Epidemiology of muscle injuries in professional football (soccer)

Physical performance tests - a relationship of risk factors for muscle injuries in elite level male football players

The purpose of the present study was to investigate whether there is a relationship between the outcome of preseason physical performance tests and the risk of sustaining lower extremity muscle injuries within the same season, in male football players at elite level. This is a cohort study of a male football team (63 players) from the first league in Swe-den. The football players are prospectively followed, in terms of muscle injuries of the lower extremity during five seasons between 2010 and 2014. All muscle injuries were evaluated and diagnosed with ultraso-nography. The following physical performance tests were included: squats, chin-ups, YoYo intermittent recovery level 2, counter movement jump, squat jump, standing long jump, sprint, one leg squat test, and a functional movement screen. A total of 86 muscle injuries occurred during the study period. No significant correlation was found between the results of the physical performance tests and muscle injuries of the lower extremity. None of the evaluated tests predicted the risk of sus-taining muscle injuries of the lower extremity. We conclude that muscle injury risk factors are more complex than solely related to the results of the preseason physical performance tests.

[Biomechanical screening for injury prevention : The importance of 3D-motion analysis in high performance sports]

Standardized clinical diagnostic procedures cannot assess the functionality of the anatomical structures in sport-specific movement. Biomechanical screening is able to detect deficits but is not sufficiently and objectively precise with the current clinical examination tools including conventional imaging techniques. The fields of use of functional testing methods are versatile and range from injury prevention analysis, screening during rehabilitation phases up to the return-to-play decision. Using simple musculoskeletal function analysis it is difficult to assess the risk of injuries. The main advantage of instrumented 3D-motion analysis is its potential to generate objective, reliable and reproducible data with exact joint angles, muscle activity, as well as loading inside the joints during movement. These marker-based motion analysis procedures are more time-consuming and more cost intensive and necessitate in particular biomechanical and medical knowledge to assess the analytical data in terms of clinical relevance. In the absence of scientific studies on biomechanical analyses in professional sports, this study shows preliminary approaches to this topic.

Exposure to radial extracorporeal shock waves modulates viability and gene expression of human skeletal muscle cells: a controlled in vitro study

BACKGROUND

Recent clinical and animal studies have shown that extracorporeal shock wave therapy has a promoting influence on the healing process of musculoskeletal disorders. However, the underlying biological effects of extracorporeal shock wave therapy on human skeletal muscle cells have not yet been investigated.

METHODS

In this study, we investigated human skeletal muscle cells after exposure to radial extracorporeal shock waves in a standardized in vitro setup. Cells were isolated from muscle specimens taken from adult patients undergoing spine surgery. Primary muscle cells were exposed once or twice to radial extracorporeal shock waves in vitro with different energy flux densities. Cell viability and gene expression of the paired box protein 7 (Pax7), neural cell adhesion molecule (NCAM), and myogenic factor 5 (Myf5) and MyoD as muscle cell markers were compared to non-treated muscle cells that served as controls.

RESULTS

Isolated muscle cells were positive for the hallmark protein of satellite cells, Pax7, as well as for the muscle cell markers NCAM, MyoD, and Myf5. Exposure to radial extracorporeal shock waves at low energy flux densities enhanced cell viability, whereas higher energy flux densities had no further significant impact. Gene expression analyses of muscle specific genes (Pax7, NCAM, Myf5, and MyoD) demonstrated a significant increase after single exposure to the highest EFD (4 bar, 0.19 mJ/mm²) and after double exposure with the medium EFDs (2 and 3 bar; 0.09 and 0.14 mJ/mm², respectively). Double exposure of the highest EFD, however, results in a significant down-regulation when compared to single exposure with this EFD.

CONCLUSIONS

This is the first study demonstrating that radial extracorporal shock wave therapy has the potential to modulate the biological function of human skeletal muscle cells. Based on our experimental findings, we hypothesize that radial extracorporal shock wave therapy could be a promising therapeutic modality to improve the healing process of sports-related structural muscle injuries.

The associations between training load and baseline characteristics on musculoskeletal injury and pain in endurance sport populations: A systematic review

OBJECTIVES

To determine the associations between training load, baseline characteristics (e.g. age or previous injury) and rate of musculoskeletal injury and/or pain specifically within an Endurance Sporting Population (ESP).

DESIGN

Prospectively registered systematic review.

METHODS

Eight electronic databases were searched by two independent reviewers. Studies were required to prospectively monitor both (i) training loads and (ii) musculoskeletal injury and/or pain for >3 months. Methodological quality and risk of bias were determined utilising the Critical Skills Appraisal Program (CASP). Reported effect sizes were categorised as small, medium or large.

RESULTS

Twelve endurance sport studies were eligible (running, triathlon, rowing). Increased injury and/or pain risk was associated with: (i) high total training distances per week/month (medium effect size) (ii) training frequency <2 sessions/week (medium effect size) and (iii) both low weekly (<2hours/week) and high monthly (large effect size) training durations. None of the studies reported internal training load data or acute:chronic workload ratios. Baseline characteristics found to increase the rate of injury and/or pain included: (i) a history of previous injury (medium effect size), (ii) age >45 years (small effect size), (iii) non-musculoskeletal comorbidities (large effect size), (iv) using older running shoes (small effect size) and (v) non-competitive behaviour.

CONCLUSIONS

This review identifies a range of external training load factors and baseline characteristics associated with an increased rate of injury and/or pain within ESPs. There is an absence of research relating to internal training loads and acute:chronic workload ratios in relation to rate of injury and/or pain within ESPs.

Low-Intensity Sprint Training With Blood Flow Restriction Improves 100-m Dash

Behringer, M, Behlau, D, Montag, JCK, McCourt, ML, and Mester, J. Low-intensity sprint training with blood flow restriction improves 100-m dash. J Strength Cond Res 31(9): 2462-2472, 2017-We investigated the effects of practical blood flow restriction (pBFR) of leg muscles during sprint training on the 100-m dash time in well-trained sport students. Participants performed 6 × 100-m sprints at 60-70% of their maximal 100-m sprinting speed twice a week for 6 weeks, either with (intervention group [IG]; n = 12) or without pBFR (control group [CG]; n = 12). The 100-m dash time significantly decreased more in the IG (-0.38 ± 0.24 seconds) than in the CG (-0.16 ± 0.17 seconds). The muscle thickness of the rectus femoris increased only in the IG, whereas no group-by-time interactions were found for the muscle thickness of the biceps femoris and the biceps brachii. The maximal isometric force, measured using a leg press, did not change in either group. However, the rate of force development improved in the IG. Growth hormone, testosterone, insulin-like growth factor 1, and cortisol concentrations did not significantly differ between both groups at any measurement time point (pre, 1 minute, 20 minutes, 120 minutes, and 24 hours after the 6 all-out sprints of the first training session). The muscle damage marker h-FABP increased significantly more in the CG than in the IG. The pBFR improved the 100-m dash time significantly more than low-intensity sprint interval training alone. Other noted benefits of training with pBFR were a decreased level of muscle damage, a greater increase of the rectus femoris muscle thickness, and a higher rate of force development. However, the tested hormones were unable to explain the additional beneficial effects.

Muscle injuries of the dominant or non-dominant leg in male football players at elite level

PURPOSE

The aim was to study possible differences of muscle injuries regarding type, localization and the extent of injury between the dominant and non-dominant leg in elite male football players. Another aim was to study the injury incidence of muscle injuries of the lower extremity during match and training.

METHODS

Data were consecutively collected between 2007 and 2013 in a prospective cohort study based on 54 football players from one team of the Swedish first league. The injury incidence was calculated for both match and training, injuries to the hip adductors, quadriceps, hamstrings and triceps surae were diagnosed and evaluated with ultrasonography, and their length, depth and width were measured to determine the extent of structural muscle injuries.

RESULTS

Fifty-four players suffered totally 105 of the studied muscle injuries. Out of these 105 injuries, the dominant leg was affected in 53 % (n = 56) of the cases. A significantly greater extent of the injury was found in the dominant leg when compared with the non-dominant leg with regard to structural injuries of the hamstrings. No other significant differences were found.

CONCLUSIONS

Structural hamstring muscle injuries were found to be of greater extent in the dominant leg when compared with the non-dominant leg. This new finding should be taken into consideration when allowing the football player to return to play after leg muscle injuries.

LEVEL OF EVIDENCE

IV.

Awareness among Indian professional football players about injury prevention strategies: A national survey

OBJECTIVE

To determine the awareness and application of the injury prevention strategies by professional Indian football players through Standard Questionnaire Based Survey.

