, trivial-small differences between the first and last second, demonstrating minimal drift. The commercially available strain gauge was found to be valid when compared to the known loads. Further investigation of the strain gauge is required to assess the concurrent validity when compared to gold standard methods of assessment, such as force plates, in a range of test designs.
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Background: Hamstring strain injuries are one of the most common injuries in Rugby Union, representing up to 15% of all injuries sustained. We aimed to systematically review and summarize the scientific literature that addressed hamstring strain injury incidence, risk factors, injury prevention or strengthening strategies, and strength or asymmetry measures in Rugby Union. Methods: We conducted a systematic search to locate published peer-reviewed articles from PubMed, SPORTDiscusTM, Web of Science®, and Scopus® e-databases. Studies included were original research conducted in Rugby Union that evaluated hamstring strength, hamstring strengthening interventions, and/or hamstring injury outcomes. Included studies were quality assessed using the Newcastle-Ottawa Scale. Results: Twenty-four studies met inclusion and altogether involved 2866 participants. Isokinetic testing was the most common method used to quantify hamstring strength and imbalances in Rugby Union; with data indicating that professionals are stronger than amateurs, and forwards are stronger than backs. Regarding risk factors, we identified playing position, fatigue, previous injuries, between leg strength imbalances, lack of readiness to return to play post injury, and game actions (i.e., running). There is evidence to support the use of Nordic eccentric strength measures to inform practice, with strength and imbalances useful in predicting injuries. Strengthening programs with Nordic exercises significantly increased hamstring strength, increased muscle thickness, and decreased imbalance ratios in female and male players. A significant reduction in injury incidence and severity in professional players has been observed in players performing routines incorporating progressive Nordic exercises. Conclusion: The aetiology of hamstring strain injuries is multifactorial, with playing position, fatigue, previous injuries, leg imbalances, lack of readiness to return to play, and running actions identified as contributing factors across levels. Combining strategies to prevent hamstring injuries and recurrences, and to inform return to play, is likely worthwhile and should include Nordic strength assessment and Nordic exercises.
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Objectives Lower limb posterior chain injury (PCI) is common among athletic populations, with multifactorial risk factors including age, previous injury, strength measurements, range of motion and training load. Biomechanics are commonly considered in the prevention and rehabilitation of PCI by performance staff. However, there is no documented testing method to assess for associations between biomechanics and PCI. The aim of this study was to investigate whether there is an association between an easily applicable, novel biomechanical assessment tool and PCI. Methods Fifty male elite-level rugby union athletes (age 22.83±5.08) participating in the highest tier of England were tested at the start of the 2019 preseason period and PCIs (N=48) were recorded over the 2019/2020 playing season. Participants’ biomechanics were analysed using two-dimensional video analysis against an injury risk score (IRS) system in the performance of the combined movement—prone hip extension and knee flexion. Participants’ biomechanics in carrying out this movement were scored against the 10-point IRS, where the more compensatory movement recorded sees an increase in an individual’s IRS. Participants’ IRS was then compared against the number of PCIs sustained and Spearman’s correlation coefficient was used for statistical analysis. Results There is a significant association between IRS and PCI (R=0.542, p<0.001). Linear regression demonstrated that an increase in 1 in IRS was associated with a 35% increase in PCI incidence (R²=0.346). Conclusion A significance between the IRS and PCI provides preliminary support for its use as an injury risk assessment tool.
Article
Hamstring strain injury (HSI) is a very common lower-body injury in field sports, and eccentric (ECC) hamstring strength is a potential modifiable risk factor, therefore having reliable eccentric hamstring strength assessments is critical. The aim of this study was to access test–retest reliability of the hip extension lower (HEL) exercise as a measure of ECC hamstring strength and inter-limb asymmetries. Twelve male elite level soccer players (mean; age: 21.8 years; height: 180.4 cm; weight: 75.7 kg) volunteered to participate in this study. Participants were from the same soccer club, covered all playing positions, and had no current injury issues. Participants performed two familiarization sessions to acquaint themselves with the device and exercise protocol. During testing, each participant performed three repetitions with 60s intra-set recovery provided. Average and peak force (N) was recorded for both limbs. Testing sessions took place on the same day and time over a two-week pre-season period and followed a full recovery day. Intraclass Correlation Coefficient (ICC), Coefficient of Variation (CV%), Minimal Detectable Change (MDC) and Typical Error (TE) were used to assess reliability. The HEL showed excellent reliability for average force (N) in the left (ICC (95% CI) = 0.9 (0.7–0.97); TE = 14.1 N, CV% = 1.87; MDC = 39.06 N) and right (ICC (95% CI) = 0.91 (0.73–0.97); TE = 20.89 N, CV% = 3.26; MDC = 57.87 N) limb, and also excellent reliability for peak force in the left (ICC (95% CI) = 0.91 (0.71–0.97); TE = 13.55 N, CV% = 1.61; MDC = 57.87 N) and right (ICC (95% CI) = 0.9 (0.7–0.97); TE = 21.70 N, CV% = 3.31; MDC = 60.11 N) limb. This data suggests the HEL as a reliable measure of both ECC hamstring strength and inter-limb asymmetries. Practitioners should consider the HEL as a reliable choice for measuring and monitoring eccentric hamstring strength in their athletes.
