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ObjectiveInjuries in women's football (soccer) have scarcely been investigated, and no study has been conducted in the highest competitive level involving club teams from different countries. Our aim was to investigate the time-loss injury epidemiology and characteristics among women's elite football players over four seasons.Methods596 players from 15 elite women's teams in Europe were studied prospectively during the 2018/2019 to 2021/2022 seasons (44 team seasons). Medical staff recorded individual player exposure and time-loss injuries. Injury incidence was calculated as the number of injuries per 1000 playing hours and injury burden as the number of days lost per 1000 hours.Results1527 injuries were recorded in 463 players with an injury incidence of 6.7 (95% CI 6.4 to 7.0) injuries per 1000 hours and a nearly fourfold higher incidence during match play compared with training (18.4, 95% CI 16.9 to 19.9 vs 4.8, 95% CI 4.5 to 5.1; rate ratio 3.8, 95% CI 3.5 to 4.2). Thigh muscle injuries (hamstrings 12%, 188/1527, and quadriceps 11%, 171/1527) were the most frequent injury, while anterior cruciate ligament (ACL) injury had the highest burden (38.0 days lost per 1000 hours, IQR 29.2-52.1) with median days lost of 292 (IQR 246-334) days. Concussions constituted 3% (47/1527) of all injuries, with more than half of them (55%, 26/47) due to ball-related impact.ConclusionAn elite women's football team can expect approximately 35 time-loss injuries per season. Thigh muscle injury was the most common injury and ACL injury had the highest injury burden., Funding Agencies|UEFA

ObjectivesTo: (1) describe hamstring injury incidence and burden in male professional football players over 21 seasons (2001/02 to 2021/22); (2) analyse the time-trends of hamstring muscle injuries over the most recent eight seasons (2014/15 to 2021/22); and (3) describe hamstring injury location, mechanism and recurrence rate. Methods3909 players from 54 teams (in 20 European countries) from 2001/02 to 2021/22 (21 consecutive seasons) were included. Team medical staff recorded individual player exposure and time-loss injuries. Time-trend analyses were performed with Poisson regression using generalised linear models. Results2636 hamstring injuries represented 19% of all reported injuries, with the proportion of all injuries increasing from 12% during the first season to 24% in the most recent season. During that same period, the percentage of all injury absence days caused by hamstring injuries increased from 10% to 20%. Between 2014/15 and 2021/22, training hamstring injury incidence increased (6.7% annually, 95% CI 1.7% to 12.5%) as did burden (9.0% annually, 95% CI 1.2% to 18.3%). During those years, the match hamstring injury incidence also increased (3.9% annually, 95% CI 0.1% to 7.9%) and with the same trend (not statistically significant) for match hamstring injury burden (6.2% annually, 95% CI -0.5% to 15.0%). ConclusionsHamstring injury proportions-in number of injuries and total absence days-doubled during the 21-year period of study. During the last eight seasons, hamstring injury rates have increased both in training and match play., Funding Agencies|Union of European Football Associations; Swedish Football Association; Swedish National Centre for Research in Sports

ObjectivesTo describe the perceived importance of suggested hamstring injury risk factors according to chief medical officers (CMOs) of European male professional football clubs. A secondary objective was to compare if these perceptions differed between teams with a lower-than-average hamstring injury burden and teams with a higher than average hamstring injury burden.MethodsFirst, CMOs of 15 European professional male football clubs were asked to suggest risk factors for hamstring injury in their club. The perceived importance of the suggested risk factors was then rated by all participants on a 5-graded Likert scale. Participating teams were divided in two groups depending on their hamstring injury burden during the 2019/2020 and 2020/2021 seasons. The LOW group consisted of seven teams that had a lower than average hamstring injury burden. The HIGH group consisted of eight teams that had a higher-than-average hamstring injury burden.ResultsTwenty-one risk factors were suggested. The majority were extrinsic in nature, associated with coaching staff, team or club rather than players themselves. Lack of communication between medical staff and coaching staff had the highest average importance (weighted average=3.7) followed by Lack of regular exposure to high-speed football during training sessions (weighted average=3.6). The HIGH group perceived the player factors fatigue and wellness as more important than the LOW group.ConclusionAccording to CMOs recruited in this study, most risk factors for hamstring injuries are extrinsic and associated with the club and coaching staff, and not the players themselves.

