Rehabilitation of hamstring muscle injuries: a literature review

Hamstring injuries are among the most frequent in sports. The high relapse rate is a challenge for sports medicine and has a great impact on athletes and sport teams. The treatment goal is to provide the athlete the same functional level as before the injury. Thus, functional rehabilitation is very important to the success of the treatment. Currently, several physical therapy modalities are used, according to the stage of the lesion, such as cryotherapy, laser therapy, therapeutic ultrasound, therapeutic exercise, and manual therapy. However, the evidence of the effectiveness of these modalities in muscle injuries is not fully established due to the little scientific research on the topic. This article presents an overview of the physiotherapy approach in the rehabilitation of hamstring muscle injuries.

Higher Drop in Speed during a Repeated Sprint Test in Soccer Players Reporting Former Hamstring Strain Injury

Aim: Hamstring strain injury is common in soccer. The aim of this study was to evaluate the physical capacity of players who have and have not suffered from hamstring strain injury in a sample of semi-professional and professional Norwegian soccer players in order to evaluate characteristics and to identify possible indications of insufficient rehabilitation. Method: Seventy-five semi-professional and professional soccer players (19 ± 3 years) playing at the second and third level in the Norwegian league participated in the study. All players answered a questionnaire, including one question about hamstring strain injury (yes/no) during the previous 2 years. They also performed a 40 m maximal sprint test, a repeated sprint test (8 × 20 m), a countermovement jump, a maximal oxygen consumption (VO_2max) test, strength tests and flexibility tests. Independent sample t-tests were used to evaluate differences in the physical capacity of the players who had suffered from hamstring strain injury and those who had not. Mixed between-within subject's analyses of variance was used to compare changes in speed during the repeated sprint test between groups. Results: Players who reported hamstring strain injury during the previous two years (16%) had a significantly higher drop in speed (0.07 vs. 0.02 s, p = 0.007) during the repeated sprint test, compared to players reporting no previous hamstring strain injury. In addition, there was a significant interaction (groups × time) (F = 3.22, p = 0.002), showing that speed in the two groups changed differently during the repeated sprint test. There were no significant differences in relations to age, weight, height, body fat, linear speed, countermovement jump height, leg strength, VO_2max, or hamstring flexibility between the groups. Conclusion: Soccer players who reported hamstring strain injury during the previous 2 years showed significant higher drop in speed during the repeated sprint test compared to players with no hamstring strain injury. The maximal speed, leg strength, ability to produce maximal power, endurance capacity, and hamstring flexibility was similar for both groups. Thus, a repeated sprint test consisting of 8 × 20 m could be used as a field-based diagnostic tool to identify players in need of reconditioning programs to ensure complete post-injury rehabilitation.

Prevention of Hamstring Injuries in Collegiate Sprinters

BACKGROUND

No studies have been reported on how strength, agility, and flexibility training reduce the occurrence of hamstring injuries in sprinters. Therefore, a program for preventing hamstring injury in these athletes has not been established.

PURPOSE

To document the incidence of hamstring injuries during times when different prevention strategies were employed to see whether a particular prevention program reduced their occurrence.

STUDY DESIGN

Descriptive epidemiology study.

METHODS

The study subjects were a total of 613 collegiate male sprinters trained by the same coach over 24 seasons. Tow training was used throughout the research period as a normal sprint training method. The hamstring injury prevention program evolved over time. From 1988 to 1991 (period 1), prevention focused on strength training alone; from 1992 to 1999 (period 2), a combination of strength and agility training was used; and from 2000 to 2011 (period 3), the program incorporated strength, agility, and flexibility training. The incidence of hamstring injuries was compared for each of the 3 prevention strategies.

RESULTS

The incidence of hamstring injuries per athlete-seasons was 137.9 for period 1, 60.6 for period 2, and 6.7 for period 3. A significant difference was observed in the incidence of hamstring injury according to the different prevention programs (χ²(2) = 31.78, P < .001, effect size: Cramer V = 0.23, 1 - β = 0.999). Residual analysis showed that the number of hamstring injuries for period 1 was significantly greater than the expected value (P < .01), whereas that for period 3 was significantly lower than the expected value (P < .01).

CONCLUSION

The incidence of hamstring injuries in sprinters decreased as agility and flexibility were added to strength training.

Running exposure is associated with the risk of hamstring strain injury in elite Australian footballers

Background

To investigate the association between running exposure and the risk of hamstring strain injury (HSI) in elite Australian footballers.

Methods

Elite Australian footballers (n=220) from 5 different teams participated. Global positioning system (GPS) data were provided for every athlete for each training session and match for the entire 2015 season. The occurrences of HSIs throughout the study period were reported. Receiver operator characteristic curve analyses were performed and the relative risk (RR) of subsequent HSI was calculated for absolute and relative running exposure variables related to distance covered above 10 and 24 km/hour in the preceding week/s.

Results

30 prospective HSIs occurred. For the absolute running exposure variables, weekly distance covered above 24 km/hour (>653 m, RR=3.4, 95% CI 1.6 to 7.2, sensitivity=0.52, specificity=0.76, area under the curve (AUC)=0.63) had the largest influence on the risk of HSI in the following week. For the relative running exposure variables, distance covered above 24 km/hour as a percentage of distance covered above 10 km/hour (>2.5%, RR=6.3, 95% CI 1.5 to 26.7, sensitivity=0.93, specificity=0.34, AUC=0.63) had the largest influence on the risk of HSI in the following week. Despite significant increases in the RR of HSI, the predictive capacity of these variables was limited.

Conclusions

An association exists between absolute and relative running exposure variables and elite Australian footballers' risk of subsequent HSI, with the association strongest when examining data within 7–14 days. Despite this, the use of running exposure variables displayed limited clinical utility to predict HSI at the individual level.

No Association Between Return to Play After Injury and Increased Rate of Anterior Cruciate Ligament Injury in Men's Professional Soccer

BACKGROUND

Studies have shown that previous injury, not necessarily anatomically related, is an important injury risk factor. However, it is not known whether a player runs an increased risk of anterior cruciate ligament (ACL) injury after returning to play from other injury types.

PURPOSE

To analyze whether professional soccer players are more susceptible to ACL injury after returning to play from any previous injury.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

A total of 101 elite male soccer players suffering a first-time complete ACL injury between 2001 and 2014 were included and matched according to team, age, and playing position with control players who did not have a current injury (1:1 match). For each injured player, the 90-day period prior to the ACL injury was analyzed for injuries and compared with that of control players by using odds ratios (ORs) and 95% CIs.

RESULTS

The odds of a player with an ACL injury sustaining a previous injury in the 90-day period did not differ significantly from that of controls (OR, 1.20; 95% CI, 0.66-2.17; P = .65). Testing the frequency of absence periods due to injury between the groups revealed that the odds of a player with an ACL injury having a previous period of absence due to injury did not differ compared with controls (OR, 1.14; 95% CI, 0.64-2.01; P = .77).

