Full article hamstring injuries in professional football players final complete draft

UNIVERSITY OF SOUTH WALES MSC IN SPORTS AND EXERCISE MEDICINE 2016

Hamstring Injuries in Professional Football Players A treatment model based on a critical review of injury prevention, rehabilitation and return to play protocols.

Authors: Mr Nicola Acampora Dr Karl New

Hamstring Injuries in Professional Football Players

TABLE OF CONTENTS INTRODUCTION.................................................................................................................................2 METHOD:.............................................................................................................................................3 Research design:................................................................................................................................3 Inclusion Criteria:..............................................................................................................................3 Exclusion Criteria:.............................................................................................................................3 Study Selection:.................................................................................................................................3 Data:..................................................................................................................................................3 Bias Avoidance:.................................................................................................................................4 RESULTS:.............................................................................................................................................5 Study selection:.....................................................................................................................................5 Study Characteristics:........................................................................................................................6 Risk of Bias Within Studies:..............................................................................................................6 Synthesis of Results:..........................................................................................................................7 DISCUSSION.........................................................................................................................................19 Suggested injury prevention protocol..............................................................................................19 Injury Screening Methods:...........................................................................................................19 Injury prevention strategies.........................................................................................................20 Suggested protocol from time of injury to RTP...............................................................................24 Clinical assessment:.....................................................................................................................24 Acute phase:................................................................................................................................26 Sub-Acute Phase:.........................................................................................................................28 Functional phase:.........................................................................................................................30 Return to on field football-based exercises (RTP 1).....................................................................32 Return to full competitive training (RTP 2)...................................................................................33 Treatment model for hamstring muscle injuries..............................................................................34 CONCLUSION.......................................................................................................................................35 BIBLIOGRAPHY...............................................................................................................................36 APPENDIX A......................................................................................................................................39

1

Hamstring Injuries in Professional Football Players INTRODUCTION Hamstring muscle injuries (HMI) are the single most common football injury at elite levels and these injuries are associated with significant time loss (Ekstrand et al., 2011 ; Hagglund et al., 2009). According to Ekstrand et al. (2011) a professional team with 25 players could be expected to suffer about five HMI per season. Taking into account the rehabilitation process an estimation of 80-90 days of football could be lost throughout each season on hamstring injuries with the average injury causing the loss of three to four matches [ CITATION Bru121 \l 7177 ]. This along with the high risk of recurrence, said to be between 12-63%, can lead to disturbing effects both on economical and performance paremeters for clubs and players involved (Petersen et al., 2010 ; Wood et al., 2004).

The main functions of the hamstring muscle group are hip extension and knee flexion. This bi-articulate function drastically increases the demands on the muscle when an individual is required to sprint because the hamstrings act eccentrically during the late swing and terminal stance phases of the running cycle with the greatest torques seen during the late swing to midstance phase [ CITATION Sch11 \l 7177 ]. Due to this, the majority of HMI seen in professional football occur while high-speed running or sprinting [ CITATION Woo \l 7177 ].

Brukner and Khan (2012) decribes these as the common type I hamstring injury whilst type II, which are less common in football, occur during movements leading to extensive lengthening of the hamstring when in hip flexion such as high kicking and slide tackling.The high rate of re-injury in HMI could be due to inadequate rehabilitation programmes and/or poor return to play (RTP) standards. (Askling et al. 2013).

The primary objective of any rehabilitation protocol is to return the player back to the field of play in the shortest time possible whilst still ensuring that the risk of injury reaccurence is minimal. This makes it a fine balance between getting right and being back to pre injury state after 20 days or getting it wrong and being in and out of rehab for a prolonged period of time.

The standard protocol of increasing the eccentric strenght of the hamstring muscles has been the proposed method of prevention and rehabilitation [ CITATION Pet11 \l 7177 ]. Brukner and Khan (2012) describe how little scientific evidence is available on which to base the management of hamstring injuries making it a problem in clinical practice as many approaches are experience based. Mendighucia and Brughelli, (2011) proposed a return to sport algorithm for acute hamstring strains. Although extremely usefull, especially in the acute setting which may not differ between sports, the data was gathered from different codes of sport, levels of competion and genders meaning that football specific demands on elite male players were not taken into account when developping the later phases of the algorithm. FC Barcelona have developped a muscle injury clinical guideline which they apply at their club from the academy level right through to the 1 st team [CITATION FCB09 \l 7177 ] but this does not include a detailed exercise prescription for HMI rehabilitation. FIFA have also placed a large importance on football related injuries and have created the ‘11+’ warm-up and injury prevention manual which was developped by a group of international experts based on practical experience [ CITATION FIF07 \l 7177 ]. According to FIFA the the ‘11+’ can lead to a 30-50% reduction in injuries.

2

Hamstring Injuries in Professional Football Players Despite all research being put into injury prevention and rehabilitation there is still a current lack of evidence based rehabilitation protocols for HMI in footbal players. The purpose of this study was to critically analyse the current literature available pertaining to hamstring injury prevention and rehabilitation protocols in professional football to develop a standardized and reputable method of rehabilitation to implement in order to improve hamstring injury or reinjury rates in football players.

METHOD: Research design: The study was a review of literature. The University of South Wales online database was used for article research (http://studentlibrary.southwales.ac.uk/findit/). The research was performed between January-April 2016. Combinations of key words used were: “Professional football”; “Hamstring Injury”; “Rehabilitation protocol”; “Injury Prevention”; “Return to play protocol”. The researchers were searching for any level of evidence literature concerning hamstring injury prevention, rehabilitation and RTP in professional football players.

Inclusion Criteria: The inclusion criteria making literature eligible to be included in the study was: 1. Evidence involving semi-professional or professional, male football players.

2. Evidence pertaining to hamstring injuries occurred during football actions.

3. Evidence analysing methods of injury assessment, prevention rehabilitation and RTP specific to hamstring injuries in male football players.

Exclusion Criteria: The Exclusion criteria making literature not eligible to be included in the study was: 1. Evidence involving amateur football players in order to ensure gathered data would be based on players with high conditioning levels.

2. Evidence involving female football players in order to exclude physiological differences between genders.

3. Evidence pertaining to hamstring injuries occurred during non-football related actions.

Study Selection: In order to identify relevant literature, titles and abstracts were screened by the author. Full text articles were read if eligibility could not be determined based on information found in the abstracts.

Data: The extracted information included methods, trial participant characteristics, type of intervention, type of outcomes and results.

Bias Avoidance: The risk of bias was diminished due to the inclusion/exclusion criteria which focused the research on hamstring injuries in male football players. Any level of evidence was accepted 3

Hamstring Injuries in Professional Football Players in the review. This allowed for a larger database of evidence to work with and base the review on. Due to the heterogeneity of the data, the researchers decided to assess the quality of the studies by determining their level of evidence according to the Oxford Centre for EvidenceBased Medicine’s levels of evidence [CITATION Med11 \l 7177 ].

4

Hamstring Injuries in Professional Football Players RESULTS: Study selection: The systemic search of the University of South Wales online database provided a total of 567 citations. Six additional articles were identified via manual search of the reference lists in the selected articles. Once duplicates were removed, 465 studies were retained. After screening the Headings and Abstracts of the articles 422 were removed because they failed to meet the inclusion criteria. After analyzing the full text of the remaining 43 articles for eligibility, 21 failed to meet the inclusion criterias set by the author leaving 22 articles to include in the review (Figure 1).

Figure 1. Study flowchart

5

Hamstring Injuries in Professional Football Players

Study Characteristics: The sample sizes of the studies ranged from a case study [ CITATION Bru14 \l 7177 ] to n=2376 [ CITATION Woo \l 7177 ]. The other larger sample sizes came from the studies of Petersen et al. (2011) and Croisier et al. (2008) with 942 and 462 participants respectively.

Four studies did not provide specific participant numbers but instead provided team numbers ranging from 50 (Bahr et al., 2015) to 27 (Bengtsson et al., 2013) elite teams. The studies were dated from 2004 [ CITATION Woo \l 7177 ] to 2016 (McCall et al., 2016) with 19 out of the 22 studies being published during or after 2010. 21 out of 22 studies involved professional players with 1 study involving semi-professional footballers [ CITATION Men14 \l 7177 ]. The studies were then divided into different groups based on what parameter of hamstring injuries in football players they focused on, as seen in figure 2.

Notebly some studies belonged to more than one group and these were allocated accordingly.

Five studies (22%) focused on the clinical assessment of hamstring injuries with 9 studies (41%) providing results on epidemiology. The main bulk of the studies focused on the rehabilitation parameters of Injury prevention (IP)(32%), injury rehabilitation (IR)(32%) and RTP (32%). In 16 out of 22 studies (73%) results crossed over one or all of the rehabilitation parameters (IP,IR,RTP).

Risk of Bias Within Studies: As seen in Table 1 ; 4 studies were classified as having level 1 evidence (Petersen et al., 2011; Askling et al., 2013; De Vos et al., 2014; Tol et al., 2014), 7 studies as level 2 (Wood et al., 2004; Croisier et al., 2008;Arnason et al., 2008; Ekstrand et al., 2011; Bengtsson et al., 2013; McCall et al., 2014; McCall et al., 2016), 5 studies as level 3 (Mendiguchia et al., 2014; Brukner et al., 2014; Eastwood, 2014; Garcia-Pinillos et al., 2015; Fournier-Farley et al., 2015), 5 studies as level 4 (Askling et al., 2010; Thorborg, 2012; Delvaux et al., 2013; Bahr et al., 2015; Timmins et al., 2015) and 1 level 5 (Schmitt et al., 2012).

