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Abstract

Purpose: Are eccentric hamstring strength and between-limb imbalance in eccentric strength, measured during the Nordic hamstring exercise, risk factors for hamstring strain injury (HSI)? Methods: Elite Australian footballers (n = 210) from five different teams participated. Eccentric hamstring strength during the Nordic exercise was obtained at the commencement and conclusion of preseason training and at the midpoint of the season. Injury history and demographic data were also collected. Reports on prospectively occurring HSI were completed by the team medical staff. Relative risk (RR) was determined for univariate data, and logistic regression was employed for multivariate data. Results: Twenty-eight new HSI were recorded. Eccentric hamstring strength below 256 N at the start of the preseason and 279 N at the end of the preseason increased the risk of future HSI 2.7-fold (RR, 2.7; 95% confidence interval, 1.3 to 5.5; P = 0.006) and 4.3-fold (RR, 4.3; 95% confidence interval, 1.7 to 11.0; P = 0.002), respectively. Between-limb imbalance in strength of greater than 10% did not increase the risk of future HSI. Univariate analysis did not reveal a significantly greater RR for future HSI in athletes who had sustained a lower limb injury of any kind within the last 12 months. Logistic regression revealed interactions between both athlete age and history of HSI with eccentric hamstring strength, whereby the likelihood of future HSI in older athletes or athletes with a history of HSI was reduced if an athlete had high levels of eccentric strength. Conclusion: Low levels of eccentric hamstring strength increased the risk of future HSI. Interaction effects suggest that the additional risk of future HSI associated with advancing age or previous injury was mitigated by higher levels of eccentric hamstring strength.

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... 14,24 Many factors may contribute to hamstring injuries including strength deficits, high-speed running, previous injury and fatigue. [48][49][50][51] The predominant injury mechanisms for hamstring injuries in Australian football have been shown to be high-speed running (60.7%), kicking (17.9%) and collecting the ball from the ground (7.1%). 50 Gaelic football has many similarities to Australian football both in game rules and its physiological demands, 3 thus it is possible that these three factors may play a role in the genesis of hamstring injuries in Gaelic football. ...
... [48][49][50][51] The predominant injury mechanisms for hamstring injuries in Australian football have been shown to be high-speed running (60.7%), kicking (17.9%) and collecting the ball from the ground (7.1%). 50 Gaelic football has many similarities to Australian football both in game rules and its physiological demands, 3 thus it is possible that these three factors may play a role in the genesis of hamstring injuries in Gaelic football. Although similarities exist between the two sports, the incidence of hamstring injuries during match-play in elite Gaelic football (8.4/1000 h) is greater than Australian football (5/1000 h). ...
... More specifically, greater age has been found to be a risk factor for the development of hamstring injuries in elite Gaelic football athletes 7 which is consistent with both soccer and Australian football. 50,[52][53][54] Although there is a trend for global injury rates to be less in younger athletes (both adolescent and adult), Gaelic football athletes in the 18-20 age group have the same level of risk as those in the >30 age group for sustaining a hamstring injury in elite settings. 7 Given that a previous hamstring injury is a risk factor for future hamstring injuries, 53 care should be taken with younger athletes coming into elite squads. ...
Article
Objectives To quantify the incidence, location and severity of injuries in Gaelic football and to identify potential moderators of those injuries. Design Systematic review and meta-analysis. Methods A comprehensive search strategy of six electronic databases was undertaken independently by two researchers in March 2020. Studies must have prospectively investigated injuries sustained by Gaelic footballers over a minimum duration of six months. The Newcastle-Ottawa Scale was used to assess risk of bias. Studies were combined in a pooled analysis using an inverse variance method. Results Twelve prospective cohort studies were eligible. The total injury incidence was 10.7 injuries/1000 h of exposure. Match incidence (55.9 injuries/1000 h) was much higher than training (4.6 injuries/1000 h). The lower limb accounted for over 70% of all injuries, with hamstring injuries ranging from 22 to 24% of all injuries. Non-contact injuries were the most common injury mechanism. Players aged >30 were at greatest risk of injury with incidence risk ratios ranging from 1.2 to 2.3. High aerobic fitness and chronic workloads were associated with reduced risk of injury in elite Gaelic footballers. Conclusions Elite Gaelic football athletes are twelve times more likely to get injured during match play compared to training. The lower limb is the most affected body region, and most injuries occur by non-contact mechanisms. Athlete age of greater than 30, poor aerobic fitness and sudden increments in training workload all increase the likelihood of injury. By understanding the incidence and nature of injuries in Gaelic football, targeted injury prevention strategies can be developed and implemented.
... 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). ...
... 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). ...
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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.
... 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]. ...
... 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]. It is also unknown whether eccentric knee flexor strength has an impact on the likelihood of future HSI in athletes with a history of ACLR. ...
... 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). ...
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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.
... Strength differences between limbs have also been associated with an increased risk of prospective injury (Croisier et al., 2008;Brumitt et al., 2013), which indicates that inter-limb imbalances should be reduced. However, conflicting evidence exists to suggest that strength asymmetry may not always cause dysfunction (Lockie et al., 2014;Opar et al., 2015;Dos'Santos et al., 2018). Furthermore, larger asymmetries measured in higher division soccer players as compared to lower division players, suggests that competitive level may influence strength asymmetry (Ferreira et al., 2018). ...
... However, it should be noted that interrogation of the research quality for each evidence source was beyond the scope of this review. Silva et al., (2015) 20 Dai et al., (2018) 23 Opar et al., (2015) 22 Zwolski et al., (2015) 22 Table 1). ...
... An explanation for this is a difference between the activity level of athletes, as one study recruited athletes from elite, sub-elite and U19 premier-grade teams (Bourne et al., 2015) whereas, the other recruited elite athletes only . Furthermore, the first study took measurements during pre-season only (Bourne et al., 2015), whereas Opar et al., (2015) assessed asymmetry at three time-points throughout the season. Hence, differences in findings between studies may be partly explained by changes in strength due to physiological adaptations to muscle architecture over-time in response to training (Nimphius et al., 2012). ...
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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.
... 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). As such, it is not uncommon for team-sport athletes to include tests of eccentric kneeflexor strength and isometric hip-abductor/adductor strength in their physical performance testing batteries (34,35). ...
... Unfortunately, there is a lack of research that has profiled these measurements in elite women team-sport athletes. The relative importance of these measurements is derived from prospective injury studies that have identified low levels of eccentric knee-flexor strength (36,44) and isometric hip-adduction and abduction strength (8) as risk factors for hamstring strain and hip/ groin injuries in male team-sport athletes. Previous research from Bourne et al. (8) has reported that greater between-limb abduction (a)symmetry (peak strength in the preferred kicking limb relative to the nonpreferred limb) and lower levels of peak adduction and abduction strength were independently associated with a greater risk of future hip/groin injuries in elite male soccer players. ...
... Although hamstring injuries are likely to be more prevalent in male teamsport athletes, these injuries are also common among women athletes (14). One modifiable risk factor is eccentric knee flexor strength (7,43), whereby low levels of eccentric knee flexor strength are associated with an increase in the risk of future hamstring injuries in male athletes from different football codes (36,44). Similar to hip/groin injuries, there have been no prospective hamstring injury studies in women athletes, so it remains unclear whether low levels of eccentric knee flexor strength are a risk factor for hamstring injury risk in elite women athletes. ...
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.
... A topical literature review [20] highlighted numerous modifiable risk factors, including flexibility, fatigue, high speed running loads, sprint running, lumbo-pelvic hip control, insufficient/inadequate warm-up, strength and intra-limb and inter-limb asymmetry and biceps femoris fascicle length. To date, hamstring strength is the most researched, with various types of muscular strength deficits being associated with a higher risk of in HSI numerous studies [21][22][23][24][25]. As a result, strength and conditioning professionals actively seek additional techniques to improve hamstring strength to minimise the incidence of HSI with non-traditional methods of strength training such as Flywheel Inertial Training (FIT) gaining popularity. ...
... In sports with high intensity running demands, such as soccer [50] and Australian rules football [24], eccentric hamstring weakness has been identified as a risk factor for future HSI. Timmins et al. [50] assessed the eccentric hamstring strength of 152 professional soccer players in a sizeable prospective study. ...
... Players with eccentric hamstring strength below 4.35 N·kg −1 were 4.4 times more likely (RR; 95% CI 1.1 to 17.5) to sustain an HSI in the following season than stronger players. In agreement with this, Opar et al. [24] found that eccentric strength below 256 Newtons (N) at the start of pre-season and 279 (N) at the end of pre-season were said to associate with an increased risk of HSI (2.7-and 4.3-fold, respectively) in a population of 210 elite Australian footballers. Such research highlights the importance of eccentric hamstring strength in HSI and may explain why it is so prevalent in injury prevention programs and in the research. ...
