Epidemiology of muscle injuries in professional football (soccer)

Diagnosis and prognosis of acute hamstring injuries in athletes

PURPOSE

Identification of the most relevant diagnostic and prognostic factors of physical examination and imaging of hamstring injuries in (elite) athletes.

METHODS

A literature search was conducted in MEDLINE and EMBASE for articles between 1950 and April 2011. A survey was distributed among the members of the European Society of Sports Traumatology, Knee Surgery and Arthroscopy, which focused on physical examination, prognosis, imaging and laboratory tests of hamstring injuries in (elite) athletes.

RESULTS

Medical history, inspection and palpation of the muscle bellies and imaging are most valuable at the initial assessment according to the literature. Experts considered medical history, posture and gait inspection, inspection and palpation of muscle bellies, range of motion tests, manual muscle testing, referred pain tests and imaging to be most important in the initial assessment of hamstring injuries. Magnetic resonance imaging (MRI) is preferred over ultrasonography and should take place within 3 days post-trauma. Important prognostic factors are injury grade, length of the muscle tear on MR images, MRI-negative injuries and trauma mechanism.

CONCLUSIONS

Posture and gait inspection, inspection and palpation of muscle bellies, range of motion tests, manual muscle testing and referred pain tests within 2 days post-trauma were identified as the most relevant diagnostic factors.

LEVEL OF EVIDENCE

Literature review and expert opinion, Level V.

Risk factors for lower extremity muscle injury in professional soccer: the UEFA Injury Study

BACKGROUND

Muscle injury is the most common injury type in professional soccer players. Despite this, risk factors for common lower extremity injuries remain elusive.

PURPOSE

To evaluate the effects of various player- and match-related risk factors on the occurrence of lower extremity muscle injury in male professional soccer.

STUDY DESIGN

Cohort study; level of evidence, 2.

METHODS

Between 2001 and 2010, 26 soccer clubs (1401 players) from 10 European countries participated in the study. Individual player exposure and time loss muscle injuries in the lower extremity were registered prospectively by the club medical staffs during 9 consecutive seasons. Hazard ratios (HRs) were calculated for player-related factors from simple and multiple Cox regression, and odds ratios (ORs) were calculated for match-related variables from simple and multiple logistic regression, presented with 95% confidence intervals (CIs).

RESULTS

There were 2123 muscle injuries documented in the major lower extremity muscle groups: adductors (n = 523), hamstrings (n = 900), quadriceps (n = 394), and calf (n = 306). Injuries to the adductors (56%; P = .015) and quadriceps (63%; P< .001) were more frequent in the kicking leg. Multiple analysis indicated that having a previous identical injury in the preceding season increased injury rates significantly for adductor (HR, 1.40; 95% CI, 1.00-1.96), hamstring (HR, 1.40; 95% CI, 1.12-1.75), quadriceps (HR, 3.10; 95% CI, 2.21-4.36), and calf injuries (HR, 2.33; 95% CI, 1.52-3.57). Older players (above mean age) had an almost 2-fold increased rate of calf injury (HR, 1.93; 95% CI, 1.38-2.71), but no association was found in other muscle groups. Goalkeepers had reduced injury rates in all 4 muscle groups. Match play on away ground was associated with reduced rates of adductor (OR, 0.56; 95% CI, 0.43-0.73) and hamstring injuries (OR, 0.76; 95% CI, 0.63-0.92). Quadriceps injuries were more frequent during preseason, whereas adductor, hamstring, and calf injury rates increased during the competitive season.

CONCLUSION

Intrinsic factors found to increase muscle injury rates in professional soccer were previous injury, older age, and kicking leg. Injury rates varied during different parts of the season and also depending on match location.

Localized bioimpedance to assess muscle injury

Injuries to lower limb muscles are common among football players. Localized bioimpedance analysis (BIA) utilizes electrical measurements to assess soft tissue hydration and cell membrane integrity non-invasively. This study reports the effects of the severity of muscle injury and recovery on BIA variables. We made serial tetra-polar, phase-sensitive 50 kHz localized BIA measurements of quadriceps, hamstring and calf muscles of three male football players before and after injury and during recovery until return-to-play, to determine changes in BIA variables (resistance (R), reactance (Xc) and phase angle (PA)) in different degrees of muscle injury. Compared to non-injury values, R, Xc and PA decreased with increasing muscle injury severity: grade III (23.1%, 45.1% and 27.6%), grade II (20.6%, 31.6% and 13.3%) and grade I (11.9%, 23.5% and 12.1%). These findings indicate that decreases in R reflect localized fluid accumulation, and reductions in Xc and PA highlight disruption of cellular membrane integrity and injury. Localized BIA measurements of muscle groups enable the practical detection of soft tissue injury and its severity.