6

Hamstring Injuries in Professional Football Players Table 1. Study stratification and level of evidence

Synthesis of Results: Clinical assessment. Five studies included clinical assessment of HMI in football players.

Ekstrand et al. (2011) examined 516 hamstring injuries from 15 UEFA Champions League (UCL) teams. Magnetic Resonance Imaging (MRI) was conducted in 58% of injuries with 40% of those undergoing initial ultrasound (US) scans concomitantly; 29% were examined

by US only and 13% were examined clinically without the use of imagery. According to MRI results 13% of injuries were of grade 0, 57% were of grade 1, 27% were of grade 2 and 3% were of grade 3. Eastwood (2014) used the injury database of Sunderland AFC to look at the HMI which occurred over 4 years. The effected players (n=27) all received an MRI scan and a clinical assessment to evaluate injury severity. MRI scans classified 7.4% of injuries as grade 0, 55.5% as grade 1, 37% as grade 2 and 0% as grade 3 whilst Clinical judgment classified 3.7% of injuries as grade 0, 62.9% as grade 1, 25.9% as grade 2 and 7.4% as grade 3. These results suggest that MRI grading appeared to underestimate injuries when compared to clinical grading although this was only true for 9 out of 27 injuries. Askling et al. (2013) clinically confirmed hamstring injuries on 75 cases with a combination of MRI’s clinical examination and this was a useful tool in differentiating between muscles involved and associating the injury type (sprint vs stretch) with muscles involved. Clinical examination was conducted 2 days post injury whilst MRI’s were conducted 5 days post injury. Clinical examination included manual flexibility and strength assessment as well as palpation and was conducted every week until there were no signs of remaining injury. Brukner et al. (2014) 7

Hamstring Injuries in Professional Football Players followed a clinical case over 5 months relying on clinical and radiological assessments to make a clinical diagnosis of hamstring injuries. The player substained 5 hamstring injuries in 5 months rating from grade 0 to grade 2 of biceps femoris muscle in the right leg.Slight descreptencies were noted between clinical and radiological assessments of injury severy but these had no effect on time to full recovery. De Vos et al. (2014) looked to compare baseline MRI findings and post RTP clinical assessments to predict re-injury. Out of 45 football players MRI scans found 28% to have suffered a grade 1 injury with 72% suffering a grade 2 injury. None of the baseline MRI paramenters were seen as a predictor of hamstring re-injury whilst clinical assessments such presence of localised discomfort on palpation after RTP were associated with a higher re-injury rate. In a systemic review, Fournier-Farley et al.

(2015) looked at the determinants which can positively or negatively affect RTP after hamstring injury. It concluded that ,with the use of clinical assessments, stretching type injuries, greater ROM deficit, time to first consultation > 1 week, increased maximal pain score and >1 day post injury to be able to walk pain-free were all associated with longer recovery times. With the use of MRI scans the following correlated with longer recovery times: positive findings, higher grade of injury, >75% muscle involvement, central tendon disruption of bicep femoris, shorter distance to ischial tuberosity, length of injury and depth volume and large cross-sectional area. US determinants of longer lay-off time included large cross-sectional area, injury outside of the musculotendinous junction, hematoma, structural injury and injury involving biceps femoris. Based on these results clinical and radiological assessment used together were seen as a usefull tools in assessing HMI severity and provided accurate insight into lay off time and preventing future re-injury.

Epidemiology. Nine studies included results on epidemiology of HMI in football players.

Table 2 represents a summary of the studies which looked at cause, anatomy and lay off time from injury. Woods et al. (2004) looked at normative injury data from 91 clubs over 2 years across 4 professional divisions. Ninety-four percent of HMI were classified as Hamstring strains, which accounted for 12% of the total injuries sustained over the 2 seasons and on average contributed to 18 days of absence or 3 missed matches per injury. No difference in frequency was noted between dominant and non-dominant limbs. The study found that there was a significantly higher rate of hamstring injuries (28%) in Premier league players when compared to the other 3 divisions. The bicep femoris was found to be the most effected hamstring muscle with 53% when compared to the semitendinosus and semimembranosus with 16 and 13% respectively. Player to player contact was responsible for 7% of injuries whilst 91% occurred during non-contact football actions with 57% arising during running actions. One third (32%) of hamstring strains were sustained during training with 67% occurring during matches. Of the injuries that occurred during the matches, nearly half (47% occurred during the last 15 minutes of the first and second halves. Playing position also affected injury rates as goalkeepers sustained significantly fewer hamstring strains when compared to outfield players. Race was found to be a risk factor as players of black origin sustained significantly more hamstring strains when compared to white players. Age was also a factor as players aged 17 to 22 sustained fewer hamstring injuries when compared to older players. Re-injury rate was seen at 12% with no correlation being found between severity of initial injury and re-injury. Ekstrand et al. (2011) found that biceps femoris injuries accounted 8

Hamstring Injuries in Professional Football Players for 84% of injuries with semimembranosus and semitendinosus accounting for 11 and 5 % respectively. This finding was similar of that to Vos et al. (2014) where Biceps femoris long head was the most frequently injured muscle (88%) whilst the remaining 12% of injuries effected the semitendinosus and semimembrinosus. Ekstrand et al. (2011) found no significant difference in lay off time between the three different muscles. Lay off time showed a significant difference between the grades of injury as grade 0 accounted for 8 days on average whilst grade 1, 2 and 3 accounted for 17, 22 and 73 days respectively. Seventy percent of these injuries occurred during sprinting or high-speed running with other mechanisms including stretching (5%), shooting, twisting (4%), passing and jumping (2%).

Overuse injuries mostly presented as grade 0 (69%) grade 1,2 and 3 injuries were more likely to occur from traumatic injuries. According to this study 95% of HMI occurred during noncontact actions with no significant difference found between dominant and non-dominant leg.

In this study re-injuries accounted for 16% of all HMI and they all occurred in the bicep femoris muscle. Bengtsson et al. (2013) looked at the correlation of injury rates and fatigue 27 UCL teams over 11 seasons. According to the results when matches with four or less recovery days were compared with matches with six or more recovery days, a significant increase in injury rates was noticed. Hamstring injuries rates along with quadriceps injuries were particularly affected by the shorter recovery time whilst calf and adductor injury rates were not. Askling et al. (2013) found that 72% of injuries were attributed to sprinting whilst 28% were attributed to stretch type activities. Furthermore, in 69% of players the primary injury was to the bicep femoris long head with secondary injury commonly occurring at the semitendinosus in 48% of cases. Twenty-one percent of primary injuries occurred in the semimembranosus. Sprint-type injuries were clearly seen to affect bicep femoris long head on 94% of occasions whilst 76% of all stretch-type injuries occurred in the semimembranosus.

Pinillos et al. (2015) looked at the effects of hamstring flexibility on football specific skills.

Forty-three male participants took part in the study and were divided into a flexible and nonflexible group. The comparative analysis between the 2 groups showed significant differences in passive straight leg raise (77° vs 61°), 5 m sprint (0.92s vs 0.98s), 10m sprint (1.64s vs 1.71s), 20m sprint (2.94s vs 3.04s), Balson agility test (11.91s vs 12.42s), counter movement jump (35.16cm vs 31.47cm), kicking speed in dominant leg (26.53ms-1 vs 24.71ms-1) and kicking speed in non-dominant leg (23.25ms-1 vs 21.39ms-1). Timmins et al. (2015) looked at risks of HMI being attributed to weak knee flexors and short bicep femoris fascicles. Elite soccer players (n=152) took part in pre-season testing and were followed for the season where 27 sustained hamstring injuries. These athletes who went on to be injured were significantly older (24 vs 27). Of the 27 injuries, 10 occurred during the pre-season whilst 17 occurred during the competitive season. Eight of these went on to reoccur in the same season (29.6%). Of the 27 initial injuries, time lost was 17.7 days with the re-occurring injuries losing 28.4 days on average. Bicep femoris was injured in 88.8% of occasions with semimembranosus and semitendinosus accounting for 11.2% and 2.7% respectively.

Mechanisms responsible for HMI were high-speed running (81.5%), stretching (11.1%) and kicking (7.4%). The bicep femoris long head fascicles were found to be significantly shorter in the players that ended up with an injury and the results showed that for every 0.5cm increase in biceps femoris long head fascicle length the risk of subsequent hamstring injury is reduced by 73.9%. Muscle thickness had no effect on injury prevalence. Absolute knee 9

Hamstring Injuries in Professional Football Players flexor eccentric force showed that subsequently injured players were weaker in both injured limb (260.6 N vs 309.5 N) and uninjured limb (262.6N vs 309.5N) when compared to uninjured players two-limb average. These results showed how eccentric knee flexor strength had a significant inverse relationship with the incidence of hamstring injuries and with every 10N increase in eccentric hamstring strength, the risk of hamstring injury would be reduced by 8.9%. Bahr et al. (2015) examined the implementation of Nordic Hamstring (NH) injury prevention protocol in 50 professional teams. In the survey 12 % reported that they were not familiar with the NH protocol. In 2012 4 clubs were fully compliant, 3 were partly compliant and 43 were non-compliant. In the 2013 and 2014 seasons the corresponding numbers were 6, 3 and 41 clubs meaning that of the 150 club seasons over the 3 years, 10.7% were compliant, 6% were partly compliant and 83.3% were non-compliant. Based on the results of the epidemiology:          

HMI were the most common muscle injury in football players.