DESIGN

Descriptive Epidemiological Study.

SETTING

Professional football clubs in India.

PARTICIPANTS

Among 150 professional footballers playing in India, 109 football players participated..

PROCEDURE

The online questionnaire was made in the Google drive application. An online URL (www.tinyurl.com/futbolscptrc) was made in Google accounts by Google drive. 150 professional footballers playing in India were identified and invited to participate in this descriptive epidemiological online survey. All duly filled questionnaire responses were automatically reached in the Google drive inbox. Descriptive analysis was used for the data analysis.

RESULTS

Questionnaires were distributed to 150 professional players at nine Indian League clubs. 109 players responded, which represents a response rate of 73%. The player age and number of years as a professional footballers were 25 (4) years (range 18-38 years) and 6 (4) years (range 1-16 years) respectively. The players were from one Premier (9), two Division One (6 and 16), and two Division Two (9 and 15) teams.

CONCLUSIONS

Most of the professional Indian football players are aware about the injury prevention strategies. However, the application of these strategies is consistently followed by Premier division players.

Characteristics of goalkeeping injuries: a retrospective, self-reported study in adolescent soccer players

BACKGROUND

Characteristic types of actions and training/matches loads of soccer goalkeepers show that goalkeeper's performance differs from other soccer's formations. Such situation may predispose to the occurrence of other kinds of injuries in this position. The aim of this study was to analyze epidemiology of injuries in young soccer goalkeepers.

METHODS

Forty-eight soccer goalkeepers (aged:15.2±1.9 years) filled the questionnaire aimed at collecting information about all injuries sustained within 12 months before the data collection. The anthropometric data, soccer experience and information regarding the injury types and occurrence were analyzed. The injury rate proportion for acute and overuse injuries and values of injuries including the burden of the match game and training were evaluated. The level of significance was set at P<0.05.

RESULTS

Thirty-three (68.8%) questionnaires were given back. Twenty-four (72.7%) goalkeepers reported the history of soccer related injury within a year before the survey. 52 injuries were reported. Significantly higher number of acute (76.9%) vs. overuse (23.1%) injuries was described (P=0.0012). Acute injuries involved fractures/subluxations of the fingers and thigh muscle strain/tears. The group of overuse injuries was dominated by trauma of the knee and pelvic girdle muscles. Majority of injuries occurred during training (88.5% of all injuries), and there was significant higher number of injuries sustained on artificial vs. natural grass for all, acute and overuse types of injuries (P<0.0001).

CONCLUSIONS

Young soccer goalkeepers suffer mostly acute injuries (within the fingers of hands and muscles of thighs). It might be associated with specific characteristic of performance related to goalkeeper's position.

Higher frequency of hamstring injuries in elite track and field athletes who had a previous injury to the ankle - a 17 years observational cohort study

Background

Inversion injury to the ankle and hamstring injuries are common problems in most sports. It is not known whether these injuries constitute a predisposing factor or a precursor of injury or re-injury of these anatomical locations. Therefore, we wished to test the hypothesis that a previous inversion ankle injury exerted a significant effect on the chance of an athlete suffering from a subsequent ipsilateral hamstring injury and vice versa.

Methods

In an observational cohort study over 17 years (1998–2015), 367 elite track and field athletes, were grouped according to their first traumatic isolated ankle or hamstring injury. Fifty athletes experienced both injuries. The Mann-Whitney U and Chi-square tests (p < 0.05) were performed to test possible associations of ankle and hamstring injury with age, gender, athletics discipline, grade, and type of antecedent injury.

Results

Athletes with a preceding ankle injury had a statistically significantly higher chance of experiencing a subsequent hamstring injury compared with athletes who had experienced a hamstring injury as their first traumatic event (x² = 4.245, p = 0.039). The proportion of both ankle and hamstring injury events was not statistically different between female (18%) and male (11%) athletes. Age and grade of injury did not influence the proportion of ankle and/or hamstring injury events.

Conclusion

There is a statistically significantly higher frequency of hamstring injuries in elite track and field athletes having experienced a previous ankle ligament injury.

The elite player performance plan: the impact of a new national youth development strategy on injury characteristics in a premier league football academy

The objective of this study was to investigate the injury incidence and patterns in elite youth football at a category 1 Premier League Academy before and after the introduction of a new development strategy, the Elite Player Performance Plan (EPPP). A prospective study was performed over six consecutive seasons encompassing three years before and after the introduction of the EPPP. The findings revealed a most likely moderate increase in total exposure per player per season when the post-EPPP football exposure (640.86 ± 83.25 hours per player per year) was compared with the pre-EPPP football exposure (539.08 ± 71.59). The total injury incidence pre-EPPP was 3.0/1000 hours compared to 2.1/1000 hours post-EPPP (rate ratio 1.43). 6% of all injuries were re-injuries (20.24 ± 33.43 days) but did not result in a substantially longer absence (16.56 ± 15.77 days). The injury burden decreased for the U12-U15 from pre- to post-EPPP, whereas the injury burden increased for the U16-U18 (respectively 125 and 47% higher). These findings suggest that following the introduction of the EPPP there has been a reduction in injuries in the younger age groups U12-U15 but in the older age groups U16-U18 there has been an increase in the severity of the injuries sustained at this club.

Central Tendon Injuries of Hamstring Muscles: Case Series of Operative Treatment

Background:

As compared with injuries involving muscle only, those involving the central hamstring tendon have a worse prognosis. Limited information is available regarding the surgical treatment of central tendon injuries of the hamstrings.

Purpose:

To describe the operative treatment and outcomes of central tendon injuries of the hamstrings among athletes.

Study Design:

Case series; Level of evidence, 4.

Methods:

Eight athletes (6 top level, 2 recreational) with central hamstring tendon injuries underwent magnetic resonance imaging and surgical treatment. The indication for surgery was recurrent (n = 6) or acute (n = 2) central hamstring tendon injury. All patients followed the same postoperative rehabilitation protocol, and return to play was monitored.

Results:

Magnetic resonance imaging found a central tendon injury in all 3 hamstring muscles (long head of the biceps femoris, semimembranosus, and semitendinosus) with disrupted tendon ends. In acute and recurrent central tendon injuries, full return to play was achieved at 2.5 to 4 months. There were no adverse events during follow-up.

Conclusion:

Central tendon injuries of the hamstrings can be successfully repaired surgically after acute and recurrent ruptures.

Professional football players at risk for non-acute groin injuries during the first half of the season: A prospective cohort study in The Netherlands

OBJECTIVES

To study the incidence, diagnostics, treatment, anatomical region and return to play of non-acute groin injuries among professional footballers in the Netherlands.

DESIGN

Prospective cohort study.

METHODS

Medical staff members of all Dutch professional football clubs, recording prospectively injury occurrence of all professional footballers in their clubs, were asked to fill in an injury form about time-loss (⩾ 8 days) non-acute groin injury over the 2012-2013 season.

RESULTS

A cohort of 410 players from 12 professional football clubs were included (response rate = 44%). The season incidence of non-acute groin injuries was nearly 7% (29 non-acute groin injuries). In 82% of all cases, the player suffered from non-acute groin injury in the first half of the season. The average time to return to play was 35 days, ranging from 8 to 84 days. The adductors were the most affected anatomical regions (82%), with the most frequent diagnosis being overuse of the adductors (36%), followed by adductor tendinopathy (18%). In addition to medical history and physical examination, ultrasound (50%) and MRI (32%) were the diagnostic methods most frequently mentioned. As well as physical therapy, treatment consisted mostly of manual therapy (96%) and dry needling (61%).

CONCLUSIONS

A professional club with a squad of 25 players can expect on average two non-acute groin injuries per season with an average time-loss of 35 days. Players are more at risk in the first half of the season. In Dutch professional football, ultrasound is commonly used to diagnose non-acute groin injury, while manual therapy is the most commonly applied treatment.

Time to recovery of sciatic function index after induced tibialis anterior strain in rats

Background

Muscle strain is a common injury with a high recurrence rate. Due to the heterogeneity of strain injuries, experimental animals provide controlled and reproducible models to investigate such injuries. Sciatic Function Index (SFI) is a clinically feasible method to assess hind limb recovery in rodents after induced injuries.

Objectives

To investigate time to recovery of SFI after induced-strain in tibialis anterior (TA) muscle in rats.

