The financial cost of hamstring strain injuries in the Australian Football League

Influence of combined transcranial and peripheral electromagnetic stimulation on the autonomous nerve system on delayed onset muscle soreness in young athletes: a randomized clinical trial

BACKGROUND

Delayed Onset Muscle Soreness (DOMS) represents a common challenge for athletes and has been a focal point of research in sports science. Eccentric exercise, known to induce DOMS, significantly impacts recovery and physiological processes. Electromagnetic stimulation, both transcranial and peripheral, has gained attention in sports medicine due to its demonstrated benefits in various conditions, offering potential as a recovery-enhancing tool for athletes.

PURPOSE

This study aimed to evaluate the effects of combined transcranial and peripheral electromagnetic stimulation on the autonomic nervous system response and recovery in young athletes experiencing DOMS.

METHODS

A randomized, double-blind study was conducted with 48 young athletes divided into four groups: Control (n = 12), Peripheral Stimulation (n = 13), Transcranial Stimulation (n = 11), and Combined Stimulation (n = 12). Participants underwent an eccentric exercise session to induce DOMS, followed by their respective interventions: no stimulation for the Control group, 5 min of peripheral electromagnetic stimulation (LTP protocol) for the Peripheral group, 20 min of transcranial stimulation for the Transcranial group, and a combination of both (30 min total) for the Combined group. The autonomic nervous system was assessed through Heart Rate Variability (HRV) parameters measured before, immediately after, and at 24 h, 48 h, and 72 h post-intervention.

RESULTS

The Combined Stimulation group exhibited significant improvements in HRV parameters, including increased Low Frequency (LF, p < 0.001), High Frequency (HF, p < 0.001), and LF/HF power ratio (p < 0.001) at 72 h post-intervention compared to other groups. These findings suggest that paired-associative electromagnetic stimulation effectively enhances autonomic regulation and promotes recovery after eccentric exercise-induced DOMS.

CONCLUSIONS

Combined transcranial and peripheral electromagnetic stimulation positively influences autonomic nervous system responses, accelerating recovery in young athletes without disrupting natural physiological recovery mechanisms. This approach presents a promising recovery intervention for athletes experiencing DOMS.

Relationship Between the Pain Intensity at the Time of the Hamstring Muscle Injury and the Hyperintense T2 Weighted Volume of the Hamstring Muscle Lesion Measured by MRI

OBJECTIVES

The primary objective of this study was to analyze the correlation between the pain experienced at the time of a hamstring muscle injury and the hyperintense T2 weighted volume of the lesion measured on MRI. The secondary objectives were to analyze the differences in this pain with the lesion grade and the hamstring muscle head involved.

DESIGN

We performed a retrospective analysis of the data collected in a prospective, multicenter, noninterventional cohort study (HAMMER).

PATIENTS

A total of 61 patients were included in this analysis.

INTERVENTIONS

Patients with suspected hamstring muscle injury had an MRI after the injury.

MAIN OUTCOMES MEASURES

They were evaluated for their pain intensity experienced at the time of injury with a Numeric Pain Rating Scale (NPRS) from 0 to 10.

RESULTS

There was a significant but weak correlation between the pain experienced at the time of hamstring muscle injury and the hyperintense T2 weighted volume (r = 0.287; P = 0.025). There were no significant differences in the pain according to the lesion grade (F(3,57) = 0.982; P = 0.408) nor according to the muscle involved (F(3,57) = 1.013; P = 0.394).

CONCLUSIONS

Pain at the time of injury seemed to be weakly correlated with the extent of muscle lesion at medical imaging. Pain at the time of injury alone seems not enough to give us a clinical meaningful indication of the MRI hyperintense T2 weighted volume.

Increased anterior pelvic tilt angle elevates the risk of hamstring injuries in soccer player

OBJECTIVE

This study aims to determine the impact of increased anterior pelvic tilt angle on hamstring muscle injuries in football players. An independent t-test was performed to compare right and left anterior pelvic tilt angles.

DESIGN

The study was conducted by monitoring 76 different players from a professional club in the Premier Division of Professional Football League over a period of five years. During this time, the hamstring injuries sustained by the players and their severity were recorded using MRI imaging techniques.

RESULT

The comparison of the right and left anterior pelvic tilt angles among players was analysed using an independent t-test for independent groups. The Receiver Operating Characteristic (ROC) analysis was used to determine the threshold value that categorizes the right and left angles. According to the results, a significant impact of the variation in right-left anterior pelvic tilt angle on hamstring muscle injuries was observed (p < 0.05). However, no significant effects were found for the Q angle, tibial torsion, or knee posture (p > 0.05).

CONCLUSION

In conclusion, it can be stated that an increase in the anterior pelvic tilt angle is associated with a higher frequency of hamstring injuries.

Dilemma in the Treatment of Sports Injuries in Athletes: Tendon Overuse, Muscle Strain, and Tendon Rupture

Injuries to the musculoskeletal system are frequent in elite sports and they are detrimental to athletic performance. This can be due to, for example, (1) overuse disorders of tendon (tendinopathy) that not only lower the training efficiency but also, in many cases, are career-ending for the athlete due to pain; (2) acute muscle strain injury that both causes prolonged absence from competition and results in many re-injuries; or (3) tendon rupture that, apart from a very long rehabilitation period, will also result in many athletes never resuming their original high level of competitive sports. For all three injury examples, several evidence-based prevention programs and treatments are available, and yet the incidence of these injuries remains high and single treatments often provide only partial recovery. In this paper, we highlight the current treatments of these three conditions and focus on the unsolved dilemmas that exist in these sports injuries.

Systematic Video Analysis of ACL Injuries in Male Professional English Soccer Players: A Study of 124 Cases

Background

Improving our understanding of the situations and biomechanics that result in anterior cruciate ligament (ACL) injury will support the design of effective injury risk mitigation programs. A few video analyses have been published in recent years, but not specifically involving English soccer.

Purpose

To describe the mechanisms, situational patterns, and biomechanics (kinematics) of ACL injuries of players involved in matches involving teams in the top 2 tiers of professional English soccer (the Premier League and the Championship).

Study Design

Case series; Level of evidence, 4.

Methods

We identified 148 consecutive ACL injuries across 11 seasons of professional English soccer. Overall, 124 (84%) injury videos were analyzed for mechanism and situational patterns, while biomechanical analysis was possible in 91 injuries. Three independent reviewers evaluated each video. ACL injury epidemiology (month, timing within the match, and location on the playing field at the time of injury) was also reported.

Results

More injuries occurred in defensive (n = 79; 64%) than offensive (n = 45; 36%) playing situations; 24 (19%) injuries were direct contact, 52 (42%) indirect contact, and 47 (38%) noncontact. Of the indirect and non-contact ACL injuries (n = 100), most (91%) occurred during 4 main situational patterns: (1) pressing/tackling (n = 50; 50%); (2) being tackled (n = 18; 18%), (3) landing from a jump (n = 13; 13%), and (4) regaining balance after kicking (n = 10; 10%). These injuries generally involved a knee flexion strategy (with minimal hip/trunk flexion and reduced plantarflexion) in the sagittal plane and appearance of knee valgus in most cases (70%; 96% of identifiable cases). More (n = 71; 57%) injuries occurred in the first half of matches than in the second half (P < .01).

Conclusion

Indirect contact rather than noncontact was the main ACL injury mechanism in male elite English soccer players. Four main situational patterns were described, with pressing/tackling and being tackled accounting for two-thirds of all indirect and noncontact injuries. Biomechanical analysis confirmed a multiplanar mechanism, with knee loading patterning in the sagittal plane accompanied with dynamic valgus. More injuries occurred in the first half of matches.

Smaller Biceps Femoris Aponeurosis Size in Legs with a History of Hamstring Strain Injury

Biceps femoris long head (BFLH) aponeurosis size was compared between legs with and without prior hamstring strain injury (HSI) using two approaches: within-group (injured vs. uninjured legs of previous unilateral HSI athletes) and between-group (previously injured legs of HSI athletes vs. legs of No Prior HSI athletes). MRI scans were performed on currently healthy, competitive male athletes with Prior HSI history (n=23;≥1 verified BFLH injury; including a sub-group with unilateral HSI history; most recent HSI 1.6±1.2 years ago) and pair-matched athletes with No Prior HSI history (n=23). Anonymized axial images were manually segmented to quantify BFLH aponeurosis and muscle size. Prior unilateral HSI athletes' BFLH aponeurosis maximum width, aponeurosis area, and aponeurosis:muscle area ratio were 14.0-19.6% smaller in previously injured vs. contralateral uninjured legs (paired t-test, 0.008≤P≤0.044). BFLH aponeurosis maximum width and area were also 9.4-16.5% smaller in previously injured legs (n=28) from Prior HSI athletes vs. legs (n=46) of No Prior HSI athletes (unpaired t-test, 0.001≤P≤0.044). BFLH aponeurosis size was smaller in legs with prior HSI vs. those without prior HSI. These findings suggest BFLH aponeurosis size, especially maximum width, could be a potential cause or consequence of HSI, with prospective evidence needed to support or refute these possibilities.

Cross-cultural adaptation, reliability and validity of the persian version of the functional assessment scale for acute hamstring injuries

BACKGROUND

The Functional Assessment Scale for Acute Hamstring Injuries (FASH) which measure symptom's severity and impact on physical activity and sports ability in individuals with acute hamstring muscle injury, is not available in Persian. The aim of this study was to translate and cross-culturally adapt the FASH questionnaire to Persian and to assess the psychometric properties of the translated version.