ObjectivesThe primary objective was to study the reach, effectiveness, adoption, implementation and maintenance of the Nordic Hamstring Exercise (NHE) programme in womens elite teams in Europe in the 2020-21 season. The secondary objective was to compare hamstring injury rates between teams that used the NHE programme regularly in team training and teams that did not.MethodsEleven teams participating in the Womens Elite Club Injury Study during the 2020-21 season provided data about injury rates and the implementation of the NHE programme.ResultsOne team (9%) used the full original NHE programme, and four teams used the programme in the team training during parts of the season (team training group, n=5). Five teams did not use the NHE, or used it only sporadically for individual players, and one team used NHE only for players with a previous or current hamstring injury (no team training group, n=6). The team training group had a lower incidence of hamstring injuries during match-play (1.4 vs 4.0, p=0.028) than the non-team training group while no difference between groups was shown for the hamstring injury incidence in training (0.6 vs 0.7, p=0.502).ConclusionA low adoption of the NHE programme was reported during the 2020-21 season. However, teams that used NHE for the whole team or most players had a lower hamstring injury incidence at match-play than teams that did not use the NHE or used it for individual players only.

Objective To evaluate whether a change of head coach or other head staff before or during a season is correlated to hamstring injury (HI) burden in male elite-level football (soccer) in Europe.Methods The survey was conducted using a questionnaire reporting any staff change within the team. Data about the head staff changes and hamstring injury burdens were collected from 14 teams participating in the Elite Club Injury Study (ECIS) during the 2019/2020, 2020/2021 and 2021/2022 seasons.Results On average, replacing the head coach before or during a season happens in every second season. All changes, except for the change of the head coach during a season, indicate an association with an increase in HI burden (ranging from 10% to 81%). However, only changes in the fitness coach and team doctor roles reached statistical significance. The HI burden seems to be influenced by adding new staff members, such as the head of fitness/performance coach in 36% of the teams and the team doctor in 17%. New head coaches starting the season with their own, for the team new, fitness/performance coach was highly associated with increased HI burden (p<0.001).Conclusions Bringing their own fitness/performance coaches is common for managers entering a new elite male football club. However, this paper has highlighted that this trend seems to lead to a three times increase in HI burden. Similarly, replacing the team doctor was also associated with increased HI burden. Instability among head staff members in male elite-level football teams seems associated with increased HI burden during the season., Funding Agencies|The authors thank the participating clubs for their participation in the study. A special thanks to Bruno Vanhecke, CMO, at Club Brugge KV, Ricard Pruna, CMO, at FC Barcelona and Maikel van Wijk, Sports Physician at AFC Ajax, for valuable comments on this

Objectives The primary objective was to study the adoption of the NHE programme in European football teams in the 2020/21 season and to compare it to the previous study. A second objective was to compare hamstring injury rates between teams that used the NHE programme in the team training and teams that used the NHE only for players with previous or current hamstring injuries. Methods Data about the implementation of the NHE programme and injury rates were included for 17 teams participating in the Elite Club Injury Study during the 2020/2021 season. Results One team (6%) used the full original NHE programme, and another four teams used it for all or most players in the team (team training group, n=5). Eleven teams used NHE only for players with a previous or current hamstring injury (individual training group), and one team did not use NHE. The team training group had fewer hamstring injuries (5 vs 11 per team, p=0.008) and a lower injury burden (12 vs 35 lay-off days per 1000 hours, p=0.003) than the individual training group. Conclusion Similar to previous reports, low adoption of the NHE programme was seen in the 2020/2021 season. The low adoption rate (13%) relates to the number of teams fully or partly using NHE programmes. Teams that used NHE for the whole team or most players had a lower hamstring injury burden than teams that used NHE only for individual players., Funding Agencies|UEFA