CONCLUSION

Players with ACL injury did not have a greater occurrence of absence due to injury in the 3 months preceding their ACL injury compared with matched controls. This indicates that previous injury of any type does not increase the risk of suffering an ACL injury.

Hamstring injuries in elite Gaelic football: an 8-year investigation to identify injury rates, time-loss patterns and players at increased risk

Background

Hamstring injuries occur frequently in field sports, yet longitudinal information to guide prevention programmes is missing.

Aim

Investigate longitudinal hamstring injury rates and associated time loss in elite Gaelic football, while identifying subgroups of players at increased risk.

Methods

38 data sets from 15 elite male Gaelic football teams were received by the National Gaelic Athletic Association (GAA) Injury Surveillance Database between 2008 and 2015. Injury and exposure data were provided by the team's medical staff via an online platform.

Results

391 hamstring injuries were sustained accounting for 21% (95% CI 20.0% to 21.7%) of all injuries. Prevalence was 21% (95% CI 19.2% to 23.4%). Incidences were 2.2 (95% CI 1.9 to 2.4) per 1000 exposure hours, and 7.0 (95% CI 6.5 to 7.1) times greater in match play than in training. Typically each team sustained 9.0 (95% CI 7.0 to 11.0) hamstring injuries per season affecting the: bicep femoris belly (44%; 95% CI 39.4% to 48.7%); proximal musculotendinous junction (13%; 95% CI 9.8% to 16.3%); distal musculotendinous junction (12%; 95% CI 8.6% to 14.9%) and semimembranosis/semitendinosis belly (9%; 95% CI 6.3% to 11.7%). ∼36% (95% CI 31.5% to 41.0%) were recurrent injuries. Mean time loss was 26.0 (95% CI 21.1 to 33.0) days, which varied with age, injury type and seasonal cycle. Hamstring injuries accounted for 31% (95% CI 25.8% to 38.2%) of injury-related time loss. Previously injured players (rate ratio (RR)=3.3), players aged 18–20 years (IRR=2.3) or >30 years (RR=2.3), as well as defensive (IRR=2.0) and midfield players (RR=1.5), were most at risk of sustaining a hamstring injury. Comparisons of 2008–2011 with 2012–2015 seasons revealed a 2-fold increase in hamstring injury incidences. Between 2008 and 2015 training incidence increased 2.3-fold and match-play incidences increased 1.3-fold.

Conclusions

Hamstring injuries are the most frequent injury in elite Gaelic football, with incidences increasing from 2008–2011 to 2012–2015. Tailoring risk management strategies to injury history, age and playing position may reduce the burden of hamstring injuries.

Muscle fiber type diversification during exercise and regeneration

The plasticity of skeletal muscle can be traced down to extensive metabolic, structural and molecular remodeling at the single fiber level. Skeletal muscle is comprised of different fiber types that are the basis of muscle plasticity in response to various functional demands. Resistance and endurance exercises are two external stimuli that differ in their duration and intensity of contraction and elicit markedly different responses in muscles adaptation. Further, eccentric contractions that are associated with exercise-induced injuries, elicit varied muscle adaptation and regenerative responses. Most adaptive changes are fiber type-specific and are highly influenced by diverse structural, metabolic and functional characteristics of individual fiber types. Regulation of signaling pathways by reactive oxygen species (ROS) and oxidative stress also plays an important role in muscle fiber adaptation during exercise. This review focuses on cellular and molecular responses that regulate the adaptation of skeletal muscle to exercise and exercise-related injuries.

Repeated bouts of fast eccentric contraction produce sciatic nerve damage in rats

INTRODUCTION

We evaluated sciatic nerve impairment after eccentric contractions (ECs) in rat triceps surae.

METHODS

Wistar rats were randomly assigned to different joint angular velocity: 180°/s (FAST), 30°/s (SLOW), or nontreated control (CNT). FAST and SLOW groups were subjected to multiple (1-4) bouts of 20 (5 reps, 4 sets) ECs. Nerve conduction velocity (NCV) and isometric tetanic ankle torque were measured 24 h after each ECs bout. We also assessed nerve morphology.

RESULTS

After 4 ECs bouts, NCVs and isometric torque in the FAST group were significantly lower than those in the CNT (NCV: 42%, torque: 66%; P < 0.05). After 4 bouts, average nerve diameter was significantly smaller in the FAST group [2.39 ± 0.20 μm vs. 2.69 ± 0.20 μm (CNT) and 2.93 ± 0.24 μm (SLOW); P < 0.05] than that in other two groups.

CONCLUSIONS

Chronic ECs with high angular velocity induce serious nerve damage. Muscle Nerve 54: 936-942, 2016.

Hamstring Architectural and Functional Adaptations Following Long vs. Short Muscle Length Eccentric Training

Most common preventive eccentric-based exercises, such as Nordic hamstring do not include any hip flexion. So, the elongation stress reached is lower than during the late swing phase of sprinting. The aim of this study was to assess the evolution of hamstring architectural (fascicle length and pennation angle) and functional (concentric and eccentric optimum angles and concentric and eccentric peak torques) parameters following a 3-week eccentric resistance program performed at long (LML) vs. short muscle length (SML). Both groups performed eight sessions of 3–5 × 8 slow maximal eccentric knee extensions on an isokinetic dynamometer: the SML group at 0° and the LML group at 80° of hip flexion. Architectural parameters were measured using ultrasound imaging and functional parameters using the isokinetic dynamometer. The fascicle length increased by 4.9% (p < 0.01, medium effect size) in the SML and by 9.3% (p < 0.001, large effect size) in the LML group. The pennation angle did not change (p = 0.83) in the SML and tended to decrease by 0.7° (p = 0.09, small effect size) in the LML group. The concentric optimum angle tended to decrease by 8.8° (p = 0.09, medium effect size) in the SML and by 17.3° (p < 0.01, large effect size) in the LML group. The eccentric optimum angle did not change (p = 0.19, small effect size) in the SML and tended to decrease by 10.7° (p = 0.06, medium effect size) in the LML group. The concentric peak torque did not change in the SML (p = 0.37) and the LML (p = 0.23) groups, whereas eccentric peak torque increased by 12.9% (p < 0.01, small effect size) and 17.9% (p < 0.001, small effect size) in the SML and the LML group, respectively. No group-by-time interaction was found for any parameters. A correlation was found between the training-induced change in fascicle length and the change in concentric optimum angle (r = −0.57, p < 0.01). These results suggest that performing eccentric exercises lead to several architectural and functional adaptations. However, further investigations are required to confirm the hypothesis that performing eccentric exercises at LML may lead to greater adaptations than a similar training performed at SML.