METHODS

The Persian-translation and cross-cultural adaptation processes were based on World Health Organization method. A total of 160 participants compromising of four groups: (1) acute hamstring injury (N = 40), (2) other lower extremity injury (N = 40), (3) risk of acute injury (N = 40), and (4) healthy control (N = 40) were recruited to complete the Persian version of FASH (FASH-P) questionnaire twice with an interval of 48-60 h. The Short Form Health Survey (SF-36) and Lower Extremity Functional Scale (LEFS) were used to assess the criterion validity. Test-retest reliability, internal consistency, criterion validity, Dimensionality and floor/ceiling effects were evaluated to assess the FASH-P psychometric properties.

RESULTS

The FASH questionnaire were translated to Persian without any major problems. The FASH-P showed excellent power of differentiation because the scores were significantly different among the four groups. Regarding psychometric performances, excellent test-retest reliability (Intraclass correlation coefficient of 0.997) and a high level of internal consistency (Cronbach's alpha of 0.966) were observed. The FASH-P total score was significantly correlated with SF-36 and LEFS questionnaires representing an excellent criterion validity. No floor or ceiling effect were found for total score in Hamstring muscle injury group.

CONCLUSIONS

Due to the excellent psychometric performance, the FASH-P can be used as a reliable and valid tool for evaluating the severity of symptoms and sports ability in Persian-speaking patients with hamstring muscle injury.

Multiscale hamstring muscle adaptations following 9 weeks of eccentric training

BACKGROUND

Eccentric training, such as Nordic hamstring exercise (NHE) training, is commonly used as a preventive measure for hamstring strains. Eccentric training is believed to induce lengthening of muscle fascicles and to be associated with the addition of sarcomeres in series within muscle fibers. However, the difficulty in measuring sarcomere adaptation in human muscles has severely limited information about the precise mechanisms of adaptation. This study addressed this limitation by measuring the multiscale hamstring muscle adaptations in response to 9 weeks of NHE training and 3 weeks of detraining.

METHODS

Twelve participants completed 9 weeks of supervised NHE training, followed by a 3-week detraining period. We assessed biceps femoris long-head (BFlh) muscle fascicle length, sarcomere length, and serial sarcomere number in the central and distal regions of the muscle. Additionally, we measured muscle volume and eccentric strength at baseline, post-training, and post-detraining.

RESULTS

NHE training over 9 weeks induced significant architectural and strength adaptations in the BFlh muscle. Fascicle length increased by 19% in the central muscle region and 33% in the distal muscle region. NHE also induced increases in serial sarcomere number (25% in the central region and 49% in the distal region). BFlh muscle volume increased by 8%, and knee flexion strength increased by 40% with training. Following 3 weeks of detraining, fascicle length decreased by 12% in the central region and 16% in the distal region along with reductions in serial sarcomere number.

CONCLUSION

Nine weeks of NHE training produced substantial, region-specific increases in BFlh muscle fascicle length, muscle volume, and force generation. The direct measurement of sarcomere lengths revealed that the increased fascicle length was accompanied by the addition of sarcomeres in series within the muscle fascicles.

Comparing activity of the gluteus maximus and hamstring muscles in fatigue conditions between hamstring injury-experienced and inexperienced individuals

INTRODUCTION

Muscle fatigue is considered a risk factor for hamstring injury (HSI), which occurs during high-speed running. To decrease this risk, higher gluteal muscle activity may have a role to play. This study aimed to compare the muscle activities of the gluteus maximus (GMax) and hamstring (HS) muscles between HSI-experienced and inexperienced people in pre- and post-fatigue conditions during the swing and stance phases of running.

METHODS

Participants were asked to run 13 sets of 20 km/h on the treadmill. GMax and HS muscle activities of the (i) injured and (ii) uninjured legs in the HSI-experienced group and (iii) dominant leg (healthy leg) in the inexperienced group were collected using the first run as pre-fatigue data, and the last (13th) run as post-fatigue data.

RESULTS

GMax activity of the injured legs was higher than in the healthy leg during the stance phase in pre-fatigue condition (p < 0.05). The activity of the GMax and semitendinosus were higher in the uninjured legs than in the healthy legs during the swing phase in pre-fatigue condition (p < 0.05). However, no differences in muscle activities between pre- and post-fatigue or the injured and uninjured legs were found.

CONCLUSION

The GMax may prevent HSI recurrence during the stance phase of running. The GMax and semitendinosus of the uninjured leg may act as stabilizers of the body while the injured leg is placed on the ground.

Potential financial loss and risk factors for hamstring muscle injuries in elite male Brazilian soccer players: a season-long prospective cohort pilot study

Purpose

The aim of this pilot study was to analyze the potential financial loss and a range of potential risk factors for hamstring muscle injuries in elite Brazilian soccer.

Methods

Thirty-four male players (age: 25 ± 6 years; stature: 180 ± 8 cm; body mass: 78 ± 9 kg; minutes played in matches: 2243 ± 1423 min) from an elite professional soccer club were monitored during a 12-month season. Muscle injury was identified by magnetic resonance imaging and the severity was defined according to the number of days away: minimal (1-3 days), mild (4-7 days), moderate (8-28 days), severe (>28 days). Potential financial loss due to the team's under achievements was determined. Dorsiflexion range of motion, eccentric knee flexor strength and isokinetic tests were performed during the pre-season. Association between dependent variables and the occurrence of injury was evaluated.

Results

Nine hamstring muscle injuries with moderate severity were found in 8 athletes. Recovery time was 22 days off the field on average. Potential financial loss was $-43.2 million USD and earnings on merit money was 21%. Previous injury, increased flexor deficit 60° /sec and increased flexor fatigue index 300°/sec were all associated with a greater chance of hamstring muscle injury. Ankle dorsiflexion range of motion was significantly lower in the injured group (35.6 ± 3° vs. 39.1 ± 4.9°; p = 0.017, effect size = -0.74).

Conclusion

High financial burden was found in elite Brazilian soccer during one full season. Injured athletes had high hamstring fatigue index, knee flexor strength deficit, ankle range of motion restriction and previous hamstring muscle injury when compared to non-injured athletes. Therefore, preventive approaches in professional soccer players with previous hamstring injuries should be a priority.

Lower Limb Joint Mechanics during Maximal Accelerative and Decelerative Running

INTRODUCTION

Maximal acceleration and deceleration tasks are frequently required in team sports, often occurring rapidly in response to external stimuli. Accelerating and decelerating can be associated with lower limb injuries; thus, knowledge of joint mechanics during these tasks can improve the understanding of both human high performance and injury mechanisms. The current study investigated the fundamental differences in lower limb joint mechanics when accelerating and decelerating by directly comparing the hip, knee, and ankle joint moments and work done between the two tasks.

METHODS

Twenty participants performed maximal effort acceleration and deceleration trials, with three-dimensional marker trajectories and ground reaction forces collected simultaneously. Experimental data were combined with inverse dynamics analysis to compute joint moments and work.

RESULTS

Net joint work for all lower limb joints was positive during acceleration and negative during deceleration. This occurred because of significantly greater positive work production from the ankle and hip during acceleration and significantly greater negative work production from all joints during deceleration. The largest contributions to positive work during acceleration came from the ankle, followed by the hip and knee joints, whereas the largest contributions to negative work during deceleration came from the knee and hip joints, followed by the ankle. Peak joint moments were significantly greater when decelerating compared with accelerating, except for the peak ankle plantarflexion and hip flexion moments, which were significantly greater when accelerating.

CONCLUSIONS

Our findings may help to guide training interventions, which aim to enhance the performance of acceleration and deceleration tasks, while also mitigating the associated injury risk.

Effect of supervision and athlete age and sex on exercise-based injury prevention programme effectiveness in sport: A meta-analysis of 44 studies

We aimed to evaluate the influence of supervision, athlete age and sex and programme duration and adherence on exercise-based injury prevention programme effectiveness in sport. Databases were searched for randomized controlled trials evaluating exercise-based injury prevention programme effectiveness compared to "train-as-normal". A random effects meta-analysis for overall effect and pooled effects by sex and supervision and meta-regression for age, intervention duration and adherence were performed. Programmes were effective overall (risk ratio (RR) 0.71) and equally beneficial for female-only (0.73) and male-only (0.65) cohorts. Supervised programmes were effective (0.67), unlike unsupervised programmes (1.04). No significant association was identified between programme effectiveness and age or intervention duration. The inverse association between injury rate and adherence was significant (β=-0.014, p = 0.004). Supervised programmes reduce injury by 33%, but there is no evidence for the effectiveness of non-supervised programmes. Females and males benefit equally, and age (to early middle age) does not affect programme effectiveness.