The bicep femoris muscle was the more likely to be injured.

Bicep femoris long head fascicle length and eccentric strength of knee flexors had an effect on injury rates.

High-speed running was the likely mechanism of hamstring injury followed by stretching.

Sprint-type injuries most commonly affected the biceps femoris long head whilst stretch-type injuries commonly affected the semimembranosus.

Age and race had an impact on injury incidence.

Shorter recovery between matches increased hamstring injury incidence.

Hamstring inflexibility had negative effects on football specific movements.

Lack of team compliance to injury prevention programs could have been the reason for high incidence rates.

Re-injury rates ranged from 12 to 30% and this had significant impact on lay off time.

Injury Prevention. Seven studies included results on hamstring injury prevention in football Table 2. Summary of hamstring injury epidemiology in professional football players

players (Table 3). Croisier et al. (2008) screened 462 professional players during the pre-season of their respective seasons for isokinetic deficits as part of an injury prevention strategy. Of the 462 players 53% had a normal profile and 47% had significant isokinetic 10

Hamstring Injuries in Professional Football Players strength disorders. From the imbalanced players, the most specific test was shown to be mixed Hecc/Qconc ratio which was reduced in 87% of the players. The players were then divided into 4 groups with 35 out of 462 sustaining subsequent hamstring injuries. No players with a mixed Hecc/Qconc ratio of higher than 1.40 sustained a hamstring injury. Group A consisted of players without strength deficits in pre-season and showed an injury frequency of 4.1%. Group B consisted of players with untreated imbalances and had an injury frequency of 16.5% which meant that having a strength imbalance significantly increased relative risk by 4-fold. Group C consisted of players who took part in a specific conditioning programme without verifying isokinetic normalization and they did not see a significant reduction in injury frequency (11%). Group D consisted of players with imbalances who took part in a specific conditioning programme with subsequent isokinetic tests using a precise criterion to reach normalization and a significantly reduced injury frequency was noted (5.7%). The quasi-experimental study by Arnason et al. (2008) reported a 65% lower injury incidence in a group of elite players completing a training program consisting of warm up stretching, flexibility training, and nordic hamstring curls compared with warm up strteching and flexibility training alone. This suggestes that the preventative effect was solely as a result of the nordic exercises although the re-injury rate was not significantly different (36% vs 39%).

No training related injuries derived from the eccentric exercises themselves suggesting that the programme appeared to be save in this specific population. Petersen et al. (2011) looked at the preventative effects of eccentric strengthening in football players. Hamstring injuries were seen in 67 players over the 1 year follow up where 15 injuries (22%) occurred in the intervention group who took part in eccentric exercises and 52 injuries (78%) occurred in the control group who followed the normal training routine. Recurrence of injuries was even further impacted on as the intervention group suffered 85% less re-injuries (3 vs 20) when compared to the control group. Based on these results the number needed to treat to prevent a hamstring re-injury was only 3 (players at high risk) which is extremely low .Thorborg et al.

(2012) concluded that the results of the study by Petersen et al. (2011) indicate that the preventative effect is solely a result of the Nordic hamstring exercise programme and it could almost be considered negligence not to provide eccentric strengthening in this form for athletes with a history of HMI. McCall et al. (2014) conducted a survey on 44 professional football clubs and found that sports science staff and physiotherapists are more involved in injury prevention programs when compared to team doctors. All the clubs (100%) tested for injury risk during the pre-season, 81.2% during in-season and 40.9% at the end of season. All clubs tested the blood profile of the players whilst 50% of the clubs also underwent MRI and X-ray scans, running function tests and verbal interviews with players. All the clubs stated there were benefits in having injury prevention programs and all prescribed an injury prevention programme to their players. Furthermore, 32 (72.7%) clubs prescribed an individualized and global injury prevention programme to their players. The most common injury prevention exercises were seen as ‘core’ exercises in 100% of teams, with proprioception (95%), stretching (81.8%), eccentric (79.5%), Nordic (65.9) and functional (40.9%) being used commonly. The most common screening tools was functional movement screening (FMS) in 66% of clubs, when physical capacity testing and isokinetic testing only occurred in 27% and 41% of clubs despite the importance of fatigue and muscle imbalances in increased injury risk. General eccentric exercise was rated with the most importance in the 11

Hamstring Injuries in Professional Football Players injury prevention programme by clubs whilst hamstring eccentrics and nordic exercises rated third and fifth respectively. Bahr et al. (2015) found that 44 of 50 professional clubs used specific exercise programs other than the nordic hamstring programme. Two clubs reported that the nordic hamstring programme is the only one they would use whilst 35 clubs reported that the nordic rehabilitation programme was part of, but not the only strategy they would use in future. McCall et al. (2016) analyzed 33 surveys based on perceptions and practices of the medical staff in UEFA elite teams. Testing and monitoring of players was a practice conducted in 31 of 33 teams with 27 of the 33 teams conducting this continuously during preseason and in-season. Two teams did not assess individual player risk profiles. The most commonly used injury screening was side to side muscle imbalance (31 teams), flexibility (29), peak muscle strength and assessment of joint mobility (28). The top three monitoring tools used by the clubs were; (1) Measures of workload, (2) Subjective markers of wellness and (3) Medical screen. Measures of workload included; number of matches/minutes played (11 of 33 clubs), heart rate (8), rating of perceived exertion (RPE) (7), Global Positioning System (GPS) (7) as seen in Figure 2. Subjective markers of wellness included; fatigue (15 of 33 clubs), muscle soreness (7), perceived recovery (7) and sleep (3). The medical screen included player complaint, mood and general medical screening. Of the 31 teams implementing an exercise based prevention programme, 26 prescribed both individualistic and team programs. Five teams implement individualized prevention only and one team did not implement any injury prevention at all. The top three exercises used by the UEFA elite club teams were eccentric exercises, proprioception and core. Of the 33 teams 32 believed that their injury prevention practices were effective but could have been better. Two believed that they could not have done better and one club found that their injury prevention practices were not effective. Based on the results of the studies involving injury prevention:    

 

 

Muscle imbalance, especially a Hecc/Qconc ratio lower than 1.40, was a major risk factor in hamstring injuries.

Eccentric exercises had a good effect on decreasing injury rates as well as re-injury rates in players at high risk.

Pre-season testing was a common practice among all elite clubs whilst in-season and post-season testing was less common.

Most elite clubs preferred to use a global injury prevention programme for all players whilst simultaneously using an individualized programme on players classified as being at ‘high risk’.

Core and eccentric exercises were the most frequently used exercises whilst functional training was not seen as a common practice.

Teams classified general eccentric exercises as the most important whilst nordic hamstring exercises only ranked 5th behind core, proprioception and hamstring eccentrics.

Teams rated measures of workload, subjective markers of wellness and general medical screening as their preferred athlete monitoring tool.

Most teams believed that their injury prevention routines were useful in preventing injuries but could be better.

Table 3. Summary of main findings from injury prevention studies.

12

Figure 2. Monitoring tools used to assess injury risk in UEFA Elite Clubs

Hamstring Injuries in Professional Football Players

Injury Rehabilitation. Seven studies looked at hamstring injury rehabilitation protocols. The summary of these protocols can be seen in Table 4. Schmitt et al. (2012) introduced a new concept for post injury rehabilitation protocols focusing on lengthened stage eccentric training and it was divided into 3 stages before RTP. The acute 1st stage focused on protecting the injury and minimizing ROM as well as strength loss using modalities such as ice, massage and ultrasound. After 48 hours post injury the athletes could then begin submaximal isometric strengthening without stretching the hamstring into a painful range. The goal of the acute 1st stage was to normalize gait and obtain knee flexion strength greater

than 50% of uninjured leg. After goals were reached the 2nd phase was introduced and this involved progressively regaining strength throughout the ROM and improving neuromuscular control of hips and pelvis in order to prepare the athlete for sports specific movement. The 13

Hamstring Injuries in Professional Football Players

goal of the 2nd phase was achieve full strength or be within 20% of uninjured leg between 0 and 90 degree range and be able to jog both forward and backwards at moderate speed. The 14

Hamstring Injuries in Professional Football Players final 3rd phase focused on functional movements and eccentric strengthening in the lengthened state. At the end of this stage the athlete should have full strength throughout the ROM and be able to confidently perform all sports related tasks without limitation. Thorborg (2012) described how eccentric muscle strength training should be performed at longer muscle-tendinous lengths mimicking movements and muscle length occurring at both the hip and knee simultaneously. Askling et al. (2013) conducted a randomized controlled trial comparing two rehabilitation protocols in 75 players. Each protocol consisted of 3 different exercises, where 1 exercise aimed at increasing flexibility, the next one combined strength with pelvic stability and the last one was a more specific strengthening exercise. The Lprotocol focused on loading the hamstrings during extensive lengthening of eccentric muscle actions. The C-protocol consisted of conventional exercises for hamstrings with less emphasis on lengthening. The time to return from injury was considerably shorter in those who took part in the L-protocol with a mean of 28 days when compared to those in the Cprotocol who took a mean of 51 days. This was the 1st study to show a difference in time to return between a sprint-type and stretch-type injury and the results showed that sprinting-type injuries took a significantly shorter time to return, especially in those taking part in the Lprotocol. Only one re-injury was seen in the 12-month follow-up period and this occurred in the C-protocol 6 months after initial injury at the same site with the same mechanism.