Article
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The purpose of this narrative review is to examine the efficacy of flywheel inertia training to increase hamstring strength. Hamstring strain injury is common in many sports, and baseline strength deficits have been associated with a higher risk of hamstring strain injury. As a result, strength and conditioning professionals actively seek additional techniques to improve hamstring strength with the aim of minimising the incidence of hamstring strain injury. One method of strength training gaining popularity in hamstring strength development is flywheel inertia training. In this review, we provide a brief overview of flywheel inertia training and its supposed adaptions. Next, we discuss important determinants of flywheel inertia training such as familiarisation, volume prescription, inertia load, technique and specific exercise used. Thereafter, we investigate its effects on hamstring strength, fascicle length and hamstring strain injury reduction. This article proposes that hamstring specific flywheel inertia training can be utilised for strength development, but due to the low number of studies and contrary evidence, more research is needed before a definite conclusion can be made. In addition, as with any training modality, careful consideration should be given to flywheel inertia training determinants. This review provides general recommendations of flywheel inertia training determinants that have value when integrating flywheel inertia training into a hamstring strengthening program.
... Recent work has focused on identifying modifiable risk factors that can be targeted via interventions. For example, elite Australian Football players with low levels of eccentric knee flexor strength during the Nordic hamstring exercise (NHE) were 2.7 times more likely to sustain an HSI than their stronger counterparts (4). Interactions were also observed between strength, prior injury and age, whereby higher levels of eccentric knee flexor strength ameliorated the risk of injury associated with older age or prior HSI. ...
... 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. ...
... Eccentric knee flexor strength and between-limb imbalance at the start of preseason were not associated with an increased risk of future HSI. Earlier work (4) reported that elite Australian Football players with lower levels of eccentric knee flexor strength (<256 N) during the NHE at the start of preseason, were 2.7 times more likely to suffer an HSI than their stronger counterparts. The findings of our study and another in Australian football (5) have failed to replicate the associations between eccentric knee flexor strength during the NHE and prospective HSI risk. ...
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.
... During high-speed running, the terminal swing phase is considered the most likely time of injury due to the hamstrings being active, rapidly lengthening, and absorbing energy to decelerate the advancing limb. (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. ...
... (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. ...
... Calculations were based on results of a similar study involving Australian football athletes. (11) We assumed 10% of athletes would experience an HSI each year and conservatively adjusted for 10% attrition due to situations such as non-HSI injury and graduation. Based on these assumptions, n=300 unique athletes would result in 91% power with alpha=0.05 to detect a 2-fold decreased risk of HSI for every N/kg increase in relative eccentric hamstring strength. ...
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.
... Some devices to assess Nordic hamstring (NH) strength are available, which have been used to predict hamstring strain injury risks [10,11]. NH exercise is also often performed as a preventative measure of hamstring strain injuries [12] with the assumption that it can increase eccentric strength of the knee flexors [13]. ...
... N) [10] and NH torque (143 Nm) [16] at 30˚/s was measured for sub-elite male athletes, the NH force in the present study (NH force: 325.6 N, NH torque: 130 Nm) appeared to be smaller, but larger than that of other studies (average: 298.6-301 N) in which professional male football players or professional and sub-elite rugby players were tested [11,15]. It should be noted that the device to measure NH strength in the present study was not the same as that used in the previous studies. ...
Article
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Nordic hamstring exercise is performed to prevent knee flexor muscle strain injuries and used to assess their injury risks. However, what exactly Nordic hamstring strength indicates is not clear. We investigated the relationship between Nordic hamstring strength and maximal voluntary contraction (MVC) torque of the knee flexors measured by an isokinetic dynamometer. Sixteen healthy young men who had not experienced hamstring strain injuries participated in the study. In Nordic hamstring, each participant was instructed to lean forward as far as possible in 3 s (approximately 30°/s), and force at the ankle joint of the dominant leg was measured during the movement. The force was multiplied by lower leg length and converted into torque. MVC torque of the knee flexors was measured isometrically at 30°, 45°, 60°, and 90° knee flexion joint angles, and concentrically and eccentrically at 30°/s and 60°/s in 10°–90° knee flexion for the dominant leg in a prone position. Correlations among the dependent variables were assessed using Pearson’s correlation coefficients. Peak Nordic hamstring torque ranged 96.8–163.5 Nm, and peak MVC eccentric torque ranged 50.7–109.4 Nm at 30°/s and 59.2–121.2 Nm at 60°/s. No significant correlations were evident between the peak Nordic hamstring torque and peak eccentric knee flexion torque (r = 0.24–0.3, p = 0.26–0.4). This was also the case for the Nordic hamstring torque and MVC torque of isometric (r = −0.03–0.1, p = 0.71–0.92) and concentric contractions (r = 0.28–0.49, p = 0.053–0.29). These results show that Nordic hamstring strength is not associated with the knee flexor torque measured by an isokinetic dynamometer. It may be that other factors than static and dynamic hamstring strengths affect Nordic hamstring strength.
... 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.
... Additionally, there are modifiable factors such as muscle flexibility [17], fatigue [18] and muscle strength [15,16,19,20] which can be modulated to reduce the likelihood of hamstring muscle injury. Modifiable risk factors such as muscle weakness [21] and poor hamstring muscle flexibility [22,23] have received much attention in the literature. It is well recognized that approximately 60% of hamstring muscle strains identified in football players were associated with a high-speed running action [24] and it has been speculated that the injury is produced due a failure of the tissues to tolerate the forces applied during the sprint [15]. ...
... The data gathered in this investigation does not explain why this sign of hamstring muscle fatigue was not present in the dominant limb, but a non-significant reduction of 0.75% was also present in this side. From epidemiological point of view, this finding suggests a higher likelihood of hamstring muscle injury in referees towards the end of the match, as hamstring muscle fatigue and weakness in a potent predictor of hamstring injury occurrence in football players [20,21]. On the other hand, assistant referees covered a lower running distance than main referees at all speed thresholds above 7 km·h −1 which may explain that isometric knee flexion values post-match were not different from pre-match measurement in this subgroup of football officials. ...
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The aim of this study was to examine the acute effect of officiating a football (soccer) match on isometric knee flexion strength and passive hip flexion range-of-motion (ROM) in referees and assistant football referees. Twelve referees (25.3 ± 3.3 years) and twenty-three assistant referees (25.1 ± 4.8 years) underwent measurements on isometric knee flexion strength and passive hip flexion ROM before and after officiating an official football match. Referees' and assistant referees' running patterns were monitored during the match using GPS technology. In comparison to pre-match values, referees reduced their isometric knee flexion strength (−12.36%, p = 0.046, Effect size [ES] = −0.36) in the non-dominant limb, while no significant differences were reported in the dominant limb (−0.75%, p = 0.833, ES = −0.02). No effect of the match was found in hip flexion ROM values in dominant (−4.78%, p = 0.102, ES = −0.15) and non-dominant limb (5.54%, p = 0.544, ES = 0.19). In assistant referees, the pre-to-post-match changes in isometric knee flexion strength (dominant limb −3.10%, p = 0.323, ES = −0.13; non-dominant limb −2.18%, p = 0.980, ES= 0.00) and hip flexion ROM (dominant limb 1.90% p = −0.816, ES = 0.13; non-dominant limb 3.22% p = 0.051, ES = 0.23) did not reach statistical significance. Officiating a match provoked a reduction in isometric knee flexion strength in the non-dominant limb of football referees, while no differences were reported in assistant referees.
... Consequently, the time under tension near full knee extension was frequently very short due to neuromuscular fatigue (Delahunt et al., 2016;Ditroilo et al., 2013;Lovell et al., 2018). This might have diminished the training progress as this specific ROM (30-0° knee flexion), where muscle operates at long fascicle length which is presumably crucial for an effective strength program in sports (i.e., injury prevention and competitive success) (Guex et al., 2016;Timmins et al., 2015). For such reason, we hypothesised that participants' placement (e.g., ankle position) during the NH E might enable us to perform the exercise not only during more time (i.e., longer time under tension) but also closer to knee total extension may benefit training-induced effects on fascicle length where muscles are capable to apply more force. ...
... With regard to implications for training, the effectiveness of the NH E on improvements in knee flexor strength, sprint performance and injuries are likely associated with variables such as exercise volume and intensity of the exercise (Bourne et al., 2017;Opar et al., 2015;. Training volume manipulation is relatively easy to accomplish by changing the number of repetitions or sets and may also be impacted by manipulating time under tension. ...
Article
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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.
... Recently, eccentric force during the NHE has been recognized as an indicator of eccentric hamstring strength. Previous studies have investigated the relationship between the peak eccentric force during the NHE and the risk of HSI (Opar et al., 2015;Timmins et al., 2016) and reported that athletes with peak eccentric force, reported relative to body mass (N/kg), of less than 4.35 N/kg were at a 2.5-fold greater risk of subsequent HSI than stronger players (Timmins et al., 2016). Thus, testing of eccentric force during the NHE has replaced isokinetic strength assessment as a predictive factor for HSI. ...
... To the best of our knowledge, this is the first study to examine the relationship between ankle position and peak eccentric force during the NHE. Previous studies revealed that a greater peak eccentric force during the NHE decreases future risks of HSI (Opar et al., 2015;Timmins et al., 2016) and that a peak eccentric force, reported relative to body mass (N/kg), of less than 4.35 N/kg was associated with a 2.5-fold greater risk of a subsequent HSI (Timmins et al., 2016). The results of the present study showed that peak eccentric force during the NHE was significantly greater with the ankle plantarflexed position than the dorsiflexed position, suggesting the importance of considering ankle position for measurement of peak eccentric force during the NHE. ...