Relationships between quantitative magnetic resonance imaging measures at the time of return to sport and clinical outcomes following acute hamstring strain injury

Hamstring strain injuries (HSI) are a common occurrence in athletics and complicated by high rates of reinjury. Evidence of remaining injury observed on magnetic resonance imaging (MRI) at the time of return to sport (RTS) may be associated with strength deficits and prognostic for reinjury, however, conventional imaging has failed to establish a relationship. Quantitative measure of muscle microstructure using diffusion tensor imaging (DTI) may hold potential for assessing a possible association between injury-related structural changes and clinical outcomes. The purpose of this study was to determine the association of RTS MRI-based quantitative measures, such as edema volume, muscle volume, and DTI metrics, with clinical outcomes (i.e., strength and reinjury) following HSI. Spearman's correlations and Firth logistic regressions were used to determine relationships in between-limb imaging measures and between-limb eccentric strength and reinjury status, respectively. Twenty injuries were observed, with four reinjuries. At the time of RTS, between-limb differences in eccentric hamstring strength were significantly associated with principal effective diffusivity eigenvalue λ1 (r = -0.64, p = 0.003) and marginally associated with mean diffusivity (r = -0.46, p = 0.056). Significant relationships between other MRI-based measures of morphology and eccentric strength were not detected, as well as between any MRI-based measure and reinjury status. In conclusion, this preliminary evidence indicates DTI may track differences in hamstring muscle microstructure, not captured by conventional imaging at the whole muscle level, that relate to eccentric strength.

Maximum speed exposures in Australian rules football: do methods matter?

This study compared weekly near-to-maximum speed exposure data when determined via different methods and criteria. Forty-seven professional Australian rules football (AF) players undertook pre-season sprint assessments (PSSA) via 3 × 50 m maximal efforts using 10 Hz GPS over two consecutive seasons. The same technology was used continually during the in-season to identify maximum speeds attained in training and matches. Weekly near-to-maximal speed (MS) exposure counts were aggregated for speeds ≥80%, ≥85%, ≥90% and ≥95% of their individual maximum for both determination approaches. Weekly near-to-MS exposures was lower (p < 0.0001) when determined from in-season monitoring for ≥80% (-1.26; CI: -1.58 to -0.93), ≥85% (-0.78; CI: -0.97 to -0.59), ≥90% (-0.42; CI: -0.53 to -0.32), and ≥95% (-0.09; CI: -0.12 to -0.06) versus PSSA, with no effect of playing position (P ≥ 0.161). Although ≥80% and ≥85% near-to-maximum speed exposure data was meaningfully influenced by the determination method, the effect was somewhat trivial at higher speed criteria (≥90% and ≥95%) often considered important for performance gains and injury risk reduction purposes. Maximum speed determination methods therefore may be used interchangeably, and discrete sprint assessments may not be necessary for this purpose.

Economic impact of muscle injury rate and hamstring strain injuries in professional football clubs. Evidence from LaLiga

The aims of this study were: 1) to describe the total muscular injuries, and specifically HSIs, and their corresponding missed matches; 2) to analyse their economic impact; and 3) to estimate the loss of incomes due to TV rights, in first division clubs from LaLigaTM depending on the expected and actual ranking position during the 2018/2019 season. To do that, a cross-sectional study for season 18/19 and for all players of the 20 Spanish professional football clubs was performed. The economic impact of injuries was estimated considering the missed matches and salary cost of all players and the audio-visual income loss was estimated considering the Spanish Royal Decree of Law (RDL 5/2015). The high number of muscular (270) and hamstring injuries (57) implies a high cost for professional first division football clubs, specifically € 365,811 per month for the former and € 47,388 per month for the latter. In addition, reaching a worse than expected position in LaLigaTM ranking involved a loss of 45,2 million € in TV rights incomes. The high cost of muscle injuries in first division teams justifies the need for multidisciplinary teams that are capable of reducing the number of injuries as well as recovery times.

Estimating the cost of sports injuries: A scoping review

OBJECTIVES

Provide an overview of the methods used to estimate the cost of sports-related injury published to date, and to highlight considerations and opportunities for future research.

DESIGN

Scoping review.

METHODS

Scopus, MEDLINE and CINHAL were searched from 1st January 2000 to 1st January 2023. Studies were screened by two independent reviewers and were eligible if they reported on a cost analysis or cost estimation of sports related injury.

RESULTS

Thirty-one studies fulfilled the inclusion criteria. Twenty-seven studies (87 %) were published since 2014. The type of costs included direct healthcare costs (12 studies), indirect costs (10 studies) and a combination of both (9 studies). Twenty-one studies (68 %) used a bottom-up costing approach to measure costs of sports injury and estimated direct costs from the service rates or fee schedules of health systems, hospital, insurance companies or national insurance boards. A top-down approach was used in seven studies (23 %) to estimate the indirect salary cost of time-loss injuries using data from publicly available resources. Ten studies were from the cost perspective of a sporting organisation (32 %). There was a lack of explicit reporting of the costing method used and the perspective of those bearing the costs.

CONCLUSIONS

Estimating the cost of sports injuries is an emerging area of research, with publications increasing in recent years. However, there remains a lack of methodological guidance to inform or appraise these studies. The expansion of established cost of illness checklists with sport injury explanations to guide future cost of sports injury studies is recommended.

Epidemiology of hamstring injuries in 538 cases from an FC Barcelona multi sports club

OBJECTIVES

Hamstring injuries are the most common muscle injuries in team sports. The aims of this study were to describe the epidemiology of hamstring muscle injuries in the professional and amateur sport sections of a multi-sport club Football Club Barcelona (FCB) and to determine any potential correlation between return-to-play (RTP) and injury location, severity of connective tissue damage, age, sex, and athlete's level of competition.

METHODS

This descriptive epidemiological study with data collected from September 2007 to September 2017 stored in the FCB database. The study included non-contact hamstring injuries sustained during training or competition.

RESULTS

A total of 538 hamstring injuries were reported in the club's database, of which 240 were structurally verified by imaging as hamstring injuries. The overall incidence for the 17 sports studied was 1.29 structurally verified hamstring injuries per 100 athletes per year. The muscle most commonly involved in hamstring injuries was the biceps femoris, and the connective tissue most frequently involved was the myofascial. There was no evidence of a statistically significant association between age and RTP after injury, and no statistically significant difference between sex and RTP. However, the time loss by professionals was shorter than for amateurs, and proximal hamstring injuries took longer RTP than distal ones.

CONCLUSION

In the 17 sports practiced at multi-sport club, the incidence of hamstring injury was 1.29 per 100 athletes per year. Players from sports in which high-speed sprinting and kicking are necessary, and amateurs, were at higher risk of suffering a hamstring injury. In addition, proximally located hamstring injuries involving tendinous connective tissue showed the longest RTP time. Age did not seem to have any influence on RTP. Documenting location and the exact tissue involved in hamstring injuries may be beneficial for determining the prognosis and RTP.

Epidemiology of quadriceps muscle strain injuries in elite male Australian football players

OBJECTIVE

To describe the epidemiology of quadriceps muscle strain injury (QMSI) in elite Australian Football League (AFL) players, explore recovery milestones and determine whether recovery is impacted by factors such as injury type (index vs. re-injury), the primary muscle injured and the mechanism of injury.

MEASURES

All QMSI data reported to the Soft Tissue Injury Registry of the AFL from the 2014 to 2020 seasons were evaluated. Player demographic data, circumstances of injury, MRI reports and recovery outcomes following injury were extracted. Descriptive statistics and frequency distributions are presented. Recovery outcomes for injury type, primary muscle injured and the mechanism of injury were compared using univariate analyses.

RESULTS

There were 164 QMSIs from 122 players reported (134 index; 30 re-injuries). Almost all (91.3%) QMSIs involved the rectus femoris. Half (48.4%) of the QMSIs occurred during kicking and most commonly affected the dominant kicking leg (72%). The majority occurred at training (64.6%). All re-injuries involved the rectus femoris, most occurred from kicking (63.0%) and within 6 months of the preceding injury (70%). The mean return to play (RTP) time was 25.4 days (95%CI = 22.6-28.2) and rectus femoris injuries took around 14 days longer to RTP than vastii injuries (p = 0.001). QMSIs with a kicking mechanism took the longest to RTP of all injury mechanisms.

CONCLUSION

In AFL players, QMSIs occur mostly in the dominant leg from a kicking mechanism. Rectus femoris injuries are more prevalent and result in longer RTP time frames. Re-injuries exclusively involved the rectus femoris, primarily from kicking.

Association of quantitative diffusion tensor imaging measures with time to return to sport and reinjury incidence following acute hamstring strain injury

Hamstring strain injuries (HSI) are a common occurrence in athletics and complicated by limited prognostic indicators and high rates of reinjury. Assessment of injury characteristics at the time of injury (TOI) may be used to manage athlete expectations for time to return to sport (RTS) and mitigate reinjury risk. Magnetic resonance imaging (MRI) is routinely used in soft tissue injury management, but its prognostic value for HSI is widely debated. Recent advancements in musculoskeletal MRI, such as diffusion tensor imaging (DTI), have allowed for quantitative measures of muscle microstructure assessment. The purpose of this study was to determine the association of TOI MRI-based measures, including the British Athletic Muscle Injury Classification (BAMIC) system, edema volume, and DTI metrics, with time to RTS and reinjury incidence. Negative binomial regressions and generalized estimating equations were used to determine relationships between imaging measures and time to RTS and reinjury, respectively. Twenty-six index injuries were observed, with five recorded reinjuries. A significant association was not detected between BAMIC score and edema volume at TOI with days to RTS (p-values ≥ 0.15) or reinjury (p-values ≥ 0.13). Similarly, a significant association between DTI metrics and days to RTS was not detected (p-values ≥ 0.11). Although diffusivity metrics are expected to increase following injury, decreased values were observed in those who reinjured (mean diffusivity, p = 0.016; radial diffusivity, p = 0.02; principal effective diffusivity eigenvalues, p-values = 0.007-0.057). Additional work to further understand the directional relationship observed between DTI metrics and reinjury status and the influence of external factors is warranted.