Brukner et al. (2014) implemented a seven point programme based on limited evidence in the professional football setting which looked at addressing recurrent hamstring injuries. The programme, which was successful in the case study, consisted of 7 interventions; (1) Biomechanical assessment and correction, (2) Neurodynamics, (3) Core stability / neuromuscular control / lumbar spine strengthening, (4) Increase hamstring strength with eccentric-biased programme, (5) Overload running programme, (6) Injection therapies and (7) Stretching / yoga / relaxation therapies. The authors concluded that it was impossible to determine whether any one of the interventions was a key factor in the success of the rehabilitation. De Vos et al. (2014) utilized a progressive-phased, criteria based rehabilitation programme based on the best available evidence. The programme consisted of twice-weekly training sessions combined with daily home-based exercises. The home based programme consisted of a progressive agility and trunk stabilization exercise protocol. The mean percentage adherence for the supervised programme was 80% whilst the percentage for the home exercise programme was 64%. Tol et al. (2014) utilized a detailed six-stage rehabilitation protocol including ROM exercises, progressive strengthening exercises, core stability training and agility exercises. Stage 1 focused on injury recovery and maintaining pain-free state until athlete was able complete a single leg squat, painless cycling for 5 minutes and full knee extension in supine. Stage 2 progressively improved strength until athlete run at 70%, have 75% ROM when compared to uninjured side. Stage 3 included more functional exercises as well as eccentric hamstring exercises until 100% running speed and painless high-speed direction changes were achieved. Stages 4 -6 implemented the RTP exercises and drills in order to prepare the athlete for match situations. Fournier-Farley et al.

(2015) found that rehabilitation incorporating hamstring loading during extensive lengthening led to a shorter rehabilitation period. Based on these recommendations involving injury rehabilitation: 15

Hamstring Injuries in Professional Football Players  

   

There was a lack of evidence supporting different rehabilitation protocols specific to football players.

Multi-articulate function of the hamstring muscles was seen as one of the reasons these muscles are prone to injury in football player meaning that exercises involving simultaneous movement at the knee and hip needed to be used.

Protocol stages ranged between 3 and 7 stages based on reaching certain recovery criteria before implementing a RTP protocol.

Lengthening based exercises improved recovery speed as well as re-injury rates when compared to conventional rehabilitation exercises.

One study suggested that injury type made a difference on recovery time.

Home based exercises as well as supervised exercises were used in most of the protocols.

Table 4. Summary of rehabilitation recommendations from injury rehabilitation studies

Return to play. Seven studies analyzed RTP factors in football players. Askling et al. (2010) developed a new hamstring test to complement the clinical examination before RTP after hamstring injury. The ‘Askling H-test’ was seen to be highly reliable and sensitive enough to 16

Hamstring Injuries in Professional Football Players detect differences both in active flexibility and insecurity after an acute hamstring strain at the point of time where the common clinical examinations (such as palpation, manual strength and passive flexibility tests) failed to reveal injury signs. Askling et al. (2013) used the Askling H-test when no signs of remaining injury were shown with the standard clinical examination. If players experienced insecurity they were not allowed to return to sport and rehabilitation period was extended by 3-5 days until insecurity was eliminated. Between the L and C protocol a significant difference was seen as 35% of players involved in the lengthening protocol experienced insecurity compared to the 71% of players involved in the conventional protocol. Failure to pass the Asking H-test resulted in a prolonged rehabilitation period of 6-7 days. Thorborg (2012) suggested that criteria for RTP should be hamstring function dependent, not time dependent, using reliable and valid assessments such as hamstring strength recovery, Askling H-test to report insecurity and high intensity running performance. Delvaux et al. (2013) looked at the actual medicine practice in professional team when it comes to RTP. Thirty-seven Doctors from teams were questioned on their methods and 80% declared to use at least 7 criteria in order to assess a players ability to return to competitive football after a hamstring injury again emphasizing the importance of using a ‘criteria-approach’ rather than a ‘time-based’ approach. The most important criteria were seen as; complete pain relief, normalized muscle strength assessment, subjective feeling reported by the player, normalized flexibility and achievement of a soccer specific test. The opinion of the physiotherapists and physical trainers is also considered in the final RTP decision. Mendiguchia et al. (2014) used semi-professional players (n=28) in his study to assess the mechanical properties of sprinting on players after they has been cleared to return to sport following a HMI. The main finding was that, despite being cleared to play, players returning from a recent hamstring injury had substantially lower sprinting speed performance and reduced mechanical horizontal properties when compared to uninjured players. Two months of regular soccer training saw a substantial improvement in those parameters. De Vos et al. (2014) emphasized symptom-based criteria for RTP. According to a standardized rehabilitation protocol the athlete was ready for RTP once they met the following criteria: symptom-free during: (1) full ROM; (2) full speed training; (3) sports specific movements.

The clinical assessment which was conducted post-RTP consisted of hamstring flexibility test, strength testing and muscle palpation. The authors found that just after RTP, 66% of athletes reported a complete recovery on the Likert Scale. Discomfort during hamstring flexibility, hamstring resistance testing or on localized palpation was present in 25% of cases who had been cleared to RTP. These results were relevant as the athletes with localized discomfort after RTP were almost four times more likely to sustain re-injury compared with athletes with absence of discomfort. Tol et al. (2014) implemented football-specific training after the players successfully completed the 1st three stages of rehabilitation. This training consisted of staged progression of volume and intensity of direction changes, sprints, jumps, passes, shooting, interval running, one on one attacking and defense drills, mimicking muscle fatigue and competitiveness during football training and game situations. After the football specific phase isokinetic testing was conducted to evaluate the knee flexors and extensors.

The guidelines for making the final RTP decision included a number of elements including successful and asymptomatic completion of progressive rehabilitation programme and results of isokinetic assessment. This study found that 67% of hamstring-injured professional players 17

Hamstring Injuries in Professional Football Players who followed the criteria based RTP guidelines showed at least one hamstring isokinetic testing deficit of more than 10% meaning that normalization of isokinetic function was not an automatic outcome of completing the football-specific programme. In a systemic review, Fournier-Farley et al. (2015) looked at the determinants which can positively or negatively affect RTP after hamstring injury as seen in table 5. It concluded that stretching type injuries, greater ROM deficit, time to first consultation > 1 week, increased maximal pain score and >1 day post injury to be able to walk pain-free were all associated with longer recovery times.

Based on the findings on RTP in football players:      

RTP criteria should be hamstring function dependent, not time dependent.

Askling H-test has good sensitivity and should be implemented when making a RTP decision.

Most team Doctors use multifactorial criteria to analyze a players ability.

Football specific movements and exercises need to make up the RTP phase of the programme.

Isokinetic testing throughout the rehabilitation should be done in order to ensure the normalization of the injured side.

No studies were found which looked at a detailed RTP protocol in professional football players.

Table 5. Factors prolonging RTP from acute hamstring injuries. (Fournier-Farley et al., 2015)

DISCUSSION The study investigated the common football specific practices which professional and semiprofessional medical teams utilize in order to improve hamstring injury rates and ensure a safe RTP for those who suffered a hamstring injury. With the use of the results from the 18

Hamstring Injuries in Professional Football Players studies above the authors would like to propose a protocol, which is specific to football players, which will help to analyze, prevent and rehabilitate hamstring injuries.

Suggested injury prevention protocol Table 6. Non-modifiable and modifiable risk factors for hamstring muscle injury (HMI)

Injury Screening Methods:

Preventing injury implies the identification and understanding of the factors leading to that injury [ CITATION Cro08 \l 7177 ]. This statement is especially true when it comes to hamstring injuries and the above studies have linked clear risk factors, non-modifiable and modifiable, leading to increased incidence of such injuries (Table 6). It is therefore important that injury screenings are implemented into the periodization programme of a professional team.

General injury risk screenings should be conducted during pre-season, in-season and off-season. These screenings include FMS, subjective markers of wellness questionnaires and Measures of workload and general strength testing. To further focus on decreasing hamstring injuries, the authors suggest the following be added to the pre-season screening (Table 7).

In the event that a player is found to be at risk following this hamstring specific screening tool, they should undergo an individualized injury prevention protocol as well as follow up assessments of a similar nature on a monthly basis to ensure that the modifiable parameters return within ‘low risk’ standards.

19

Hamstring Injuries in Professional Football Players Table 7. Hamstring injury specific screening modalities

Injury prevention strategies

Non-contact injuries in football can be best prevented through thorough preparation of the players with the use of the multidisciplinary team available at each club. Every individual, from coach to players and back room staff need to take responsibility when implementing injury prevention strategies. The main non-modifiable risk of hamstring injury is a previous history of HMI and because of this, prevention of the initial injury should be of paramount importance. The ‘11+’ injury prevention programme developed by FIFA (2007), as seen in Figure 3, was developped by a 20

Hamstring Injuries in Professional Football Players group of international experts on their practical experience with different injury prevention programmes. Teams that performed the ‘11+’ regularly at least twice a week had 37% fewer training injuries and 29% fewer match injuries whilst severe injuries were reduced by almost 50%.