Hamstring and Quadriceps Isokinetic Strength Deficits Are Weak Risk Factors for Hamstring Strain Injuries: A 4-Year Cohort Study

BACKGROUND

A hamstring strain injury (HSI) has become the most common noncontact injury in soccer. Isokinetic muscle strength deficits are considered a risk factor for HSIs. However, underpowered studies with small sample sizes unable to determine small associations have led to inconclusive results regarding the role of isokinetic strength and strength testing in HSIs.

PURPOSE

To examine whether differences in isokinetic strength measures of knee flexion and extension represent risk factors for hamstring injuries in a large cohort of professional soccer players in an adequately powered study design.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

A total of 614 professional soccer players from 14 teams underwent isokinetic strength testing during preseason screening. Testing consisted of concentric knee flexion and extension at 60 deg/s and 300 deg/s and eccentric knee extension at 60 deg/s. A clustered multiple logistic regression analysis was used to identify variables associated with the risk of HSIs. Receiver operating characteristic (ROC) curves were calculated to determine sensitivity and specificity.

RESULTS

Of the 614 players, 190 suffered an HSI during the 4 seasons. Quadriceps concentric strength at 60 deg/s (odds ratio [OR], 1.41; 95% CI, 1.03-1.92; P = .03) and hamstring eccentric strength at 60 deg/s (OR, 1.37; 95% CI, 1.01-1.85; P = .04) adjusted for bodyweight were independently associated with the risk of injuries. The absolute differences between the injured and uninjured players were 6.9 N·m and 9.1 N·m, with small effect sizes (d < 0.2). The ROC analyses showed an area under the curve of 0.54 and 0.56 for quadriceps concentric strength and hamstring eccentric strength, respectively, indicating a failed combined sensitivity and specificity of the 2 strength variables identified in the logistic regression models.

CONCLUSION

This study identified small absolute strength differences and a wide overlap of the absolute strength measurements at the group level. The small associations between lower hamstring eccentric strength and lower quadriceps concentric strength with HSIs can only be considered as weak risk factors. The identification of these risk factors still does not allow the identification of individual players at risk. The use of isokinetic testing to determine the association between strength differences and HSIs is not supported.

Acute neuromuscular and performance responses to Nordic hamstring exercises completed before or after football training

The optimal scheduling of Nordic Hamstring exercises (NHEs) relative to football training sessions is unknown. We examined the acute neuromuscular and performance responses to NHE undertaken either before (BT) or after (AT) simulated football training. Twelve amateur players performed six sets of five repetitions of the NHE either before or after 60 min of standardised football-specific exercise (SAFT⁶⁰). Surface electromyography signals (EMG) of the hamstring muscles were recorded during both the NHE, and maximum eccentric actions of the knee flexors (0.52 rad · s^-1) performed before and after the NHE programme, and at 15 min intervals during SAFT⁶⁰. Ten-metre sprint times were recorded on three occasions during each 15 min SAFT⁶⁰ segment. Greater eccentric hamstring fatigue following the NHE programme was observed in BT versus AT (19.8 %; very likely small effect), which was particularly apparent in the latter range of knee flexion (0-15°; 39.6%; likely moderate effect), and synonymous with hamstring EMG declines (likely small-likely moderate effects). Performing NHE BT attenuated sprint performance declines (2.0-3.2%; likely small effects), but decreased eccentric hamstring peak torque (-14.1 to -18.9%; likely small effects) during football-specific exercise. Performing NHE prior to football training reduces eccentric hamstring strength and may exacerbate hamstring injury risk.

The Effectiveness of Injury Prevention Programs to Modify Risk Factors for Non-Contact Anterior Cruciate Ligament and Hamstring Injuries in Uninjured Team Sports Athletes: A Systematic Review

BACKGROUND

Hamstring strain and anterior cruciate ligament injuries are, respectively, the most prevalent and serious non-contact occurring injuries in team sports. Specific biomechanical and neuromuscular variables have been used to estimate the risk of incurring a non-contact injury in athletes.

OBJECTIVE

The aim of this study was to systematically review the evidences for the effectiveness of injury prevention protocols to modify biomechanical and neuromuscular anterior cruciate and/or hamstring injuries associated risk factors in uninjured team sport athletes.

DATA SOURCES

PubMed, Science Direct, Web of Science, Cochrane Libraries, U.S. National Institutes of Health clinicaltrials.gov, Sport Discuss and Google Scholar databases were searched for relevant journal articles published until March 2015. A manual review of relevant articles, authors, and journals, including bibliographies was performed from identified articles.

MAIN RESULTS

Nineteen studies were included in this review. Four assessment categories: i) landing, ii) side cutting, iii) stop-jump, and iv) muscle strength outcomes, were used to analyze the effectiveness of the preventive protocols. Eight studies using multifaceted interventions supported by video and/or technical feedback showed improvement in landing and/or stop-jump biomechanics, while no effects were observed on side-cutting maneuver. Additionally, multifaceted programs including hamstring eccentric exercises increased hamstring strength, hamstring to quadriceps functional ratio and/or promoted a shift of optimal knee flexion peak torque toward a more open angle position.

CONCLUSIONS

Multifaceted programs, supported by proper video and/or technical feedback, including eccentric hamstring exercises would positively modify the biomechanical and or neuromuscular anterior cruciate and/or hamstring injury risk factors.

Susceptibility to Hamstring Injuries in Soccer: A Prospective Study Using Muscle Functional Magnetic Resonance Imaging

BACKGROUND

Running-related hamstring strain injuries remain a delicate issue in several sports such as soccer. Their unremittingly high incidence and recurrence rates indicate that the underlying risk has not yet been fully identified. Among other factors, the importance of neuromuscular coordination and the quality of interplay between the different hamstring muscle bellies is thought to be a key determinant within the intrinsic injury risk. Muscle functional magnetic resonance imaging (mfMRI) is one of the tools that has been proven to be valid for evaluating intermuscular coordination.

PURPOSE

To investigate the risk of sustaining an index or recurring soccer-related hamstring injury by exploring metabolic muscle characteristics using mfMRI.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

A total of 27 healthy male soccer players and 27 soccer players with a history of hamstring injuries underwent standardized mfMRI. The mfMRI protocol consisted of a resting scan, a strenuous bilateral eccentric hamstring exercise, and a postexercise scan. The exercise-related T2 change, or the signal intensity shift between both scans, was used to detect differences in metabolic characteristics between (1) the different hamstring muscle bellies and (2) the prospective cohorts based on the (re)occurrence of hamstring injuries during a follow-up period of 18 months.