Background While football injury and illness epidemiology surveillance at professional club level in Europe is available, epidemiological data from other continents are lacking. Purpose Investigating injury and illness epidemiology in professional Asian football. Study design Descriptive prospective study. Methods Professional teams from the Asian Football Confederation (AFC) league were followed prospectively for three consecutive AFC seasons (2017 through 2019, 13 teams per season, 322 team months). Time-loss injuries and illnesses in addition to individual match and training exposure were recorded using standardised digital tools in accordance with international consensus procedures. Results In total, 232 665 hours of exposure (88.6% training and 11.4% matches) and 1159 injuries were recorded; 496 (42.8%) occurred during matches, 610 (52.6%) during training; 32 (2.8%) were reported as not applicable and for 21 injuries (1.8%) information was missing. Injury incidence was significantly greater during match play (19.2 +/- 8.6 injuries per 1000 hours) than training (2.8 +/- 1.4, p<0.0001), resulting in a low overall incidence of 5.1 +/- 2.2. The injury burden for match injuries was greater than from training injuries (456 +/- 336 days per 1000 hours vs 54 +/- 34 days, p<0.0001). The two specific injuries causing the greatest burden were complete ACL ruptures (0.14 injuries (95% CI 0.9 to 0.19) and 29.8 days lost (29.1 to 30.5) per 1000 hours) and hamstring strains (0.86 injuries (0.74 to 0.99) and 17.5 days (17.0 to 18.1) lost per 1000 hours). Reinjuries constituted 9.9% of all injuries. Index injuries caused 22.6 +/- 40.8 days of absence compared with 25.1 +/- 39 for reinjuries (p=0.62). The 175 illnesses recorded resulted in 1.4 +/- 2.9 days of time loss per team per month. Conclusion Professional Asian football is characterised by an overall injury incidence similar to that reported from Europe, but with a high rate of ACL ruptures and hamstring inj

Background Studies on subsequent anterior cruciate ligament (ACL) ruptures and career length in male professional football players after ACL reconstruction (ACLR) are scarce. Aim To investigate the second ACL injury rate, potential predictors of second ACL injury and the career length after ACLR. Study design Prospective cohort study. Setting Mens professional football. Methods 118 players with index ACL injury were tracked longitudinally for subsequent ACL injury and career length over 16.9 years. Multivariable Cox regression analysis with HR was carried out to study potential predictors for subsequent ACL injury. Results Median follow-up was 4.3 (IQR 4.6) years after ACLR. The second ACL injury rate after return to training (RTT) was 17.8% (n=21), with 9.3% (n=11) to the ipsilateral and 8.5% (n=10) to the contralateral knee. Significant predictors for second ACL injury were a non-contact index ACL injury (HR 7.16, 95% CI 1.63 to 31.22) and an isolated index ACL injury (HR 2.73, 95% CI 1.06 to 7.07). In total, 11 of 26 players (42%) with a non-contact isolated index ACL injury suffered a second ACL injury. RTT time was not an independent predictor of second ACL injury, even though there was a tendency for a risk reduction with longer time to RTT. Median career length after ACLR was 4.1 (IQR 4.0) years and 60% of players were still playing at preinjury level 5 years after ACLR. Conclusions Almost one out of five top-level professional male football players sustained a second ACL injury following ACLR and return to football, with a considerably increased risk for players with a non-contact or isolated index injury., Funding Agencies|Union of European Football Associations