Methods

Sixteen adult male Wister rats were randomly and equally divided to a normal control group that received no intervention, and TA induced muscle strain group. Muscle strain was induced using an external weight that corresponded to 150% of the animal body weight. SFI was tested only once in the control group. For the muscle strain group, SFI was tested on the 1^st, 2^nd, 3^rd, 4^th, 7^th, 11^th, 20^th and 24^th days after strain induction.

Results

Comparisons between group showed significant difference in SFI on the 1^st, 2^nd, 3^rd and 4^th days (p= 0.012, 0.012, 0.012 and 0.028, respectively).

Conclusions

In a rat animal model of TA induced muscle strain, functional recovery measured by SFI is evident on the 7^th day post-injury, which corresponds to the sub-acute phase of injury.

Level of evidence

V.

Career Length and Injury Incidence After Anterior Cruciate Ligament Reconstruction in Major League Soccer Players

Background:

Little is known about career length after anterior cruciate ligament (ACL) reconstruction in Major League Soccer (MLS), the top men’s professional soccer league in the United States. Further, it is unspecified whether athletes returning to soccer after ACL reconstruction are at a higher risk for injuries, beyond new knee injuries.

Purpose:

To examine career length and the incidence of lower extremity injuries in MLS athletes after ACL reconstruction in comparison with age-matched controls.

Study Design:

Cohort study; Level of evidence, 3.

Methods:

Injuries and athletic exposures (AEs; games and training sessions) were recorded in the HealtheAthlete database, the injury surveillance system of MLS. All athletes who had undergone ACL reconstruction and returned to MLS were identified and age-matched with controls. Multivariate analyses of variance were used to compare career length and percentage of regular/postseason games that athletes started, substituted, or did not play. Generalized linear model regressions were used to examine the injury risk.

Results:

Athletes in the ACL group had shorter careers (1.3 ± 1.3 years) than those in the control group (2.5 ± 1.3 years) (P < .01), but while they were playing, athletes in the ACL group participated in a similar number of AEs as those in the control group (169.9 ± 129.0 vs 171.6 ± 124.9 AEs, respectively; P = .95). Athletes in the ACL group started fewer regular/postseason games (36.7% ± 34.3% vs 60.1% ± 33.8%, respectively; P < .01) and did not play in more regular/postseason games (47.4% ± 35.5% vs 31.0% ± 34.4%, respectively; P = .03) compared with those in the control group. The ACL group was not at a significantly greater risk for lower extremity injuries compared with the control group (relative risk, 0.87; 95% CI, 0.55-1.37).

Conclusion:

Although MLS athletes after ACL reconstruction are not at a greater risk for lower extremity injuries, this study suggests that they are not utilized in regular/postseason games as frequently and that their careers in MLS are shorter than age-matched controls. Further research is necessary to elucidate reasons for these athletes’ shortened MLS careers. This study supports the view of return to sport not as a single time point but as a continuum from return to participation to return to play and return to performance.

High final energy of gallium arsenide laser increases MyoD gene expression during the intermediate phase of muscle regeneration after cryoinjury in rats

The aim of this study was to determine the effects of gallium arsenide (GaAs) laser on IGF-I, MyoD, MAFbx, and TNF-α gene expression during the intermediate phase of muscle regeneration after cryoinjury 21 Wistar rats were divided into three groups (n = 7 per group): untreated with no injury (control group), cryoinjury without GaAs (injured group), and cryoinjury with GaAs (GaAs-injured group). The cryoinjury was induced in the central region of the tibialis anterior muscle (TA). The region injured was irradiated once a day during 14 days using GaAs laser (904 nm; spot size 0.035 cm², output power 50 mW; energy density 69 J cm^-2; exposure time 4 s per point; final energy 4.8 J). Twenty-four hours after the last application, the right and left TA muscles were collected for histological (collagen content) and molecular (gene expression of IGF-I, MyoD, MAFbx, and TNF-α) analyses, respectively. Data were analyzed using one-way ANOVA at P < 0.05. There were no significant (P > 0.05) differences in collagen density and IGF-I gene expression in all experimental groups. There were similar (P < 0.05) decreases in MAFbx and TNF-α gene expression in the injured and GaAs-injured groups, compared to control group. The MyoD gene expression increased (P = 0.008) in the GaAs-injured group, but not in the injured group (P = 0.338), compared to control group. GaAs laser therapy had a positive effect on MyoD gene expression, but not IGF-I, MAFbx, and TNF-α, during intermediary phases (14 days post-injury) of muscle repair.

Cohen's MRI scoring system has limited value in predicting return to play

PURPOSE

Numerous authors have hypothesised that MRI scoring systems provide a valid means of predicting return to play duration following an acute hamstring muscle strain. The purpose is to prospectively investigate the predictive value of the MRI scoring system of Cohen for return to sport (RTS), following an acute hamstring injury.

METHODS

Male football (soccer) players (n = 139) with acute onset posterior thigh pain underwent standardised clinical and MRI examinations within 5 days after injury. All players underwent a standardised physiotherapy regimen with RTS documented. The MRI scoring was statistically evaluated against RTS.

RESULTS

One hundred and ten MRI-positive hamstring injuries were evaluated with RTS duration ranging from 1 to 66 days. Total Cohen's MRI score accounted for approximately 4% of the variance in RTS duration. When comparing those with an MRI score of 10 or more took on average 9.8 days longer to RTS than those with an MRI score less than 10 (effect size: 0.85, p < 0.01).

CONCLUSIONS

Utilising the Cohen's MRI scoring system previously described, we were unable to provide a clinically useful prognosis for RTS in male soccer players. This may reflect the broader challenges of attempting to accurately determine RTS duration from imaging performed at a single point in time.

LEVEL OF EVIDENCE

Prospective case series, IV.

ORTHOPEDIC INJURIES IN MEN'S PROFESSIONAL SOCCER IN BRAZIL: PROSPECTIVE COMPARISON OF TWO CONSECUTIVE SEASONS 2017/2016

PURPOSE

The purpose is to compare the incidence and characteristics of injuries sustained in two consecutive seasons of the São Paulo State Football Championship.

METHODS

Prospective study performed using an electronic form previously developed by the Medical Committee of the São Paulo State Football Federation, sent to the physicians responsible for the tournament's series A1 and A2 teams, after each round.

RESULTS

17.63 injuries sustained per 1000 hours of matches in the A1 series and 14.91 injuries sustained per 1000 hours of matches in the A2 series. Incidence of injuries per 1000 hours of matches decreased from 24.16 to 17.63 in the A1 series (p<0.037) and from 19.10 to 14.01 in the A2 series (p<0.064). External defenders suffered most injuries, while muscular injuries were most common and lower limbs, the most affected areas. Most injuries occurred between 30 and 45 minutes of the match and only 11.9% of the injuries required surgery.

CONCLUSIONS

Prevalence and frequency of injuries decreased between seasons. Most injuries were sustained in the lower limbs; strains were the most common injuries, followed by strains and contusions; MRIs were the most frequently requested exams and most injuries were classified as moderate (8-28 days). Level of evidence III, Cross-Sectional Study.

Does Platelet-Rich Plasma Lead to Earlier Return to Sport When Compared With Conservative Treatment in Acute Muscle Injuries? A Systematic Review and Meta-analysis

PURPOSE

To compare the time to return to sport and reinjury rate after platelet-rich plasma (PRP) injection versus control therapy (i.e., physiotherapy or placebo injection) in patients with acute grade I or II muscle strains.

METHODS

All eligible studies comparing PRP against a control in the treatment of acute (≤7 days) grade I or II muscle strains were identified. The primary outcome was time to return to play. The secondary outcome was the rate of reinjury at a minimum of 6 months of follow-up. Subgroup analysis was performed to examine the efficacy of PRP in hamstring muscle strains alone. The checklist to evaluate a report of a nonpharmacologic trial (CLEAR-NPT) was used to assess the quality of studies.

RESULTS

Five randomized controlled trials including a total of 268 patients with grade I and II acute muscle injuries were eligible for review. The pooled results revealed a significantly earlier return to sport for the PRP group when compared with the control group (mean difference, -5.57 days [95% confidence interval, -9.57 to -1.58]; P = .006). Subgroup analysis showed no difference in time to return to sport when comparing PRP and control therapy in grade I and II hamstring muscle strains alone (P = .19). No significant difference was noted in the rate of reinjury between the 2 groups (P = .50) at a minimum of 6 months of follow-up.