RESULTS

The risk of sustaining a first hamstring injury was associated with alterations in the intermuscular hierarchy in terms of the magnitude of the metabolic response after a heavy eccentric effort, with the dominant role of the semitendinosus set aside for a higher contribution of the biceps femoris (P = .017). Receiver operating characteristic (ROC) curve analysis demonstrated that this variable was significantly able to predict the occurrence of index injuries with a sensitivity of 100% and a specificity of 70% when the metabolic activity of the biceps femoris exceeded 10%. The risk of sustaining a reinjury was associated with a substantial deficit in hamstring strength endurance (P = .031). Soccer players who sustained a reinjury were only able to perform prone leg curls for a mean duration of 146.50 ± 76.16 seconds, whereas those with an injury history but no recurrence during follow-up were able to continue for a mean of 237.45 ± 110.76 seconds (95% CI, 11.9-230.5 seconds; P = .031).

CONCLUSION

This was the first study to assess the causal relation between the intramuscular recruitment pattern and the risk of sustaining an index or secondary hamstring strain. Changes in intermuscular interplay seem to significantly increase the risk of sustaining index hamstring injuries in male amateur soccer players. Inadequate eccentric muscle endurance could be associated with an increased risk of sustaining a recurring hamstring injury.

Strength and Conditioning Practices of University and High School Level Cricket Coaches: A South African Context

Pote, L and Christie, CJ. Strength and conditioning practices of University and high school level cricket coaches: a South African context. J Strength Cond Res 30(12): 3464-3470, 2016-Although the sport of cricket is well established, the strength and conditioning practices of cricket players are not well known. Therefore, the purpose of this study was to examine the current strength and conditioning practices that coaches implement for South African schoolboy and University level cricket players. An online survey, adapted from previous strength and conditioning questionnaires, was sent to 38 schoolboy and 12 University teams that participated in the top competitions in the country (n = 50). Of these, 24 replied indicating a response rate of 48%. Results indicated that although some forms of conditioning, workload monitoring and injury prevention were being implemented, the correct practices were not being administered. Furthermore, it was identified that most coaches had insufficient qualifications and experience to administer the correct training techniques. It was concluded that coaches require further education so that scientifically based training programs can be implemented. This was deemed particularly necessary for adolescent bowlers who are at an increased risk of injury, specifically in the lower back region.

In Vivo Reconstruction of Lumbar Erector Spinae Architecture Using Diffusion Tensor MRI

STUDY DESIGN

Diffusion tensor magnetic resonance imaging (DT-MRI) reconstruction of lumbar erector spinae (ES) compared with cadaver dissection.

OBJECTIVE

The aim of this study was to reconstruct the human lumbar ES from in vivo DT-MRI measurements and to compare the results with literature and cadaver dissection.

SUMMARY OF BACKGROUND DATA

DT-MRI enables 3-dimensional in vivo reconstruction of muscle architecture. Insight in ES architecture may improve the understanding of low back function. Furthermore, DT-MRI reconstructions allow individualized biomechanical modeling, which may serve as a clinical tool in injury evaluation and in improvement of understanding of pathologies like scoliosis.

MATERIALS AND METHODS

The lumbar spine of 1 healthy male volunteer was scanned using a 3.0 T clinical MRI scanner. MRI data acquisition consisted of 3 parts: (1) high-resolution T1-weighted turbo spin echo for anatomical reference; (2) DT-MRI measurements for fiber tractography; (3) dual echo gradient echo sequence for signal correction purposes. After processing, DT-MRI data were exported to a custom-built software program for fiber tractography. The resulting reconstructions were anatomically validated by comparison with cadaver dissection and literature.

RESULTS

DT-MRI reconstruction of 4 parts of the lumbar ES (thoracic part of iliocostalis lumborum, lumbar part of iliocostalis lumborum, thoracic part of longissimus thoracis, and lumbar part of longissimus thoracis) adequately reflected its complex geometry. Some inaccuracies were found in reconstruction details. DT-MRI reconstructions were generally in agreement with anatomical descriptions from literature and with findings in a dissected cadaver specimen.

CONCLUSIONS

DT-MRI enables anatomically valid reconstruction of ES architecture. However, for reliable reconstruction of the smallest fascicles and attachments a higher resolution or application of higher-order models is needed. Reconstructions can be used as input for estimation of muscle architecture parameters in individualized biomechanical modeling. Such models are promising as a tool in clinical evaluation and in research of low back pain mechanisms.

The Epidemiology of Injuries in Australian Professional Rugby Union 2014 Super Rugby Competition

Background:

Rugby union is a collision-based ball sport played at the professional level internationally. Rugby union has one of the highest reported incidences of injury of all team sports.

Purpose:

To identify the characteristics, incidence, and severity of injuries occurring in Australian professional Super Rugby Union.

Design:

Descriptive epidemiology study.

Methods:

The present study was a prospective epidemiology study on a cohort of 180 professional players from 5 Australian Super Rugby teams during the 2014 Super Rugby Union Tournament. Team medical staff collected and submitted daily training and match-play injury data through a secure, web-based electronic platform. The injury data included the main anatomic location of the injury, specific anatomic structure of the injury, injury diagnosis, training or match injury occurrence, main player position, mechanism of injury, and the severity of the injury quantified based on the number of days lost from training and/or competition due to injury.

Results:

The total combined incidence rate for injury during training and match-play across all Australian Super Rugby Union teams was 6.96 per 1000 hours, with a mean injury severity of 37.45 days lost from training and competition. The match-play injury incidence rate was 66.07 per 1000 hours, with a mean severity of 39.80 days lost from training and competition. No significant differences were observed between forward- and back-playing positions for match or training injury incidence rate or severity.

Conclusion:

The incidence of injury for the present study was lower during match-play than has previously been reported in professional rugby union; however, the overall time loss was higher compared with previous studies in professional rugby union. The high overall time loss was due fundamentally to a high incidence of injuries with greater than 28 days’ severity.

Injury Scheme Claims in Gaelic Games: A Review of 2007-2014

CONTEXT

Gaelic games (Gaelic football and hurling) are indigenous Irish sports with increasing global participation in recent years. Limited information is available on longitudinal injury trends. Reviews of insurance claims can reveal the economic burden of injury and guide cost-effective injury-prevention programs.

OBJECTIVE

To review Gaelic games injury claims from 2007-2014 for male players to identify the costs and frequencies of claims. Particular attention was devoted to lower limb injuries due to findings from previous epidemiologic investigations of Gaelic games.

DESIGN

Descriptive epidemiology study.

SETTING

Open-access Gaelic Athletic Association Annual Reports from 2007-2014 were reviewed to obtain annual injury-claim data.

PATIENTS OR OTHER PARTICIPANTS

Gaelic Athletic Association players.

MAIN OUTCOME MEASURE(S)

Player age (youth or adult) and relationships between lower limb injury-claim rates and claim values, Gaelic football claims, hurling claims, youth claims, and adult claims.