Objective To compare injury rates among professional mens football teams that have a winter break in their league season schedule with corresponding rates in teams that do not. Methods 56 football teams from 15 European countries were prospectively followed for seven seasons (2010/2011-2016/2017)-a total of 155 team-seasons. Individual training, match exposure and time-loss injuries were registered. Four different injury rates were analysed over four periods within the season, and linear regression was performed on team-level data to analyse the effect of winter break on each of the injury rates. Crude analyses and analyses adjusted for climatic region were performed. Results 9660 injuries were reported during 1 447 011 exposure hours. English teams had no winter break scheduled in the season calendar: the other European teams had a mean winter break scheduled for 10.0 days. Teams without a winter break lost on average 303 days more per season due to injuries than teams with a winter break during the whole season (pamp;lt;0.001). The results were similar across the three periods August-December (p=0.013), January-March (pamp;lt;0.001) and April-May (p=0.050). Teams without a winter break also had a higher incidence of severe injuries than teams with a winter break during the whole season (2.1 severe injuries more per season for teams without a winter break, p=0.002), as well as during the period JanuaryMarch (p=0.003). A winter break was not associated with higher team training attendance or team match availability. Climatic region was also associated with injury rates. Conclusions The absence of a scheduled winter break was associated with a higher injury burden, both before and during the two periods following the time that many European teams take a winter break. Teams without a winter break (English clubs) had a higher incidence of severe injuries following the time of the year that other teams (other European clubs) had their scheduled break., Funding Agencies|UEFA; Swedish Football Association; Swedish Research Council for Sport Science

Aim To determine the epidemiology of isolated syndesmotic injuries in professional football players. Methods Data from 15 consecutive seasons of European professional football between 2001 and 2016 contributed to the dataset of this study. Match play and training data from a total of 3677 players from 61 teams across 17 countries have been included. Team medical staff recorded player exposure and time loss injuries. Injury incidence was defined as the number of injuries per 1000 player-hours. Injury burden was defined as number of days absence per 1000 player-hours. Seasonal trends for isolated syndesmotic injury incidence, isolated syndesmotic injury proportion of ankle ligament injuries and isolated syndesmotic injury burden were analysed via linear regression. Results The isolated syndesmotic injury incidence was 0.05 injuries per 1000 hours of exposure (95% CI 0.04 to 0.06) or one injury per team every three seasons. The injury incidence during match play was 13 times higher compared with during training, 0.21 (95% CI 0.16 to 0.26) and 0.02 (95% CI 0.01 to 0.02), respectively. Out of the 1320 ankle ligament injuries registered during the 15 seasons, 94 (7%) were diagnosed as isolated syndesmotic injuries. An annual increase in injury incidence was observed (R-2=0.495, b=0.003, 95% CI 0.001 to 0.004, P=0.003). However, no significant annual change of injury burden was observed (R-2=0.033, b=0.032, 95% CI -0.073 to 0.138, P=0.520). Seventy-four per cent of the injuries were contact related, and the mean (+/- SD) absence following an isolated syndesmotic injury was 39 (+/- 28) days. Conclusions The incidence of isolated syndesmotic injuries in elite professional European football annually increased between 2001 and 2016., Funding Agencies|UEFA; Swedish Football Association; Football Association Premier League Limited; Swedish National Centre for Research in Sports