Quantifying demands on the hamstrings during high-speed running: A systematic review and meta-analysis

INTRODUCTION

Hamstring strain injury (HSI) remains a performance, economic, and player availability burden in sport. High-speed running (HSR) is cited as a common mechanism for HSI. While evidence exists regarding the high physical demands on the hamstring muscles in HSR, meta-analytical synthesis of related activation and kinetic variables is lacking.

METHODS

A systematic search of Medline, Embase, Scopus, CINAHL, SportDiscus, and Cochrane library databases was conducted in accordance with the PRISMA 2020 guidelines. Studies reporting hamstring activation (electromyographic [EMG]) or hamstring muscle/related joint kinetics were included where healthy adult participants ran at or beyond 60% of maximum speed (activation studies) or 4 m per second (m/s) (kinetic studies).

RESULTS

A total of 96 studies met the inclusion criteria. Run intensities were categorized as "slow," "moderate," or "fast" in both activation and kinetic based studies with appropriate relative, and raw measures, respectively. Meta-analysis revealed pooled mean lateral hamstring muscle activation levels of 108.1% (95% CI: 84.4%-131.7%) of maximal voluntary isometric contraction (MVIC) during "fast" running. Meta-analysis found swing phase peak knee flexion internal moment and power at 2.2 Newton meters/kilogram (Nm/kg) (95% CI: 1.9-2.5) and 40.3 Watts/kilogram (W/kg) (95% CI: 31.4-49.2), respectively. Hip extension peak moment and power was estimated as 4.8 Nm/kg (95% CI: 3.9-5.7) and 33.1 W/kg (95% CI: 17.4-48.9), respectively.

CONCLUSIONS

As run intensity/speed increases, so do the activation and kinetic demands on the hamstrings. The presented data will enable clinicians to incorporate more objective measures into the design of injury prevention and return-to-play decision-making strategies.

Injury mechanisms and situational patterns of severe lower limb muscle injuries in male professional football (soccer) players: a systematic video analysis study on 103 cases

OBJECTIVE

The objective of this study is to describe the mechanism of injury and situational patterns (based on ball possession and playing action leading to injury) of severe (lay-off time >28 days) lower limb muscle injuries in professional male football (soccer) players during match play.

METHODS

Players experiencing a severe muscle injury of the lower limb during Italian first (Serie A) division male football matches over three consecutive seasons (2018-2021) were identified. Video footage was obtained and three raters independently categorised injury mechanism and situational patterns using a standardised checklist. Injury epidemiology (month), timing of injuries within the match and location of injuries on the pitch were also examined.

RESULTS

We identified 121 lower limb severe muscle injuries. Videos of sufficient quality were available for 103 (85%) cases, including 61 (60%) hamstring, 17 (16%) calf, 16 (15%) adductor and 9 (9%) quadricep muscle injuries. Nearly two-thirds of injuries involved the dominant/kicking leg (n=65, 63%). Eighty-five (83%) injuries were non-contact and 18 (17%) indirect contact. Four main situational patterns were identified and accounted for 88% of injuries: (1) running/acceleration (n=35, 34%); (2) closed kinetic chain stretching (n=21, 20%); (3) open kinetic chain stretching (n=19, 18%) and (4) kicking (n=16, 16%), with differences between muscle groups. 71% of injuries occurred in the first half of the match (p<0.01), with a gradual increase through the first half.

CONCLUSION

Most severe muscle injuries during football matches were non-contact and occurred in the first half during running/acceleration, open and closed kinetic chain stretching, or kicking.

Managing Lower Limb Muscle Reinjuries in Athletes: From Risk Factors to Return-to-Play Strategies

Muscle injuries and subsequent reinjuries significantly impact athletes, especially in football. These injuries lead to time loss, performance impairment, and long-term health concerns. This review aims to provide a comprehensive overview of the current understanding of muscle reinjuries, delving into their epidemiology, risk factors, clinical management, and prevention strategies. Despite advancements in rehabilitation programs and return-to-play criteria, reinjury rates remain alarmingly high. Age and previous muscle injuries are nonmodifiable risk factors contributing to a high reinjury rate. Clinical management, which involves accurate diagnosis, individualized rehabilitation plans, and the establishment of return-to-training and return-to-play criteria, plays a pivotal role during the sports season. Eccentric exercises, optimal loading, and training load monitoring are key elements in preventing reinjuries. The potential of artificial intelligence (AI) in predicting and preventing reinjuries offers a promising avenue, emphasizing the need for a multidisciplinary approach to managing these injuries. While current strategies offer some mitigation, there is a pressing need for innovative solutions, possibly leveraging AI, to reduce the incidence of muscle reinjuries in football players. Future research should focus on this direction, aiming to enhance athletes' well-being and performance.

Hamstring Injury Treatments and Management in Athletes: A Systematic Review of the Current Literature

BACKGROUND

The field of sports medicine presents a varied landscape of research on hamstring injuries in athletes, characterized by inconclusive and sometimes conflicting findings on effective treatment and rehabilitation strategies. This discordance prompted the current systematic investigation.

METHODS

Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed for conducting the systematic review. Multiple international bibliometric databases (Scopus, PubMed, Web of Science, and Embase) were searched to identify studies evaluating any treatment option for the management of hamstring injuries in athletes. Eligible studies were appraised for quality using Joanna Briggs Institute and Risk of Bias 2 tools.

RESULTS

A total of 30 studies with 1,195 participants were included. Of the reviewed studies, treatments varied from aggressive rehabilitation, platelet-rich plasma (PRP) injections, manual techniques, various exercise protocols to modalities like high-power laser and nonsteroidal anti-inflammatory drugs. Evidence suggested benefits from treatments like extensive muscle lengthening during eccentric actions, progressive agility, and trunk stabilization. PRP injections produced mixed results regarding return to sport and reinjury rates. Stretching exercises, sometimes combined with cryotherapy, showed benefits.

CONCLUSION

Treatments for hamstring injuries exhibit varied efficacy. Although rest, ice, compression, and elevation remains essential for acute management, rehabilitation focusing on muscle strengthening and flexibility is crucial. The potential benefits of PRP injections, especially for chronic cases, require more conclusive research. A comprehensive approach, combining evidence-based practices and patient-centric factors, is vital for effective management and recovery.

LEVEL OF EVIDENCE

Level IV. See Instructions for Authors for a complete description of levels of evidence.

Effects of combined treatment with transcranial and peripheral electromagnetic stimulation on performance and pain recovery from delayed onset muscle soreness induced by eccentric exercise in young athletes. A randomized clinical trial

Background: There is a common interest in finding a common consensus in the approach of athletes suffering from DOMS with the aim of accelerating recovery and thereby enhancing performance. The objective of this study was to observe the effects of a paired-associative transcranial and peripheral electromagnetic stimulation on young athletes suffering from DOMS, induced by 1 h of eccentric and plyometric exercises. Methods: Forty-eight young athletes participated in this randomized control trial: 13 were assigned to the peripheral group (P); 12 were in the control group (Cont); 11 were assigned to the transcranial group (T) and 12 were included in the paired-associative group (Comb). The Visual Analogue Scale (VAS) of pain perception and the mechanical Pressure Pain Threshold (PPT) were the tools used to analyze the symptoms of DOMS. On the other hand, the Half Squat (HS) test evaluated with an accelerometer, and the 30 m sprint velocity (30-mSP) test were used to observe the evolution of the sports performance of the lower limbs. All evaluations were performed before and after the eccentric exercise session that caused DOMS, as well as at 24-48, and 72 h afterward. Results: The AS group improved the symptoms of the induced DOMS, since significant positive differences were observed in the VAS and PPT compared to the other groups (p < 0.001). In addition, the AS group showed a significant improvement in the HS and the 30-mSP tests (p < 0.001). Based on the results a treatment with both peripheral and transcranial electromagnetic stimulation improves recovery and performance in athletes at 72 h, although these data would need to be verified in future research with a larger sample size. Conclusion: Paired-associative electromagnetic stimulation improved DOMS symptomatology, velocity, and sports performance in the lower limbs.

Epidemiology of Injuries in Professional and Amateur Football Men (Part II)

Background (1): Men's football is a physically demanding contact sport that involves intermittent bouts of sprinting, jogging, walking, jumping and changes of direction. The physical demands of the game vary by level of play (amateur club, sub-elite and open club or international), but injury rates at all levels of the men's football game remain the highest of all sports. Objective: The aim of this study is to conduct a systematic review of data from the epidemiological literature regarding the profile, severity and mechanisms of injuries and the frequency of recurrent injuries in professional and amateur football players. Methods (2): A systematic review, according to PRISMA guidelines, was performed up to June 2023 in the databases of PubMed, Web of Science, Google academic, Google scholar and the Diva portal. Twenty-seven studies that reported data on the type, severity, recurrence and mechanisms of injury in professional and amateur men's football were selected and analyzed. Two reviewers independently audited data and assessed the study quality using the additional and adapted version of the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement and the Newcastle Ottawa Scale (NOS) to assess risk of bias for the quality of external validity. Results (3): In professional male football players, the mean prevalence of muscle/tendon injuries was 39.78%, followed by joint and ligament injuries-21.13%, contusions-17.86%, and fractures-3.27%, and for amateur football players, the prevalence's were 44.56% (muscle/tendon injuries), 27.62% (joint and ligament injuries), 15.0% (contusions) and 3.05% (fracture), respectively. The frequency of traumatic injuries was higher in amateur football players (76.88%) compared to professional football players (64.16%), the situation being reversed in the case of overuse injuries: 27.62% in professional football players and 21.13% in amateur football players. Most contact injuries were found in professional footballers (50.70%), with non-contact injuries predominating in amateur footballers (54.04%). The analysis of the severity of injuries showed that moderate injuries dominated in the two categories of footballers; the severe injuries in amateur footballers exceeded the severe injuries recorded in professional footballers by 9.60%. Recurrence proportions showed an inverse relationship with the level of play, being higher in amateur footballers (16.66%) compared to professional footballers (15.25%). Conclusions (4): Football-related injuries have a significant impact on professional and amateur football players and their short- and long-term health status. Knowing the frequency of severe diagnoses, such as strains, tears and cramps of the thigh muscles, ankle ligament sprains and hip/groin muscle strain requires the establishment of adequate programs to prevent them, especially in amateur football players, who are more prone to serious injuries.