Recurrent hamstring muscle injury: applying the limited evidence in the professional football setting with a seven-point programme

Recurrent hamstring injuries are a major problem in sports such as football. The aim of this paper was to use a clinical example to describe a treatment strategy for the management of recurrent hamstring injuries and examine the evidence for each intervention. A professional footballer sustained five hamstring injuries in a relatively short period of time. The injury was managed successfully with a seven-point programme—biomechanical assessment and correction, neurodynamics, core stability, eccentric strengthening, an overload running programme, injection therapies and stretching/relaxation. The evidence for each of these treatment options is reviewed. It is impossible to be definite about which aspects of the programme contributed to a successful outcome. Only limited evidence is available in most cases; therefore, decisions regarding the use of different treatment modalities must be made by using a combination of clinical experience and research evidence.

Video analysis of situations with a high-risk for injury in Norwegian male professional football; a comparison between 2000 and 2010

BACKGROUND

A recent study from Norwegian male professional football found that the risk of acute match injuries increased from 2002 to 2007.

OBJECTIVE

To compare the incidence of incidents with a propensity for injury, from the 2000 season to the 2010 season in Norwegian male professional football using video analysis.

METHODS

We conducted a video analysis of incidents in Norwegian professional football. An incident was recorded if the match was interrupted by the referee, and the player lay down for more than 15 s, and appeared to be in pain or received medical treatment. We also conducted a video analysis of all player-to-player contact situations occurring during 30 randomly selected matches.

RESULTS

A total of 1287 incidents were identified during the two seasons. The corresponding rate of incidents was 74.4 (95% CI 67.3 to 81.5) in the 2000 season and 109.6 (95% CI 102.3 to 116.9) in the 2010 season, a significant increase from 2000 to 2010 (rate ratio 1.47, 95% CI 1.31 to 1.66). We observed a significantly higher rate of opponent-to-player contact and non-contact incidents in the 2010 season, but no change in the proportion of fouls or sanctions awarded by the referee. The rate of player-to-player contact situations in both heading and tackling duels was lower during the 2010 season.

CONCLUSIONS

We found an increased rate of non-contact and opponent-to-player contact incidents in both heading and tackling duels in the 2010 season compared with 10 years earlier, even if there was no increase in the frequency of player-to-player contact situations.

Terminology and classification of muscle injuries in sport: the Munich consensus statement

Objective

To provide a clear terminology and classification of muscle injuries in order to facilitate effective communication among medical practitioners and development of systematic treatment strategies.

Methods

Thirty native English-speaking scientists and team doctors of national and first division professional sports teams were asked to complete a questionnaire on muscle injuries to evaluate the currently used terminology of athletic muscle injury. In addition, a consensus meeting of international sports medicine experts was established to develop practical and scientific definitions of muscle injuries as well as a new and comprehensive classification system.

Results

The response rate of the survey was 63%. The responses confirmed the marked variability in the use of the terminology relating to muscle injury, with the most obvious inconsistencies for the term strain. In the consensus meeting, practical and systematic terms were defined and established. In addition, a new comprehensive classification system was developed, which differentiates between four types: functional muscle disorders (type 1: overexertion-related and type 2: neuromuscular muscle disorders) describing disorders without macroscopic evidence of fibre tear and structural muscle injuries (type 3: partial tears and type 4: (sub)total tears/tendinous avulsions) with macroscopic evidence of fibre tear, that is, structural damage. Subclassifications are presented for each type.

Conclusions

A consistent English terminology as well as a comprehensive classification system for athletic muscle injuries which is proven in the daily practice are presented. This will help to improve clarity of communication for diagnostic and therapeutic purposes and can serve as the basis for future comparative studies to address the continued lack of systematic information on muscle injuries in the literature.

What are the new things

Consensus definitions of the terminology which is used in the field of muscle injuries as well as a new comprehensive classification system which clearly defines types of athletic muscle injuries.