Background Internal workload (ie, from training and matches) is considered one of the most important injury risk factors for elite European football teams, however there is little published evidence to support this belief. Objective We examined the association and predictive power of internal workload and non-contact injuries. Methods Five elite European teams, 171 players (age: 25.1 +/- 4.9 years; height:181.6 +/- 6.7 cm; body mass: 77.5 +/- 7.2 kg) participated over one full competitive season. Using the session-rating of perceived exertion (s-RPE) method players internal workloads were calculated for acute week, week-to-week changes, cumulated weeks, chronic weeks and acute:chronic ratios and analysed for association with non-contact injury (using generalised estimating equations (GEE)). Associated variables from GEE analysis were categorised into very low to very high workload zones and checked for increased relative risks (RRs). Associated workload variables were also analysed for predictive power (receiver operating characteristics). Results Acute:chronic workload ratios at 1:3 and 1:4 weeks were associated with non-contact injury (Pamp;lt;0.05). Specifically, a greater risk of injury was found for players with an acute:chronic workload at 1:4 weeks of 0.97 to 1.38 (RR 1.68; 95% CI 1.02 to 2.78, likely harmful) and amp;gt;1.38 (RR 2.13; 95% CI 1.21 to 3.77, very likely harmful) compared with players whose acute:chronic workload was 0.60 to 0.97. An acute:chronic workload 1:3 of amp;gt;1.42 compared with 0.59 to 0.97 displayed a 1.94 times higher risk of injury (RR 1.90; 95% CI 1.08 to 3.36, very likely harmful). Importantly, acute:chronic workload at both 1:4 and 1:3 showed poor predictive power (area under the curve 0.53 to 0.58) despite previous reports and beliefs that it can predict injury. Conclusions This study provides evidence for the acute:chronic internal workload (measured using s-RPE) as a risk factor for non-contact injury in elite European footba, Funding Agencies|UEFA; Swedish National Centre for Research in Sports

n/a, Funding Agencies|Eastern Norway Regional Health Authority; International Olympic Committee; Royal Norwegian Ministry of Culture; Norwegian Olympic and Paralympic Committee & Confederation of Sport; UEFA; Swedish Football Association; Swedish National Centre for Research in Sports; Norsk Tipping AS

Background The association between match congestion and injury rates in professional football has yielded conflicting results. Aim To analyse associations between match congestion on an individual player level and injury rates during professional football matches. Methods Data from a prospective cohort study of professional football with 133 170 match observations were analysed with Poisson regressions. Associations between short-term match congestion, defined as number of days between two match exposures (3, 4, 5, 6 and 7-10 days) and injury rates were analysed. To analyse the influence of long-term match congestion, defined as individual match exposure hours in the 30 days preceding a match, observations were categorised into three groups (low, 4.5; medium, amp;gt;4.5to 7.5; and high, amp;gt;7.5hours). Results No differences in total match injury rates were found between the reference category (3 days) and the other categories of short-term congestion. Muscle injury rates were significantly lower in matches preceded by 6 (rate ratio (RR) 0.79; 95%CI 0.65 to 0.95) or 7-10 days (RR 0.81; 95%CI 0.71 to 0.93) compared with 3 days since the last match exposure. No differences in total and muscle injury rates between the three long-term match congestion groups were found. Conclusions In this study of male professional football players, there were no match congestion-related differences in total match injury rates, but muscle injury rates during matches were lower when players were given at least 6days between their match exposures., Funding Agencies|Union of European Football Associations; Swedish National Centre for Research in Sports

Background Previous injury is a well-documented risk factor for football injury. The time trends and patterns of recurrent injuries at different playing levels are not clear. Aim To compare recurrent injury proportions, incidences and patterns between different football playing levels, and to study time trends in recurrent injury incidence. Methods Time-loss injuries were collected from injury surveillance of 43 top-level European professional teams (240 team-seasons), 19 Swedish premier division teams (82 team-seasons) and 10 Swedish amateur teams (10 team-seasons). Recurrent injury was defined as an injury of the same type and at the same site as an index injury within the preceding year, with injury amp;lt;2 months defined as an early recurrence, and amp;gt;2 months as a delayed recurrence. Seasonal trend for recurrent injury incidence, expressed as the average annual percentage of change, was analysed using linear regression. Results 13 050 injuries were included, 2449 (18.8%) being recurrent injuries, with 1944 early (14.9%) and 505 delayed recurrences (3.9%). Recurrence proportions were highest in the second half of the competitive season for all cohorts. Recurrence proportions differed between playing levels, with 35.1% in the amateur cohort, 25.0% in the Swedish elite cohort and 16.6% in the European cohort (chi(2) overall effect, pamp;lt;0.001). A decreasing trend was observed in recurrent injury incidence in the European cohort, a -2.9% average annual change over the 14-year study period (95% CI -5.4% to -0.4%, p=0.026). Similarly, a decreasing tendency was also seen in the Swedish premier division. Conclusions Recurrence proportions showed an inverse relationship with playing level, and recurrent injury incidence has decreased over the past decade., Funding Agencies|UEFA; Swedish Football Association; Football Association Premier League Limited; Swedish National Centre for Research in Sports