Synergistic Dominance Induced by Hip Extension Exercise Alters Biomechanics and Muscular Activity During Sprinting and Suggests a Potential Link to Hamstring Strain

ABSTRACT

Iguchi, J, Hojo, T, Fujisawa, Y, Kuzuhara, K, Yanase, K, Hirono, T, Koyama, Y, Tateuchi, H, and Ichihashi, N. Synergistic dominance induced by hip extension exercise alters biomechanics and muscular activity during sprinting and suggests a potential link to hamstring strain. J Strength Cond Res 37(9): 1770-1776, 2023-Hamstring strain is likely to occur during the late swing phase or the first half of the stance phase in sprinting. During the late swing phase, the hamstrings and gluteus maximus (Gmax) contract eccentrically to decelerate the lower limb. We hypothesized that, when the Gmax becomes dysfunctional because of delayed onset muscle soreness (DOMS), the hamstring workload is increased (i.e., there is synergetic dominance), which could lead to an increased risk of strain. A total of healthy 15 male undergraduate or graduate students (age 23.1 ± 1.28 years) were recruited to perform exercises and maximal sprints. On day 1, before subjects performing DOMS-causing exercises, and on day 3, while subjects were experiencing DOMS in the Gmax, lower-limb biomechanical and muscle activity data were recorded using a motion analysis system and electromyography (EMG), respectively. Data were analyzed and compared between day 1 and day 3. Hip flexion angle on day 3 was significantly lower than that on day 1, but the opposite was true for the knee flexion angle (P < 0.05). Vastus medialis (VM), biceps femoris (BF), and Gmax muscle activities on day 3 were significantly higher than those on day 1 (P < 0.05). Peak propulsive forces on day 3 were significantly higher than those on day 1 (P < 0.05). Kinematic changes such as decreased hip flexion angle and EMG changes such as increased BF EMG activity on day 3 to compensate for the loss of function of the Gmax may potentially increase the risk of hamstring strain.

Intramuscular Tendon Injuries of the Hamstring Muscles: A More Severe Variant? A Narrative Review

Hamstring strain injuries (HSI) are one of the most common sport-related injuries. They have a high injury burden and a high recurrence rate. The development of novel muscle injury grading systems has provided new insights into the possible impact of injury location on the time to return to play (TTRTP) and re-injury following HSI. In particular, injuries to the intramuscular tendon (IMT) may be present in up to 41% of all HSI and have been described as a 'serious thigh muscle strain'. Re-injury rates as high as 60% have been described in elite track and field athletes, as well as prolonged TTRTP. A systematic search was carried out using appropriate keywords to identify articles reporting on HSI involving the IMT in athletes. The primary aim was to determine whether IMT injuries warrant being classified as a distinct clinical entity with different expected outcomes to other hamstring muscle injuries. This narrative review summarises the existing evidence on: (1) the anatomy of the IMT and its response to injury; (2) the role of MRI and novel grading scales in IMT injury management (3) clinical assessment of IMT injuries, (4) TTRTP and re-injury rates across sports following IMT, (5) conservative rehabilitation and the role of specific 'IMT-oriented' strategies, and (6) indications for and approaches to surgery. The review found that important clinical outcomes such as re-injury rates and TTRTP vary across populations, cohorts and sports which suggest that outcomes are specific to the sporting context. Bespoke rehabilitation, tailored to IMT injury, has been shown to significantly reduce re-injuries in elite track and field athletes, without compromising TTRTP. Continued prospective studies across other sports and cohorts, are warranted to further establish relevant clinical findings, indications for surgical intervention and outcomes across other sporting cohorts.

The Role of Extracorporeal Shock Wave Therapy in the Treatment of Muscle Injuries: A Systematic Review

Muscle injuries commonly occur in sports and can be classified as indirect and direct, according to the 2013 Munich Consensus Statement (MCS). Since recent evidence suggests that extracorporeal shock wave therapy (ESWT) improves muscular microcirculation and may increase regeneration after acute muscle injury, we performed a systematic review following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement guidelines to access the efficacy and safety of ESWT in the treatment of patients with muscle injuries. PubMed and Cochrane were searched to screen for potentially relevant articles and the literature search was last updated in June 2023. The inclusion criteria were randomized controlled trials, observational studies, or case controls published in English, Portuguese, or Spanish that studied the effect of ESWT on indirect and direct muscle injuries in individuals aged ≥18, with at least one of the following reported outcomes: pain on the visual analog scale (VAS), functionality assessed either with disability scales or subjectively, time for return to play (RTP), re-injury rate, and ultrasonographic evaluation. The exclusion criteria were literature reviews, systematic reviews, studies in animals, studies in other languages, studies that failed to meet the targeted population or intervention and studies that didn't report any of the outcomes of interest. The quality of the studies was analyzed using the Cochrane Assessment Tool, the Newcastle-Ottawa Quality Assessment Scale, and the JBI Critical Appraisal Checklist. Eight studies were included in the systematic review (two randomized controlled trials, one prospective observational study, two retrospective observational studies, and three case reports), with a total of 143 adult participants. ESWT was associated with less pain on VAS, better function, reduction of size of lesion on ultrasound evaluation, faster RTP and/or lower re-injury rate in patients with indirect and direct muscle injuries and muscular hematomas, a frequent secondary complication of muscle injuries. The evidence regarding the use of ESWT for these types of injuries is therefore promising. Nevertheless, higher-quality studies are needed in the future to prove its efficacy, better comprehend its mechanisms of action and define treatment protocols (timing, type and parameters of ESWT).

Effects of peripheral electromagnetic stimulation after an eccentric exercise-induced delayed-onset muscle soreness protocol in professional soccer players: a randomized controlled trial

Introduction: To examine the effects of peripheral electromagnetic stimulation in male professional soccer players on markers of Delayed Onset Muscular Soreness (DOMS), induced by a protocol of exercise (60 min of eccentric and plyometric). Methods: A randomized controlled trial with fourty-five professional soccer players aged 22.33 ± 4.82 years participated in the study. Twenty-three participants were assigned to the experimental group with peripheral electromagnetic stimulation (5 stimulations of 5 s at 100 HZ with 55 s of rest for a total of 5 min of treatment) and the remaining 22 participants were assigned to the control group. Pain pressure threshold (PPT) of the vastus medialis, the Visual Analogue Scale-Fatigue (VAS-F), half squat (HS) test and the maximum voluntary contraction of the quadriceps were assessed. All evaluations were performed before and after 1 h of the eccentric exercise induced DOMS, as well as at post 24-48, and 72 h. Results: Group-by-time interaction was observed in PPT of the vastus medialis (p = 0.040) with a medium effect size (η² p = 0.069). From 48 to 72 h the experimental group showed an increase of PPT compared to control group (p = 0.015). There was no group-by-time interaction for HS, quadriceps strength and VAS-F (p > 0.05). Discussion: Peripheral electromagnetic stimulation in male professional soccer players did not produce significant improvements in the power and strength of the lower limbs but decreased the peripheral sensitization of the vastus medialis after eccentric exercise protocol. Clinical Trial Registration: https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=384050&isReview=true, Identifier: ACTRN12622000841774.

Comparison of utilizing modified hold-relax, muscle energy technique, and instrument-assisted soft tissue mobilization on hamstring muscle length in healthy athletes: Randomized controlled trial

INTRODUCTION

The hamstring muscle shortness is the primary risk factor for sports-related injuries. Numerous treatments are available for lengthening of hamstring muscle. The main purpose of this study was to compare the immediate effect of modified hold-relax, muscle energy technique (MET), and instrument assisted soft tissue mobilization-Graston techniques (IASTM-GT) on length of hamstring muscle in young healthy athletes.

METHODS

60 athletes comprising of 29 females and 31 males were recruited in the present study. Participants were allocated to 3 groups of IASTM-GT (N = 20, 13 male, 7 female), Modified Hold-relax (N = 20, 8 male, 12 female), and MET (N = 20, 7 male, 13 female). Active knee extension and passive straight leg raising (SLR), and toe touch test were performed before and immediately after the intervention by a blinded assessor. For the comparison of dependent variables across time, 3*2 repeated measure ANOVA was utilized.