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Objectives The mechanisms of hamstring strain injuries (HSIs) in professional Rugby Union are not well understood. The aim of this study was to describe the mechanisms of HSIs in male professional Rugby Union players using video analysis. Methods All time-loss acute HSIs identified via retrospective analysis of the Leinster Rugby injury surveillance database across the 2015/2016 to 2017/2018 seasons were considered as potentially eligible for inclusion. Three chartered physiotherapists (analysts) independently assessed all videos with a consensus meeting convened to describe the injury mechanisms. The determination of the injury mechanisms was based on an inductive process informed by a critical review of HSI mechanism literature (including kinematics, kinetics and muscle activity). One of the analysts also developed a qualitative description of each injury mechanism. Results Seventeen acute HSIs were included in this study. Twelve per cent of the injuries were sustained during training with the remainder sustained during match-play. One HSI occurred due to direct contact to the injured muscle. The remainder were classified as indirect contact (ie, contact to another body region) or non-contact. These HSIs were sustained during five distinct actions—‘running’ (47%), ‘decelerating’ (18%), ‘kicking’ (6%), during a ‘tackle’ (6%) and ‘rucking’ (18%). The most common biomechanical presentation of the injured limb was characterised by trunk flexion with concomitant active knee extension (76%). Fifty per cent of cases also involved ipsilateral trunk rotation. Conclusion HSIs in this study of Rugby Union were sustained during a number of playing situations and not just during sprinting. We identified a number of injury mechanisms including: ‘running’, ‘decelerating’, ‘kicking’, ‘tackle’, ‘rucking’ and ‘direct trauma’. Hamstring muscle lengthening, characterised by trunk flexion and relative knee extension, appears to be a fundamental characteristic of the mechanisms of acute HSIs in Rugby Union.
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Hamstring strain injury (HSI) may result in considerable impairment, activity limitation, and participation restriction, including time lost from competitive sports. This CPG includes sports-related overloading and overstretching injuries to myofascial or musculotendinous structures in any combination of the 3 hamstring muscles (the semitendinosus, semimembranosus, and biceps femoris). J Orthop Sports Phys Ther, Epub 14 Feb 2022. doi:10.2519/jospt.2022.0301.
Article
This study aimed to identify which preseason factors had strong evidence of risks for physical injury during the season of collision sports including rugby, American football, and Australian rules football using qualitative synthesis. Pubmed, EMBASE, MEDLINE, SPORTDiscus, Scopus, and the Cochrane Library were reviewed. Eligibility criteria for selecting studies were: studies involving the collision sports; prospective cohort studies; and studies with outcomes of relative risks, odds ratios, and correlations between players’ preseason conditions and injury during the season. The risk of bias based on the Scottish Intercollegiate Guidelines Network quality checklists for cohort studies was assessed in 57 studies. The current study identified strong evidence that 1) anthropometric characteristics (body mass index and estimated mass moment of inertia of the body around a horizontal axis through the ankle), which are calculated with weight and height; 2) physical function, in particular for the trunk and lower limb (trunk-flexion hold and wall-sit hold); and 3) Oswestry Disability Index disability, which is a patient-reported outcome measure for disability due to low back pain, were positive prognostic factors for injury during the collision sports season, regardless of playing experience.