Background Studies investigating the development of ACL injuries over time in football are scarce and more data on what happens before and after return to play (RTP) are needed. Aim To investigate (1) time trends in ACL injury rates, (2) complication rates before return to match play following ACL reconstruction, and (3) the influence of ACL injury on the subsequent playing career in male professional football players. Methods 78 clubs were followed between 2001 and 2015. Time trend in ACL injury rate was analysed using linear regression. ACL-injured players were monitored until RTP and tracked for 3 years after RTP. Results We recorded 157 ACL injuries, 140 total and 17 partial ruptures, with a non-significant average annual increase in the ACL injury rate by 6% (R-2=0.13, b=0.059, 95% CI -0.04 to 0.15, p=0.20). The match ACL injury rate was 20-fold higher than the training injury rate (0.340 vs 0.017 per 1000 h). 138 players (98.6%) with a total rupture underwent ACL reconstruction; all 134 players with RTP data (4 players still under rehabilitation) were able to return to training, but 9 of them (6.7%) suffered complications before their first match appearance (5 reruptures and 4 other knee surgeries). The median layoff after ACL reconstruction was 6.6 months to training and 7.4 months to match play. We report 3-year follow-up data for 106 players in total; 91 players (85.8%) were still playing football and 60 of 93 players (65%) with ACL reconstruction for a total rupture played at the same level. Conclusions The ACL injury rate has not declined during the 2000s and the rerupture rate before return to match play was 4%. The RTP rate within a year after ACL reconstruction was very high, but only two-thirds competed at the highest level 3 years later., Funding Agencies|UEFA; Swedish Football Association; Football Association Premier League Limited; Swedish National Centre for Research in Sports

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Aim The present study evaluated whether the MRI parameters of hamstring injuries in male professional football players correlate with time to return to play (RTP). Methods 46 elite European football teams were followed prospectively for hamstring injuries between 2007 and 2014. Club medical staff recorded individual player exposure and time-loss after hamstring injury. MRI parameters were evaluated by two independent radiologists and correlated with the RTP data. Results A total of 255 grade 1 and 2 injuries were evaluated in this study. RTP was longer for grade 2 than grade 1 injuries (24 +/- 13, 95% CI 21 to 26 days vs 18 +/- 15, 95% CI 16 to 20 days; mean difference: 6, 95% CI 2 to 9 days, p=0.004, d=0.39). 84% of injuries affected the biceps femoris (BF) muscle, whereas 12% and 4% affected the semimembranosus (SM) and semitendinosus (ST), respectively. No difference in lay-off time was found for injuries to the three different muscles (BF 20 +/- 15 days, SM 18 +/- 11 days, ST 23 +/- 14 days; p=0.83). The recurrence rate was higher for BF injuries than for SM and ST injuries combined (18% vs 2%, p=0.009). The size of the oedema weakly correlated with time to RTP (r(2)=6-12%). No correlation was found between location of injury and time to RTP. The majority of the intramuscular injuries affected the MT junction (56% in grade 1 and 2 injuries), but no difference in lay-off time was found between the different types of injuries. Conclusions The radiological grade and size of the oedema correlate with time to RTP for both, grade 1 and 2 injuries. No correlations were found between time to RTP and the location and type of injury., Funding Agencies|Union of European Football Associations; Swedish Football Association; Football Association Premier League Limited; Swedish National Centre for Research in Sports