RESULTS

Interaction of group by time was significant for passive SLR (P < 0.001). Interaction of group by time was not significant for active knee extension (P = 0.17). The results showed that dependent variables increased significantly in all groups. The effect size (Cohen's d) in the groups of IASTM-GT, modified Hold-relax, and MET was 1.7, 3.17, and 3.12, respectively.

CONCLUSION

Although the measures were improved in all groups, it seems that IASTM-GT can be used as a safe and efficient treatment, which can be a suitable candidate alongside modified hold-relax and MET for increasing the hamstrings muscle length in healthy athletes.

Therapeutic Exercises and Modalities in Athletes With Acute Hamstring Injuries: A Systematic Review and Meta-analysis

CONTEXT

Hamstring strain is a common injury to the lower limbs. Early intervention in the acute phase aids with restoring hamstring function and prevents secondary related injury.

OBJECTIVE

To systematically review and summarize the effectiveness of exercise-based interventions combined with physical modalities currently used in athletes with acute hamstring injuries.

DATA SOURCES

Five databases (EMBASE, Medline, Cochrane Library, SPORTDiscus, and Web of Science) were searched from inception to July 2021.

STUDY SELECTION

A total of 4569 studies were screened. Nine randomized controlled trials (RCTs) on the effect of therapeutic exercise programs with and without physical agents in athletes with acute hamstring injuries were identified for meta-analysis.

STUDY DESIGN

Systematic review and meta-analysis.

LEVEL OF EVIDENCE

Level 1.

DATA EXTRACTION

The studies were screened, and the evidence was rated using the PEDro scale. Nine RCTs with PEDro scores ranging between 3 and 9 were included and extracted pain intensity, time to return to play (TTRTP), and reinjury rate in the study.

RESULTS

Loading exercises during extensive lengthening were shown to facilitate TTRTP at P < 0.0001 but did not prevent recurrence (P = 0.17), whereas strengthening with trunk stabilization and agility exercise did not reduce the duration of injury recurrence (P = 0.16), but significantly reduced the reinjury rate (P < 0.007) at a 12-month follow-up. The results of the stretching programs and solely physical modalities could not be pooled in the statistical analysis.

CONCLUSION

The meta-analysis indicated that a loading program helps athletes to return to sports on a timely basis. Although strengthening with trunk stabilization and agility exercise cannot significantly reduce recovery time, the program can prevent reinjury. The clinical effects of stretching programs and pure physical modality interventions could not be concluded in this study due to limited evidence.

PROSPERO REGISTRATION

CRD42020183035.

Should We Use the Men Load-Velocity Profile for Women in Deadlift and Hip Thrust?

Injuries are common in team sports and can impact both team and individual performance. In particular, hamstring strain injuries are some of the most common injuries. Furthermore, hamstring injury ratios, in number of injuries and total absence days, have doubled in the last 21 seasons in professional soccer. Weakness in hip extensor strength has been identified as a risk factor in elite-level sprinters. In addition, strength imbalances of the hamstring muscle group seem to be a common cause of hamstring strain injuries. In this regard, velocity-based training has been proposed to analyze deficits in the force-velocity profile. Previous studies have shown differences between men and women, since there are biomechanical and neuromuscular differences in the lower limbs between sexes. Therefore, the aim of this study was to compare the load-velocity profile between males and females during two of the most important hip extension exercises: the hip thrust and the deadlift. Sixteen men and sixteen women were measured in an incremental loading test following standard procedures for the hip thrust and deadlift exercises. Pearson's correlation (r) was used to measure the strength of the correlation between movement velocity and load (%1RM). The differences in the load-velocity relationship between the men and the women were assessed using a 2 (sex) × 15 (load) repeated-measures ANOVA. The main findings revealed that: (I) the load-velocity relationship was always strong and linear in both exercises (R² range: 0.88-0.94), (II) men showed higher velocities for light loads (30-50%1RM; effect size: 0.9-0.96) than women for the deadlift, but no significant differences were found for the hip thrust. Based on the results of this study, the load-velocity equations seem to be sex-specific. Therefore, we suggest that using sex-specific equations to analyze deficits in the force-velocity profile would be more effective to control intensity in the deadlift exercise.

London International Consensus and Delphi study on hamstring injuries part 3: rehabilitation, running and return to sport

Hamstring injuries (HSIs) are the most common athletic injury in running and pivoting sports, but despite large amounts of research, injury rates have not declined in the last 2 decades. HSI often recur and many areas are lacking evidence and guidance for optimal rehabilitation. This study aimed to develop an international expert consensus for the management of HSI. A modified Delphi methodology and consensus process was used with an international expert panel, involving two rounds of online questionnaires and an intermediate round involving a consensus meeting. The initial information gathering round questionnaire was sent to 46 international experts, which comprised open-ended questions covering decision-making domains in HSI. Thematic analysis of responses outlined key domains, which were evaluated by a smaller international subgroup (n=15), comprising clinical academic sports medicine physicians, physiotherapists and orthopaedic surgeons in a consensus meeting. After group discussion around each domain, a series of consensus statements were prepared, debated and refined. A round 2 questionnaire was sent to 112 international hamstring experts to vote on these statements and determine level of agreement. Consensus threshold was set a priori at 70%. Expert response rates were 35/46 (76%) (first round), 15/35 (attendees/invitees to meeting day) and 99/112 (88.2%) for final survey round. Statements on rehabilitation reaching consensus centred around: exercise selection and dosage (78.8%-96.3% agreement), impact of the kinetic chain (95%), criteria to progress exercise (73%-92.7%), running and sprinting (83%-100%) in rehabilitation and criteria for return to sport (RTS) (78.3%-98.3%). Benchmarks for flexibility (40%) and strength (66.1%) and adjuncts to rehabilitation (68.9%) did not reach agreement. This consensus panel recommends individualised rehabilitation based on the athlete, sporting demands, involved muscle(s) and injury type and severity (89.8%). Early-stage rehab should avoid high strain loads and rates. Loading is important but with less consensus on optimum progression and dosage. This panel recommends rehabilitation progress based on capacity and symptoms, with pain thresholds dependent on activity, except pain-free criteria supported for sprinting (85.5%). Experts focus on the demands and capacity required for match play when deciding the rehabilitation end goal and timing of RTS (89.8%). The expert panellists in this study followed evidence on aspects of rehabilitation after HSI, suggesting rehabilitation prescription should be individualised, but clarified areas where evidence was lacking. Additional research is required to determine the optimal load dose, timing and criteria for HSI rehabilitation and the monitoring and testing metrics to determine safe rapid progression in rehabilitation and safe RTS. Further research would benefit optimising: prescription of running and sprinting, the application of adjuncts in rehabilitation and treatment of kinetic chain HSI factors.

Effectiveness of Conservative Interventions After Acute Hamstrings Injuries in Athletes: A Living Systematic Review

BACKGROUND

Hamstrings injuries are common in sports and the reinjury risk is high. Despite the extensive literature on hamstrings injuries, the effectiveness of the different conservative (i.e., non-surgical) interventions (i.e., modalities and doses) for the rehabilitation of athletes with acute hamstrings injuries is unclear.

OBJECTIVE

We aimed to compare the effects of different conservative interventions in time to return to sport (TRTS) and/or time to return to full training (TRFT) and reinjury-related outcomes after acute hamstrings injuries in athletes.

DATA SOURCES

We searched CINAHL, Cochrane Library, EMBASE, PubMed, Scopus, SPORTDiscus, and Web of Science databases up to 1 January, 2022, complemented with manual searches, prospective citation tracking, and consultation of external experts.

ELIGIBILITY CRITERIA

The eligibility criteria were multi-arm studies (randomized and non-randomized) that compared conservative treatments of acute hamstrings injuries in athletes.

DATA ANALYSIS

We summarized the characteristics of included studies and conservative interventions and analyzed data for main outcomes (TRTS, TRFT, and rate of reinjuries). The risk of bias was judged using the Cochrane tools. Quality and completeness of reporting of therapeutic exercise programs were appraised with the i-CONTENT tool and the certainty of evidence was judged using the GRADE framework. TRTS and TRFT were analyzed using mean differences and the risk of reinjury with relative risks.

RESULTS

Fourteen studies (12 randomized and two non-randomized) comprising 730 athletes (mostly men with ages between 14 and 49 years) from different sports were included. Nine randomized studies were judged at high risk and three at low risk of bias, and the two non-randomized studies were judged at critical risk of bias. Seven randomized studies compared exercise-based interventions (e.g., L-protocol vs C-protocol), one randomized study compared the use of low-level laser therapy, and three randomized and two non-randomized studies compared injections of platelet-rich plasma to placebo or no injection. These low-level laser therapy and platelet-rich plasma studies complemented their interventions with an exercise program. Only three studies were judged at low overall risk of ineffectiveness (i-CONTENT). No single intervention or combination of interventions proved superior in achieving a faster TRTS/TRFT or reducing the risk of reinjury. Only eccentric lengthening exercises showed limited evidence in allowing a shorter TRFT. The platelet-rich plasma treatment did not consistently reduce the TRFT or have any effect on the risk of new hamstrings injuries. The certainty of evidence was very low for all outcomes and comparisons.

CONCLUSIONS

Available evidence precludes the prioritization of a particular exercise-based intervention for athletes with acute hamstrings injuries, as different exercise-based interventions showed comparable effects on TRTS/TRFT and the risk of reinjuries. Available evidence also does not support the use of platelet-rich plasma or low-level laser therapy in clinical practice. The currently available literature is limited because of the risk of bias, risk of ineffectiveness of exercise protocols (as assessed with the i-CONTENT), and the lack of comparability across existing studies.