Article
This study aimed to explore the association between hamstring strength, age and lower limb soft tissue injury history and subsequent hamstring injury among Australian Football League (AFL) players. This prospective cohort study recruited 125 players from three professional AFL teams. Eccentric knee flexor strength was assessed while performing the Nordic hamstring exercise in pre-season, and injury data were collected retrospectively (hamstring, groin, calf, quadriceps and knee), and prospectively (hamstring injuries) for one AFL playing season. Fourteen players (11%) sustained a hamstring injury in the subsequent playing season. Nordic strength was not significantly associated with future hamstring injury (Odds Ratio (OR) 1.9, p = 0.36), whereas player age greater than 25 years (OR = 2.9, p < 0.05), report of a hamstring injury within the previous year (OR = 3.7, p = 0.01), or greater than 1-year (OR = 3.6, p = 0.01), a previous groin (OR = 8.6, p < 0.01) or calf injury (OR = 4.6, p = 0.01) were factors significantly associated with subsequent hamstring injury. Based on these findings, increasing age and previous hamstring, groin and calf injury are all associated with an elevated risk of subsequent hamstring injury in AFL players.
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Abstract This study describes the body composition traits of modern-day elite rugby union athletes according to playing position and ethnicity. Thirty-seven international Australian rugby athletes of Caucasian and Polynesian descent undertook body composition assessment using dual-energy X-ray absorptiometry and surface anthropometry. Forwards were significantly taller, heavier and had a greater total fat mass and lean mass than backs. Backs displayed a higher percentage lean mass and lower sum of seven skinfolds and percentage fat mass. While no whole body composition differences were seen between ethnicities, significant regional differences were observed. In the periphery (arm and leg) regions, Polynesians had a greater proportion of fat mass (53.1% vs. 51.3%, P = 0.052, d = 0.5) and lean mass (49.7% vs. 48.6%, P = 0.040, d = 0.9), while in the trunk region a lower proportion of fat mass (37.2% vs. 39.5%, P = 0.019, d = 0.7) and lean mass (45.6% vs. 46.8%, P = 0.020, d = 1.1). Significant differences were also seen between Caucasian and Polynesian forwards in leg lean mass (31.4 kg vs. 35.9 kg, P = 0.014, d = 2.4) and periphery lean mass (43.8 kg vs. 49.6 kg, P = 0.022, d = 2.4). Elite Polynesian rugby athletes have different distribution patterns of fat mass and lean mass compared to Caucasians, which may influence their suitability for particular positions.
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Reliability and case-control injury study. 1) To determine if a novel device, designed to measure eccentric knee flexors strength via the Nordic hamstring exercise (NHE), displays acceptable test-retest reliability; 2) to determine normative values for eccentric knee flexors strength derived from the device in individuals without a history of hamstring strain injury (HSI) and; 3) to determine if the device could detect weakness in elite athletes with a previous history of unilateral HSI. HSIs and reinjuries are the most common cause of lost playing time in a number of sports. Eccentric knee flexors weakness is a major modifiable risk factor for future HSIs, however there is a lack of easily accessible equipment to assess this strength quality. Thirty recreationally active males without a history of HSI completed NHEs on the device on 2 separate occasions. Intraclass correlation coefficients (ICCs), typical error (TE), typical error as a co-efficient of variation (%TE), and minimum detectable change at a 95% confidence interval (MDC95) were calculated. Normative strength data were determined using the most reliable measurement. An additional 20 elite athletes with a unilateral history of HSI within the previous 12 months performed NHEs on the device to determine if residual eccentric muscle weakness existed in the previously injured limb. The device displayed high to moderate reliability (ICC = 0.83 to 0.90; TE = 21.7 N to 27.5 N; %TE = 5.8 to 8.5; MDC95 = 76.2 to 60.1 N). Mean±SD normative eccentric flexors strength, based on the uninjured group, was 344.7 ± 61.1 N for the left and 361.2 ± 65.1 N for the right side. The previously injured limbs were 15% weaker than the contralateral uninjured limbs (mean difference = 50.3 N; 95% CI = 25.7 to 74.9N; P < .01), 15% weaker than the normative left limb data (mean difference = 50.0 N; 95% CI = 1.4 to 98.5 N; P = .04) and 18% weaker than the normative right limb data (mean difference = 66.5 N; 95% CI = 18.0 to 115.1 N; P < .01). The experimental device offers a reliable method to determine eccentric knee flexors strength and strength asymmetry and revealed residual weakness in previously injured elite athletes.J Orthop Sports Phys Ther, Epub 25 July 2013. doi:10.2519/jospt.2013.4837.