Article
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Peak eccentric force during the Nordic hamstring exercise (NHE) is recognized as a predictive factor for hamstring strain injury (HSI). During the NHE, the knee flexor muscles are eccentrically contracting to resist the knee joint extension. Therefore, it is thought that the action of the gastrocnemius muscle, and thus the ankle position, influences peak eccentric force during the NHE. However, the effect of ankle position on peak eccentric force during the NHE remains unclear. Therefore, we investigated the effect of ankle position on peak eccentric force during the NHE in a cohort of 50 healthy young male rugby players (mean age, 18.7 ± 1.2 years; mean body mass, 81.7 ± 15.2 kg; height, 1.72 ± 0.06 m) with no history of HSI. Each participant performed NHE strength testing with the ankle dorsiflexed or plantarflexed position and was instructed to fall forward as far as possible within 3 s. Peak eccentric force, reported relative to body mass (N/kg), of both legs was recorded, and the mean values of both legs were compared in both ankle positions. The mean peak eccentric force was significantly greater with the ankle plantarflexed position than the dorsiflexed position (3.8 ± 1.1 vs. 3.5 ± 1.1 N/kg, respectively, p = 0.049). These results indicate that ankle position should be carefully considered when measuring peak eccentric force during the NHE and performing NHE training.
... The hamstring is susceptible to acute muscle strain resulting from excessive force during sprinting 1,2) , because the hamstring requires substantial eccentric contraction power at longer muscle lengths to absorb hip flexion and knee extension moment to decelerate lower limb momentum during the late swing phase of sprinting 4,5) . Therefore, greater eccentric hamstring strength 6,7) and production of larger muscle force at longer muscle lengths might decrease the risk of hamstring strain injury 8,9) . ...
... Previous studies reported that greater eccentric hamstring strength 6,7) and production of larger muscle force at longer muscle lengths 8,9) might decrease the risks of hamstring strain injury. In the present study, higher passive stiffness of hamstring was associated with peak eccentric knee flexion torque and greater eccentric knee flexion torque at longer muscle lengths. ...
Article
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Larger hip flexion range of motion with knee extension (hip flexion ROM) and passive stiffness of the hamstring is associated with greater production of isometric and concentric knee flexion torque at longer muscle lengths. Nevertheless, associations among hip flexion ROM, passive stiffness of hamstring, and eccentric knee flexion torque at a longer muscle length remain unclear. Therefore, we aimed to investigate the association among hip flexion ROM, passive stiffness of hamstring and eccentric knee flexion angle-torque relationship. Seventeen healthy male college students participated in this study, and all measurements were performed on both legs (34 legs). No participants had any previous hamstring strain injury. Hip flexion ROM, passive stiffness of hamstring, peak torque and peak torque angle during isokinetic eccentric knee flexion were measured. The correlation among the variables of interest were assessed. Passive stiffness of hamstring and eccentric peak knee flexion torque negatively correlated with the peak torque angle (r = −0.39). On the other hand, peak torque angle was not correlated with hip flexion ROM (r = 0.08). The present study revealed that higher passive stiffness of hamstring was associated with greater production of eccentric knee flexion torque at longer muscle lengths.
... 5 The hamstrings are prone to injury in sports that involve sprinting. 6 Hence, optimising sprinting technique is a HSI prevention strategy worth considering. 7 Although two studies support this suggestion, 8,9 there is limited evidence supporting sprinting technique as a HSI risk factor. ...
Article
Objective: The aim of this study was to explore expert opinion to identify the components of sprinting technique they believed to be risk factors for hamstring strain injuries (HSI). Design: Mixed-method research design. Methods: The Concept Systems groupwisdom™ web platform was used to analyse and collect data. Participants brainstormed, sorted and rated the components of sprinting technique to consider in a HSI prevention strategy. Results: Twenty-three experts (academic/researcher, physiotherapist, strength and conditioning coaches and sprint coaches) brainstormed 66 statements that were synthesised and edited to 60 statements. Nineteen participants sorted the statements into clusters and rated them for relative importance and confidence they could be addressed in a hamstring injury prevention program. Multidimensional scaling and cluster analysis identified a 8-cluster solution modified to a 5-cluster solution by the research team: Training prescription (10 statements, mean importance: 3.79 out of 5 and mean confidence: 3.79); Neuromuscular and tendon properties (9, 3.09, 3.08); Kinematics parameters/Technical skills (27, 2.99, 2.98); Kinetics parameters (10, 2.85, 2.92); and Hip mechanics (4, 2.70, 2.63). The statement: "low exposure to maximal sprint running" located in the cluster "Training prescription" received the highest mean importance (4.55) and confidence ratings (4.42) of all statements. Conclusion: The five clusters of components of sprinting technique believed to be risk factors for HSIs in order of most to least important were: training prescription, neuromuscular and tendon properties, kinematics parameters/technical drills, kinetics parameters and hip mechanics.
... romuscular performance, which may contribute to an increase in acute injury risk associated with a high recent match exposure. For example, eccentric hamstring strength, which has been demonstrated to protect against hamstring injury [30], is compromised for up to 96 hours following football matches [2]. This is particularly relevant given the high incidence of thigh injuries in field hockey [18]. ...
Article
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Fixture congestion increases injury risk in football, but how it impacts other sports is unclear. The aim of this study was to identify associations between match density and injury incidence in field hockey players. Injury data from a prospective cohort study of professional and youth players was analysed in two ways. Inter-match intervals were clustered into<2424-hours, 3–7-days, and 13 + days, and injury rate ratios (IRR) were calculated to identify differences between clusters in match injuries. Separately, a Lasso-penalised Poisson regression model was used to determine the association between match load across the previous 24-hours, 3-days, 7-days and 14-days, and match and training injuries. Injury rates in matches within 24-hours of the previous match were mostly significantly higher when compared to matches after 3–7-days (IRRs: 3.78; 6.77, P = 0.003; 0.005). While a higher match exposure in the preceding 24-hour and 3-day periods was associated with higher combined match and training injury rates (β̂ = 0.0001; 0.0018), a higher match exposure in the previous 7-and 14-day periods was associated with a reduced injury rate (β̂ = –0.0001; –0.0005). Due to the increased injury risk in matches 3-days and especially 24-hours following the previous fixture, match distribution should be cautiously planned.
... Weaker hamstring muscles have negated many other functions associated with sprinting. 17 Therefore, manual treadmills have been utilized more frequently when compared to solely ground force training. The ability to adjust settings has also manipulated eccentric loads of the running motion. ...
Article
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Purpose: Speed training and short distance sprints have become an essential component of preparation for professional football players. Current trends in speed training have included the application of non-curved, manual treadmills, as they may enhance peak speeds with less biomechanical stress. A lack of data currently exists in regards to the effectiveness of different settings and peak speed response. Therefore, we proposed to compare peak speeds during different settings of non-curved, manual treadmills. It was hypothesized that as resistance/incline increased, peak sprinting speeds would decrease and vice versa. Methods: Fourteen male professional football players (27.14 ± 3.11 yrs., 183.93 ± 8.52 cm, 100.36 ± 15.60 kg) sprinted at peak speeds during four different incline/resistance bouts. Paired samples T-tests examined differences between bouts, and significance was set at p ≤ 0.008. Results: A significant difference (p < 0.001) existed for peak speeds between each incline/resistance bout (i.e. INC15R8, INC15R5, INC20R3, INC20R1). Conclusions: The observed data differences existed between all bouts, indicating that as resistance and/or incline increased, peak speed decreased. This also indicated that as resistance and/or incline decreased, peak speed increased during sprint bouts in professional football players.
... Notably, it is suggested that the high levels of activation and subsequent torque generated by the hamstring muscles (i.e., as high as 8 times bodyweight) can predispose an athlete to an increased risk of hamstring muscle strain injury (HSI) when performing sprint actions (104,187,206,212). Debate exists in relation to whether the mechanistic basis for HSI is explained for in the end swing phase or early stance phase (104); however, it has been shown that hip extensor concentric (186) and knee flexor eccentric strength (153) are both considered risk factors for HSI. Moreover, the activation levels (45) and force generating capacity (135) of these muscle groups are compromised in individuals who have previously sustained an HSI. ...
... This type of training would increase the number of serial sarcomeres, a mechanism that would allow the muscles to work at longer lengths [24], thus reducing the amount of work done in the descending and more unstable limb of the length-tension curve [25] . It has been systematically reported that eccentric training increases the optimum length of tension development [25][26][27], this being linked to a reduction in the risk of HSI [28], as well as to an improvement in the strength of the lower limbs [21,27,29] and small-to-medium improvements in sprint performance [29]. However, we should highlight that the effects of this type of training can be negatively affected after a subsequent detraining period [21,22]. ...
Article
Eccentric training has been shown to be important for hamstring strain injuries rehabilitation and prevention. The Askling L-PROTOCOL (L-P), comprising three exercises aimed at eccentric training and hamstring lengthening, was shown to improve this injuries recovery and relapse times in comparison with other traditional exercise-based protocols. However, the causes of these results remain unclear. This study looks at the impact of an 8-week L-P followed by 4 weeks of detraining on the architecture of the biceps femoris long head, hamstring flexibility and sprint performance. Twenty-eight healthy individuals were divided into two groups: an experimental group, which carried out the L-P, and a control group with no training. Muscle architecture was measured using 2Dultrasound, hamstring flexibility using goniometry and sprint performance using sports radar equipment before(M1) and after(M2) the training period and after detraining(M3). No significant changes were observed between M1 and M2 in the experimental group with regard to fascicle length(t=-0.79,P>.05), theoretical maximum speed (t=-1.43,P>.05), horizontal force (t=0.09,P>.05), force application during sprint running(t=-0.09,P>.05) and horizontal power (t =-0.97,P>.05), but, however, changes were observed in hamstring flexibility (t=-4.42,d=0.98,P<.001) returning to pre-training values after detraining period(t=-1.11,P>.05). L-P has been shown to be an eccentric protocol of moderate intensity and easy implementation that could be interesting to include throughout a sport season.