RESULTS

Between 2007 and 2014, €64 733 597.00 was allocated to 58 038 claims. Registered teams had annual claim frequencies of 0.36 with average claim values of €1158.4 ± 192.81. Between 2007 and 2014, average adult claims were always greater than youth claims (6217.88 versus 1036.88), while Gaelic football claims were always greater than hurling claims (5395.38 versus 1859.38). Lower limb injuries represented 60% of all claims. The number of lower limb injury claims was significantly correlated with annual injury-claim expenses (r = 0.85, P = .01) and adult claims (r = 0.96, P = .01) but not with youth claims (r = 0.69, P = .06).

CONCLUSIONS

Reducing lower limb injuries will likely reduce injury-claim expenses. Effective injury interventions have been validated in soccer, but whether such changes can be replicated in Gaelic games remains to be investigated. Injury-claim data should be integrated into current elite injury-surveillance databases to monitor the cost effectiveness of current programs.

Clinical Practice Patterns and Beliefs in the Management of Hamstrings Strain Injuries

CONTEXT

Hamstrings strain injuries (HSIs) are among the most commonly occurring injuries in sport and are top causes of missed playing time. Lingering symptoms, prolonged recovery, and a high reinjury rate (12%-34%) make HSI management a frustrating and challenging process for the athletic trainer (AT). The clinical practice patterns and opinions of ATs regarding HSI treatment and rehabilitation are unknown.

OBJECTIVE

To examine the frequency of method use and opinions about current HSI management among ATs.

DESIGN

Cross-sectional study.

SETTING

Survey administered to registrants at the 2013 National Athletic Trainers' Association Clinical Symposia and AT Expo.

PATIENTS OR OTHER PARTICIPANTS

A total of 1356 certified ATs (691 men, 665 women; age = 35.4 ± 10.5 years, time certified = 11.92 ± 9.75 years).

DATA COLLECTION AND ANALYSIS

A survey was distributed electronically to 7272 registrants and on paper to another 700 attendees. Validity and reliability were established before distribution. Participants reported demographic information and rated their frequency of treatment and rehabilitation method use and agreement with questions assessing confidence, satisfaction, and desire for better clinical practice guidelines. Exploratory factor analysis and principal axis factor analysis were used. We also calculated descriptive statistics and χ(2) tests to assess practice patterns.

RESULTS

The response rate was 17% (n = 1356). A 2-factor solution was accepted for factor analysis (r = 0.76, r = 0.70), indicating that ATs follow either a contemporary or traditional management style. Various practice patterns were evident across employment settings and years of clinical experience. Satisfaction with the current HSI management plan was high (73.6%), whereas confidence in returning an athlete to play was lower (62.0%). Rates of use were associated with belief in effectiveness for all methods assessed (P < .001). Higher confidence levels were associated with high use of several methods; we observed increased satisfaction (χ(2)2 = 22.5, P = .002) but not increased confidence levels in more experienced ATs.

CONCLUSIONS

Our study demonstrated the lack of consensus in HSI treatment and rehabilitation and the ATs' desire for better clinical practice guidelines. Future research in which multimodal strategies, including both traditional and contemporary methods, are studied is warranted for effective management of HSI.

Injury prediction in veteran football players using the Functional Movement Screen™

The Functional Movement Screen™ (FMS™) is aimed at assessing fundamental movements and is often used to identify players' injury risk. The purpose of this study was to determine whether the FMS™ can be used to predict injuries in veteran footballers (aged > 32 years). Eighteen veteran football teams (n = 238) were recruited and prospectively followed for 9 months. The players (44 ± 7 years; 178 ± 7 cm, 84 ± 11 kg) performed the FMS™ at the start of the study period. Players' exposure hours and injuries were recorded. The difference of FMS™ overall score between injured and uninjured players was not significant (11.7 ± 2.9 vs 12.2 ± 2.8 points; Mann-Whitney U-test P = 0.17). Players scoring <10 (score < 1 standard deviation [SD]) below the mean) had a significantly higher injury incidence (z-statistics P < 0.05) compared to an intermediate reference group (mean ± 1 SD; scores of 10-14). No lower injury incidence for players with scores of >14 (score > 1 SD above the mean) was found. Further analyses of potential risk factors suggest higher age, lower body mass and a longer football career to be risk factors for injuries. The findings of this study suggest that the suitability of the FMS™ for injury prediction in veteran footballers is limited.

Comparisons of eccentric knee flexor strength and asymmetries across elite, sub-elite and school level cricket players

Background. There has been a continual increase in injury rates in cricket, with hamstring strain injuries (HSIs) being the most prominent. Eccentric knee flexor weakness and bilateral asymmetries are major modifiable risk factors for future HSIs. However, there is a lack of data relating to eccentric hamstring strength in cricket at any skill level. The objective of this study was to compare eccentric knee flexor strength and bilateral asymmetries in elite, sub-elite and school level cricket players; and to determine if playing position and limb role influenced these eccentric knee flexor strength indices. Methods. Seventy four male cricket players of three distinct skill levels performed three repetitions of the Nordic hamstring exercise on the experimental device. Strength was assessed as the absolute and relative mean peak force output for both limbs, with bilateral asymmetries. Differences in mean peak force outputs between skill level and playing positions were measured. Results. There were no significant differences between elite, sub-elite and school level athletes for mean peak force and bilateral asymmetries of the knee flexors. There were no significant differences observed between bowler's and batter's mean peak force and bilateral asymmetries. There were no significant differences between front and back limb mean peak force outputs. Discussion. Skill level, playing position and limb role appeared to have no significant effect on eccentric knee flexor strength and bilateral asymmetries. Future research should seek to determine whether eccentric knee flexor strength thresholds are predictive of HSIs in cricket and if specific eccentric knee flexor strengthening can reduce these injuries.

Predicting Musculoskeletal Injury in National Collegiate Athletic Association Division II Athletes From Asymmetries and Individual-Test Versus Composite Functional Movement Screen Scores

CONTEXT

Functional Movement Screen (FMS) scores of ≤14 have been used to predict injury in athletic populations. Movement asymmetries and poor-quality movement patterns in other functional tests have been shown to predict musculoskeletal injury (MSI). Therefore, movement asymmetry or poor-quality movement patterns on the FMS may have more utility in predicting MSI than the composite score.

OBJECTIVE

To determine if an asymmetry or score of 1 on an individual FMS test would predict MSI in collegiate athletes.

DESIGN

Cohort study.

SETTING

National Collegiate Athletic Association Division II university athletic program.

PATIENTS OR OTHER PARTICIPANTS

A total of 84 Division II rowers, volleyball players, and soccer players (men: n = 20, age = 20.4 ± 1.3 years, height = 1.77 ± 0.04 m, mass = 73.5 ± 4.8 kg; women: n = 64, age = 19.1 ± 1.2 years, height = 1.69 ± 0.09 m, mass = 64.8 ± 9.4 kg).