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Rugby Union has one of the highest reported incidences of match injuries amongst all professional team sports. The majority of research within this field has focused on elite male cohorts; in this study we present the first meta-analytic review of these data. The aim of this study was to summarise the incidence and severity of injuries in senior men's professional Rugby Union, and determine the overall effects of level of play, new versus recurrent injuries, playing position, type of injuries, location of injuries, severity of injuries, period of match, and injury incident. Electronic databases were searched using keywords 'Rugby Union' and 'inj*'. Fifteen papers addressing injuries in senior men's professional Rugby Union (from 1995 through September 2012) were included in the review. A maximum of ten of these papers provided incidence data that could be modelled via a Poisson mixed-effects generalised linear model, while up to nine studies provided severity data that could be modelled via a general linear mixed model. Magnitude based inferences were used to assess differences between factors. A descriptive analysis was provided for studies that could not be included in the pooled analysis due to incongruent injury definitions. The overall incidence of injuries in senior men's professional Rugby Union matches was 81 per 1,000 player hours (95 % CI 63-105), and 3 per 1,000 player hours (95 % CI 2-4) during training. Estimated mean severity for match injuries was 20 days (95 % CI 14-27), and 22 days (95 % CI 19-24) for training injuries. A higher level of play was associated with a greater incidence of injuries in matches, with no clear difference in severity. New injuries occurred substantially more often than recurrent injuries, while the severity of recurrent injuries was, on average, 10 days (95 % CI 4-17) greater than new injuries. Trivial differences were found in injury incidence and severity between forwards and backs. Muscle/tendon and joint (non-bone)/ligament injuries were the two most prevalent injury groups, whereas fractures and bone stress injuries had the highest average severity. The lower limb was the body region with the highest injury incidence, while upper limb injuries were most severe. The third quarter (40-60 min) of matches had the highest injury rate, and injuries most commonly occurred as a result of being tackled. This meta-analysis confirms match injury incidence rates in professional Rugby Union can be considered high in comparison with other team sports, but similar to other collision sports. In order to markedly reduce overall injury burden, efforts should target lower-limb injury prevention strategies and technique during contact, as these may render the largest effect.
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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.
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Acute hamstring injuries are the most prevalent muscle injuries reported in sport. Despite a thorough and concentrated effort to prevent and rehabilitate hamstring injuries, injury occurrence and re-injury rates have not improved over the last three decades. This failure is most likely due to the following: (1) a lack of studies with high level of evidence into the identification and prevention of hamstring injuries and (2) a reductionist approach of the current literature. The objectives of this article are to review and critique the current literature regarding isolated risk factors, and introduce a new concept for a more comprehensive scientific understanding of how multiple risk factors contribute to hamstring strain injury. The authors hope that this new conceptual model can serve as a foundation for future evidence-based research and aid in the development of new prevention methods to decrease the high incidence of this type of injury.
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To identify the intrinsic risk factors of non-contact strains in the hamstrings and quadriceps muscles of professional soccer players via a cohort prospective design. A total of 100 professional soccer players (aged 19.4-27.8 years) from four professional teams underwent a composite musculoskeletal assessment at preseason. Intrinsic risk factors included dichotomies of asymmetries in muscle strength, flexibility, proprioception, anthropometry and knee joint stability, and of previous injuries. Muscle strains were prospectively monitored during the subsequent season using questionnaires. The data were analysed via binary logistic regression. Thirty-eight percent of the players sustained one or more lower-extremity muscle strains. Sixteen (42.1 %) and seven (18.4 %) of them were clinically diagnosed as having non-contact muscle strains at their hamstrings and quadriceps, respectively. Players with eccentric hamstring strength asymmetries (OR=3.88; 95% CI 1.13 to 13.23), functional leg length asymmetries (OR=3.80; 95% CI 1.08 to 13.33) and no previous hamstrings injuries (OR=0.15; 95% CI 0.029 to 0.79) were at greater risk of sustaining a hamstring muscle strain. Players with eccentric strength (OR=5.01; 95% CI 0.92 to 27.14) and flexibility asymmetries (OR=4.98; 95% CI 0.78 to 31.80) in their quadriceps as well as heavier (OR=10.70; 95% CI 0.73 to 156.37) and shorter players (OR=0.08; 95% CI 0.00 to 1.35) were at greater risk of sustaining a strain in this muscle group. Professional soccer players with functional asymmetries possess a higher risk of sustaining hamstring strains. Previous injury seems not to constitute a risk factor. The systematic isokinetic evaluation of the lower extremities during the preseason period can provide therapists and trainers with valuable data regarding the predictive elements of non-contact hamstring strains in professional soccer players.