... Hamstring strength is one of the muscle properties that has received more attention in current research both as preventive and performance-enhancing strategy [8][9][10]. It seems that hamstring strength deficit is a good predictor of HSI [6]. ...
Article
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Background: The aim of the study was to systematically evaluate the biceps femoris long head activation across cross-sectional hamstring strength exercise studies. Methods: A systematic review design was followed. The search strategy conducted in PubMed, Cochrane Library, and Web of Sciences databases found a total of 3643 studies. Once inclusion and exclusion criteria were applied, 29 studies were finally included in this systematic review. A total of 507 participants and 114 different exercises were analyzed. Exercises were evaluated individually and grouped into several categories: Nordics, isokinetic exercises, lunges, squats, deadlifts, good mornings, hip thrusts, bridges, leg curls, swings, hip and back extensions, and others. Results: Results showed the isokinetic and Nordic exercises as the categories with highest biceps femoris activation (>60% of Maximal Voluntary Isometric Contraction). Nordic hamstring exercise ankle dorsiflexion was the exercise that achieved the highest biceps femoris long head activation (128.1% of its Maximal Voluntary Isometric Contraction). Conclusions: The results from this systematic review suggest that isokinetic and Nordic exercises seem to be the best option to activate biceps femoris long head. Future studies evaluating the implementation of these exercises in prevention programs are needed.
... Measurement of test values were generated by cells that can analyze the axial load on the board. The maximum values of eccentric movement of hamstrings from each side were obtained and recorded as Newton for each limb [21] ( Figure 3). ...
Article
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Objectives This study aimed to examine the effects of COVID-19 confinement on hamstring eccentric strength, hip adduction-abduction strength and posterior chain flexibility in professional male soccer players. We also aimed to investigate whether muscle strength and flexibility would change when the players returned to play after COVID-19 confinement. Methods Thirty professional male soccer (Age; 24.9±4.8 yrs, BMI; 22.7±1.4 kg/m²) players participated in this study. Hamstring eccentric strength, hip abduction-adduction strength and posterior chain flexibility (PCF) were measured before (time 1) and after the home confinement period (time 2) and after return to play (time 3). Repeated measures of ANOVA was used for statistical analysis. Results PCF decreased from time 1 to time 2 (p=0.005) but it increased from time 2 to time 3 (p=0.03). Hamstring eccentric strength decreased from time 1 to time 2 for both dominant (p=0.002) and non-dominant (p=0.04) limbs and no difference was observed between time 2 and time 3 (p>0.05). Hip abductor and adductor strength did not change between time 1 and time 2 (p>0.05) but they increased from time 2 and time 3 in the dominant limb (p<0.05). Five players (16%) had muscle injuries including hamstrings and adductors when they returned to play. Conclusion This study showed that 8-week COVID-19 confinement had an adverse effect on hamstring eccentric strength and PCF and 3 players had hamstring muscle injuries when they returned to play. Therefore, soccer players can be at risk of hamstring muscle injuries due to long-term detraining. Hip abductor and adductor strength seem not to be negatively affected by 8-week COVID-19 confinement. However, 2 players had adductor strain when they returned to play.
... As a typical non-contact injury, the intrinsic factors that predispose athletes to HSI have received great attention [6]. Older age and previous HSI are well-accepted non-modifiable risk factors [1], while prospective studies have pointed that athletes with low levels of hamstring eccentric strength [7][8][9][10] and short BF LH fascicle length [7] are more susceptible to sustaining HSI. ...
Article
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Background Muscular responses to training programs with the Nordic hamstring exercise (NHE) have been widely investigated to understand its preventive effects on muscle strain injury. Conversely, little is known about muscular responses to the stiff-leg deadlift (SLD), an exercise that preferably activate the biceps femoris long head, precisely the knee flexor muscle most commonly injured.AimsThe aim of the current study was to verify the effect of training programs using the NHE or the SLD on muscle architecture, strength, and functional performance of well-trained rugby players.Methods Twenty-three male rugby union players completed a 5-week training program using either the NHE (n = 12) or the SLD (n = 11). Biceps femoris long head muscle architecture, hamstring and quadriceps isokinetic peak torques, and countermovement jump performance were assessed before and after the training program.ResultsThere was no significant group-by-time interaction for any outcome (p > 0.05). NHE group experienced higher percent increases than SLD group for biceps femoris fascicle length (~ 14% vs. ~ 6%; p = 0.015). Within-group analysis indicated that NHE group presented greater effect sizes for muscle architecture outcomes, hamstring eccentric peak torque and hamstring-to-quadriceps functional ratio; conversely, SLD group presented greater effect sizes for hamstring concentric peak torque and countermovement jump height.Conclusions The NHE should preferably be used to enhance the hamstring eccentric strength and the biceps femoris fascicle length (our primary outcomes, supported by previous studies as risk factors for hamstring strain injury), while the SLD favor improvements in hamstring concentric strength and jump performance.
... Hence, athletes who display superior physical characteristics give themselves or their respective team a greater chance of success. Furthermore, there is increasing evidence that superior physical performance characteristics are also associated with less injury (Case, Knudson, & Downey, 2020;Opar et al., 2015). ...
Article
Objective This review aims to provide a succinct and critical analysis of the current physical and mechanical demands of elite Australian football while examining lower-limb injury and the associated physical and kinanthropometric risk factors. Methods MEDLINE, PubMed, Web of Science and SPORTSDiscus electronic databases were searched for studies that investigated the playing demands, injury trends, and physical and kinanthropometric injury risk factors of elite Australian football. Articles from similar team sports including soccer and rugby (union and league) were also included. Results While the physical demands of elite AF have steadied over the past decade, injury rates continue to rise with more than two-thirds of all injuries affecting the lower-limbs. Body composition and musculoskeletal morphological assessments are regularly adopted in many sporting settings with current research suggesting high and low body mass are both associated with heightened injury risk. However, more extensive investigations are required to determine whether the proportions of muscle and fat are linked. Repeated assessment of musculoskeletal morphology may also provide further insight into stress fracture rates. Conclusions While kinanthropometric and physical attributes are highly valued within elite sporting environments, establishing a deeper connection with injury may provide practitioners with more insight into current injury trends.
... Estimating the Dynamic Ratio of the Lateral/Medial Hamstrings. A Case Control Study 80% of hamstring strains involve the long head of the biceps femoris (2). A systematic review of hamstring muscle strain injuries in sport found the most consistent risk factors for this injury to be intrinsic factors such as age, previous hamstring injury and an increase in quadriceps peak torque (3)(4)(5). ...
Article
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Purpose. Hamstring injuries are among the most common injuries in sports. The current study estimates the hamstrings dynamic ratio (HDR) between the mean muscle activation of lateral (biceps femoris longus) and medial part (semitendinosus) of the hamstring muscles during a maximal voluntary isometric contraction in elite uninjured track and field athletes. Methods. Following isokinetic assessment to estimate the hamstrings to quadriceps dynamic ratio (H:Q), the participants were divided in two groups (Group 1 (N = 10): athletes with a H:Q ratio range 55-70% and no side to side difference of the ratios more than 6 units; and Group 2 (N = 8) athletes with a H:Q ratio outside of the 55-70% range and/or a side to side difference of the ratios greater than 6 units). All athletes were assessed by electromyography during a maximum voluntary isometriccontraction of their hamstrings. Results. There was difference on the range and means between the two groups regarding hamstrings dynamic ratio (78% and 69% respectively), although this difference did not reach statistical significance. Conclusions. A proposed HDR of 78% between lateral to medial hamstrings could be used as a risk factor for hamstring injuries in athletes with hamstring muscle imbalances. Better characterisation of the normal patterns of hamstring muscle activation will allow targeted rehabilitation to address specific neuromuscular coordination patterns.
... To regain strength, eccentric training is performed with the help of isokinetic dynamometer and many exercises such as Nordic hamstring exercise and Razor hamstring curl are applied (Pollard, Opar, Williams, Bourne, & Timmins, 2019). After these training programs, hamstring muscle strength increases and the incidence of injuries decreases (Al Attar, Soomro, Sinclair, Pappas, & Sanders, 2017;Lovell, et al., 2018;Opar, et al., 2015;Petersen, Thorborg, Nielsen, Budtz-Jørgensen, & Hölmich, 2011;van der Horst, Smits, Petersen, Goedhart, & Backx, 2015). For example, Nordic hamstring exercise programs, which researchers mostly prefer, reduce injuries by up to 51% (Yu, et al., 2008). ...