MAIN OUTCOME MEASURE(S)

The FMS was administered during preseason preparticipation examinations. Injury-incidence data were tracked for an academic year by each team's certified athletic trainer via computer software. An MSI was defined as physical damage to the body secondary to athletic activity or an event for which the athlete sought medical care, and resulted in modified training or required protective splitting or taping. Composite FMS scores were categorized as low (≤14) or high (>14). Pearson χ(2) analyses were used to determine if MSI could be predicted by the composite FMS score or an asymmetry or score of 1 on an individual FMS test (P < .05).

RESULTS

Athletes with FMS scores of ≤14 were not more likely to sustain an injury than those with higher scores (relative risk = 0.68, 95% confidence interval = 0.39, 1.19; P = .15). However, athletes with an asymmetry or individual score of 1 were 2.73 times more likely to sustain an injury than those without (relative risk = 2.73, 95% confidence interval = 1.36, 5.4; P = .001).

CONCLUSIONS

Asymmetry or a low FMS individual test score was a better predictor of MSI than the composite FMS score.

Effectiveness Analysis of Active Stretching Versus Active Stretching Plus Low-Frequency Electrical Stimulation in Children Who Play Soccer and Who Have the Short Hamstring Syndrome

OBJECTIVE

To determine the effectiveness of active stretching (AS) versus AS plus electrical stimulation (stretching + TENS) in young soccer players with the short hamstring syndrome (SHS).

DESIGN

Randomized, controlled, single-blind parallel clinical trial with 3 arms and a 2-month follow-up. The assignment ratio was 1:1:1.

SETTING

The study involved young federated soccer players in the town of Jumilla, in the region of Murcia (Spain), who were controlled in a physiotherapy office in 2012.

PARTICIPANTS

Fifty-one young soccer players (10-16 years) with SHS.

INTERVENTIONS

Stretching + TENS, AS, and conventional stretching.

MAIN OUTCOME MEASURES

Straight leg raise (SLR) test, popliteal angle with the passive knee extension (PKE) test, and the toe-touch test (TT).

RESULTS

Significant results (P < 0.05) were group 1 versus 2: (1) SLR, -5.5 degrees right; (2) PKE, +10.2 degrees right and +6.2 degrees left; and (3) range of values of clinically relevant parameters (RVCRP): relative risk (RR), 0.35 to 0.38; relative risk reduction (RRR), 0.62 to 0.65; absolute risk reduction (ARR), 0.32 to 0.39; number needed to treat (NNT), 3 to 4. Group 1 versus 3: (1) SLR, -12.3 degrees right and -10 degrees left; (2) PKE, +12.9 degrees right and +8.5 degrees left; (3) TT, -8.9 cm; and (4) RVCRP: RR, 0.12 to 0.28; RRR, 0.72 to 0.88; ARR, 0.60 to 0.83; NNT, 2 to 2. Group 2 versus 3: (1) SLR, -6.8 degrees right and -6.2 degrees left; (2) TT, -6.7 cm; (3) RVCRP: RR, 0.44 to 0.53; RRR, 0.47 to 0.56; ARR, 0.40 to 0.56; NNT, 2 to 3.

CONCLUSIONS

Stretching + TENS produces greater improvement than AS alone, and these are both better than conventional stretching.

CLINICAL RELEVANCE

The use of electrical stimulation combined with AS is a relevant technique for habitual clinical practice that should be systematically integrated in children aged 10 to 16 years who play soccer and who have the SHS.

Short biceps femoris fascicles and eccentric knee flexor weakness increase the risk of hamstring injury in elite football (soccer): a prospective cohort study

BACKGROUND/AIM

To investigate the role of eccentric knee flexor strength, between-limb imbalance and biceps femoris long head (BFlh) fascicle length on the risk of future hamstring strain injury (HSI).

METHODS

Elite soccer players (n=152) from eight different teams participated. Eccentric knee flexor strength during the Nordic hamstring exercise and BFlh fascicle length were assessed at the beginning of preseason. The occurrences of HSIs following this were recorded by the team medical staff. Relative risk (RR) was determined for univariate data, and logistic regression was employed for multivariate data.

RESULTS

Twenty seven new HSIs were reported. Eccentric knee flexor strength below 337 N (RR=4.4; 95% CI 1.1 to 17.5) and possessing BFlh fascicles shorter than 10.56 cm (RR=4.1; 95% CI 1.9 to 8.7) significantly increased the risk of a HSI. Multivariate logistic regression revealed significant effects when combinations of age, history of HSI, eccentric knee flexor strength and BFlh fascicle length were explored. From these analyses the likelihood of a future HSI in older athletes or those with a HSI history was reduced if high levels of eccentric knee flexor strength and longer BFlh fascicles were present.

CONCLUSIONS

The presence of short BFlh fascicles and low levels of eccentric knee flexor strength in elite soccer players increases the risk of future HSI. The greater risk of a future HSI in older players or those with a previous HSI is reduced when they have longer BFlh fascicles and high levels of eccentric strength.

Hamstring Muscle Injuries, a Rehabilitation Protocol Purpose

Context:

Hamstring acute muscle injuries are prevalent in several sports including AFL football (Australian Football League), sprinting and soccer, and are often associated with prolonged time away from sport.

Evidence Acquisition:

In response to this, research into prevention and management of hamstring injury has increased, but epidemiological data shows no decline in injury and re-injury rates, suggesting that rehabilitation programs and return to play (RTP) criteria have to be improved. There continues to be a lack of consensus regarding how to assess performance, recovery and readiness to RTP, following hamstring strain injury.

Results:

The aim of this paper was to propose rehabilitation protocol for hamstring muscle injuries based on current basic science and research knowledge regarding injury demographics and management options.

Conclusions:

Criteria-based (subjective and objective) progression through the rehabilitation program will be outlined along with exercises for each phase, from initial injury to RTP.

Medial and lateral hamstrings and quadriceps co-activation affects knee joint kinematics and ACL elongation: a pilot study

Background

Many injury prevention and rehabilitation programs aim to train hamstring and quadriceps co-activation to constrain excessive anterior tibial translation and protect the anterior cruciate ligament (ACL) from injury. However, despite strong clinical belief in its efficacy, primary evidence supporting training co-activation of the hamstrings and quadriceps muscles for ACL injury prevention and rehabilitation is quite limited. Therefore, the purpose of the study presented in this paper was to determine if hamstring-quadriceps co-activation alters knee joint kinematics, and also establish if it affects ACL elongation.