CONCLUSIONS

Evidence from the current literature, although limited, suggests that the use of PRP may result in an earlier return to sport among patients with acute grade I or II muscle strains without significantly increasing the risk of reinjury at 6 months of follow-up. However, no difference in time to return to sport was revealed when specifically evaluating those with a grade I or II hamstring muscle strain.

LEVEL OF EVIDENCE

Level II, meta-analysis of level I and II studies.

MR Imaging of Muscle Trauma: Anatomy, Biomechanics, Pathophysiology, and Imaging Appearance

Muscle is an important component of the muscle-tendon-bone unit, driving skeletal motion through contractions that alter the length of the muscle. The muscle and myotendinous junction (MTJ) are most commonly injured in the young adult, as a result of indirect mechanisms such as overuse or stretching, direct impact (penetrating or nonpenetrating), or dysfunction of the supporting connective tissues. Magnetic resonance (MR) imaging is widely used for assessment of muscle injuries. This review illustrates the MR imaging appearance of a broad spectrum of acute, subacute, and chronic traumatic lesions of muscle, highlighting the pathophysiology, biomechanics, and anatomic considerations underlying these lesions. Concentric (shortening) contractions are more powerful, but it is eccentric (lengthening) contractions that produce the greatest muscle tension, leading to indirect injuries such as delayed-onset muscle soreness (DOMS) and muscle strain. Strain is the most commonly encountered muscle injury and is characteristically located at the MTJ, where maximal stress accumulates during eccentric exercise. The risk of strain varies among muscles based on their fiber composition, size, length, and architecture, with pennate muscles being at highest risk. Direct impact to muscle results in laceration or contusion, often accompanied by intramuscular interstitial hemorrhage and hematoma. Disorders related to the muscle's collagen framework include compartment syndrome, which is related to acute or episodic increases in pressure, and muscle herniation through anatomic defects in the overlying fascia. The healing response after muscle trauma can result in regeneration, degeneration with fibrosis and fatty replacement, or disordered tissue proliferation as seen in myositis ossificans. In athletes, accurate grading of the severity and precise location of injury is necessary to guide rehabilitation planning to prevent reinjury and ensure adequate healing. In elite athletes, MR imaging grading of muscle trauma plays an increasingly important role in recently developed comprehensive grading systems that are replacing the imprecise three-grade injury classification system currently used. ^©RSNA, 2017.

Imaging-detected acute muscle injuries in athletes participating in the Rio de Janeiro 2016 Summer Olympic Games

BACKGROUND

Acute muscle injuries in elite athletes are responsible for a large portion of time loss injuries.

AIM

To describe the frequency, the anatomic distribution, and severity of imaging-detected acute muscle injuries among athletes who competed in the Rio de Janeiro 2016 Summer Olympics.

METHODS

We recorded all sports injuries reported by the National Olympic Committee medical teams and the Organising Committee medical staff during the 2016 Summer Olympics. Imaging of acute muscle injuries was performed at the IOC's polyclinic within the Olympic Village using ultrasound and 3.0 T and 1.5 T MRI scanners. The assessment of images was performed centrally by three musculoskeletal radiologists. The distribution of injuries by anatomic location and sports discipline and the severity of injuries were recorded.

RESULTS

In total, 11 274 athletes from 207 teams were included. A total of 1101 injuries were reported. Central review of radiological images revealed 81 acute muscle injuries in 77 athletes (66% male, mean age: 25.4 years, range 18-38 years). Athletics (track and field) athletes were the most commonly affected (n=39, 48%), followed by football players (n=9, 11%). The majority of injuries affected muscles from lower limbs (n=68, 84%), with the hamstring being the most commonly involved. Most injuries were grade 2 injuries according to the Peetrons classification (n=44, 54%), and we found 18 injuries exhibiting intramuscular tendon involvement on MRI.

CONCLUSION

Imaging-detected acute muscle injuries during the 2016 Summer Olympics affected mainly thigh muscles in athletics disciplines.

Discussion about different cut-off values of conventional hamstring-to-quadriceps ratio used in hamstring injury prediction among professional male football players

OBJECTIVE

To measure the sensitivity and specificity of differences cut-off values for isokinetic Hcon/Qcon ratio in order to improve the capacity to evaluate (retrospectively) the injury of hamstring muscles in professional soccer screened with knee isokinetic tests.

DESIGN

Retrospective study.

METHODS

Medical and biomechanical data of professional football players playing for the same team for at least one season between 2010 and 2016 were analysed. Hamstring strain injury cases and the reports generated via isokinetic testing were investigated. Isokinetic concentric(con) hamstring(H) and quadriceps(Q) absolute strength in addition with Hcon/Qcon ratio were examined for the injured versus uninjured limbs among injured players, and for the injured and non-injured players. 2 x 2 contingency table was used for comparing variables: predicted injured or predicted uninjured with actual injured or actual uninjured. Sensitivity, specificity, accuracy, positive and negative predictive values, and positive and negative likelihood ratio were calculated for three different cut-off values (0.47 vs. 0.6 vs. 0.658) to compare the discriminative power of an isokinetic test, whilst examining the key value of Hcon/Qcon ratio which may indicate the highest level of ability to predispose a player to injury. McNemar's chi2 test with Yates's correction was used to determine agreement between the tests. PQStat software was used for all statistical analysis, and an alpha level of p <0.05 was used for all statistical comparisons.

RESULTS

340 isokinetic test reports on both limbs of 66 professional soccer players were analysed. Eleven players suffered hamstring injuries during the analysed period. None of these players sustained recurrence of hamstring injury. One player sustained hamstring strain injury on both legs, thus the total number of injuries was 12. Application of different cut-off values for Hcon/Qcon significantly affected the sensitivity and specificity of isokinetic test used as a tool for muscle injury detection. The use of 0.47 of Hcon/Qcon as a discriminate value resulted in significantly lower sensitivity when compared to 0.658 threshold (sensitivity of 16.7% vs. 91.7%, respectively; t = 6.125,p = 0.0133). Calculated values of specificity (when three different cut-off were applied) were also significantly different. Threshold of 0.6 of Hcon/Qcon resulted with significantly lower specificity compared to 0.47 value (specificity of 46.9% vs. 94.5%, respectively; t = 153.0,p<0.0001), and significantly higher specificity when compared to 0.658 (specificity of 46.9% vs. 24.1%, respectively; t = 229.0, p<0.0001).

CONCLUSION

The use of different cut-off values for Hcon/Qcon significantly affected the sensitivity and specificity of isokinetic testing. The interpretation of usefulness of isokinetic test as a screening tool in a group of male professional football players to predict hamstring injury occurrence within the next 12 months might be therefore significantly biased due to the different threshold values of Hcon/Qcon. Using one "normative" value as a cut-off (e.g. 0.47 or 0.60, or 0.658) to quantify soccer players (or not) to the group with a higher risk of knee injury might result in biased outcomes due to the natural strength asymmetry that is observed within the group of soccer players.

Eccentric hamstring strength deficit and poor hamstring-to-quadriceps ratio are risk factors for hamstring strain injury in football: A prospective study of 146 professional players

OBJECTIVES

The purpose of this study was to investigate whether preseason isokinetic strength measures were predictive of future HSI among professional football players.

DESIGN

Prospective cohort study, Level of evidence 2.

METHODS

A total of 169 professional players participated in a preseason isokinetic strength screening, followed by a 10-month competitive season. Testing protocol included the concentric performance of both knee flexion and extension at 60degs^-1 and 240degs^-1 and the eccentric performance of the knee flexor at 30degs^-1. Strength deficits, bilateral differences, and hamstring to quadriceps strength ratios were computed. Univariate and multivariate logistic regressions were used to identify potential risk factors of HSI. Receiver operating characteristic (ROC) curves were used to investigate the sensitivity and specificity of the strength measures.

RESULTS

Forty-one acute HSIs were sustained, and 12% (n=5) reoccurred within the study period. In the multivariate analysis, we have shown an association between the injury risk and eccentric hamstring peak torque below 2.4Nmkg^-1 (OR=5.59; 95% CI, 2.20-12.92); concentric H/Q ratio below 50.5% (OR=3.14; 95% CI, 1.37-2.22); players with previous injury of HSI (OR=3.57; 95% CI, 3.13-8.62). ROC analysis displayed an area under curve (AUC) of 0.77, indicating fair combined sensitivity and specificity of the overall predicting model.

CONCLUSIONS

Professional football players with significant lower isokinetic hamstring strength, lower hamstring-to-quadriceps strength ratio, and a previous injury of HSI were linked to an increased risk of acute HSI.