CLINICAL TRIAL REGISTRATION

PROSPERO CRD42021268499 and OSF ( https://osf.io/3k4u2/ ).

Larger interface area at the human myotendinous junction in type 1 compared with type 2 muscle fibers

The myotendinous junction (MTJ) is structurally specialized to transmit force. The highly folded muscle membrane at the MTJ increases the contact area between muscle and tendon and potentially the load tolerance of the MTJ. Muscles with a high content of type II fibers are more often subject to strain injury compared with muscles with type I fibers. It is hypothesized that this is explained by a smaller interface area of MTJ in type II compared with type I muscle fibers. The aim was to investigate by confocal microscopy whether there is difference in the surface area at the MTJ between type I and II muscle fibers. Individual muscle fibers with an intact MTJ were isolated by microscopic dissection in samples from human semitendinosus, and they were labeled with antibodies against collagen XXII (indicating MTJ) and type I myosin (MHCI). Using a spinning disc confocal microscope, the MTJ from each fiber was scanned and subsequently reconstructed to a 3D-model. The interface area between muscle and tendon was calculated in type I and II fibers from these reconstructions. The MTJ was analyzed in 314 muscle fibers. Type I muscle fibers had a 22% larger MTJ interface area compared with type II fibers (p < 0.05), also when the area was normalized to fiber diameter. By the new method, it was possible to analyze the structure of the MTJ from a large number of human muscle fibers. The finding that the interface area between muscle and tendon is higher in type I compared with type II fibers suggests that type II fibers are less resistant to strain and therefore more susceptible to injury.

Effect of an Isometric or Eccentric Hip Extension Exercise Intervention on Hamstring Strength, Architecture, and Morphology

PURPOSE

This study aimed to investigate hamstring architectural, strength, and morphological adaptations after an eccentric or isometric hip extension exercise intervention.

METHODS

Twenty-four recreationally active males performed either an eccentric ( n = 12) or an isometric hip extension ( n = 12) exercise intervention, twice per week for 6 wk, followed by a 4-wk detraining period. Biceps femoris long head (BFlh) architecture was assessed pre-intervention, mid-intervention, post-intervention, and post-detraining via two-dimensional ultrasound. Strength was assessed pre-intervention, post-intervention, and post-detraining during an isokinetic knee flexion, an isometric hip extension, a Nordic hamstring exercise, and a single-leg hamstring bridge repetition to fatigue test. Hamstring muscle morphology was assessed via magnetic resonance imaging before strength testing sessions.

RESULTS

The eccentric hip extension exercise intervention significantly lengthened BFlh fascicles (+19.7%, P < 0.001, d = 1.57), increased eccentric knee flexion torque (ECC 60°·s -1 , +12%, P < 0.005, d = 0.66; ECC 180°·s -1 , +8.3%, P < 0.05, d = 0.41), and increased BFlh (+13.3%, P < 0.001, d = 1.96) and semimembranosus (SM) muscle volume (+12.5%, P < 0.001, d = 2.25). After 4 wk of detraining, BFlh fascicles were significantly shortened in the eccentric group (-14.8%, P < 0.005, d = -1.25), whereas eccentric knee flexion torque and BFlh and SM volumes were unchanged. The isometric hip extension exercise intervention significantly increased isometric knee flexion torque (+10.4%, P < 0.05, d = 0.54), isometric hip extension force (+12.4%, P < 0.05, d = 0.41), and semitendinosus volume (+15%, P = 0.054, d = 1.57). All other outcome measures saw no significant changes. After 4 wk of detraining, no significant changes to any variables were observed in the isometric group.

CONCLUSIONS

The eccentric but not isometric hip extension exercise intervention significantly increased BFlh fascicle length. Both exercise interventions demonstrated contraction mode-specific increases in strength. However, the eccentric hip extension exercise intervention resulted in preferential hypertrophy of BFlh and SM, and the isometric hip extension exercise intervention led to selective hypertrophy of semitendinosus.

Body composition variations between injured and non-injured professional soccer players

Professional soccer is characterized by its physical demands, making players' exposure to high injury risks a growing problem. It is crucial to study the factors associated with injuries in professional soccer. This study aimed to investigate the relationship between age, body composition, and others variables related with the injury profile of professional soccer players of a specific Portuguese team. Also, it analyzed the impact of the injury profile on soccer's variations in body fat (BF%), skeletal muscle mass (SMM) and total body water (TBW) throughout the season. The sample comprised 31 male professional soccer players competing in the First Portuguese Soccer League. Older players had a higher prevalence of muscular injuries. Midfielders and forwards showed the highest number of muscular injuries during the season being quadriceps the most affected zone. Considering players' BF% [Wilks' Lambda = 0.42, F (7, 23) = 4.61, p = 0.002, r = 0.58], SMM [Wilks' Lambda = 0.59, F (6, 23) = 2.70, p = 0.039, r = 0.41] and TBW [Wilks' Lambda = 0.54, F (7, 23) = 2.80, p = 0.029, r = 0.46] there was a substantial main effect for the assessments performed throughout the season and the injury status. Age assumes relevance in explaining the injury profile. The impact of the injury profile on soccer's variations in BF%, SMM and TBW throughout the season must be analyzed considering the clinical relevance.

The effect of theta burst stimulation over the primary motor cortex on experimental hamstring pain: A randomised, controlled study

Theta burst stimulation (TBS) over the primary motor cortex (M1) is an emerging technique that may have utility in the treatment of musculoskeletal pain. However, previous work exploring the analgesic effects of noninvasive brain stimulation has been limited largely to the arm or hand, despite 80% of acute musculoskeletal injuries occurring in the lower limb. This is a pertinent point, given the functional and neurophysiological differences between upper and lower limb musculature, as well as evidence suggesting that reorganization of corticomotor pathways is region-specific. This study investigated the effect of excitatory TBS on pain, function, and corticomotor organization during experimentally induced lower limb pain. Twenty-eight healthy participants attended 2 experimental sessions. On Day 0, participants completed 10 sets of 10 maximal eccentric contractions of the right hamstring muscles to induce delayed onset muscle soreness. Four consecutive blocks of either active or sham TBS were delivered on Day 2. Measures of mechanical sensitivity, pain (muscle soreness, pain intensity, pain area) function (single-leg hop distance, maximum voluntary isometric contraction, lower extremity functional scale), and corticomotor organization were recorded before and after TBS on Day 2. Pain and function were also assessed daily from Days 2 to 10. Active TBS reduced mechanical sensitivity compared to sham stimulation (P = .01). Corticomotor organization did not differ between groups, suggesting that improvements in mechanical sensitivity were not mediated by changes in M1. Subjective reports of pain intensity and function did not change following active TBS, contrasting previous reports in studies of the upper limb. PERSPECTIVE: M1 TBS reduces mechanical sensitivity associated with experimentally induced hamstring pain. Though further work is needed, these findings may hold important implications for those seeking to expedite recovery or reduce muscle sensitivity following hamstring injury.

Preseason Body Composition Is Associated With In-season Player Availability in Elite Male Australian Footballers

ABSTRACT

McCaskie, CJ, Sim, M, Newton, RU, Heasman, J, Rogalski, B, and Hart, NH. Preseason body composition is associated with in-season player availability in elite male Australian footballers. J Strength Cond Res XX(X): 000-000, 2022-The purpose of this study was to examine whether end of preseason body composition characteristics was associated with in-season match availability and injury. Sixty (n = 60) elite Australian football players had body composition characteristics assessed using dual-energy X-ray absorptiometry across 3 seasons (2016, 2018, and 2021). Match availability and injury were recorded throughout each season. Pearson's correlations were calculated to assess the associations between body composition and in-season match availability and injury. Logistic regression models were used to assess the odds of missing games as a result of injury throughout a season. Regional lean soft tissue mass asymmetry and its relationship to injury and availability was explored. Statistical significance was set at p ≤ 0.05. Body composition characteristics expressed as relative values seemed to be more highly associated with in-season availability and injury than characteristics expressed as absolute values. Players with lower relative fat mass (FM) (<12.1% total body FM) were available for 89.7% of in-season matches compared with 80.7% for players with higher relative FM (>12.1% total body FM). Subsequently, players with higher relative FM had 3.3-3.5 times greater odds of missing one game to injury (odds ratio [OR] = 3.33; 95% confidence interval [CI] = 1.00-11.14; p ≤ 0.05) and missing 2 or more games to injury (OR = 3.50; 95% CI = 1.20-10.20; p ≤ 0.05) throughout a season compared with players with lower relative FM. Higher proportions of fat mass may accelerate the onset of fatigue and place players at a greater risk of injury. Reducing players' FM across the preseason phase should be a key aim for practitioners to reduce the odds of injury throughout the competitive season.

Preseason Eccentric Strength Is Not Associated with Hamstring Strain Injury: A Prospective Study in Collegiate Athletes

INTRODUCTION

Established risk factors for hamstring strain injuries (HSI) include older age and prior HSI. However, these are nonmodifiable 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

This study aimed 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 nonsignificant ( FTotal : odds ratio [OR], 0.99 (95% confidence interval (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.

Early versus delayed lengthening exercises for acute hamstring injury in male athletes: a randomised controlled clinical trial

Background

To evaluate the efficacy of early versus delayed introduction of lengthening (ie, eccentric strengthening) exercises in addition to an established rehabilitation programme on return to sport duration for acute hamstring injuries in a randomised controlled superiority trial.