Methods

A computed tomography (CT) scan from each participant’s dominant leg was acquired prior to performing two step-ups under fluoroscopy: one with ‘natural’ hamstring-quadriceps co-activation, one with deliberate co-activation. Electromyography was used to confirm increased motor unit recruitment. The CT scan was registered to fluoroscopy for 4-D modeling, and knee joint kinematics subsequently measured. Anterior cruciate ligament attachments were mapped to the 4-D models and its length was assumed from the distance between attachments. Anterior cruciate ligament elongation was derived from the change in distance between those points as they moved relative to each other.

Results

Reduced ACL elongation as well as knee joint rotation, abduction, translation, and distraction was observed for the step up with increased co-activation. A relationship was shown to exist for change in ACL length with knee abduction (r = 0.91; p ≤ 0.001), with distraction (r = −0.70; p = 0.02 for relationship with compression), and with anterior tibial translation (r = 0.52; p = 0.01). However, ACL elongation was not associated with internal rotation or medial translation. Medial hamstring-quadriceps co-activation was associated with a shorter ACL (r = −0.71; p = 0.01), and lateral hamstring-quadriceps co-activation was related to ACL elongation (r = 0.46; p = 0.05).

Conclusion

Net co-activation of the hamstrings and quadriceps muscles will likely reduce ACL elongation provided that the proportion of medial hamstring-quadriceps co-activation exceeds lateral.

Epidemiology of Hamstring Strains in 25 NCAA Sports in the 2009-2010 to 2013-2014 Academic Years

BACKGROUND

The epidemiology of hamstring strains among student-athletes has been extensively researched. However, there is a paucity of recent data describing patterns of hamstring strains.

PURPOSE

To describe the epidemiology of hamstring strains in 25 National Collegiate Athletic Association (NCAA) championship sports.

STUDY DESIGN

Descriptive epidemiology study.

METHODS

Hamstring strains data were analyzed from the NCAA Injury Surveillance Program during the 2009-2010 to 2013-2014 academic years. Hamstring strain injury rates, rate ratios (RRs), and injury proportion ratios were reported with 95% CIs.

RESULTS

During the study period, 1142 hamstring strains were reported, leading to an injury rate of 3.05 per 10,000 athlete-exposures (AEs). Most hamstring strains occurred during practices (68.2%). However, the competition rate (5.24 per 10,000 AEs) was larger than the practice rate (2.56 per 10,000 AEs; RR = 2.05; 95% CI, 1.81-2.32). A slight majority occurred during the regular season (52.9%). However, the preseason rate (5.00 per 10,000 AEs) was larger than the regular season/postseason rate (2.34 per 10,000 AEs; RR = 2.14; 95% CI, 1.90-2.40). Men's football, men's soccer, and women's soccer contributed the greatest proportion of hamstring strains (35.3%, 9.9%, and 8.3%, respectively). Most hamstring strains were due to noncontact (72.3%). Of all hamstring strains, 12.6% were recurrent, 37.7% resulted in a time loss of <24 hours, and 6.3% resulted in a time loss >3 weeks. Variations in hamstring strain patterns existed by sport. The hamstring strain rate was larger in men than in women in soccer (RR = 1.60; 95% CI, 1.22-2.11), baseball/softball (RR = 1.66; 95% CI, 1.07-2.59), and indoor track (RR = 1.88; 95% CI, 1.26-2.78). In addition, proportions of hamstring strains that were recurrent were higher among men in most sex-comparable sports, but this difference was not significant.

CONCLUSION

Hamstring strain rates were higher in the preseason and in competition. Student-athletes should be acclimatized to the rigors of preseason participation. Meanwhile, further surveillance should investigate the effectiveness of prospective prevention programs in an effort to reduce the prevalence of initial and recurrent hamstring strain injuries.

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

BACKGROUND

Hamstring strain injuries (HSIs) represent the most common cause of lost playing time in rugby union. Eccentric knee flexor weakness and between-limb imbalance in eccentric knee flexor strength are associated with a heightened risk of HSIs in other sports; however, these variables have not been explored in rugby union.

PURPOSE

To determine if lower levels of eccentric knee flexor strength or greater between-limb imbalance in this parameter during the Nordic hamstring exercise are risk factors for HSIs in rugby union.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

This prospective study was conducted over the 2014 Super Rugby and Queensland Rugby Union seasons. In total, 178 rugby union players (mean age, 22.6 ± 3.8 years; mean height, 185.0 ± 6.8 cm; mean weight, 96.5 ± 13.1 kg) had their eccentric knee flexor strength assessed using a custom-made device during the preseason. Reports of previous hamstring, quadriceps, groin, calf, and anterior cruciate ligament injuries were also obtained. The main outcome measure was the prospective occurrence of HSIs.

RESULTS

Twenty players suffered at least 1 HSI during the study period. Players with a history of HSIs had a 4.1-fold (95% CI, 1.9-8.9; P = .001) greater risk of subsequent HSIs than players without such a history. Between-limb imbalance in eccentric knee flexor strength of ≥15% and ≥20% increased the risk of HSIs by 2.4-fold (95% CI, 1.1-5.5; P = .033) and 3.4-fold (95% CI, 1.5-7.6; P = .003), respectively. Lower eccentric knee flexor strength and other prior injuries were not associated with an increased risk of future HSIs. Multivariate logistic regression revealed that the risk of reinjuries was augmented in players with strength imbalances.

CONCLUSION

Previous HSIs and between-limb imbalance in eccentric knee flexor strength were associated with an increased risk of future HSIs in rugby union. These results support the rationale for reducing imbalance, particularly in players who have suffered a prior HSI, to mitigate the risk of future injuries.

Influence of the MCT1 rs1049434 on Indirect Muscle Disorders/Injuries in Elite Football Players

Background

The aim of this study was to investigate the association between MCT1 rs1049434 polymorphism and indirect muscle injuries in elite football players. One hundred and seventy-three male elite Italian football players (age = 19.2 ± 5.3 years) were recruited from a first-league football club participating at the Official National Italian Football Championship (Serie A, Primavera, Allievi, Giovanissimi). The cohort was genotyped for the MCT1 rs1049434 polymorphism, and muscle injuries data were collected during the period of 2009–2014 (five football seasons).

Methods

Genomic DNA was extracted using a buccal swab, and genotyping was performed using PCR method. Structural-mechanical injuries and functional muscle disorder were included in the acute indirect muscle injury group.

Results

Participants with the MCT1 AA (AA = 1.57 ± 3.07, n = 69) genotype exhibit significantly higher injury incidents compared to participants with the TT genotype (TT = 0.09 ± 0.25, n = 22, P = 0.04).

Conclusions

The MCT1 rs1049434 polymorphism is associated with the incidence of muscle injuries in elite football players. We anticipate that the knowledge of athletes’ genetic predisposition to sports-related injuries might aid in individualizing training programs.