Sprint and jump performance in elite male soccer players following a 10-week Nordic Hamstring exercise Protocol: a randomised pilot study

OBJECTIVE

The preseason Nordic Hamstring Protocol (NHP) reduces hamstring strain injuries in football players. Despite persisting injury rates, elite clubs are reluctant to apply the NHP often over concerns of negative impacts on performance. This pilot study investigated if sprint or jump-performance outcomes tended to increase or decrease following implementation of the NHP in elite male soccer-players.

RESULTS

Nineteen male soccer players from the Danish 1st division were randomised to perform NHP (27 sessions) during pre-season, or to control group (CG). Sprint performance (30 m with 5 and 10 m split times) and countermovement jump (CMJ height) was measured before the mid-seasonal break and again after 10 weeks of performing the NHP at the end of pre-season. Dropouts were due to transfers and injuries unrelated to performing NHP (NHP = 0, CG = 5). Sprint performance on the short split distances improved for most players in the NHP (6 out of 9 improved, median changes for 5 m split: - 0.068 s; 10 m split: - 0.078 s), but not CG (2 out of 5 improved, median changes for 5 m split: + 0.1 s; 10 m split: CG: + 0.11 s), but both groups had small declines at 30 m sprint (NHP: 7 out of 9 declined, median changes: + 0.116 s; CG: 4 out of 5 declined, median changes: + 0.159 s). CMJ height mostly improved in both groups (NHP: 6 out of 9 improved, median changes: + 2.1 cm; CG: 4 out of 8 improved, median changes: + 0.55 cm). Performing the NHP in elite soccer players did therefore not seem to negatively affect sprint and vertical jump performance outcomes in the present study, while in fact showing some promise for the more explosive characteristics such as the short 5 and 10 m split-times and maximal CMJ height, which all are highly relevant performance parameters in elite football.

The FIFA 11+ injury prevention program for soccer players: a systematic review

Background

Soccer is one of the most widely played sports in the world. However, soccer players have an increased risk of lower limb injury. These injuries may be caused by both modifiable and non-modifiable factors, justifying the adoption of an injury prevention program such as the Fédération Internationale de Football Association (FIFA) 11+. The purpose of this study was to evaluate the efficacy of the FIFA 11+ injury prevention program for soccer players.

Methodology

This meta-analysis was based on the PRISMA 2015 protocol. A search using the keywords “FIFA,” “injury prevention,” and “football” found 183 articles in the PubMed, MEDLINE, LILACS, SciELO, and ScienceDirect databases. Of these, 6 studies were selected, all of which were randomized clinical trials.

Results

The sample consisted of 6,344 players, comprising 3,307 (52%) in the intervention group and 3,037 (48%) in the control group. The FIFA 11+ program reduced injuries in soccer players by 30%, with an estimated relative risk of 0.70 (95% confidence interval, 0.52–0.93, p = 0.01). In the intervention group, 779 (24%) players had injuries, while in the control group, 1,219 (40%) players had injuries. However, this pattern was not homogeneous throughout the studies because of clinical and methodological differences in the samples. This study showed no publication bias.

Conclusion

The FIFA 11+ warm-up program reduced the risk of injury in soccer players by 30%.

Hamstring Injuries in Professional Soccer Players: Extent of MRI-Detected Edema and the Time to Return to Play

Background:

Discrepancies exist in the literature regarding the association of the extent of injuries assessed on magnetic resonance imaging (MRI) with recovery times.

Hypothesis:

MRI-detected edema in grade 1 hamstring injuries does not affect the return to play (RTP).

Study Design:

Retrospective cohort study.

Level of Evidence:

Level 4.

Methods:

Grade 1 hamstring injuries from 22 professional soccer players were retrospectively reviewed. The extent of edema-like changes on fluid-sensitive sequences from 1.5-T MRI were evaluated using craniocaudal length, percentage of cross-sectional area, and volume. The time needed to RTP was the outcome. Negative binomial regression analysis tested the measurements of MRI-detected edema-like changes as prognostic factors.

Results:

The mean craniocaudal length was 7.6 cm (SD, 4.9 cm; range, 0.9-19.1 cm), the mean percentage of cross-sectional area was 23.6% (SD, 20%; range, 4.4%-89.6%), and the mean volume was 33.1 cm³ (SD, 42.6 cm³; range, 1.1-161.3 cm³). The mean time needed to RTP was 13.6 days (SD, 8.9 days; range, 3-32 days). None of the parameters of extent was associated with RTP.

Conclusion:

The extent of MRI edema in hamstring injuries does not have prognostic value.

Clinical Relevance:

Measuring the extent of edema in hamstring injuries using MRI does not add prognostic value in clinical practice.

Including the Copenhagen Adduction Exercise in the FIFA 11+ Provides Missing Eccentric Hip Adduction Strength Effect in Male Soccer Players: A Randomized Controlled Trial

BACKGROUND

The FIFA 11+ was developed as a complete warm-up program to prevent injuries in soccer players. Although reduced hip adduction strength is associated with groin injuries, none of the exercises included in the FIFA 11+ seem to specifically target hip adduction strength.

PURPOSE

To investigate the effect on eccentric hip adduction strength of the FIFA 11+ warm-up program with or without the Copenhagen adduction exercise.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 1.

METHODS

We recruited 45 eligible players from 2 U19 elite male soccer teams. Players were randomized into 2 groups; 1 group carried out the standard FIFA 11+ program, while the other carried out the FIFA 11+ but replaced the Nordic hamstring exercise with the Copenhagen adduction exercise. Both groups performed the intervention 3 times weekly for 8 weeks. Players completed eccentric strength and sprint testing before and after the intervention. Per-protocol analyses were performed, and 12 players were excluded due to low compliance (<67% of sessions completed). The main outcome was eccentric hip adduction strength (N·m/kg).

RESULTS

Between-group analyses revealed a significantly greater increase in eccentric hip adduction strength of 0.29 Nm/kg (8.9%; P = .01) in favor of the group performing the Copenhagen adduction exercise, whereas no within-group change was noted in the group that used the standard FIFA 11+ program (-0.02 N·m/kg [-0.7%]; P = .69).

CONCLUSION

Including the Copenhagen adduction exercise in the FIFA 11+ program increases eccentric hip adduction strength, while the standard FIFA 11+ program does not. Registration: Registration: ISRCTN13731446 (International Standard Randomised Controlled Trial Number registry).

MRI detection of soleus muscle injuries in professional football players

OBJECTIVES

To describe magnetic resonance imaging (MRI) characteristics of soleus muscle injuries in symptomatic professional football players stratified according to both the Munich consensus statement and the British Athletics Muscle Injury Classification (BAMIC), and to investigate the association between specific MRI features and the "return to play" (RTP).

MATERIALS AND METHODS

Professional football players with an episode of acute posterior calf pain and impaired function, subsequent to sports activity, underwent ultrasound followed by MRI examination reviewed by two different radiologists with more than 10 years of experience in the musculoskeletal system. MRI features and RTP outcome were evaluated for all types of injuries.

RESULTS

During a 36-month period, a total of 20 professional football players were evaluated. According to the Munich consensus, 11 were type 3A, 8 were type 3B, and 1 was type 4, whereas according to the BAMIC, 11 lesions were considered grade 1, 4 grade 2, 4 grade 3, and 1 grade 4. RTP data were available for all patients (mean 3.3 ± 1.6 weeks). Both the Munich consensus and the BAMIC correlated with RTP (Spearman correlation = 0.982 and p < 0.0001 and 0.886 and p < 0.0001 respectively). Extension of edema was an independent prognostic factor for RTP in two different models of multivariate regression analysis (p = 0.044 model A; p = 0.031 model B).

CONCLUSIONS

The Munich consensus and BAMIC grading systems are useful tools for defining the patient's prognosis and proper rehabilitation time after injury. The MRI feature that we should carefully look for is the extension of edema, as it seems to significantly affect the RTP.

Can a Clinical Examination Demonstrate Intramuscular Tendon Involvement in Acute Hamstring Injuries?

Background:

Involvement of the intramuscular (central) tendon in acute hamstring injuries, as detected on magnetic resonance imaging (MRI), may prolong recovery times. To date, it is unclear whether hamstring injuries exhibiting intramuscular tendon involvement can be identified though routine clinical examinations that assess flexibility and strength.

Purpose:

To test whether MRI-detected intramuscular tendon involvement could be identified by a clinical assessment of muscle strength and flexibility.

Study Design:

Case-control study; Level of evidence, 3.