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Hamstring injuries are common in sprinters. Identifying preseason risk factors is essential to target injury-prone athletes and develop injury preventive measures. To investigate the incidence of hamstring muscle injury in sprinters over an athletic season and to explore the preseason predictor of this injury. Prospective cohort study. 44 sprinters from the Hong Kong Sports Institute, the Hong Kong Amateur Athletic Association and intercollegiate athletic teams were recruited. Preseason assessment of hamstring flexibility, concentric and eccentric isokinetic peak torque and peak torque angle were obtained at the beginning of an athletic season. The athletes were followed over 12 months and were asked to report all injuries resulting from training and competition. Eight athletes sustained hamstring injuries over the season. The injury rate was 0.87 per 1000 h of exposure. The incidence of injuries was higher at the beginning of the season, with 58.3% injuries occurring in the first 100 h of exposure. Cox regression analysis revealed that athletes with a decrease in the hamstring : quadriceps peak torque ratio of less than 0.60 at an angular velocity of 180 degrees/s have a 17-fold increased risk of hamstring injury. Performing preseason hamstring : quadriceps peak torque ratio assessments may be useful to identify sprinters susceptible to hamstring injury.
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Eleven sprinters with recent hamstring injuries were compared with nine uninjured runners. The flexibility of the hamstrings and the eccentric and concentric muscle torque were measured in the hamstrings and quadriceps muscles at different angular velocities. Sprinters with a previous hamstring injury had significantly tighter hamstrings than uninjured sprinters had. The uninjured sprinters had significantly higher eccentric hamstring torques at all angular velocities. They also had significantly higher concentric quadriceps and hamstring torques at 30 deg/sec but not at higher velocities. Sprinters with a history of hamstring injury thus differed from uninjured runners, being weaker in eccentric contractions and in concentric contractions at low velocities.
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The injury risk in football is high, but little is known about causes of injury. To identify risk factors for football injuries using a multivariate model. Prospective cohort study. Participants were 306 male football players from the two highest divisions in Iceland. Before the 1999 football season started, the following factors were examined: height, weight, body composition, flexibility, leg extension power, jump height, peak O(2) uptake, joint stability, and history of previous injury. Injuries and player exposure were recorded throughout the competitive season. Older players were at higher risk of injury in general (odds ratio [OR] = 1.1 per year, P = 0.05). For hamstring strains, the significant risk factors were age (OR = 1.4 [1 year], P < 0.001) and previous hamstring strains (OR = 11.6, P <0.001). For groin strains, the predictor risk factors were previous groin strains (OR = 7.3, P = 0.001) and decreased range of motion in hip abduction (OR = 0.9 [1 degrees ], P = 0.05). Previous injury was also identified as a risk factor for knee (OR = 4.6) and ankle sprains (OR = 5.3). Age and previous injury were identified as the main risk factors for injury among elite football players from Iceland.
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To undertake a detailed, large scale epidemiological study of match injuries sustained by professional rugby union players in order to define their incidence, nature, severity, and causes. A two season prospective design was used to study match injuries associated with 546 rugby union players at 12 English Premiership clubs. Team clinicians reported all match injuries on a weekly basis and provided details of the location, diagnosis, severity, and mechanism of each injury. Match exposures for individual players were recorded on a weekly basis. Loss of time from training and match play was used as the definition of an injury. The overall incidence of injury was 91 injuries/1000 player-hours, and each injury resulted on average in 18 days lost time. Recurrences, which accounted for 18% of injuries, were significantly more severe (27 days) than new injuries (16 days). Thigh haematomas were the most common injury for forwards and backs, but anterior cruciate ligament injuries for forwards and hamstring injuries for backs caused the greatest number of days absence. Contact mechanisms accounted for 72% of injuries, but foul play was only implicated in 6% of injuries. The ruck and maul elements of the game caused most injuries to forwards, and being tackled caused most injuries to backs. The hooker and outside centre were the playing positions at greatest risk of injury. On average, a club will have 18% of their players unavailable for selection as a consequence of match injuries.