The 11+ has three parts with a total of 15 exercises and it should replace the conventional warm-up routine. Part 1 is comprised of slow speed running exercises, active stretches and low intensity partner contacts. Part 2 consists of 6 sets of exercises , with 3 levels of difficulty, focusing on leg strenght, balance and plyometrics. Part 3 is made up of running exercises at moderate to high speed with intergrated planting and cutting movements.This protocol seen in figure 3 should be the main team warm-up strategy followed by elite clubs in order to adequately prepare the players for football actions. FC Barcelona Medical Services (2015) suggested a more in-depth primary prevention protocol which not only included exercises during training warm-up routines but mixed football and prevention content as part of the training sessions. The protocol is divided into 4 levels which occur simultaneously depending on the demands of the footballling week. At 1st level they use an indoor prevention programme which is divided into a squad prevention programme (specific exercises depending on the training period and type of football week) once a week and a player individual strength programme twice a week. The 2nd level is the daily prevention warm-up , which similar to the ‘11+’, can be used at the start of a training session to achieve the prevention objectives. The 3rd level are multi-station prevention circuits done on the pitch involving football and prevention exercises done 1-2 times per week. The 4th level are on field football specific strength training circuits and this is also conducted 1-2 times per week.

Table 8. Suggested primary injury prevention routine for elite football players

Based on these preventative methods used by elite clubs, table 8 shows the suggested primary prevention protocol adapted from FC Barcelona Medical Services (2015) and FIFA (2007).

A more specialised protocol is, however, suggested for those players who classify as being at ‘high risk’ after the hamstring screening protocol. Those players can then take part in the ‘Individual Hamstring Prevention’ programme seen in table 8 along with the general primary 21 Table 9. Individual hamstring injury prevention exercises.

Hamstring Injuries in Professional Football Players prevention routine. A more in-depth protocol based on the above studies is suggested using the exercises from table 9 and it aims at restoring midifiable risk factors to within normal or ‘low-risk’ standards.

Since the intervention needs to be individualised, it is not possible to develop a set protocol as all players at ‘high risk’of hamstring injury will need a different modality of exercises in order to achive their goals. This is where the knowledge and experience of medical and rehabilitative teams comes in as it is crutial that the different circumstances are taken into account when developping a prevention protocol for these players in need. The circumstances include:         

A player may be at risk due to a multitude of factors or may have a single specific risk factor There may be double or single leg involvment There may be other muscular problems and not sole hamstring involvment A player who has done no previous hamstring prevention should not start with advanced exercises and should be progressed accordingly Football week needs to always be taken into account as some exercises may cause muscular pain Easier exercises should be used during weeks of higher football loads Some players may need more flexibility training where some may need more eccentric training Sets and repetitions for the exercises need to be prescribed with the goal in mind (strength development vs endurance development) These exercises should not replace the general squad preventative exercises but should be done in conjuction as training load allows.

Figure 3. Breakdown of the '11+" warm up protocol.

22

Hamstring Injuries in Professional Football Players

Suggested protocol

from time of

injury to

RTP Based on the above studies an individualized, 5 stage, criteria based protocol will be suggested in order to return the player from acute hamstring injuries. After the clinical assessment confirms an HMI, the protocol will then be divided into the phases below:

23

Hamstring Injuries in Professional Football Players 1.

2.

3.

4.

5.

Acute 1 & 2 Sub-Acute Functional Return to on field football-based exercises Return to full competitive training

Clinical assessment:

Due to the frequency of hamstring injuries in football it is important to get a clear diagnosis in order to roughly determine the time away from football before the player is able to return to training and competitive matches. The medical team must always remember that although protocol should be followed, each player is unique and they should be treated like that.

Immediately after injury is suspected through observation of the injury occurring, it is important to remove the player from the field of play. As hamstring strains are seen as obvious injuries the medical staff can quickly determine the need for the player to leave the field. This phase is crucial as a slight strain can quickly turn into a severe injury if the player is left to play on. During this post injury phase a clinical history of injury (Table 10) should be taken along with a simple physical exam (Table 11). The treatment modality for this stage should follow the standard RICE protocol [ CITATION Bru121 \l 7177 ]. At this time establishing severity through further investigations may not be sensitive enough and medical teams are therefore encouraged to wait at least 12-24 hours.

Table 11. Proposed post injury physical examination adapted from FC Barcelona Medical Services (2009) Table 10. Proposed history taking structure

Twenty-four hours post injury, MRI and US can give a clearer diagnosis and prognosis. US is cost effective, easily available and non-invasive and it therefore should be the go to initial modality although it has the disadvantage of being radiologist experience dependent and may not be sensitive enough for minor muscular injuries. MRI does provide more specific anatomical and pathological information when it comes to hamstring injury and therefore 24

Hamstring Injuries in Professional Football Players should be modality used in conjunction with US. Due to availability, US can be useful in following the healing process providing essential feedback to both the athlete and clinician whereas MRI may have a more specific role to play when it comes to making return to sport decisions in elite football players.

Based on these findings the hamstring injuries can then be classified according to severity on order to derive the prognosis. The table below (Table 12) shows the classification of these injuries according to imaging criteria and is adapted from Medical Services, Futbol Club Barcelona (2009).

Table 12.Classification of muscular injuries according to imaging criteria

Brukner and Khan (2012) has described certain factors relating to the prognosis of hamstring injuries and these need to be also taken into account when prescribing an individualised protocol. The following have been associated with an increased length of time to RTP:  

   

A longer time to walk at normal pace pain-free (in days) has been shown to be associated with RTP (>1day= 4 times more likely to take > 3 weeks).

‘Days to jog pain-free’ is the strongest predictor of RTP. o 1-2 days = < 2 weeks o 3-5 days = > 2 weeks o > 5 days = > 4 weeks MRI-negative hamstring strains are associated with a rapid RTP. The more proximal the site of injury, the longer the time to RTP. Stretch type injuries are associated with a prolonged RTP although initial signs and symptoms may present as less severe.

Length of tear (>60mm) and cross sectional area (>55% of total) on MRI are correlated with a prolonged RTP.

Based on the results of the clinical and radiological examination the medical team can then decide on the course of action in order to manage the acute hamstring injury. This management consists of a multi-factorial rehabilitation process and only in extreme cases of complete ruptures to the proximal attachment of the musculotendinous junction should surgical repair be considered.

25

Hamstring Injuries in Professional Football Players Acute phase: The acute phase of hamstring injuries will not differ from the standardized rehabilitation algorithm by Mendiguchia and Brughelli, (2011) or the treatment protocol found in Medical Services, Futbol Club Barcelona (2009) and therefore will be adapted from their recommendations.

Treatment modalities have been derived from the above studies and a criteria based progression to the sub-acute phase will need to be assessed prior to advancing the athlete to the next phase of the programme. It is suggested that the acute stage of muscle injuries is divided into 2 phases. Phase 1 will be implemented from immediately after the injury and phase 2 can be implemeted from 3 days onwards.The goals of the acute phase should include:      

Preventing re-injuries to the injured site Preventing excessive inflammation and scar tissue build up Increase tensile strength, adhesion and elasticity of the new granulation tissue Reduce interstitial fluid build up Detect and treat any lumbo-pelvic dysfunction Normalize gait and regain pain-free ROM

In order to achieve these goals the following modalities should be implemented as part of the Acute Phase 1 Protocol (Table 13).

Table 13. Acute Phase 1 Recommendations

Table 14. Acute Phase 2 Recommendations

Once enough time has surpassed the player can then be progressed onto phase 2 of the acute stage where muscle activation and other modalities of treatment can begin to take place in order to build up towards the Sub-Acute phase of the protocol (Table 14).

26

Hamstring Injuries in Professional Football Players

The criteria needed to be achieved at this acute stage are:     

Pain free walking No pain or discomfort during exercises Full, active, pain free, knee ROM Isometric knee flexion strength in prone, with knee flexion at 45° and hip at 0°, > 50% of previous data or compared to uninjured leg with the use of a dynamometer Knee flexion strength > 50% of uninjured leg at 45° and 90° knee flexion with the use of manual strength tests (if dynamometer is not available)

Once all these criteria have been reached the player may be advanced to the next phase of rehabilitation. If not all criteria are met the player should be advised to continue with the same phase for an additional 2-3 days before being re-tested.

Sub-Acute Phase:

The sub-acute phase of hamstring injuries will be implemented once the player has reached the advancement criteria set out during the acute phase. On minor injuries, such as Grade 1 tears, advancement to this phase may take as little as 5 days whilst on more serious grade 2 injuries this may take up to 14 days. The goals of this sub-acute phase include:   

Improve strength and symmetry during prone isometric hamstring contractions at various angles Improve hamstring flexibility of both legs Improving overall core stability

27

Hamstring Injuries in Professional Football Players ď&#x201A;ˇ ď&#x201A;ˇ

Improve neuromuscular control of trunk and pelvis with progressive increase in movement speed preparing for functional phase Maintain cardiovascular fitness

In order to achieve these goals the following modalities should be implemented as part of the sub-acute phase of hamstring injury rehabilitation (Table 15). These recommended exercises need to be implemented by a physical therapist or biokineticist in charge of the team and can be adapted and modified to suit each and every players needs based on the severity and injury mechanism of the HMI as well as taking into account each players predisposing risks.