Methods:

Participants were drawn from a multicenter randomized controlled trial on the effect of platelet-rich plasma in acute hamstring injuries. Clinical parameters assessed within 5 days of injury were active knee extension and passive straight-leg raise for hamstring flexibility and isometric knee flexion force with 15° and 90° of knee flexion. Also, 1.5-T MRI of the thigh was performed within 5 days of injury and was evaluated for the presence of different types of intramuscular tendon involvement. One-way analysis of variance was used to determine whether clinical parameters could discriminate injuries with intramuscular tendon involvement from those without such involvement.

Results:

A total of 74 acute hamstring injuries were included, with 52 (70.3%) injuries affecting the myotendinous junction. Injuries exhibiting intramuscular tendon discontinuity on MRI had an increased mean absolute flexibility deficit for active knee extension (20.4° ± 14.9° vs 10.7° ± 9.0°, respectively; P = .006) and decreased mean strength at 15° (62.2 ± 26.7 N vs 76.6 ± 22.5 N, respectively; P = .05) compared with injuries without intramuscular tendon discontinuity. Flexibility and strength showed major overlap and variance among injuries with and without intramuscular tendon involvement.

Conclusion:

Hamstring flexibility and strength cannot be used to discriminate the presence of intramuscular tendon involvement.

M. biceps femoris - A wolf in sheep's clothing: The downside of a lower limb injury prevention training

Both, hamstring and ACL injuries are among the most typical injuries, particularly in change of direction and high speed running sports. They're also difficult to treat. Therefore, in the past few years, sports medicine practitioners and exercise scientists have mainly been focusing on the development and implementation of preventive programs in order to reduce the number of lower limb injuries, mainly by improving knee alignment. A number of studies have been able to prove the success of these training interventions, which are mainly addressing sensorimotor abilities and plyometric activities. The number of non-contact hamstring injuries has nevertheless been on the rise, particularly in sports like soccer and football. Therefore, the purpose of the following article is to introduce the hypothesis that the above-mentioned training interventions have a massive influence on the activation patterns on the targeted muscle group, and on the M. biceps femoris in particular. Muscle function and the resulting internal load are directly related to muscle architecture at the insertion. Training induced adaptations in hamstring activation patterns can thus lead to an increased injury susceptibility. In this case, a simulation model that directly relates to an acute deceleration maneuver provides valuable insights into the function of the biceps femoris muscle, especially when the rate of activity and the muscle geometry at the insertion area are taken into consideration. We conclude that there needs to be a greater individualization of prevention programs, especially in regards to anatomical requirements, in order to further reduce injury rates in elite sports. Moreover, it would also seem reasonable to apply a similar approach to aspects of chronic pain such as chronic non-specific low back pain.

Genetic biomarkers in non-contact muscle injuries in elite soccer players

PURPOSE

Damage to skeletal muscle necessitates regeneration to maintain proper muscle form and function. Interindividual differences in injury severity, recovery time, and injury rate could be explained by the presence of single nucleotide polymorphisms (SNPs) in genes involved in the reparation and regeneration of connective tissue . We wished to identify new genetic biomarkers that could help to prevent or minimize the risk of non-contact muscle injuries and are associated with a predisposition to developing muscle injuries.

METHODS

Using allelic discrimination techniques, we analysed 12 SNPs in selected genes from the genomic DNA of 74 elite soccer players.

RESULTS

SNPs in the hepatocyte growth factor (HGF) gene showed evidence of a statistically significant association with injury incidence, severity, and recovery time. SNPs in the SOX15 gene showed evidence of a statistically significant association with injury incidence. SNPs in the GEFT and LIF genes showed evidence of a statistically significant association with recovery time.

CONCLUSIONS

Genetic profile could explain why some elite soccer players are predisposed to suffer more injuries than others and why they need more time to recover from a particular injury. SNPs in HGF genes have an important role as biomarkers of biological processes fragility within muscle injuries related to injury rate, severity, and long recovery time.

Adding a post-training FIFA 11+ exercise program to the pre-training FIFA 11+ injury prevention program reduces injury rates among male amateur soccer players: a cluster-randomised trial

QUESTION

Does adding a post-training Fédération Internationale de Football Association (FIFA) 11+ exercise program to the pre-training FIFA 11+ injury prevention program reduce injury rates among male amateur soccer players?

DESIGN

Cluster-randomised, controlled trial with concealed allocation.

PARTICIPANTS

Twenty-one teams of male amateur soccer players aged 14 to 35 years were randomly assigned to the experimental group (n=10 teams, 160 players) or the control group (n=11 teams, 184 players).

INTERVENTION

Both groups performed pre-training FIFA 11+ exercises for 20minutes. The experimental group also performed post-training FIFA 11+ exercises for 10minutes.

OUTCOME MEASURES

The primary outcomes measures were incidence of overall injury, incidence of initial and recurrent injury, and injury severity. The secondary outcome measure was compliance to the experimental intervention (pre and post FIFA 11+ program) and the control intervention (pre FIFA 11+ program).

RESULTS

During one season, 26 injuries (team mean=0.081 injuries/1000 exposure hours, SD=0.064) were reported in the experimental group, and 82 injuries were reported in the control group (team mean=0.324 injuries/1000hours, SD=0.084). Generalised Estimating Equations were applied with an intention-to-treat analysis. The pre and post FIFA 11+ program reduced the total number of injuries (χ² (1)=11.549, p=0.001) and the incidence of initial injury (χ² (2)=8.987, p=0.003) significantly more than the pre FIFA 11+ program alone. However, the odds of suffering a recurrent injury were not different between the two groups (χ² (1)=2.350, p=0.125). Moreover, the severity level of injuries was not dependent upon whether or not the pre and post FIFA 11+ program was implemented (χ² (1)=0.016, p=0.898).

CONCLUSION

Implementation of the FIFA 11+ program pre-training and post-training reduced overall injury rates in male amateur soccer players more than the pre FIFA 11+ program alone.

TRIAL REGISTRATION

ACTRN12615001206516. [Al Attar WSA, Soomro N, Pappas E, Sinclair PJ, Sanders RH (2017) Adding a post-training FIFA 11+ exercise program to the pre-training FIFA 11+ injury prevention program reduces injury rates among male amateur soccer players: a cluster-randomised trial. Journal of Physiotherapy 63: 235-242].

Does the FIFA 11+ Injury Prevention Program Reduce the Incidence of ACL Injury in Male Soccer Players?

BACKGROUND

The FIFA 11+ injury prevention program has been shown to decrease the risk of soccer injuries in men and women. The program has also been shown to decrease time loss resulting from injury. However, previous studies have not specifically investigated how the program might impact the rate of anterior cruciate ligament (ACL) injury in male soccer players.

QUESTIONS/PURPOSES

The purpose of this study was to examine if the FIFA 11+ injury prevention program can (1) reduce the overall number of ACL injuries in men who play competitive college soccer and whether any potential reduction in rate of ACL injuries differed based on (2) game versus practice setting; (3) player position; (4) level of play (Division I or II); or (5) field type.

METHODS

This study was a prospective cluster randomized controlled trial, which was conducted in 61 Division I and Division II National Collegiate Athletic Association men's soccer teams over the course of one competitive soccer season. The FIFA 11+ is a 15- to 20-minute on-the-field dynamic warm-up program used before training and games and was utilized as the intervention throughout the entire competitive season. Sixty-five teams were randomized: 34 to the control group (850 players) and 31 to the intervention group (675 players). Four intervention teams did not complete the study and did not submit their data, noting insufficient time to complete the program, reducing the number for per-protocol analysis to 61. Compliance to the FIFA 11+ program, athletic exposures, specific injuries, ACL injuries, and time loss resulting from injury were collected and recorded using a secure Internet-based system. At the end of the season, the data in the injury surveillance system were crosshatched with each individual institution's internal database. At that time, the certified athletic trainer signed off on the injury collection data to confirm their accuracy and completeness.