Level of evidence

Expert opinion, Level V.

Effectiveness of an injury prevention programme for adult male amateur soccer players: a cluster-randomised controlled trial

Background

The incidence rate of soccer injuries is among the highest in sports, particularly for adult male soccer players.

Purpose

To investigate the effect of the ‘The11’ injury prevention programme on injury incidence and injury severity in adult male amateur soccer players.

Study design

Cluster-randomised controlled trial.

Methods

Teams from two high-level amateur soccer competitions were randomly assigned to an intervention (n=11 teams, 223 players) or control group (n=12 teams, 233 players). The intervention group was instructed to perform The11 in each practice session during one soccer season. The11 focuses on core stability, eccentric training of thigh muscles, proprioceptive training, dynamic stabilisation and plyometrics with straight leg alignment. All participants of the control group continued their practice sessions as usual.

Results

In total, 427 injuries were recorded, affecting 274 of 456 players (60.1%). Compliance with the intervention programme was good (team compliance=73%, player compliance=71%). Contrary to the hypothesis, injury incidences were almost equal between the two study groups: 9.6 per 1000 sports hours (8.4–11.0) for the intervention group and 9.7 (8.5–11.1) for the control group. No significant differences were found in injury severity, but a significant difference was observed in the location of the injuries: players in the intervention group sustained significantly less knee injuries.

Conclusions

This study did not find significant differences in the overall injury incidence or injury severity between the intervention and control group of adult male soccer players. More research is recommended, focusing on injury aetiology and risk factors in adult male amateur soccer players.

Intrinsic risk factors of noncontact ankle sprains in soccer: a prospective study on 100 professional players

BACKGROUND

Ankle sprain is an extremely common injury in soccer players. Despite extensive research, the intrinsic cause of this injury under noncontact conditions remains unclear.

PURPOSE

To identify intrinsic risk factors for noncontact ankle sprains in professional soccer players.

STUDY DESIGN

Cohort study; Level of evidence, 2

METHODS

One hundred professional soccer players were assessed in the preseason for potential risk factors of noncontact ankle sprains. The assessment included (A) ankle joint asymmetries (right-left) in isokinetic muscle strength, flexibility, proprioception, and stability; (B) somatometric asymmetries; (C) previous injuries; and (D) lateral dominance traits. Noncontact ankle sprains were prospectively recorded and diagnosed for a full competition period (10 months).

RESULTS

Seventeen of the players sustained at least 1 noncontact ankle sprain. Logistic regression revealed that players with (A) eccentric isokinetic ankle flexion strength asymmetries (odds ratio [OR] = 8.88; 95% confidence interval [CI], 1.95-40.36, P = .005), (B) increased body mass index (OR = 8.16; 95% CI, 1.42-46.63, P = .018), and (C) increased body weight (OR = 5.72; 95% CI, 1.37-23.95, P = .017 ) each had a significantly higher risk of a noncontact ankle sprain. A trend for younger players (OR = 0.28; 95% CI, 0.061-1.24, P = .092) and for players with ankle laxity asymmetries (OR = 3.38; 95% CI, 0.82-14.00, P = .093) to be at greater risk for ankle sprain was also apparent to the limit of statistical significance (.05 < P < .10).

CONCLUSION

Functional strength asymmetries of the ankle flexors and increased body mass index and body weight raise the propensity for ankle sprains in professional soccer players. Age and asymmetries in ankle laxity are potential factors worth revisiting, as there was an indication for younger players and players with ankle instability to be at higher risk for ankle injury. Proper preseason evaluation may improve prevention strategies for this type of injury in soccer.

Mechanics of the human hamstring muscles during sprinting

PURPOSE

An understanding of hamstring mechanics during sprinting is important for elucidating why these muscles are so vulnerable to acute strain-type injury. The purpose of this study was twofold: first, to quantify the biomechanical load (specifically, musculotendon strain, velocity, force, power, and work) experienced by the hamstrings across a full stride cycle; and second, to determine how these parameters differ for each hamstring muscle (i.e., semimembranosus (SM), semitendinosus (ST), biceps femoris long head (BF), biceps femoris short head (BF)).