The progression between easy, moderate and advanced exercises needs to be based on clinical experience as well as pain/ discomfort scales and any other factors which may lead to detrimental adaptations of the hamstring muscle. Eccentric hamstring strengthening has been proven to be the go to modality in HMI and any strengthening programme should build up towards implementing an eccentric strengthening protocol to get the best results. The negatives of eccentric exercises can be muscle pain and damage, which is why in minor grade 1 injuries they can be implemented from day 1 of the sub-acute phase but in more serious grade 2 injuries, where the hamstring muscle fiber recover is a prolonged process, the player may need to begin with isometric exercises and build up towards eccentrics with the use of concentric variations.

The exercises should be performed 5 to 7 days per week but do not all have to be completed on each occasion (with the exception of stretching and some sort of progressive jogging). In order to allow the muscles to recover and therefore adapt to a load a suggested weekly routine can be seen in table 16.

Table 15. Sub-Acute Phase recommendations

*

28

*Refer to Appendix A for detailed list of exercises.

Hamstring Injuries in Professional Football Players

The criteria needed to be achieved at this sub-acute stage are:     

No pain or discomfort during any exercises Ability to jog both forwards and backwards at a moderate speed Isometric knee flexion strength, at 25° knee flexion and 45° hip flexion, at less than 10% asymmetry from previous data or uninjured leg with the use of a dynamometer Full 5/5 strength without pain during prone knee flexion at 90° with manual strength tests if dynamometer is not available Player should be able to participate in functional movements such as deep squats, single leg squats and lunges without any pain or discomfort

Once all these criteria have been reached the player may be advanced to the next phase of rehabilitation. If not all criteria are met the player should be advised to continue with the same phase for an additional 2- 3 days before being re tested.

Table 16. Example of a weekly routine during the Sub-Acute phase

Functional phase:

The functional phase of hamstring injury rehabilitation can only be implemented once the player has reached all of the criteria set out during the sub-acute phase. On minor grade 1 injuries, advancement to this phase may take as little as 7 days but on more serious injuries the process may take as long as 21-30 days. The goals of this phase include: 

Increasing the optimum length on hamstrings 29

Hamstring Injuries in Professional Football Players    

Decrease leg asymmetries in optimum length Decrease leg asymmetries in concentric hip extension Decrease leg asymmetries in horizontal force production during running Integrate postural control in sports-specific movements

In order to achieve these goals the following exercises, which are gradually progressed from the end sub-acute phase, should be implemented as part of the functional phase of acute hamstring injury rehabilitation (Table 17.) A decrease in re-injury rates has been shown as a result of more time spent on the field during a rehabilitation protocol and it is suggested that players undergoing the functional phase of rehabilitation begin to spend 2/3 days a week on field taking part in the more sports specific exercises activities allowed during this phase.

Clinical experience of the medical team, like in any other phase, is required to make the correct decisions as to what exercises will be more beneficial for certain types of injuries as well as what intensity is required in order to get the correct muscular adaptations. Peak hamstring force has been shown to increase substantially with increasing running speed from 80% to 100% and it therefore crucial that this functional component is reached during this phase before returning to on field based training. In table 15 exercises have been split up into separate ‘rehabilitation goals’ even though most of the exercises fall under multiple categories and this is, again, left to interpretation by the medical team.

At this functional stage the player should be taking part in these exercises 5 to 7 times a week as well as beginning to incorporate the preventative routines set out by the medical team for other joints allowing the player to take part in these ‘controlled’ training sessions with the rest of team provided that these exercises do not compromise the injured hamstring muscle.

Table 17. Functional Phase recommendations

*

30

*Refer to Appendix A for detailed list of exercises.

Hamstring Injuries in Professional Football Players

The criteria needed to be achieved in this functional phase are:    

No pain or discomfort during exercises Isometric knee flexion strength with knee at 0° and maximum hip flexion same to that achieved on the contralateral leg. (<10% asymmetry) Normal isokinetic ratios and no more than 10% asymmetry in absolute values No asymmetry in active straight leg raise and active knee extension test

Once all these criteria have been reached the player may advance to the next phase of rehabilitation. At this point the medical team will give the ‘medical all-clear’ as the player returns to field based exercises. If not all criteria are met the player should be advised to continue with the same phase for an additional 2- 3 days before being re tested.

Return to on field football-based exercises (RTP 1)

During this phase the football player is allowed to return to the field of play, in a controlled training setting, and is able to take part in football related activities. It is of paramount importance that in order to return to on field football-based exercises the medical team ensures that all the criteria from the functional phase are met before progression.

This initial RTP phase is the transition phase between functional exercises in a ‘safe’ environment and return to training and competition. It is therefore a crucial phase in preparing the player for the demands of full football activities as well as allowing the player to regain his co-ordination and confidence on the ball after being out for an extended period of time. The goals for this phase are the following: Table 18. Football Specific drills to be used as part of the Return to on-field football- based exercises.

31

Hamstring Injuries in Professional Football Players    

Achieve normal concentric and eccentric strength through full ROM and speeds Regain football specific fitness Regain co-ordination with ball activities No pain, discomfort or apprehension with the Askling H-test

This on field phase should have a fluid transition from the functional phase and the progression of exercises will carry on from the ones seen in Table 17. The main difference between the 2 phases is that, where the functional phase only had 2 to 3 days of on field exercises, the return to football-based exercise phase will have daily on field training sessions focusing on sports specific activities. The strengthening, flexibility, proprioception and trunk stability exercises will still be used but will now become an added extra in-between the football specific drills. Table 18 shows examples of the football specific exercises to be implemented during this phase and it remains up to the medical team’s expertise to choose which other exercises from the previous phase will be used to supplement these activities.

During this phase it is important that the footballer takes part in activities specific to their role on the field: a striker will take part in more submaximal forward sprints and shooting whilst a defender could spend more time taking part in backwards running with change of direction and 1versus 1 defending. These decisions will be left in the responsibility of the medical team.

The criteria needed to be achieved during this initial on-field football-based phase are the following:   

Replication of sports specific movements at simulated competition speed without any symptoms.

Normalised isokinetic data No hesitation or discomfort during the Askling H-test

With the completion of these criteria the footballer can then move onto the final phase of the rehabilitation programme. If not all criteria are met the player should be advised to continue with the same phase for an additional 2- 3 days before being re tested.

Return to full competitive training (RTP 2)

Once the player is able to complete the initial phase of the return to on field-football based exercises he is then able to enter the final stage of his rehabilitation protocol. This can also be named the RTP phase and it will be the last chance for the medical team to determine the players ability to return to full competition.

32

Hamstring Injuries in Professional Football Players At this stage the player is required to participate in 6 full team training sessions (3 days compromising of 2 training cycles). With the help of GPS data, it is important to ensure preinjury levels are achieved in terms of overall distance covered as well as the intensity maintained during the training session. Full strength and ROM is also a pre-requisite which should have already been tested for prior to this stage but can be re-tested at the end of this phase to get a RTP baseline result.

Due to the high risk of re-injury over the two months after being given the all-clear, it is crucial that the medical team make the decision based on criteria rather than the pressure from the player and coaches alike. Once the player has completed the 6 full training sessions he will undergo a series of objective test to determine their eligibility to compete. The following is the proposed criteria based protocol to follow during this phase: 1. Clinical criteria: clinical and physical examination 2. Imaging criteria: Ultrasound 3. Functional criteria: a. Isokinetic strength testing b. General physical fitness test c. Specific hamstring test- Askling H-test (for stretch-type injury) and symptomfree high speed running (for sprint-type injury) d. On field training – 6 full team training sessions monitored by GPS where data should match pre-injury status for; step balance, individualised speed peaks, symptom-free sports specific parameters (high speed running, acceleration / deceleration) Once a player has passed these criteria he can then be given the ‘all-clear to play’ by the medical team to return to competitive matches. Since preventing re-injury remains the primary aim, it is suggested that a player gradually return to sport over 5 competitive matches where the amount of time spent on the field of play increased from 25 minutes to 35’,45’,65’ and eventually a full 90’ match. This decision to gradually return to sport needs to be weighed up with the risks of early return and should adhered to as best as possible.

If a player suffered a primary HMI for the 1st time, once he has returned to competitive sport, he will then be included in the hamstring injury prevention programme and monitored accordingly with that guideline. If this was not the first incident and the player had suffered a secondary HMI, he should then be re-placed in hamstring injury prevention programme in order to prevent any future complications.

Treatment model for hamstring muscle injuries To optimise management of HMI it is important that the multidisciplinary team is involved in the acute examination and subsequent management plan. The team doctor will normally be the principal manager of the rehabilitation protocol and will be in charge of co-ordinating the other health professionals such as physiotherapists, biokineticist, physical fitness trainers and sports scientists. This multidisciplinary approach is beneficial as it maximises the footballer’s 33

Hamstring Injuries in Professional Football Players perception of their care allowing them to remain positive of meeting ‘estimated’ time guidelines and ensuring that they are provided with the best care available to them.