Article
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The architectural features of the hamstring muscle group are important to prevent injury or to reduce the risk of re-injury. Besides, eccentric training is often used in the rehabilitation of hamstring injuries. The aim of this systematic review was to examine the changes created by eccentric training on hamstring muscle architecture and to determine the minimal values of training duration and intensity for requiring functional changes. The research was conducted on the PubMed, Scopus, Web of Science, COCHRANE, CINAHL, and Pedro databases. Full-text studies examining the effect of eccentric training on at least one parameter of the hamstring muscle architecture were included in the review. Studies on cadavers and animals and studies involving different types of training combined with eccentric training were excluded. Twelve of the 7954 studies met the set criteria. According to the results, eccentric training undoubtedly increases fiber length. However, the pennation angle tends to decrease. On the other hand, muscle thickness and cross-sectional area tends to increase depending on the eccentric training. Although the frequency, number of sets and number of repetitions in sets were similar in the examined studies, muscle architecture changes were different. We think that eccentric training duration and the number of repetitions in total or per training session seem to have an impact on muscle architecture. In order to determine the minimal eccentric training program that can create these changes, quality research is needed to examine the duration, intensity and methods of eccentric training.
... 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. ...
Article
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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.
... Hamstring injuries are highly prevalent in sports and mostly occur in non-contact circumstances when the athlete is sprinting, and approximately 80% of hamstring injuries involve the BF [15][16][17]. A critical factor in managing such injuries and planning a return to sport or training strategies is the availability of diagnostic tools. ...
Article
Full-text available
The hamstring muscle group is the most frequently injured muscle group in non-contact muscle injuries in sports involving high-speed running. A total of 84% of hamstring injuries affect the biceps femoris (BF) muscle. Clinical assessments and magnetic resonance imaging (MRI) are routinely used for diagnosis and plan management. MRI-negative scans for clinically diagnosed hamstring injuries range from 14% to 45%. We tested the hypothesis that the functional differences between injured and non-injured BF assessed by tensiomyography can be used for diagnostic and classification purposes. We compared an injured group of 53 international-level soccer players and sprinters with 53 non-injured international-level soccer players and sprinters of both sexes. Comparing the injured vs. non-injured athletes and the left vs. right side in all of the athletes, we used the percentage of absolute differences in the BF contraction time (Tc) to classify non-injured and injured BF muscles. The receiver operating characteristic (ROC) curve and the area under the curve (AUC) and the precision–recall curve (PRC) were used to measure the classification accuracy and to identify cut-off limits using the Tc differences. There was a very high ROC AUC value of 0.981 (SE = 0.009, p < 0.000), with 98.11% of the injured muscles being correctly classified (cut-off point 12.50% on Tc differences), and an AUPRC value of 0.981, with association classification criteria at >9.87. Tensiomyography has a high predictive ability to discriminate between injured and non-injured BF non-invasively and functionally.
... 11,12 Among modifiable neuromuscular characteristics, lower quadriceps, hamstring, and hamstring-to-quadriceps strength ratios have been identified to increase prospective injury risk of hamstring strains in Australian football and soccer athletes. [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. ...
Article
Full-text available
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.
... An early review by Opar et al. [10] proposed several modifiable and non-modifiable risk factors, including, but not restricted to, increased age, previous injury history, ethnicity, strength imbalances, flexibility, fascicle length and fatigue. 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. ...
... Indeed, some previous studies have been demonstrated the greater optimum length for peak force production of hamstring reduced the risk of HSIs during sprint running (Wan, Li et al. 2021). A prospective cohort study in elite Australian Rules Football identified eccentric weakness during the Nordic hamstring exercise as risk factor for a future HISs (Opar, Williams et al. 2015 Besides, the impact of the H/Q strength ratio on HSIs has received greater attention aiming to assess the risk of HSIs in the last few decades. A lower H/Q ratio was widespread to predicting the HSIs occurrence. ...
Thesis
The main objective of this thesis was to determine the influence of hamstring and quadriceps neuromuscular capacities on explosive performance and the risk of lower limb injuries in soccer players. The first study of this thesis examined the relationship between the isokinetic force capacity of the knee muscles and the deceleration performance in professional female soccer players. The results revealed the importance of the eccentric force of the knee extensors contributing to the production of braking force during the linear deceleration test. The second study of this thesis was interested in the influence of the direction of jump on the dynamic postural stability during an unipodal landing and the importance of the hamstring / quadriceps co-activation in the stabilization capacity of the legs unipodal supports. The main finding is that the dominant leg showed better dynamic postural stability during the jump landing, associated with higher H / Q co-activation in the first milliseconds of the contact phase. The third study of this thesis explores the influence of fatigue generated by maximal isokinetic contractions on the capacity for rapid strength of the hamstrings and quadriceps in footballers. The results showed that the functional and conventional ratios measured during the preseason testing are not sensitive to fatigue. In contrast, the rapid hamstring / quadriceps torque ratio is more affected by fatigue. In summary, this work has shown that the evaluation of the explosive strength and fatigability capacities of the extensor and flexor muscles of the knee on an isokinetic ergometer remains a central subject for the improvement of explosive performance and the reduction of the risk of injury in the soccer player and footballer. In addition, the results of this work show the value of systematically associating the analysis of the EMG signal with the evaluation of the isokinetic force capacities, sprint performance and stability of the supports in male and female soccer players.
... The preventive strategies organization can not characterize the top player or the adult athlete, but must be placed above all in the athlete training and athlete evolution process: in this phase the risk factors monitoring offers greater guarantees of long-term success (Opar et al., 2015;White et al., 2018;Leister et al., 2018). The identification at the young age of imbalances and strength asymmetries allow an early intervention that can contrast a potential injury risk scenario. ...
Article
Full-text available
The study purpose.The Small-side games (SSG) are high intensity drills very popular in soccer training. The knowledge of the acute effects of the exercises that make up the training session is very relevant especially to reduce youth soccer injury risk. This study aim to assessment the acute effects of SSG on hamstring eccentric strength and to know the lower limb strength asymmetries (LLSA) in young soccer players. Materials and methods. The sample is composed of male young soccer players Under 17 (n = 24, 16.6 ± 0.5 years, 168.8 ± 4.6 cm, 58.2 ± 3.5 kg). Before and after SSG (4vs4, 3×4 min, 3min recovery, no goalkeepers) the hamstring eccentric strength and the lower limb eccentric strength asymmetry were evaluated used a specific dynamometer (N3 Easytech, Italy) and relative software. Every young soccer player performed a single repetition of the Nordic hamstring exercise with dynamometer; after about 2 minutes, instead, they performed 5 repetitions of the same exercise, without interruption. For both assessments, were detected the eccentric strength and the LLSA. Results. The hamstring eccentric strength assessment show substantial and statistically significant differences in the assessment in comparison pre-post values. A significant reduction was observed for eccentric strength peak (p < 0.018 and p < 0.014 for right/left limb), for eccentric average strength (p < 0.017 and p < 0.006 for right/left limb). The eccentric peak strength asymmetry value and the average strength asymmetry value revealed a significant increase (p < 0.0001). Conclusions. The reduction of strength after SSG requires careful consideration of the exercises order in the training session. The practitioners can plan training sessions and apply SSGs more effectively, with more attention to the effects on hamstrings.
... 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, since the fascicles may then be more susceptible to rapid over-stretching 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.
... The NHE is the most studied strategy to provoke both architectural and functional changes, such as increases on eccentric force output, muscle volume, cross-sectional area, and fascicle length. 3,[41][42][43][44] However, studies focused on the assessment of the eccentric strength, torque, and relative torque seem to be limited by the lack of devices and standard protocols that evaluate the actual task. A recent systematic review aimed to search, analyze, and summarize the new technologies used to assess the eccentric strength of hamstring muscles. ...
Article
This study aimed to assess the test-retest reliability of a Wii board-based device to assess the eccentric knee strength. Healthy participants (n = 20, 22.7 [3.4] y, 1.71 [0.09] m, 69 [13] kg) performed 2 assessments-days 1 and 2-of the Nordic hamstring exercise (3 trials per day, 3 min of rest between trials, and 48 h between trials) on a padded board with an attached Wii Balance Board (WBB). A ratchet inelastic strap made the contact between the participant's distal aspect of both legs and the inverted upper surface of the WBB. The means among 3 trials were used to extract the absolute strength and the left and the right limb strengths. No between-session differences were found (P range = .691-.981). The intraclass correlation coefficient range showed excellent results (.905-.926), as the Cronbach α test (above .94). The correlation was high (r > .91; .820 < r 2 < .862). The Bland-Altman analysis returned high levels of agreement. The standard error of measurement ranged from 5.56 to 11.07 N and the minimal detectable change from 15.42 to 30.68 N. The percentage of standard error of measurement values were 2.95%, 3.74%, 2.88%, respectively, for absolute strength, right limb strength, and left limb strength. The adapted system showed an excellent cost-benefit relationship with optimal test-retest reliability. The findings suggest that the adapted system, using the WBB, is a reliable method for measuring the eccentric knee strength.
... Hamstring injury is one of the most common sports injuries. Previous studies have indicated that increased muscle stiffness 4) and decreased muscle strength 5) are associated with the risk of hamstring muscle injury. In particular, female have a lower risk of hamstring injuries than male, which has been reported to be related to estrogen-induced muscle stiffness. ...