Elastography Study of Hamstring Behaviors during Passive Stretching

INTRODUCTION

The mechanical properties of hamstring muscles are usually inferred from global passive torque/angle relationships, in combination with adjoining tissues crossing the joint investigated. Shear modulus measurement provides an estimate of changes in muscle-tendon stiffness and passive tension. This study aimed to assess the passive individual behavior of each hamstring muscle in different stretching positions using shear wave elastography.

METHODS/RESULTS

The muscle shear modulus of each hamstring muscle was measured during a standardized slow passive knee extension (PKE, 80% of maximal range of motion) on eighteen healthy male volunteers. Firstly, we assessed the reliability of the measurements. Results were good for semitendinosus (ST, CV: 8.9%-13.4%), semimembranosus (SM, CV: 10.3%-11.2%) and biceps femoris long-head (BF-lh, CV: 8.6%-13.3%), but not for biceps femoris short-head (BF-sh, CV: 20.3%-44.9%). Secondly, we investigated each reliable muscle in three stretch positions: 70°, 90° and 110° of hip flexion. The results showed different values of shear modulus for the same amount of perceived stretch, with the highest measurements in the high-flexed hip situation. Moreover, individual muscles displayed different values, with values increasing or BF-lh, SM and ST, respectively. The inter-subject variability was 35.3% for ST, 27.4% for SM and 30.2% for BF-lh.

CONCLUSION

This study showed that the hip needs to be high-flexed to efficiently tension the hamstrings, and reports a higher muscle-tendon stress tolerance at 110° of hip angle. In addition muscles have different passive behaviors, and future works will clarify if it can be linked with rate of injury.

EXTRACORPOREAL SHOCKWAVE TERAPY TO TREAT CHRONIC MUSCLE INJURY

Objective: To evaluate the low energy extracorporeal shock waves therapy (ESWT) associated with physical therapy in the treatment of chronic muscle injuries classified as grades 2 and 3 in the lower limbs of amateur athletes. Methods: Eight athletes presenting with lower limb muscle injury for more than three weeks were treated with physiotherapy and ESWT. We evaluated the following parameters during treatment: palpable gap, muscle strength, pain, and Tegner score, as well as ultrasound image features and the ability to return to sports practice. Results: The average time of the first evaluation of the injury was 8.75 weeks. All patients presented muscle strength grade V after eight weeks. The pain score evolved from 5.75 to 0.5 points of the visual analogue scale (VAS), at the end of the treatment. The Tegner score after treatment was six points on average. Patients returned to sports practice after 8.14 weeks. Conclusion: ESWT associated with physical therapy proved to be effective to treat long-term muscle injury, with good performance and the ability to return to sport practice for all patients. Level of Evidence IV, Case Series, Prospective Study.

Effects of two different injury prevention resistance exercise protocols on the hamstring torque-angle relationship: a randomized controlled trial

The effects of two different 6-week lower body injury prevention programmes on knee muscle torque-angle relationship were examined in soccer players. Thirty-two men were randomly assigned to three groups: hamstring-eccentric (ECC) (n = 11), unstable-squatting (UNS) (n = 11), and control (n = 10). Intervention groups performed three training sessions per week using only three ECC or UNS exercises, respectively. Maximal peak knee flexion torque was measured at 35°, 45°, 60°, 80°, 90°, and 100°, pre- and post-intervention. Peak torque increased at 35° (P = 0.034, Cohen's d = 0.67) and 45° (P = 0.004, Cohen's d = 0.96) in the ECC group, and at 60° (P = 0.024, Cohen's d = 1.16), 80° (P = 0.018, Cohen's d = 1.21), and 90° (P = 0.001, Cohen's d = 1.38) in the UNS group. As these specific modifications might respectively and differentially protect athletes against hamstring and knee-joint injuries, the integration of both types of exercises should be considered when designing injury prevention programmes for soccer players.

Muscle injury: current perspectives and trends in Brazil

Objective

To evaluate the management, procedures and perspectives of sports physicians and orthopedists in Brazil with regard to diagnosing and treating muscle injuries.

Methods

A questionnaire containing 20 questions relating to the topic of muscle injury was applied to sports physicians and orthopedists during the Second Brazilian Congress of Arthroscopy and Sports Traumatology, in 2013.

Results

Completely answered questionnaires were received from 168 sports physicians and orthopedists. Doctors from all regions of Brazil with a mean of 11 years of experience of treating muscle injuries were interviewed. Lower limbs were affected in 97% of the cases, particularly the quadriceps, adductor and sural triceps. The injury occurred during the eccentric phase in 62% of the interviews; 39% underwent ultrasound examination and 37% magnetic resonance imaging (MRI) for the injury to be diagnosed. Medication, rest and cryotherapy during the acute phase (87.5%) and medication, rest and physiotherapy during treatment of the injury (56%) were the prevalent options. The criteria for returning to sports were very subjective and disparate among the options presented, and most of the interviewees had already used some therapy that was adjuvant to traditional methods.

Conclusion

The number of muscle injuries treated per year was greater than 30, independent of whether in the public or private sector. These injuries occurred mainly at the muscle–tendon junction, in the lower limbs and during the eccentric phase of muscle contraction. Ultrasound was the examination most performed, while MRI was considered ideal. For most of the interviewees, the preferred treatment involved rest, medication and physiotherapy. In addition, 52% believed that platelet-rich plasma was an efficient treatment and 42% said that they had already used it.

Biceps femoris and semitendinosus--teammates or competitors? New insights into hamstring injury mechanisms in male football players: a muscle functional MRI study

BACKGROUND

The hamstring injury mechanism was assessed by investigating the exercise-related metabolic activity characteristics of the hamstring muscles using a muscle functional MRI (mfMRI) protocol.

METHODS

27 healthy male football players and 27 football players with a history of hamstring injuries (recovered and playing fully) underwent standardised mfMR Imaging. The mfMRI protocol consisted of a resting scan, a strenuous bilateral eccentric hamstring exercise and a postexercise scan. The exercise-related T2 increase or the signal intensity shift between both scans was used to detect differences in metabolic activation characteristics (1) between the different hamstring muscle bellies and (2) between the injury group and the control group.

RESULTS

A more symmetrical muscle recruitment pattern corresponding to a less economic hamstring muscle activation was demonstrated in the formerly injured group (p<0.05). The injured group also demonstrated a significantly lower strength endurance capacity during the eccentric hamstring exercise.

CONCLUSIONS

These findings suggest that the vulnerability of the hamstring muscles to football-related injury is related to the complexity and close coherence in the synergistic muscle recruitment of the biceps femoris and the semitendinosus. Discrete differences in neuromuscular coordination and activity distribution, with the biceps femoris partly having to compensate for the lack of endurance capacity of the semitendinosus, probably increase the hamstring injury risk.