RESULTS

A lower proportion of athletes in the intervention group experienced knee injuries (25% [34 of 136]) compared with the control group (75% [102 of 136]; relative risk [RR], 0.42; 95% confidence interval [CI], 0.29-0.61; p < 0.001). When the data were stratified for ACL injury, fewer ACL injuries were reported in the intervention group (16% [three of 19]) compared with the control group (84% [16 of 19]), accounting for a 4.25-fold reduction in the likelihood of incurring ACL injury (RR, 0.236; 95% CI, 0.193-0.93; number needed to treat = 70; p < 0.001). With the numbers available, there was no difference between the ACL injury rate within the FIFA 11+ group and the control group with respect to game and practice sessions (games-intervention: 1.055% [three of 15] versus control: 1.80% [12 of 15]; RR, 0.31; 95% CI, 0.09-1.11; p = 0.073 and practices-intervention: 0% [zero of four] versus control: 0.60% [four of four]; RR, 0.14; 95% CI, 0.01-2.59; p = 0.186). With the data that were available, there were no differences in incidence rate (IR) or injury by player position for forwards (IR control = 0.339 versus IR intervention = 0), midfielders (IR control = 0.54 versus IR intervention = 0.227), defenders (IR control = 0.339 versus IR intervention = 0.085), and goalkeepers (IR control = 0.0 versus IR intervention = 0.0) (p = 0.327). There were no differences in the number of ACL injuries for the Division I intervention group (0.70% [two of nine]) compared with the control group (1.05% [seven of nine]; RR, 0.30; CI, 0.06-1.45; p = 0.136). However, there were fewer ACL injuries incurred in the Division II intervention group (0.35% [one of 10]) compared with the control group (1.35% [nine of 10]; RR, 0.12; CI, 0.02-0.93; p = 0.042). There was no difference between the number of ACL injuries in the control group versus in the intervention group that occurred on grass versus turf (Wald chi square [1] = 0.473, b = 0.147, SE = 0.21, p = 0.492). However, there were more ACL injuries that occurred on artificial turf identified in the control group (1.35% [nine of 10]) versus the intervention group (0.35% [one of 10]; RR, 0.14; 95% CI, 0.02-1.10; p = 0.049).

CONCLUSIONS

This program, if implemented correctly, has the potential to decrease the rate of ACL injury in competitive soccer players. In addition, this may also enhance the development and dissemination of injury prevention protocols and may mitigate risk to athletes who utilize the program consistently. Further studies are necessary to analyze the cost-effectiveness of the program implementation and to analyze the efficacy of the FIFA 11+ in the female collegiate soccer cohort.

LEVEL OF EVIDENCE

Level I, therapeutic study.

Epidemiology of Hip Flexor and Hip Adductor Strains in National Collegiate Athletic Association Athletes, 2009/2010-2014/2015

BACKGROUND

Little research has examined the rates and patterns of hip flexor or hip adductor strains in student-athletes in the National Collegiate Athletic Association (NCAA).

PURPOSE

To describe the epidemiology of hip flexor and adductor strains in NCAA athletes during the 2009/2010-2014/2015 academic years.

STUDY DESIGN

Descriptive epidemiology study.

METHODS

Rates and patterns of hip flexor and adductor strains in collegiate sports were examined in a convenience sample of NCAA varsity teams from 25 sports. Rates and distributions of strains by mechanism, recurrence, and participation restriction time were examined. Injury rate ratios (IRRs) and proportion ratios were calculated to compare rates within and between sports by event type, sex, mechanism, recurrence, and participation restriction time.

RESULTS

A total of 770 hip flexor and 621 hip adductor strains were reported, resulting in overall injury rates of 1.60 and 1.29 per 10,000 athlete-exposures (AEs), respectively. In men, the rate of hip flexor strains was 1.81 per 10,000 AEs, and that for hip adductor strains was 1.71 per 10,000 AEs. In women, the rate of hip flexor strains was 1.59 per 10,000 AEs, and the rate of hip adductor strains was 1.15 per 10,000 AEs. The highest rates of strains were found in men's soccer and men's ice hockey (range, 2.47-3.77 per 10,000 AEs). Most hip flexor and hip adductor strains occurred in practice, but both had higher rates in competition. In sex-comparable sports, hip flexor strain rates did not differ between the sexes (IRR = 1.14; 95% CI, 0.96-1.36), but the rate of hip adductor strains was higher in men than women (IRR = 1.49; 95% CI, 1.22-1.81). Noncontact was the most common mechanism for both types of strains (hip flexor strains, 59.4%; hip adductor strains, 62.5%); 10.1% of hip flexor strains and 11.1% of hip adductor strains were recurrent. The highest rates of recurrence of both types of strain were found in men's and women's ice hockey (range, 16.0%-30.6%). Most hip flexor and hip adductor strains resulted in <1 week of participation restriction (hip flexor strains, 83.8%; hip adductor strains, 82.9%).

CONCLUSION

The NCAA sports with the highest rates of hip flexor and hip adductor strains were men's soccer and men's ice hockey. In sex-comparable sports, men had a higher rate of hip adductor, but not hip flexor, strains. Recurrence rates were remarkably high in ice hockey. Male sports teams, especially soccer and ice hockey, should place an emphasis on prevention programs for hip adductor strains. Secondary prevention programs involving thorough rehabilitation and strict return-to-play criteria should be developed and implemented to curb the high recurrence rate of these injuries, particularly in ice hockey.

Monitoring the effect of football match congestion on hamstring strength and lower limb flexibility: Potential for secondary injury prevention?

OBJECTIVES

To investigate the effect of competitive football match congestion on hamstring strength and lower limb flexibility.

DESIGN

Repeated measures.

SETTING

Elite male youth football.

PARTICIPANTS

Fifteen male elite youth football players from the national football association centre of excellence were included (age = 15.81 ±0.65 years, height = 171.95 ±6.89 cm, weight = 65.93 ±7.53 kg).

MAIN OUTCOME MEASURES

Hamstring strength and pain, ankle dorsiflexion, hip extension, knee extension and flexion range of motion.

RESULTS

Hamstring strength was highest at baseline and significantly reduced at 24 (p = 0.001, mean difference -0.19 Nm/Kg, CI₉₅ -0.28, -0.1) and 48 h post-match 1 (p = 0.002, mean difference -0.16 Nm/Kg, CI₉₅ -0.25, -0.07). Strength recovered by match day 2 before significantly reducing again 24 h post-match 2 (p = 0.012, mean difference -0.17 Nm/Kg, CI₉₅ -0.29, -0.04). Pain was lowest at baseline and increased in the post-match periods (p < 0.05) with standardised effect sizes ranging from 0.07 to 0.42. Passive knee flexion range decreased post-match (p < 0.01) with mean differences of 1.5°-2.7°. The other flexibility measures remained unaffected by match play.

CONCLUSION

Isometric hamstring strength and pain can be considered for inclusion in-season to monitor player's post-match hamstring recovery characteristics during congested match fixtures.

Practical nutritional recovery strategies for elite soccer players when limited time separates repeated matches

Specific guidelines that aim to facilitate the recovery of soccer players from the demands of training and a congested fixture schedule are lacking; especially in relation to evidence-based nutritional recommendations. The importance of repeated high level performance and injury avoidance while addressing the challenges of fixture scheduling, travel to away venues, and training commitments requires a strategic and practically feasible method of implementing specific nutritional strategies. Here we present evidence-based guidelines regarding nutritional recovery strategies within the context of soccer. An emphasis is placed on providing practically applicable guidelines for facilitation of recovery when multiple matches are played within a short period of time (i.e. 48 h). Following match-play, the restoration of liver and muscle glycogen stores (via consumption of ~1.2 g⋅kg⁻¹⋅h⁻¹ of carbohydrate) and augmentation of protein synthesis (via ~40 g of protein) should be prioritised in the first 20 min of recovery. Daily intakes of 6–10 g⋅kg⁻¹ body mass of carbohydrate are recommended when limited time separates repeated matches while daily protein intakes of >1.5 g⋅kg⁻¹ body mass should be targeted; possibly in the form of multiple smaller feedings (e.g., 6 × 20–40 g). At least 150% of the body mass lost during exercise should be consumed within 1 h and electrolytes added such that fluid losses are ameliorated. Strategic use of protein, leucine, creatine, polyphenols and omega-3 supplements could also offer practical means of enhancing post-match recovery.

Sport injuries treated at a physiotherapy center specialized in sports

Abstract Introduction: The risk of injuries related to physical activity and sports may increase if there is predisposition, inappropriate training and/or coach guidance, and absence of sports medicine follow-up. Objective: To assess the frequency of injuries in athletes treated at a physiotherapy center specialized in sports. Methods: For the data collection was carried out the survey of injuries in records of athletes treated in eight years of activities. The data collected included: characteristics of patients, sport, injury kind, injury characteristics and affected body part. Results: From 1090 patient/athlete records, the average age was 25 years old, the athletes were spread across 44 different sports modalities, being the great majority men (75%). The most common type of injury was joint injury, followed by muscular and bone injuries. Chronic injury was the most frequent (47%), while the most common body part injured was the knee, followed by ankle and shoulder. Among all the sports, soccer, futsal, and track and field presented the highest number of injured athletes, respectively. Conclusion: Soccer was the most common sport among the injured athletes, injury kind most frequent was joint injuries and knee was the body part most injured. Chronic injuries were the most common.