METHODS

Full-body kinematics and ground reaction force data were recorded simultaneously from seven subjects while sprinting on an indoor running track. Experimental data were integrated with a three-dimensional musculoskeletal computer model comprised of 12 body segments and 92 musculotendon structures. The model was used in conjunction with an optimization algorithm to calculate musculotendon strain, velocity, force, power, and work for the hamstrings.

RESULTS

SM, ST, and BF all reached peak strain, produced peak force, and formed much negative work (energy absorption) during terminal swing. The biomechanical load differed for each hamstring muscle: BF exhibited the largest peak strain, ST displayed the greatest lengthening velocity, and SM produced the highest peak force, absorbed and generated the most power, and performed the largest amount of positive and negative work.

CONCLUSIONS

As peak musculotendon force and strain for BF, ST, and SM occurred around the same time during terminal swing, it is suggested that this period in the stride cycle may be when the biarticular hamstrings are at greatest injury risk. On this basis, hamstring injury prevention or rehabilitation programs should preferentially target strengthening exercises that involve eccentric contractions performed with high loads at longer musculotendon lengths.

Eccentric strengthening effect of hip-adductor training with elastic bands in soccer players: a randomised controlled trial

BACKGROUND

Soccer players with weak hip-adductor muscles are at increased risk of sustaining groin injuries. Therefore, a simple hip-adductor strengthening programme for prevention of groin injuries is needed.

OBJECTIVE

We aimed to investigate the effect of an 8-week hip-adductor strengthening programme, including one hip-adduction exercise, on eccentric and isometric hip-adduction strength, using elastic bands as external load.

METHODS

Thirty-four healthy, sub-elite soccer players, mean (±SD) age of 22.1 (±3.3) years, were randomised to either training or control. During the mid-season break, the training group performed 8 weeks of supervised, progressive hip-adduction strength training using elastic bands. The participants performed two training sessions per week (weeks 1-2) with 3×15 repetition maximum loading (RM), three training sessions per week (weeks 3-6) with 3×10 RM and three training sessions per week (weeks 7-8) with 3×8 RM. Eccentric hip-adduction (EHAD), isometric hip-adduction (IHAD) and isometric hip-abduction (IHAB) strength, and the IHAD/IHAB ratio were measured assessor-blinded preintervention and postintervention, using reliable hand-held dynamometry procedures.

RESULTS

In the training group, EHAD strength increased by 30% (p<0.001). In the control group, EHAD strength increased by 17% (p<0.001), but the increase was significantly larger in the training group compared with the control group (p=0.044). No other significant between-group strength-differences in IHAD, IHAB or the IHAD/IHAB ratio existed (p>0.05).

CONCLUSIONS

8 weeks of hip-adduction strength training, using elastic bands, induce a relevant increase in eccentric hip-adduction strength in soccer players, and thus may have implications as a promising approach towards prevention of groin injuries in soccer.

Risk factors for hamstring injuries in male soccer players: a systematic review of prospective studies

Hamstring injuries are common injuries in soccer players. In view of the high incidence and the serious consequences, identifying risk factors related to hamstring injuries is essential. The aim of this systematic review was therefore to identify risk factors for hamstring injuries in male adult soccer players. PubMed, Embase/Medline, Cumulative Index to Nursing and Allied Health Literature, and SPORTDiscus were systematically searched, and prospective studies investigating risk factors for hamstring injuries in adult male soccer players were included. The methodological quality of the included articles was assessed using a standardized set of predefined criteria. Seven of the 11 studies identified, involving a total of 1775 players and 344 hamstring injuries, met the inclusion criteria. All but one of the included studies met at least five of nine methodological criteria, causing them to be qualified as 'high quality'. The included studies used univariate as well as multivariate analyses to identify risk factors for hamstring injury. The results from the multivariate analyses suggest that previous hamstring injury is most strongly related to hamstring injury. Conflicting evidence is found for age and hamstring length or flexibility as risk factors for the occurrence of hamstring injuries.

The epidemiology of severe and catastrophic injuries in BASE jumping

OBJECTIVE

To report the demographic characteristics, injury rate, severity, and morbidity in BASE jumping.

DESIGN

Cross-sectional survey.

SETTING

BASE jumping group meetings from 2006 to 2010.

PARTICIPANTS

Heterogenic group of 102 International BASE jumpers.

ASSESSMENT OF RISK FACTORS

Injuries reported as function of jumps made, jumping days, age, experience, and sex.