Article
[Purpose] The purpose of this study was to elucidate changes in flexibility and muscle strength during the menstrual cycle in detail and to investigate the relationship between flexibility and muscle strength. [Participants and Methods] Sixteen healthy young female and eight male participants were measured during the follicular, ovulation and luteal phases. Range of motion, passive torque at the onset of pain, passive stiffness and muscle strength were measured using an isokinetic dynamometer. Additionally, electromyography was measured during muscle strength measurement. [Results] In the female group, range of motion and passive torque at the onset of pain were significantly increased during the ovulatory and luteal phases compared with the follicular phase. Passive stiffness decreased significantly during the ovulatory phase compared with the follicular phase. Isometric muscle force and electromyographic activity were significantly increased during the luteal phase compared with the ovulation phase. There was no correlation between stiffness and muscle strength. However, there was a positive correlation between electromyographic activity and muscle strength. [Conclusion] Our findings suggest that changes in flexibility during the ovulatory and luteal phases are influenced by fluctuations in sex hormones. However, the changes in muscle strength showed little relation to flexibility, suggesting the involvement of neural mechanisms.
... e98 technique for maximal isometric and eccentric strength. 1,38 In addition, the clinical use of dual-force plate technologies has allowed for evaluation of forceetime characteristics for various upper and lower body movements. The isometric mid-thigh pull is a test designed to quantify maximal isometric strength and rate of force development and has been demonstrated to be a valid way to determine asymmetrical strength in athletes. ...
Article
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The concept of returning to sport for a professional athlete is still under debate for the professional athlete in today’s sports environment. It is critical for the professional athlete to be able to return to sport at a highly competitive level but also to return in a safe and timely measure. With no “gold standard” of sport testing, it is difficult to determine what the right progression or testing regimen should be. The Return to Sport Clearance Continuum does not look at one moment in time, but looks throughout the continuum of healing to determine readiness for sport. The purpose of this article is to explore the concept of RTS being part of an evolving continuum rather than the traditional notion that RTS is a single decision made at a discrete point in time. The principles of progressive but regular testing procedures including qualitative and quantitative movement are presented to help the professional athlete return to sport at their maximal performance level. Level of Evidence V, expert opinion.
... In lower extremity, groin, hamstring strain, knee and ankle injuries are very common especially in bowlers. [9][10][11] . There are different strategies used in cricket to prevent injuries in cricket players such as eccentric strengthening exercises and isometrics are recommended to prevent injuries of groin, 12 , lower extremity proprioception exercises and strengthening exercises are recommended to prevent hamstring injuries, 13 and plyometric exercises are recommended to prevent injuries of knee and ankle. ...
Article
Full-text available
Background: Cricket is considered 2nd most famous sports while the chances of injuries are very high. Proper warm-up, cool down exercises play important role in reduction of injuries and cricket injury prevention program may be effective in warm-up or cool-down phases of training. Objective: To compare the effects of injury prevention program on physical fitness among cricketers in warm-up and cool-down phases. Methods: A Randomized Clinical Trial (NCT04017715) was conducted at Rawalpindi cricket club. Subjects were recruited through purposive sampling. The inclusion criteria were athletes registered with Pakistan Cricket Board, age 16-30 years and attending minimum 3 sessions were week. The n=55 subjects were recruited and randomly divided into three groups by sealed and envelop method. Cricket Injury Prevention Program introduced in warm-up and cool-down phases in Group A (n=18) and B (n=20) respectively and group C (n=17) is considered as control group for 6 weeks. Assessment were taken through 100m sprint, Burpee test, Illinois Agility Run test, plank test and star excursion balance test at baseline and after 6 weeks of intervention. Data analysis was done through SPSS 25. Results: The mean age of the subjects was 19.31±2.79, mean Body Mass Index was 18.77±1.58. There is a significant difference among all groups in 100m sprint, T agility, plank test, 3 minutes burpee test and start excursion test (p value˂0.05).Conclusion: Cricket injury prevention program (CIPP) is effective in preventing injuries in cricketers in both warm up and cool down.
... 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. ...
Article
Full-text available
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.
... 2-4 30 43-45 Therefore, not only the amount of strength is of particular interest, but the controlled range of motion during NHE execution ('angle at downward acceleration') and the maintenance of a high muscle activation. 35 36 38 68 [79][80][81][82] The combination of both parameters provides a comprehensive evaluation of NHE performance. To our knowledge, appropriate studies which presented these parameters in conjunction are rare. ...
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.
... Despite the numerous advantages of being physically active, taking part in either competitive or recreational sports is accompanied by an increase in injury risk [2]. Extensive studies, mainly in the form of sophisticated biomechanical analyses, have determined the injury risk factors [3][4][5][6][7][8][9][10], providing great potential for injury prevention. These laboratory-based measures provide precise quantification of the presumed risk factors, but they entail costly equipment and large amounts of time, so performing them on large scales is impractical. ...
Article
Full-text available
Background The validity of the Functional Movement Screen (FMS) in identifying active females who are predisposed to injury has not been specifically reviewed. This study aims to synthesize the literature on the ability of the FMS to identify at-risk active females. Methods Six online databases, including PubMed, Medline, Web of Science, Science Direct, SPORTDiscus and Google Scholar, were searched for the period of April 2006 to September 2021. Out of the 61 potential references, 17 were reviewed in detail with respect to the inclusion criteria; ten were ultimately included. The risk of bias, applicability and level of the studies were then identified using the QUADAS-2 and a checklist for assessing methodological quality. The following data were obtained from the included studies: year of publication, title, study type, participants’ demographic, sample size, FMS cutoff point, injury definition, statistical analyses used, FMS results and study level. Results Generally, the quality of eight studies was poor to moderate due to both small sample sizes and short follow-up periods. Except for a study on military members, all studies were carried out on team sports players. The overall bias of the studies was low, but there was an unclear amount of bias for participant selection. Two studies reported no predictive validity for the FMS, while three defended its predictive validity; the rest partially supported the FMS as a valid diagnostic tool. The reliability of the recommended cutoff point was confirmed, though cutoffs higher than 14 were significantly associated with the predictive ability of the FMS. Conclusion Although the FMS is reliable for clinical practice, and the current literature shows promise regarding the predictive ability of the FMS among active females, concerns remain regarding its validity in identifying at-risk females. Given the lack of clarity in the literature on the use of the FMS in females, further well-organized studies with larger sample sizes and longer monitoring periods are highly recommended. The sensitivity and specificity of the recommended cutoff of ≤ 14 has considerably decreased , and higher cutoff values should be applied to increase the FMS predictive ability. Level of evidence The level of evidence was determined to be 2b.
... [3] Especially, HID is the predominant injury mechanism of hamstring strain injuries. [27] In our study, injured hockey players had a higher ACWR of HID and RHIE. However, the high-intensity distance of injured soccer players showed no significant difference between injury blocks and pre-injury blocks or season average. ...
Article
Full-text available
Our study aimed to investigate the relative workload that is related to the injury in lower extremities of female field hockey players and to identify the optimal ratio of acute to chronic workloads (ACWR) depending on the playing position to manage low risk of sports-related injuries. Data were collected using a global positioning systems unit on a full-time basis and during competition among 52 players who were enrolled in Korea National Team. The ACWR was calculated by dividing the most recent 1 week workload by the prior 4 weeks workload. Injury risk was calculated for each category from very low to very high based on a z-score. In striker and midfielder, the injury risk was the lowest in the moderate-low category of total distance covered, meters per minute (MpM), repeated high-intensity effort bouts, and acceleration bouts, and the moderate-high category of high-intensity running distance (HID). The injury risk of a defender was the lowest in the moderate-low category of HID and MpM. The ACWR in total distance covered, MpM, repeated high-intensity effort bouts, and acceleration bouts should stay within the moderate-low category in striker and midfielder positions and HID and MpM in defender positions in order to manage low-risk of non-contact and soft tissue injuries in female field hockey players.
... Isokinetic assessments, such as hamstring eccentric strength, contralateral imbalance, and intra-limbs knee strength asymmetries (e.g., hamstring-to-quadriceps ratios, H:Q) have been considered as potential risk factors for hamstring strain and knee injuries in sprint-based team sports [7][8][9][10]. However, it is not known if these outcomes could also provide predictive injury information in endurance athletes. ...
Article
Full-text available
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.
... However, while the diagnostic accuracy of this test in detecting injury has not been demonstrated, research has shown that relatively low levels of eccentric hamstring force measured during a preseason training period are associated with an increased risk of hamstring strain injury in a subsequent competition season. 53 Collectively, eccentric hamstring force appears to have limited utility in assessing a player's readiness to train (over acute timeframes), however it may provide practitioners with useful information regarding subsequent injury risk during a competition season. Future research examining associations between acute changes in eccentric hamstring force and both mechanical load (i.e. ...