Rehabilitation and return to sport after hamstring strain injury

Hamstring strain injuries are common among sports that involve sprinting, kicking, and high-speed skilled movements or extensive muscle lengthening-type maneuvers with hip flexion and knee extension. These injuries present the challenge of significant recovery time and a lengthy period of increased susceptibility for recurrent injury. Nearly one third of hamstring strains recur within the first year following return to sport with subsequent injuries often being more severe than the original. This high re-injury rate suggests that athletes may be returning to sport prematurely due to inadequate return to sport criteria. In this review article, we describe the epidemiology, risk factors, differential diagnosis, and prognosis of an acute hamstring strain. Based on the current available evidence, we then propose a clinical guide for the rehabilitation of acute hamstring strains and an algorithm to assist clinicians in the decision-making process when assessing readiness of an athlete to return to sport.

Time for a paradigm shift in the classification of muscle injuries

Muscle injuries remain one of the most common injuries in sport, yet despite this, there is little consensus on how to either effectively describe or determine the prognosis of a specific muscle injury. Numerous approaches to muscle classification and grading of medicine have been applied over the last century, but over the last decade the limitations of historic approaches have been recognized. As a consequence, in the past 10 years, clinical research groups have begun to question the historic approaches and reconsider the way muscle injuries are classified and described. Using a narrative approach, this manuscript describes several of the most recent attempts to classify and grade muscle injuries and highlights the relative strengths and weaknesses of each system. While each of the new classification and grading systems have strengths, there remains little consensus on a system that is both comprehensive and evidence based. Few of the currently identified features within the grading systems have relevance to accurately determining prognosis.

The preventive effect of the bounding exercise programme on hamstring injuries in amateur soccer players: the design of a randomized controlled trial

Background

Hamstring injuries are the most common muscle injury in amateur and professional soccer. Most hamstring injuries occur in the late swing phase, when the hamstring undergoes a stretch-shortening cycle and the hamstring does a significant amount of eccentric work. The incidence of these injuries has not decreased despite there being effective injury prevention programmes focusing on improving eccentric hamstring strength. As this might be because of poor compliance, a more functional injury prevention exercise programme that focuses on the stretch-shortening cycle might facilitate compliance. In this study, a bounding exercise programme consisting of functional plyometric exercises is being evaluated.

Methods

A cluster-randomized controlled trial (RCT). Male amateur soccer teams (players aged 18–45 years) have been randomly allocated to intervention and control groups. Both groups are continuing regular soccer training and the intervention group is additionally performing a 12-week bounding exercise programme (BEP), consisting of a gradual build up and maintenance programme for the entire soccer season. The primary outcome is hamstring injury incidence. Secondary outcome is compliance with the BEP during the soccer season and 3 months thereafter.

Discussion

Despite effective hamstring injury prevention programmes, the incidence of these injuries remains high in soccer. As poor compliance with these programmes may be an issue, a new plyometric exercise programme may encourage long-term compliance and is expected to enhance sprinting and jumping performance besides preventing hamstring injuries.

Trial registration

NTR6129. Retrospectively registered on 1 November 2016.

Injuries in Australian Rules Football: An Overview of Injury Rates, Patterns, and Mechanisms Across All Levels of Play

CONTEXT

The nature of Australian rules football (Australian football) predisposes both unique and common injuries compared with those sustained in other football codes. The game involves a combination of tackling, kicking, high-speed running (more than other football codes), and jumping. Two decades of injury surveillance has identified common injuries at the professional level (Australian Football League [AFL]).

OBJECTIVE

To provide an overview of injuries in Australian rules football, including injury rates, patterns, and mechanisms across all levels of play.

STUDY DESIGN

A narrative review of AFL injuries, football injury epidemiology, and biomechanical and physiological attributes of relevant injuries.

RESULTS

The overall injury incidence in the 2015 season was 41.7 injuries per club per season, with a prevalence of 156.2 missed games per club per season. Lower limb injuries are most prevalent, with hamstring strains accounting for 19.1 missed games per club per season. Hamstring strains relate to the volume of high-speed running required in addition to at times having to collect the ball while running in a position of hip flexion and knee extension. Anterior cruciate ligament injuries are also prevalent and can result from contact and noncontact incidents. In the upper limb, shoulder sprains and dislocations account for 11.5 missed games per club per season and largely resulted from tackling and contact. Concussion is less common in AFL than other tackling sports but remains an important injury, which has notably become more prevalent in recent years, theorized to be due to a more conservative approach to management. Although there are less injury surveillance data for non-AFL players (women, community-level, children), many of these injuries appear to also be common across all levels of play.

CLINICAL RELEVANCE

An understanding of injury profiles and mechanisms in Australian football is crucial in identifying methods to reduce injury risk and prepare players for the demands of the game.

Reduced severity of lumbo-pelvic-hip injuries in professional Rugby Union players following tailored preventative programmes

OBJECTIVES

The aim of this study was to tailor lumbo-pelvic-hip (LPH) injury reduction programmes in professional rugby union players based on screening data and examine its effectiveness.

DESIGN

Prospective case controlled study.

METHODS

Twenty-eight professional rugby union players were screened pre- and immediately post- the YO-YO intermittent recovery level 1 test using six hip and groin strength tests (adductor squeeze at 0°, 60° and 90°, prone hip extension, abductor, adductor hand held dynamometry). The changes in hip and groin measures, were analysed using hierarchical cluster analysis. Three clusters emerged and a tailored LPH injury reduction programme was administered for each cluster. In addition, 22 players who were not involved in the initial testing received a generic LPH injury reduction programme and were used as the control. Seasonal information for LPH injury incidence, severity and prevalence were compared to the previous season.

RESULTS

The same number of injuries were observed when the prospective injury surveillance data was compared to the previous season, however a reduced injury severity (936days vs 468days), average severity (78±126days vs 42±37days) and prevalence (21% vs 19%) were found. Moreover, LPH injury severity for players who were prescribed a tailored injury reduction programme (209days) were 50days less than players given a generic LPH injury reduction programme (259days).

CONCLUSIONS

Our preliminary observations support the effectiveness of grouping players and tailoring intervention based on common group characteristics in reducing the severity of LPH injuries in professional Rugby Union.

Distal Musculotendinous T Junction Injuries of the Biceps Femoris: An MRI Case Review

Background:

Injury to the distal musculotendinous T junction (DMTJ) of the biceps femoris is a distinct clinical entity that behaves differently from other hamstring injuries due to its complex, multicomponent anatomy and dual innervation. Injury in this region demonstrates a particularly high rate of recurrence, even with prolonged rehabilitation times.

Purpose:

To describe the anatomy of the DMTJ of the biceps femoris and analyze the injury patterns seen on magnetic resonance imaging (MRI) to aid prognosis and rehabilitation and minimize the risk of recurrence.

Study Design:

Cross-sectional study; Level of evidence, 3.

Methods:

Acute injury to the DMTJ of the biceps femoris was identified in 106 MRI examinations from 55 patients at a single institution. Each injury was classified as involving the long head, the short head, or both components of the DMTJ, with each component individually graded. Injuries were classified as recurrent if there was a previous MRI demonstrating an acute injury to the DMTJ or if there was scarring present at the site of an acute injury.

Results:

Of the 106 acute injuries to the DMTJ of the biceps femoris, isolated injury to the long head component was the most common (51%), with both components involved in [round 42.5% to 43%] of cases. Isolated injury to the short head component accounted for 7% of cases. The recurrence rate for reinjury to the DMTJ was 54% in this series. The date of prior injury was known in 45 of 57 recurrent cases, with 34 of these reoccurring within 3 months (76%) and 40 reoccurring within 12 months (89%). The recurrent injury was of a higher grade than the prior injury in 22 of 44 instances (50%), the same grade in 16 instances (36%), and a lower grade in 6 instances (14%). Thus, 86% of recurrent injuries were of the same or higher grade than prior injury.

Conclusion:

These results suggest that high-risk muscle injuries, such as that to the DMTJ of the biceps femoris, should be evaluated using MRI to determine the structural components involved and to assess the extent and severity of injury.