MAIN OUTCOME MEASURES

Incidence, severity, and type of injuries.

RESULTS

Responses from 68 subjects were available for analysis. The median number of jumps was estimated at 286 per respondent. The median time respondents had participated in BASE jumping was 5.8 years. There were 39 reported severe injuries sustained by 29 different jumpers. Nineteen thousand four hundred ninety-seven jumps were reported, resulting in 2 severe injuries per 1000 jumps (0.2% severe injury rate) or 2.6 severe injuries per 1000 jumping days. Forty-nine respondents (72%) had witnessed the death or serious injury of other participants in the sport. Twenty-four accidents (61%) involved the lower limbs, 8 (20%) the back/spine, 7 (18%) the chest wall, and 5 (13%) were a head injury. The mean Abbreviated Injury Score was 3.2 (range, 2-5). Fifteen (52%) of the 29 injured jumpers required 20 acute surgical interventions, which were mostly orthopedic related. There was a significant correlation between number of jumps made and injuries sustained (P < 0.05).

CONCLUSIONS

BASE jumpers have an average of 1 severe injury for every 500 jumps. Most active BASE jumpers have witnessed death or severe injury of a participant and have experienced a "close call" incident.

Determination of future prevention strategies in elite track and field: analysis of Daegu 2011 IAAF Championships injuries and illnesses surveillance

Objective

To determine the incidence and characteristics of newly incurred injuries and illnesses during international Athletics Championships, by improving the medical surveillance coverage, in order to determine future prevention strategies.

Design

Prospective recording of newly occurred injuries and illnesses.

Setting

13th International Association of Athletics Federations World Championships in Athletics 2011 in Daegu, Korea.

Participants

National team and Local Organising Committee physicians; and 1851 registered athletes.

Main outcome measures

Incidence and characteristics of newly incurred injuries and illnesses.

Results

82% of athletes were covered by medical teams participating with a response rate of 94%. A total of 249 injuries were reported, representing an incidence of 134.5 injuries per 1000 registered athletes, and 119 (48%) resulted in time loss from sport. A total of 185 injuries affected the lower limb (74%). Hamstring strain was the main diagnosis and 67% resulted in absence from sport. Overuse (n=148; 59%) was the predominant cause. A total of 126 illnesses were reported, signifying an incidence of 68.1 per 1000 registered athletes. Upper respiratory tract infection was the most common reported diagnosis (18%), followed by exercise-induced dehydration (12%), and gastroenteritis/diarrhoea (10%). The highest incidences of injuries were found in combined events and middle and long-distance events, and of illness in race walking events.

Conclusion

During elite Athletics World Championships, 135 injuries, 60 time-loss injuries and 68 illnesses per 1000 registered athletes were reported. Higher risks of injuries were found in combined events and long-distance runs. Preventive interventions should focus on overuse injuries and hamstring strains, decreasing the risk of transmission of infectious diseases, appropriate event scheduling and heat acclimatisation.

The effect of hypermobility on the incidence of injuries in elite-level professional soccer players: a cohort study

BACKGROUND

A recent meta-analysis found that generalized joint hypermobility is a risk factor for knee injuries during contact sports. The effect of hypermobility on the incidence of injuries in elite-level professional soccer players is not known.

PURPOSE

To compare the incidence of injury between hypermobile and nonhypermobile elite-level male professional soccer players.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

Fifty-four players from an English Premier League soccer club were assessed for hypermobility, using the 9-point Beighton scale (threshold, 4 points or above), at the start of the 2009-2010 season. Time-loss injuries and individual exposure times were recorded during all club training sessions and matches throughout the entire season.

RESULTS

Mean ± standard deviation incidence of injuries was 11.52 ± 11.39 injuries/1000 h, and the prevalence of hypermobility was 33.3% (18 of 54 players). There were 133 injuries during 13 897.5 hours of exposure. During the season, hypermobile participants had a higher incidence of injuries (mean [95% confidence interval] difference, 15.65 [9.18-22.13] injuries/1000 h; P = .001) and were more likely to experience at least 1 injury, a reinjury, and a severe injury compared with nonhypermobile participants. There were 9 severe knee injuries in hypermobile participants, of which 6 were cartilage injuries.

CONCLUSION

There was an increased incidence of injury in hypermobile elite-level professional soccer players from an English Premier League club, resulting in more missed days from training and match play. These findings suggest a need for routine screening for hypermobility in professional soccer.