Although the authors have suggested a guideline, the protocol always needs to be individualised and the required criteria must be reached in order to advance the player to the next phase of management. The concepts of ‘medical all-clear’ and ‘all-clear to play’ are readily interchangeable for players as they are commonly confused. It is important that the player understands the difference between the 2 concepts in order not to rush the RTP phase of the programme. Figure 4 summarises the protocol from time of injury to RTP providing a management model for HMI. Figure 4. Management model for the treatment of acute hamstring injuries.

CONCLUSION Hamstring muscle injury is a pertinent issue in professional football players. Correct prevention and management strategies need to be followed by medical teams in order to decrease the chance of hamstring injury and re-injury. Screening for risk factors and implementing the suggested preventative programme to the players in need is a way to decrease the changes of HMI. If a footballer sustains a HMI the correct rehabilitative management needs to be implemented. In order to do this a multidisciplinary team approach lead by the team doctor is suggested along with a 5 stage, criteria based, individualized rehabilitation protocol for the player in need. Up on return to sport a gradual introduction to full training and matches is suggested where the risks of early return need to be weighed up with the risks of hamstring re-injury.

In this critical review, a gap between evidence base and actual clinical practice in professional football teams was noted and it is important that the medical team always delivers interventions based on evidence that is available. Although the individual methods suggested in the above recommendations are evidence based, the protocols as a whole are 34

Hamstring Injuries in Professional Football Players novel ones and therefore further studies are needed to verify the effectiveness of the proposed preventative and rehabilitative protocols in a field setting.

BIBLIOGRAPHY Arnason , A., Endersen, T., Holme, I., Engebretsen, L. and Bahr, R. (2008) 'Prevention of hamstring strains in elite soccer: an intervention study', Scandinavian Journal of Medicine and Science in Sports, no. 18, pp. 40-48.

Askling, C.M., Nilsson, J. and Thorsetnsson, A. (2010) 'A new hamstring test to complement the common clinical examination before return to sport after injury', Knee Surgery, Sports Traumatology, Arthroscopy- Springer, no. 18, pp. 798-1803.

Askling, C., Tengvar, M. and Thorstensson, A. (2013) 'Acute hamstring injuries in swedish football: a prospective randomised controlled clinical trial comparing two rehabilitation protocols', British Journal of Sports Medicine, no. 47, pp. 953-959.

Ayala, F., Sainz de Baranda, P., De Ste Croix, M. and Santonja, F. (2012) 'Absolute reliability of five clinical tests for assessing hamstring flexibility in professional futsal players', Journal of Science and Medicine in Sports, no. 15, pp. 142-147.

Bahr, R., Thorborg, K. and Ekstrand, J. (2015) 'Evidence-based hamstring injury prevention is not adopted by the majority of Champions League or Norwegian Premier League football teams: the Nordic Hamstring survey', British Journal of Sports Medicine, no. 49, pp. 1466-1471.

Bengtsson, H., Ekstrand, J. and Hagglund, M. (2013) 'Muscle injury rates in professional football increase with fixture congestion: an 11-year follow-up of the UEFA Champions League injury study', British Journal of Sports Medicine, vol. 47, no. 12, pp. 743-747.

Brukner, P. and Khan, K. (2012) Clinical Sports Medicine, 4th edition, Australia: McGraw-Hill.

Brukner, P., Nealon, A., Morgan, C., Burgess, D. and Dunn, A. (2014) 'Recurrent hamstring injury: applying the limited evidence in the professional football setting with a seven-point programme', British Journal of Sports Medicine, no. 48, pp. 929-938.

Croisier, J., Genteaume, S., Binet , J., Genty, M. and Ferret, J. (2008) 'Strenght imbalances and prevention of hamstring injury in professional soccer players', The American Journal of Sports Medicine, vol. 36, no. 8, pp. 1469-1475.

De Vos, R., Reurink, G., Goudswaard, G., Moen, M., Weir, A. and Tol, J. (2014) 'Clinical findings just after return to play predict hamstring re-injury, but baseline MRI findings do not', British Journal of Sports Medicine, no. 48, pp. 1377-1384.

35

Hamstring Injuries in Professional Football Players Delvaux, F., Rochcogar, P., Bruyere, O., Bourlet, G., Daniel, C., Diverse, P., Reginster, J. and Croisier, J. (2013) 'Return-to-play criteria after hamstring injury: actual medicine practice in professional soccer teams', British Journal of Sports Medicine, vol. 47, no. 10.

Eastwood, D. (2014) 'Hamstring injuries in premier league football team. MRI vs. Clinical Diagnosis', British Journal of Sports Medicine, no. 48, pp. 1581-1582.

Ekstrand, J., Hagglund, M. and Walden, M. (2011) 'Epidemiology of muscle injuries in professional football', American Journal of Sports Medicine, no. 12, pp. 1126-1132.

Ekstrand, J., Healy, J., Walden, M., Lee, J., English, B. and Hagglund, M. (2011) 'Hamstring muscle injuries in professional football: the correlation of MRI findings with return to play.', British Journal of Sports Med, pp. 1-6.

FC Barcelona Medical Services (2009) 'Clinical Practice Guide for Muscular Injuries. Epidemiology, diagnosis, treatment and prevention.', Apunts Med Esport, no. 164, pp. 179-203.

FIFA (2007) The "11+" A complete warm-up programme to prevent injuries manual, FIFA Medical Assessment and Research Centre.

Fournier-Farley, C., Lamontagne, M., Gendron, P. and Gagnon, D. (2015) 'Determinants of Return to Play after the Nonoperative Management of Hamstring injuries in Athletes: A Systemic Review', American Journal of Sports Medicine, no. Online, pp. 1-7.

Garcia-Pinillos, F., Ruiz-Ariza, A., Moreno Del Castillo, R. and Latorre-Roman, P. (2015) 'Impact of limited hamstring flexibility on vertical jump, kicking speed, sprint, and agility in young football players', Journal of Sports Sciences, vol. 33, no. 12, pp. 1293-1297.

Hagglund, M., Walden, M. and Ekstrand, J. (2009) 'Injuries among male and female elite football players', Scandinavian Jounal of Medicine and Science in Sport, no. 19, pp. 819-829.

McCall, A., Carling, C., Nedelec, M., Davison, M., Le Gall, F., Berthoin, S. and Dupont, G. (2014) 'Risk factors, testing and preventative strategies for non-contact injuries in professional football: current perceptions and practices of 44 teams from various premier leagues', British Journal of Sports Medicine, no. 48, pp. 1352-1357.

McCall, A., Dupont, G. and Ekstrand, J. (2016) 'Injury prevention strategies, coach compliance and player adherance of 33 of the UEFA Elite Club Injury Study teams: a survey of teams' head medical officers', British Journal of Sports Medicine, no. 0, pp. 1-6.

Mendighucia, J. and Brughelli, M. (2011) 'A return-to-sport algorythmfor acute hamstring injuries', Physical Therapy in Sport, no. 12, pp. 2-14.

Mendiguchia, J. and Brughelli, M. (2011) 'A return to sport algorythm for acute hamstring injuries', Physical Therapy in sport, no. 12, pp. 2-14.

Mendiguchia, J., Samozino, P., Martinez-Ruiz, E., Brughelli, M., Schmikli, S., Morin, J.B. and MendezVillanueva, A. (2014) 'Progression of Mechanical Properties during On-field Sprint Running after

36

Hamstring Injuries in Professional Football Players returning to Sports from a Hamstring Muscle Injury in Soccer Players', International Journal of Sports Medicine, no. 35, pp. 690-695.

Oxford Centre for Evidence Based Medicine (2011) The Oxford 2011 Levels of Evidence, Oxford.

Petersen, J., Thorborg, K., Nielsen, M.B., Budtz-Jorgensen, E. and Holmich, P. (2011) 'Preentative effect of eccentric training on acute hamstring injuries in men's soccer. A cluster-randomized controlled trial', American Journal of Sports Medicine, no. 39, pp. 2296-2303.

Petersen, J., Thorborg, K., Nielsen, M., Budtz-Jorgensen, E. and Holmich, P. (2011) 'Preventative effect of hamstring injuries in men's soccer: a cluster randomized control trial', American Journal of Sports Medicine, vol. 11, no. 39, pp. 2296-2303.

Petersen, J., Thorborg, K., Nielsen, M. and Powel, J. (2010) 'Acute hamstring injuries in Danish elite football : a 12-month prospective registration study among 374 players', Scandinavian Journal of Medicine and Science in Sport, no. 39, pp. 588-592.

Schache, A., Blanch, P., Dorn, T., Brown, N., Rosemond, D. and Pandy, M. (2011) 'Effects of running speed on lower limb joint kinetics', Journal of medicine and science in sport, vol. 7, no. 43, pp. 12601271.

Schmitt, B., Tyler, T. and McHugh, M. (2012) 'Hamstring injury rehabilitation and prevention of reinjury using lengthened state eccentric training: a new concept', The International Journal of Sports Physical Therapy, vol. 7, no. 3, pp. 333-341.