Thesis
Full-text available
Australian football (AF) is a physically-demanding, high-intensity field-based sport with players competing in the presence of performance-related psychological stress. This requires detailed monitoring of players for training and competition to maximise their readiness for high-level performance. Historically, monitoring team sport athletes has been based on the theoretical ‘fitness-fatigue’ model whereby performance can be deduced with knowledge of fitness (positive effects of training completed) and fatigue (residual impairments of function due to an acute training dose) over acute (~15 days) and chronic timeframes (~50 days). However, in practice, individual training load is prescribed to players over acute timeframes of ~7 days prior to competition matches, dictated by scheduling of matches every 6-8 days during the competition season. The prescription of acute training load is informed by a range of athlete monitoring data measuring training load completed, training response and neuromuscular performance. However, despite anecdotal evidence of the use of individual acute training load prescription in professional AF, it has not been presented empirically. This thesis contains five studies that aim to build a novel conceptual model of acute training load prescription using a refined collection of monitoring tests with suitable measurement characteristics that relate to competition performance in professional AF. 𝘚𝘵𝘶𝘥𝘺 𝘖𝘯𝘦 and 𝘚𝘵𝘶𝘥𝘺 𝘛𝘸𝘰 evaluated the measurement characteristics of reliability and sensitivity of common tests of training response, neuromuscular performance and aerobic fitness using test-retest and signal-to-noise ratio methods. The results showed that perceived wellness questionnaires, countermovement jump tests, eccentric hamstring force tests, isometric adductor force tests and heart rate recovery tests possess acceptable reliability and sensitivity, allowing confident identification of meaningful test results for practitioners. 𝘚𝘵𝘶𝘥𝘺 𝘛𝘩𝘳𝘦𝘦 and 𝘚𝘵𝘶𝘥𝘺 𝘍𝘰𝘶𝘳 addressed the issue of monitoring data overload for team sport practitioners by applying principal component analyses (PCA) to the monitoring tests established in 𝘚𝘵𝘶𝘥𝘺 𝘖𝘯𝘦 and 𝘚𝘵𝘶𝘥𝘺 𝘛𝘸𝘰 in addition to measures of training load and extended this analysis to propose two practical methods of using the results of PCA to enhance efficiency in team sport monitoring systems. 𝘚𝘵𝘶𝘥𝘺 𝘛𝘩𝘳𝘦𝘦 demonstrated that external load, internal load and perceived wellness represent statistically separate constructs of the training process, across acute (7-day) and chronic (28-day) timeframes commonly used to categorise athlete monitoring data. 𝘚𝘵𝘶𝘥𝘺 𝘍𝘰𝘶𝘳 identified components to represent isometric adductor force, eccentric hamstring force and countermovement jump power. These findings indicate that many individual measures commonly collected and analysed in professional team sport monitoring systems assess similar aspects of the training process, and hence some variables can be excluded from monitoring systems to enhance efficiency in the use of financial and human resources. 𝘚𝘵𝘶𝘥𝘺 𝘍𝘪𝘷𝘦 analysed the effect of a refined collection of measures of training load, training response and neuromuscular output from previous studies in the thesis and showed that z-score increases in individual acute training load associated with an 18-23% increase in performance z-score. This finding indicates that team competition schedule may have a confounding effect on acute load completed prior to a match as longer between-match periods provide for opportunity and flexibility for greater load completion. 𝘚𝘵𝘶𝘥𝘺 𝘍𝘪𝘷𝘦 also found no significant relationships between a range of other commonly collected monitoring variables and performance change. Collectively, the thesis populated a novel conceptual model of acute training load prescription with individual adjustments of acute load informed by a refined range of reliable and sensitive monitoring measures that relate to individual performance changes.
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.
Article
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Background Hamstring strain injuries are the most common injuries in team sports. Biceps femoris long head architecture is associated with the risk of hamstring injury in soccer. To assess the overall predictive ability of architectural variables, risk factors need to be applied to and validated across different cohorts. Purpose To assess the generalizability of previously established risk factors for a hamstring strain injury (HSI), including demographics, injury history, and biceps femoris long head (BFlh) architecture to predict HSIs in a cohort of elite Australian football players. Study Design Cohort study; Level of evidence, 3. Methods Demographic, injury history, and BFlh architectural data were collected from elite soccer (n = 152) and Australian football (n = 169) players at the beginning of the preseason for their respective competitions. Any prospectively occurring HSIs were reported to the research team. Optimal cut points for continuous variables used to determine an association with the HSI risk were established from previously published data in soccer and subsequently applied to the Australian football cohort to derive the relative risk (RR) for these variables. Logistic regression models were built using data from the soccer cohort and utilized to estimate the probability of an injury in the Australian football cohort. The area under the curve (AUC) and Brier score were the primary outcome measures to assess the performance of the logistic regression models. Results A total of 27 and 30 prospective HSIs occurred in the soccer and Australian football cohorts, respectively. When using cut points derived from the soccer cohort and applying these to the Australian football cohort, only older athletes (aged ≥25.4 years; RR, 2.7 [95% CI, 1.4-5.2]) and those with a prior HSI (RR, 2.5 [95% CI, 1.3-4.8]) were at an increased risk of HSIs. Using the same approach, height, weight, fascicle length, muscle thickness, pennation angle, and relative fascicle length were not significantly associated with an increased risk of HSIs in Australian football players. The logistic regression model constructed using age and prior HSIs performed the best (AUC = 0.67; Brier score = 0.14), with the worst performing model being the one that was constructed using pennation angle (AUC = 0.53; Brier score = 0.18). Conclusion Applying cut points derived from previously published data in soccer to a dataset from Australian football identified older age and prior HSIs, but none of the modifiable HSI risk factors, to be associated with an injury. The transference of HSI risk factor data between soccer and Australian football appears limited and suggests that cohort-specific cut points must be established.
Chapter
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Background: There are conflicting reports regarding the association between isokinetic concentric quadriceps and hamstring strength deficits and ratios and risk for hamstring injuries in athletes. Purpose: To determine if isokinetic concentric Cybex data collected during the annual National Football League (NFL) Scouting Combine are predictive of hamstring injury in professional American football players during their first season. Study design: Case-control study; Level of evidence, 3. Methods: All 32 NFL teams identified players selected during the first 5 rounds of the NFL annual draft who had hamstring injuries during their first professional season. Of these, 164 players with 172 injuries also had Cybex data from the previous year's Combine. Analyses compared injured legs with contralateral uninjured legs and also injured players with uninjured controls using a database of Cybex data from all players who participated in the NFL Scouting Combine from 2006 to 2011. Results: No Cybex strength variable differentiated the injured legs from the contralateral uninjured legs or injured players from uninjured controls, even after taking into account days lost from activity. Mean ± SD peak torque for the injured and contralateral uninjured sides was as follows: 315.7 ± 70.0 and 313.5 ± 68.3 N · m, respectively (P = .773, paired t test), for quadriceps and 203.0 ± 42.4 and 205.3 ± 42.5 N · m, respectively (P = .608, paired t test), for hamstrings. The sensitivity and specificity for the hamstrings-to-quadriceps ratio predicting hamstring injury were 0.513 (95% confidence interval, 0.419-0.607) and 0.524 (0.495-0.554), indicating that the hamstrings-to-quadriceps ratio was not a useful predictor of injury (calculation used the mean ± SD ratio for injured legs, 0.656 ± 0.133). Side-to-side peak torque differences were also not predictive of injury, with more than a 10% difference (plus or minus) occurring commonly in both injured and uninjured players for quadriceps (53% prevalence for both injured and uninjured) and hamstrings (injured, 41% prevalence; uninjured, 43% prevalence). Conclusion: Isokinetic strength data collected from collegiate players at the NFL Scouting Combine were not useful for predicting risk of hamstring injury in subsequent professional NFL competition. These data call into question commonly accepted assumptions about risk factors for hamstring injury, at least for elite collegiate American football players, when the temporal relationship between Cybex testing and actual injury is several months.
Article
Background: Injuries are common in all professional football codes (including soccer, rugby league and union, American football, Gaelic football, and Australian football). Purpose: To report the epidemiology of injuries in the Australian Football League (AFL) from 1992-2012 and to identify changes in injury patterns during that period. Study design: Descriptive epidemiology study. Methods: The AFL commenced surveying injuries in 1992, with all teams and players included since 1996. An injury was defined as "any physical or medical condition that causes a player to miss a match in the regular season or finals (playoffs)." Administrative records of injury payments (which are compulsory as part of salary cap compliance) to players who do not play matches determined the occurrence of an injury. The seasonal incidence was measured in units of new injuries per club (of 40 players) per season (of 22 matches). Results: There were 4492 players listed over the 21-year period who suffered 13,606 new injuries/illnesses and 1965 recurrent injuries/illnesses, which caused 51,919 matches to be missed. The lowest seasonal incidence was 30.3 new injuries per club per season recorded in 1993, and the highest was 40.3 recorded in 1998. The injury prevalence (missed matches through injury per club per season) varied from a low of 116.3 in 1994 to a high of 157.1 in 2011. The recurrence rate of injuries was highest at 25% in 1992 and lowest at 9% in 2012 and has steadily fallen across the 21 years (P < .01). The most frequent and prevalent injury was hamstring strain (average of 6 injuries per club per season, resulting in 20 missed matches per club per season; recurrence rate, 26%), although the rate of hamstring injuries has fallen in the past 2 seasons after a change to the structure of the interchange bench (P < .05). The rate of knee posterior cruciate ligament injuries fell in the years after a rule change to prevent knee-to-knee collisions in ruckmen (P < .01). Conclusion: Annual public reporting (by way of media release and reports available freely online) of injury rates, using units easily understood by laypeople, has been well received. It has also paved the way for rule changes with the primary goal of improving player safety.