Methods

90 male participants (age: 18–36 years, median 26 years) with an MRI-confirmed acute hamstring injury were randomised into an early lengthening (at day 1 of rehabilitation) group or a delayed lengthening (after being able to run at 70% of maximal speed) group. Both groups received an established rehabilitation programme. The primary outcome was time to return to sport (ie, time from injury to full unrestricted training and/or match play). The secondary outcome was reinjury rate within 12 months after return to sport. Other outcomes at return to sport included the Askling H-test, hamstring strength, clinical examination and readiness questions.

Results

The return to sport in the early lengthening group was 23 (IQR 16–35) days and 33 (IQR 23–40) days in the delayed lengthening group. For return to sport (in days), the adjusted HR for the early lengthening group compared with the delayed lengthening group was 0.95 (95% CI 0.56 to 1.60, p=0.84). There was no significant difference between groups for reinjury rates within 2 months (OR=0.94, 95% CI 0.18 to 5.0, p=0.94), from 2 to 6 months (OR=2.00, 95% CI 0.17 to 23.3, p=0.58), and 6 to 12 months (OR=0.57, 95% CI 0.05 to 6.6, p=0.66).

Conclusion

Accelerating the introduction of lengthening exercises in the rehabilitation of hamstring injury in male athletes did not improve the time to return to sport nor the risk of reinjury.

Poor Reporting of Exercise Interventions for Hamstring Strain Injury Rehabilitation: A Scoping Review of Reporting Quality and Content in Contemporary Applied Research

OBJECTIVE

To review the quality of reporting and identify the content of exercise interventions prescribed for hamstring strain injury (HSI) rehabilitation in the scientific literature from 2010 to 2020.

DESIGN

Scoping review.

LITERATURE SEARCH

We searched the bibliometric databases Web of Science, CINAHL, SPORTDiscus, Scopus, Cochrane Library, MEDLINE, and Embase.

STUDY SELECTION CRITERIA

Original research articles (randomized controlled trials and cohort studies) published from 2010 to 2020 that described an exercise rehabilitation intervention for participants with acute HSIs were included. Injuries must have been confirmed within 7 days of occurrence via clinical assessment and/or diagnostic imaging.

DATA SYNTHESIS

The quality of reporting, in terms of completeness of exercise intervention description, was evaluated using the Consensus on Exercise Reporting Template (CERT), and the content of interventions was categorized into exercise types.

RESULTS

Fourteen studies were included; exercise intervention quality of reporting was moderate in 3 studies and low in 11 studies. Using the 19-item CERT, an average of 8.8 items (range, 4-14) were reported across all studies. Two studies reported sufficient exercise content and progression information to allow replication. Exercises categorized as hamstring flexibility, hamstring strength, running related, and non-hamstring specific were prescribed in 13, 11, 10, and 10 studies, respectively. Half of the included studies incorporated all 4 exercise types in their exercise interventions.

CONCLUSION

There is a wide variety of exercise interventions applied in published research that has addressed HSI rehabilitation. Researchers must improve reporting quality to support other professionals in replicating exercise interventions and help practitioners to effectively implement research in practice. J Orthop Sports Phys Ther 2022;52(3):130-141. Epub 21 Sep 2021. doi:10.2519/jospt.2022.10641.

Characteristics of Complex Systems in Sports Injury Rehabilitation: Examples and Implications for Practice

Complex systems are open systems consisting of many components that can interact among themselves and the environment. New forms of behaviours and patterns often emerge as a result. There is a growing recognition that most sporting environments are complex adaptive systems. This acknowledgement extends to sports injury and is reflected in the individual responses of athletes to both injury and rehabilitation protocols. Consequently, practitioners involved in return to sport decision making (RTS) are encouraged to view return to sport decisions through the complex systems lens to improve decision-making in rehabilitation. It is important to clarify the characteristics of this theoretical framework and provide concrete examples to which practitioners can easily relate. This review builds on previous literature by providing an overview of the hallmark features of complex systems and their relevance to RTS research and daily practice. An example of how characteristics of complex systems are exhibited is provided through a case of anterior cruciate ligament injury rehabilitation. Alternative forms of scientific inquiry, such as the use of computational and simulation-based techniques, are also discussed-to move the complex systems approach from the theoretical to the practical level.

Three Main Mechanisms Characterize Medial Collateral Ligament Injuries in Professional Male Soccer-Blow to the Knee, Contact to the Leg or Foot, and Sliding: Video Analysis of 37 Consecutive Injuries

OBJECTIVE

To describe the mechanisms, situational patterns, and biomechanics (kinematics) of medial collateral ligament (MCL) injuries in professional male soccer players.

DESIGN

Case series.

METHODS

Fifty-seven consecutive MCL injuries across 2 seasons of professional soccer matches were identified. We obtained and reviewed 37 of 57 (65%) injury videos to establish the injury mechanism, situational pattern, and knee flexion angle. We used detailed biomechanical analysis to assess the indirect and noncontact injuries. Injury layoff times, timing of injuries during the match, and location of the injuries on the pitch were also reported.

RESULTS

Twenty-three (62%) injuries were direct contact, 9 (24%) were indirect contact, and 5 (14%) were noncontact. Three main sprain mechanisms were noted: (1) direct contact/blow to the knee (n = 16), (2) contact to the leg or foot (lever like) (n = 7), and (3) sliding (n = 9). Seventy-three percent of MCL injuries occurred during 2 main situations: (1) pressing/tackling (n = 14, 38%) and (2) being tackled (n = 13, 35%). For indirect and noncontact injuries, knee valgus loading (100% of cases), hip abduction (73% of cases), and external foot rotation (92% of cases) were prominent injury kinematics, often with lateral trunk tilt (median, 10°; 64% of cases) and rotation (64% of cases). Knee flexion angles were higher for indirect and noncontact injuries (median, 100°) than for direct-contact injuries (median, 22°; P<.01).

CONCLUSION

Nearly two thirds of MCL injuries occurred after direct contact; 1 in every 4 MCL injuries occurred after indirect contact. Three sprain mechanisms characterized MCL injuries: (1) blow to the knee, (2) contact to the leg or foot (lever like), and (3) sliding. J Orthop Sports Phys Ther 2021;51(12):611-618. Epub 16 Nov 2021. doi:10.2519/jospt.2021.10529.

Can We Modify Maximal Speed Running Posture? Implications for Performance and Hamstring Injury Management

PURPOSE

Sprint kinematics have been linked to hamstring injury and performance. This study aimed to examine if a specific 6-week multimodal intervention, combining lumbopelvic control and unning technique exercises, induced changes in pelvis and lower-limb kinematics at maximal speed and improved sprint performance.

METHODS

Healthy amateur athletes were assigned to a control or intervention group (IG). A sprint test with 3-dimensional kinematic measurements was performed before (PRE) and after (POST) 6 weeks of training. The IG program included 3 weekly sessions integrating coaching, strength and conditioning, and physical therapy approaches (eg, manual therapy, mobility, lumbopelvic control, strength and sprint "front-side mechanics"-oriented drills).

RESULTS

Analyses of variance showed no between-group differences at PRE. At POST, intragroup analyses showed PRE-POST differences for the pelvic (sagittal and frontal planes) and thigh kinematics and improved sprint performance (split times) for the IG only. Specifically, IG showed (1) a lower anterior pelvic tilt during the late swing phase, (2) greater pelvic obliquity on the free-leg side during the early swing phase, (3) higher vertical position of the front-leg knee, (4) an increase in thigh angular velocity and thigh retraction velocity, (5) lower between-knees distance at initial contact, and (6) a shorter ground contact duration. The intergroup analysis revealed disparate effects (possibly to very likely) in the most relevant variables investigated.

CONCLUSION

The 6-week multimodal training program induced clear pelvic and lower-limb kinematic changes during maximal speed sprinting. These alterations may collectively be associated with reduced risk of muscle strain and were concomitant with significant sprint performance improvement.

Prediction of Hamstring Injuries in Australian Football Using Biceps Femoris Architectural Risk Factors Derived From Soccer

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.

Sprinting Biomechanics and Hamstring Injuries: Is There a Link? A Literature Review

Hamstring strain injury (HSI) is a common and costly injury in many sports such as the various professional football codes. Most HSIs have been reported to occur during high intensity sprinting actions. This observation has led to the suggestion that a link between sprinting biomechanics and HSIs may exist. The aim of this literature review was to evaluate the available scientific evidence underpinning the potential link between sprinting biomechanics and HSIs. A structured search of the literature was completed followed by a risk of bias assessment. A total of eighteen studies were retrieved. Sixteen studies involved retrospective and/or prospective analyses, of which only three were judged to have a low risk of bias. Two other case studies captured data before and after an acute HSI. A range of biomechanical variables have been measured, including ground reaction forces, trunk and lower-limb joint angles, hip and knee joint moments and powers, hamstring muscle–tendon unit stretch, and surface electromyographic activity from various trunk and thigh muscles. Overall, current evidence was unable to provide a clear and nonconflicting perspective on the potential link between sprinting biomechanics and HSIs. Nevertheless, some interesting findings were revealed, which hopefully will stimulate future research on this topic.

Sprinting technique and hamstring strain injuries: A concept mapping study

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.

Lower-limb injury in elite Australian football: A narrative review of kinanthropometric and physical risk factors

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.