Sheurmans, J., Van Tiggelen, D., Danneels, L. and Witvrouw, E. (2014) 'Biceps femoris and semitendinosus- teammates or competitors? New insight into hamstring injury mechanisms in male football players: a muscle functional MRI study', British Journal of Sports Medicine, no. 48, pp. 15991606.

Thorborg, K. (2012) 'Why hamstring eccentrics are hamstring essentials', British Journal of Sports Medicine, vol. 46, no. 7, pp. 463-465.

Timmins, R., Bourne, M., Shield, A., Williams, M., Lorenzen, C. and Opar, D. (2015) 'Short biceps femoris muscle fascicles and eccentric knee flexor weakness increase the risk of hamstring injury in elite football (soccer) : a prospective cohort study', British Journal of Sports Medicine, no. 0, pp. 1-12.

Tol, J., Hamilton, B., Eirale , C., Muxart, P., Jacobsen, P. and Whiteley, R. (2014) 'At return to play following hamstring injury the majority of professional football players have residual isokinetic deficits', British Journal of Sports Medicine, no. 48, pp. 1364-1369.

Wood, C., Hawkings, R., Maltby, S. and Bennell, K. (2004) 'The Football Association Medical Research Programme: an audit of injuries in professional football- analysis of hamstring injuries', British Journal of Sports Medicine, no. 38, pp. 36-41.

37

Hamstring Injuries in Professional Football Players

APPENDIX A. Exercise

Description Stretches The Extender:  Player in supine position, bend the hip at 90° and actively extend the knee to end ROM until a hamstring stretch is felt.  Repeat the movement in consecutive quick movements.

Seated Eccentric Knee Flexor Stretch:  Player sits on treatment table with knees at 90°  The exercise trainer grasps the players heel and places other end on distal thigh as a counter-hold  The knee is then progressively extended to full extension whilst the player resists

PNF Contract-Relax:  Player in supine position  The exercise trainer passively lifts the straight leg to end ROM ensuring the opposite leg remains on the floor.

Holds this position for 6 seconds.  The player is the asked to statically push into the trainers shoulder. Holds the contraction for 6 seconds.  The trainer then stretches the leg past the previous end ROM and repeats the process

38

Hamstring Injuries in Professional Football Players Eccentric hamstring band stretch:  Player supine on the floor with a power band around the foot pulling the hip into flexion  Actively pull hip into full extension to the floor and then eccentrically resist the inertia of the band back up to full flexion  Maintain a slow and controlled movement

Eccentric Hamstring Stretch (Final Swing phase):  Player on one knee, with foot positioned on a slider  Exercise trainer pulls the players foot bringing the knee into extension  The player attempts to resist the movement

Strength and Power Eccentric ball curl:  Athlete in supine position with his feet on a ball  Start with knees fully bent, activate glutes and lift hips into the air  Slowly roll the ball out maintain hips in the air till knees are fully extended  Roll ball back in with a quick concentric activation  Repeat the movement Single leg eccentric ball curl:  Athlete in supine position with his feet on a ball  Start with knees fully bent, activate glutes and lift hips into the air  At this point one leg is lifted and held straight up in the air throughout the exercise  Same movement as the standard eccentric ball curl

39

Hamstring Injuries in Professional Football Players Single leg eccentric windmill:  Player stands with uninjured leg on a bench  Reach down in the diagonal plane whilst keeping stance leg straight and maintaining lumbar lordosis  Reach to both sides diagonally and repeat

Mini Nordic Curl:  Athlete on knees whilst exercise trainer secures feet on the floor  Keeping hip extension the player bends slightly forward extending at the knees until a resistance is felt in the hamstrings.  At this point the player concentrically activate the hamstring and returns to starting position  Repeat the sway motion

Half Nordic curl:  Athlete on knees whilst exercise trainer secures feet on the floor  Keeping hip extension the player bends forward extending at the knees until the hamstrings cannot hold the upper body off the ground anymore and fail  At this point the player can put his hands in-front in order to soften the fall to the ground  Return to the top and start again Full Nordic Curl:  Athlete in normal nordic curl starting position  Keeping hip extension the player bends forward extending at the knees until the hamstrings cannot hold the upper body off the ground anymore  At this point hands can be placed on the floor to assist with the end ROM but the resistance must still come from the hamstrings until chest is on the floor

40

Hamstring Injuries in Professional Football Players Eccentric leg curls:  Player will utilize the leg curl machine  From full knee extension the player will use uninjured leg/ arm/ exercise trainer assistance to get the knee to full flexion  From this position he will then resist the extension of the leg against the machines resistance  Slow controlled movement using a heavy weight

Reverse deadlift:  Player starts with the barbell behind the legs  Bends forwards from the hips using a ‘good morning’ motion and maintains the barbell from touching the back of his legs.  Player bends as far forwards as possible maintaining legs as straight as possible and back straight  The power to come back up to starting position is generated from activating the posterior chain

Singe leg deadlift:  Player can use handheld weight for this movement  On single leg, player slowly bends forward from the hips keeping leg and back as straight as possible  Keep weights in line with the standing leg  Activate posterior chain to return back to starting position

The Diver:  Standing on a injured leg the player slowly bends forward from the hip extending arms as far out as possible simulating a dive  The back leg must be extended as high and back as possible whilst keeping pelvis horizontal  Try keep he standing leg straight or slightly bent  Activate posterior chain to return to starting position

41

Hamstring Injuries in Professional Football Players The Glider:  Starting in an upright trunk position with one hand holding onto support and legs slightly split  All weight on the heel of the injured leg (left in the pic)  Glide backwards on the other leg and stop before pain or over-stretch is reached on the injured leg  Movement back to starting positon should be performed with the help of the arm

Supine Bridge:  In supine position, knees bent at 90° and hands to the side  Active core and glutes; lift hips up into the air  Tuck feet in statically (try to pull the floor towards you) and hold

Supine Bridge with Single Leg:  In supine position, knees bent at 90° and hands to the side  Active core and glutes; lift hips up into the air  At this point lift one leg straight up into the air and tuck standing foot in statically  Hold position

Supine Bridge on Ball:  In Supine position with feet on ball and arms on the floor  Activate core and drive hips into the air activating the posterior chain  Push feet into the ball statically  Hold positon

Cable Pendulum:  Player uses a stationary cable machine with cable around the foot  Forward/backward hip motions are performed with the knee at approximately 20-30° flexion  Exercise should be performed slowly and can be progressed to without holding onto the machine which will involve the whole body and proprioception

42

Hamstring Injuries in Professional Football Players

Proprioception Single leg balance:  Stand on a single leg and balance for 1-2 minutes  Variations include:

o o o o o

0° > 30° > 45° knee flexion Hard> soft surface Eyes open>closed Static> dynamic Sports Specific movements

Trunk and Pelvic Stability Prone Plank:  On elbows and feet, the player lifts the hips up into the air  In doing so he must activate his core by pulling his elbows in statically as well as squeezing shoulder blades together  Hold positon ensuring hips don’t drop below shoulder level Alternate arm and leg lift plank:  On hands and knees activate core and lift opposite arm and leg  Keep a neutral pelvis and do not allow rounding of your back  Hold position whilst maintaining balance and then swap points of contact

Ball Plank:  Elbows on ball lift hips up into air  Keep back flat and attempt to squeeze the ball into the floor using your elbows  Advance by taking a single foot off the floor holding the position

43

Hamstring Injuries in Professional Football Players Side Plank:  On elbow and feet  Lift hips up into the air and tuck elbow in  Hold position statically

Side Plank with arm and leg lift:  On side and foot  Lift hips up into the air and tuck elbow in  Lift top hand and leg into the air and hold position whilst maintaining balance  To advance- take a medicine ball and hold it with the top arm  Rotate ball up towards the ceiling and back down whilst holding the side plank

Supine cycling:  On back, activate the core and lift knees into the air  Move legs around in a cycling motion  To advance- support neck and lift forehead up towards the ceiling and hold the mini crunch (as seen in the pic)  Advance further by taking one hand and pushing statically into opposite knee whilst maintaining mini crunch Lateral and retro glute band walks:  Place band below the knees and maintain feet shoulder width apart  Back should be upright and not bent over  Holding a slight squat walk sideways lifting the dragging foot off the ground (as seen in the pic)  Retro walks are done by holding the squat position and moving backwards keeping the feet shoulder width apart

TRX Hamstring bridges:  Place feet in TRX and hold a static bridge by lifting the hips up into the air  Can be advanced by: o Lifting hips up and down o Tucking feet in and out o Repeating using a single foot

44

Hamstring Injuries in Professional Football Players TRX side bridge:  With both feet in TRX lift hips into the air whilst holding body weight up onto the side elbow  Tuck elbow in as hard as possible and hold position Side bridge with manual resistance:  Exercise trainer holds the feet into the air whilst player holds side plank on one elbow  The trainer can then pull on the feet, swing the feet or add other out of control movements to the plank Medicine Ball Step ups:  On a balance board or BOSU ball the player can hold a medicine ball up in the air  He then is required to step up powerfully onto a bench whilst maintaining the ball in the air  Player then slowly controls the movement back down and repeats

Band resisted football specific movements:  Player wears a power band around the hips or the shoulders  The movements should replicate those on the field of play and can include: o Volleying a ball o Heading a ball o Passing a ball o Short bursts forwards resisting coming backwards o Short bursts backwards resisting coming forward

45