Article
Hamstring muscle strain-type injuries are common in sports that involve sprinting,1 acceleration, deceleration, rapid change in direction and jumping.2 ,3 Occurring in both recreational and professional sports, these injuries can result in substantial time lost from sport and commonly recur.4 ,5 In the Australian Football League (AFL), hamstring muscle strain-type injuries have displayed a high incidence rate, with a 10 year mean of 6.1 new injuries per club each year and a 23% average recurrence rate.6 A recurrence rate of 17% has been reported in elite soccer players7 with hamstring injuries also recorded as the most common injury accounting for 12% of all injuries and resulting in an average of four missed games per injury.8 The high incidence of hamstring muscle strain-type injuries and potential associated costs has resulted in a substantial amount of research into the factors related to such injuries. Two recent systematic reviews have been completed in an attempt to collate the evidence around risk factors for hamstring injuries.9 ,10 Both reviews identified hamstring muscle weakness and thigh muscle imbalance, muscle flexibility, previous hamstring injury, other previous injury and age as potential risk factors; however, these reviews concluded that single variables were inconsistently identified as associated factors. Both reviews provided a qualitative synthesis of the literature and included risk factor studies as well as intervention studies, where a potential risk factor was modified with a training programme. The inclusion of intervention studies may potentially complicate risk factor analyses, as such studies assume that the factor being modified is associated with the injury and that the factor can be modified by the treatment programme. The aim of the current review was to assemble all available knowledge and data to identify the intrinsic and extrinsic risk factors associated with …
Article
The incidence of acute hamstring injuries is high in several sports, including the different forms of football. The authors investigated the preventive effect of eccentric strengthening of the hamstring muscles using the Nordic hamstring exercise compared with no additional hamstring exercise on the rate of acute hamstring injuries in male soccer players. Randomized controlled trial; Level of evidence, 1. Fifty Danish male professional and amateur soccer teams (942 players) were allocated to an intervention group (461 players) or a control group (481 players). Players in the intervention group conducted a 10-week progressive eccentric training program followed by a weekly seasonal program, whereas players in the control group followed their usual training program. The main outcome measures were numbers of overall, new, and recurrent acute hamstring injuries during 1 full soccer season. Fifty-two acute hamstring injuries in the control group compared with 15 injuries in the intervention group were registered. Comparing intervention versus the control group, overall acute hamstring injury rates per 100 player seasons were 3.8 versus 13.1 (adjusted rate ratio [RR], 0.293; 95% confidence interval [CI], 0.150-0.572; P < .001). New injury rates per 100 player seasons were 3.1 versus 8.1 (RR, 0.410; 95% CI, 0.180-0.933; P = .034), whereas recurrent injury rates per 100 player seasons were 7.1 versus 45.8 (RR, 0.137; 95% CI, 0.037-0.509; P = .003). Number needed to treat [NNT] to prevent 1 acute hamstring injury (new or recurrent) is 13 (95% CI, 9-23) players. The NNT to prevent 1 new injury is 25 (95% CI, 15-72) players, and NNT to prevent 1 recurrent injury is 3 (95% CI, 2-6) players. IN male professional and amateur soccer players, additional eccentric hamstring exercise decreased the rate of overall, new, and recurrent acute hamstring injuries.
Article
This study examined differences in movement patterns between AFL (elite) and WAFL (sub-elite) players using Global Positioning System (GPS) devices. Maximum speed data and totals of high intensity efforts (>15 km h⁻¹), sprint efforts (>20 km h⁻¹) and distance covered were collected on 41 players during the 2008 season. Data were expressed per min of game time played, separated into first and second halves, and also into positions, for both elite and sub-elite players. Overall, elite players had higher movement demands, including 9% more distance covered/min (128±12 m min⁻¹ vs. 117±15 m min⁻¹; p<0.01, ES=0.84), and 21% more high intensity efforts/min (2.9±0.6 vs. 2.4±0.6; p<0.01, ES=0.83). Movement demands significantly declined (p<0.05-0.01) from first to second half, in both competition levels. For both leagues, Small Forwards/Small Backs and Midfield players covered significantly greater (p<0.05-0.01) total distances and completed more high intensity efforts than other positions. Ruckmen recorded significantly lower (p<0.05-0.01) movement demands than Small Forwards/Small Backs, Midfielders and Centre Half-Forwards/Centre Half-Backs over most variables. In conclusion, elite players recorded higher overall movement demands than sub-elite players. This information may be useful for coaches and conditioning staff in designing appropriate training drills for specific role requirements of individual players and assist in the progression of players from sub-elite to elite levels of competition.
Article
A muscle fiber was modeled as a series-connected string of sarcomeres, using an A. V. Hill type model for each sarcomere and allowing for some random variation in the properties of the sarcomeres. Applying stretches to this model led to the prediction that lengthening of active muscle on or beyond the plateau of the length tension curve will take place very nonuniformly, essentially by rapid, uncontrolled elongation of individual sarcomeres, one at a time, in order from the weakest toward the strongest. Such a "popped" sarcomere, at least in a single fiber, will be stretched to a length where there is no overlap between thick and thin filaments, and the tension is borne by passive components. This prediction allows modeling of many results that have previously been inexplicable, notably the permanent extra tension after stretch on the descending limb of the length tension curve, and the continued rise of tension during a continued stretch.
Article
Muscle strains are common injuries in Australian football and other sports involving sprinting. Between 1992 and 1999, 83,503 player-matches in the Australian Football League were analyzed for risk of muscle strain injuries using logistic regression analysis. There were 672 hamstring, 163 quadriceps, and 140 calf muscle strain injuries. All three types of muscle strains were associated with significant risk factors. For all injuries, the strongest risk factor was a recent history of that same injury and the next strongest risk factor was a past history of the same injury. History of one type of muscle strain increased the risk for certain types of other muscle strains. Age was a risk factor for hamstring and calf muscle strains (even when adjusted for injury history) but was not a risk factor for quadriceps muscle strains. Quadriceps muscle injuries were more common in shorter players and were more likely when there had been less rainfall at the match venue in the previous week. Quadriceps muscle injuries were significantly more common in the dominant kicking leg, whereas hamstring and calf muscle injuries showed no difference in frequency between the dominant and nondominant legs.
Article
To conduct a detailed analysis of preseason football injuries sustained in English professional football over two competitive seasons. Club medical staff at 91 professional football clubs annotated player injuries. A specific injury audit questionnaire was used together with a weekly form that documented each club's current injury status. 17% (1025) of the total number of injuries over the two seasons were sustained during the preseason, the mean number of days absent per injury was 22.3 days. Younger age groups (17-25 yrs) were more likely to sustain a preseason injury than more experienced players (26-35+) (p<0.01). There were relatively more "slight" and "minor" injuries (as defined in the methodology), overuse, and tendon related injuries sustained during preseason compared to the in season (p<0.01). The thigh (23%), knee (17%), and ankle (17%) were the most common locations for injuries during the preseason, there was a relatively greater number of lower leg injuries (15%) during the preseason (p<0.05). Achilles tendonitis was most prevalent in the preseason, with 33% of all Achilles related injuries sustained during this period (p<0.01). Muscle strains were the most common injury during preseason (37%). Rectus femoris muscle strains were observed twice as frequently during the preseason relative to the in season (p<0.01). Ligament sprains were the second most common injury during preseason (19%). Non-contact mechanisms were the cause of significantly more injuries during the preseason (p<0.01), with relatively more preseason injuries sustained while running or shooting (p<0.01). For 70% of the injuries reported during the preseason, the ground condition was described as dry. Players are at a greater risk of slight and minor injuries, overuse injuries, lower leg injuries (especially the Achilles tendon) and rectus femoris strains during the preseason period. Prevention of preseason injury is important to ensure availability of players for the commencement of the season and to decrease the risk of injury later in the season, we recommend the implementation of a risk management policy for this purpose. Areas requiring further investigation include methods of prevention for the common preseason injuries that have been identified, a detailed analysis of preseason and closed season training programmes, and a smaller study involving exposure data.
Article
The methodology for studies designed to investigate potential risk factors for sports injury is reviewed, using the case of hamstring strains as an example. Injuries result from a complex interaction of multiple risk factors and events. Therefore, a multivariate statistical approach should be used. In addition, the sample size of the study needs to be considered carefully. Sample size mainly depends on the expected effect of the risk factor on injury risk, and to detect moderate to strong associations 20-50 injury cases are needed, whereas small to moderate associations would need about 200 injured subjects. Studies published to date on the risk factors for hamstring strains have methodological limitations, and are too small to detect small to moderate associations.
Article
A past injury history is one of the most commonly cited risk factors for sports injury. Often, injury history data are collected by self report surveys, with the potential for recall bias. To assess the accuracy of a 12 month injury history recall in a population of 70 community level Australian football players. The retrospective, self reported injury histories of 70 community level Australian football players were compared with prospective injury surveillance records for the same 12 month period. The accuracy of the players' recall of the number of injuries, injured body regions, and injury diagnosis was assessed. Recall accuracy declined as the level of detail requested increased. All players could recall whether or not they were injured during the previous year. Almost 80% were able to accurately recall the number of injuries and body regions injured, but not the diagnoses, whereas only 61% were able to record the exact number, body region, and diagnosis of each injury sustained. The findings of this study highlight the difficulty of using retrospectively collected injury data for research purposes. Any injury research relying on self reported injury history data to establish the relation between injury history and injury risk should consider the validity of the self report injury histories.