Surgical treatment of proximal ruptures of the rectus femoris in professional soccer players

INTRODUCTION

Muscle injuries are very common in athletes. Depending on the type of sport, muscle injuries represent approximately 9-54% of total injuries. The rectus femoris muscle is very important in specific sports, such as soccer and American football, because it is the muscle involved in movements, such as sprinting and kicking the ball. Therefore, we believe that these disabling injuries need special and prompt treatment to enable athletes to return to their sporting activities.

AIM

The aim of our study is to assess the results of surgical treatment of ruptures of the rectus femoris in professional soccer players by reattachment of the tendon. We identified ten proximal rectus femoris ruptures in professional soccer players belonging to the Spanish Football League.

RESULTS

Mean follow-up was 34.8 months (SD + 28.72). The mean age of the players was 27.4 years (SD + 4.14). In six cases (60%), the tendon was repaired by direct suture with non-absorbable sutures. In four cases, where there had been complete avulsion, bone anchoring sutures were used. There is no consensus regarding the optimal treatment for ruptures of the rectus femoris muscle. There are a few reports in the literature based on isolated experiences of different surgeons.

CONCLUSION

Surgical treatment has a lower recurrence rate in our hands; we believe that surgical treatment is indicated in these cases, for a complete functional recovery for professional soccer players.

The prevalence of radiographic hip abnormalities in elite soccer players

BACKGROUND

Hip injuries, both intra- and extra-articular, are becoming a more commonly recognized, diagnosed, and treated injury in athletes of all competitive levels. Our goal is to establish a previously undefined value in this athletic population--the prevalence of radiographic hip abnormalities in elite soccer athletes.

PURPOSE

To provide a foundation for the future body of literature regarding hip pathologic abnormalities and "at-risk" hips in athletes of all ages and levels of participation.

STUDY DESIGN

Descriptive epidemiology study.

METHODS

We retrospectively reviewed the anteroposterior pelvis and frog-leg lateral radiographs of 95 elite male and female soccer players to determine the prevalence of hip abnormalities. Athletes with a history of hip or groin injuries were included. Multiple radiographic parameters were used to assess the presence of cam and pincer-type femoroacetabular impingement. Measurements were conducted by a blinded, sports medicine fellowship-trained orthopaedic surgeon with experience in treating hip disorders.

RESULTS

In total, 72% (54/75) of male and 50% (10/20) of female players demonstrated some evidence of radiographic hip abnormality. Cam lesions were present in 68% (51/75) of men (76.5% [39/51] bilateral involvement) and 50% (10/20) of women (90% [9/10] bilateral involvement). Pincer lesions were present in 26.7% (20/75) of men and 10% (2/20) of women. The average male alpha angle overall was 65.6°. Cam-positive hips averaged 70.7°. The average female alpha angle overall was 52.9°, with cam-positive hips averaging 60.8°.

CONCLUSION

The prevalence of radiographic hip abnormalities in elite soccer athletes is considerable, particularly in young male athletes. The establishment of the prevalence of these findings represents the first step in identifying the relationship between radiographic abnormalities and injuries of the hip and groin in athletes.

Eccentric hamstring muscle training can prevent hamstring injuries in soccer players

QUESTION

Does eccentric muscle training of hamstring muscles reduce the rate of hamstring injuries in male soccer players?

DESIGN

Cluster randomised, controlled trial with concealed allocation.

SETTING

The 5 top men's soccer divisions in Denmark.

PARTICIPANTS

First team squad soccer players from teams in the top 5 national soccer divisions were included. Players who joined a team after the start of the trial were excluded. Randomisation of 54 teams allocated 26 to the intervention group and 28 to a control group.

INTERVENTIONS

Both groups followed their usual training program. In addition, the intervention group completed 27 sessions of the eccentric hamstring muscle training in a 10-week period during the midseason break, and once a week in the second half of the season. The hamstring exercise (the Nordic curl) involves the player using hamstrings to resist forward falling of the trunk from a kneeling position. Players completed 2-3 sets of 5-12 repetitions of the exercise for 1-3 sessions per week.

OUTCOME MEASURES

The primary outcome was the number of overall, new, and recurrent acute hamstring injuries during one full soccer season. A hamstring injury was defined as any acute physical complaint in the region of the posterior thigh sustained during a soccer match or training. Recurrence of an injury already reported in the trial period was not included to avoid recording the same injury more than once.

RESULTS

50 teams with 942 players completed the study. At the end of the season, there had been 15 hamstring injuries (12 new, 3 recurrent) in the eccentric hamstring exercise group and 52 injuries (32 new, 20 recurrent) in the control group. The number needed to treat (NNT) to prevent 1 hamstring injury (new or recurrent) was 13 (95% CI 9 to 23). The NNT to prevent 1 new injury was 25 (95% CI 15 to 72) and the NNT for recurrent injury was 3 (95% CI 2 to 6). Apart from short term muscle soreness no adverse events were reported in the exercise group.

CONCLUSION

An eccentric strengthening exercise program for the hamstring muscles that can be performed during training can help prevent hamstring injuries in soccer players.

Thigh muscle injuries in youth soccer: predictors of recovery

BACKGROUND

Participation in soccer at younger ages with attendant risk of muscle injury is increasing.

PURPOSE

To delineate patterns of thigh muscle injury and predictors of recovery in male youth soccer academy players.

STUDY DESIGN

Cohort study (prognosis); Level of evidence, 2.

METHODS

Forty-one English Premiership soccer academy squads (all male, aged 8-16 years) over a 5-year period comprising 12 306 player seasons were studied prospectively for pattern, mechanism, and outcome after thigh muscle injury. Event analysis was used to identify independent predictors of slow recovery.

RESULTS

A total of 1288 injuries were recorded representing an incidence (mean [SD]) of 0.42 (0.24) per thousand hours of training with a mean annual incidence of 0.52. Midfield players received the most injuries, followed by defense and attack positions. The quadriceps muscle group was most likely to be injured. There were 345 reinjuries (27%). Median time off for a primary injury was 13 days (interquartile range, 7-22 days) and 12 days (7-21 days) following a reinjury. Risk of such injury increased as the game progressed toward the end of the first half period (P = .028), and this risk persisted throughout the entire second half. There were 2 peaks of incidence (January and September). The percentage of the total for hamstring, adductor, and quadriceps injuries did not significantly change with player age. However, the proportion of injuries that were severe increased with age of player (t = 3.72, P = .010). Poor prognostic factors for recovery were hamstring injuries (z = 2.182, P = .029), contact injury (z = -3.137, P = .002), and older age (z = -2.2298, P = .022).

CONCLUSION

The risk for prolonged recovery from thigh muscle injury was found to increase with age of the player and contact mechanism. The risk of injury increased toward the end of the first half, and this risk persisted throughout the second half. Delayed recovery was significantly associated with a hamstring muscle injury, first injury, and contact mechanism. This study, for the first time, allows identification of youth male soccer players at high-risk for prolonged symptoms after thigh muscle injury.

Activation and aponeurosis morphology affect in vivo muscle tissue strains near the myotendinous junction

Hamstring strain injury is one of the most common injuries in athletes, particularly for sports that involve high speed running. The aims of this study were to determine whether muscle activation and internal morphology influence in vivo muscle behavior and strain injury susceptibility. We measured tissue displacement and strains in the hamstring muscle injured most often, the biceps femoris long head muscle (BFLH), using cine DENSE dynamic magnetic resonance imaging. Strain measurements were used to test whether strain magnitudes are (i) larger during active lengthening than during passive lengthening and (ii) larger for subjects with a relatively narrow proximal aponeurosis than a wide proximal aponeurosis. Displacement color maps showed higher tissue displacement with increasing lateral distance from the proximal aponeurosis for both active lengthening and passive lengthening, and higher tissue displacement for active lengthening than passive lengthening. First principal strain magnitudes were averaged in a 1cm region near the myotendinous junction, where injury is most frequently observed. It was found that strains are significantly larger during active lengthening (0.19 SD 0.09) than passive lengthening (0.13 SD 0.06) (p<0.05), which suggests that elevated localized strains may be a mechanism for increased injury risk during active as opposed to passive lengthening. First principal strains were higher for subjects with a relatively narrow aponeurosis width (0.26 SD 0.15) than wide (0.14 SD 0.04) (p<0.05). This result suggests that athletes who have BFLH muscles with narrow proximal aponeuroses may have an increased risk for BFLH strain injuries.