Background There are limited data on hamstring injury rates over time in football. Aim To analyse time trends in hamstring injury rates in male professional footballers over 13 consecutive seasons and to distinguish the relative contribution of training and match injuries. Methods 36 clubs from 12 European countries were followed between 2001 and 2014. Team medical staff recorded individual player exposure and time-loss injuries. Injuries per 1000 h were compared as a rate ratio (RR) with 95% CI. Injury burden was the number of lay off days per 1000 h. Seasonal trend for injury was analysed using linear regression. Results A total of 1614 hamstring injuries were recorded; 22% of players sustained at least one hamstring injury during a season. The overall hamstring injury rate over the 13-year period was 1.20 injuries per 1000 h; the match injury rate (4.77) being 9 times higher than the training injury rate (0.51; RR 9.4; 95% CI 8.5 to 10.4). The time-trend analysis showed an annual average 2.3% year on year increase in the total hamstring injury rate over the 13-year period (R-2=0.431, b=0.023, 95% CI 0.006 to 0.041, p=0.015). This increase over time was most pronounced for training injuries-these increased by 4.0% per year (R-2=0.450, b=0.040, 95% CI 0.011 to 0.070, p=0.012). The average hamstring injury burden was 19.7 days per 1000 h (annual average increase 4.1%) (R-2=0.437, b=0.041, 95% CI 0.010 to 0.072, p=0.014). Conclusions Training-related hamstring injury rates have increased substantially since 2001 but match-related injury rates have remained stable. The challenge is for clubs to reduce training-related hamstring injury rates without impairing match performance., Funding Agencies|UEFA; Swedish Football Association; Football Association Premier League Limited; Swedish National Centre for Research in Sports

Purpose (1) To quantify current practice at the most elite level of professional club football in Europe with regard to injury prevention strategy; (2) to describe player adherence and coach compliance to the overall injury prevention programme. Methods A structured online survey was administered to the Head medical officers of 34 elite European teams currently participating in the UEFA Elite Club Injury Study. The survey had 4 sections; (1) risk factors for injury, (2) assessment and monitoring of injury risk, (3) prevention strategies and (4) coach compliance and player adherence to the injury prevention process. Results 33 (97%) Medical officers of the teams responded. The most important perceived injury risk factor was previous injury. Four of the top 6 risk factors physical fitness, accumulated fatigue, reduced recovery time between matches and training load-were related to player workload. The top 3 preventative exercises were eccentric, balance/proprioception and core training. Regarding monitoring, the top 3 tools implemented were measurement of workload, subjective wellness and a general medical screen. The subjectively rated level of coach compliance in UEFA teams was perceived as high, while the player adherence varied from none at all to perfect. Summary and conclusion Medical officers place importance on workload-related variables as risk factors for injury in elite European football players. A lack of consistently high player adherence may limit the effects of contemporary injury prevention programmes in elite European footballers.

Background Determining fracture risk and rehabilitation periods after specific fractures in professional football is essential for team planning. Aim To identify fracture epidemiology and absences after different types of fractures in male professional football players. Methods 2439 players from 41 professional male teams in 10 countries were followed prospectively from 2001 to 2013. Team medical staff registered fractures, absences after fractures and player exposure. Results 364 fractures were recorded, with an incidence of 0.27/1000 h of exposure (95% CI 0.25 to 0.30). The incidence of traumatic fractures was 0.25 (0.22 to 0.27) and that of stress fractures was 0.03 (0.02 to 0.04). 45% of traumatic fractures and 86% of stress fractures affected the lower extremities. Absence after a fracture was 32 days (1-278) (median (range)), compared to that after a traumatic fracture of 30 days (1-278) and a stress fracture of 65 days (6-168) (pamp;lt;0.001). Annual fracture incidence was stable during the study period (R-2=0.051, b=-0.011 (95% CI -0.043 to 0.021)). Young players had a relative risk of 10.9 (3.3 to 35.6) of sustaining stress fractures compared to old players (pamp;lt;0.01). The fracture incidence did not differ between individuals in different playing positions (p=0.10). Summary A male professional football team can expect 1 to 2 fractures per season. There are more traumatic fractures than stress fractures; while most fractures affect the lower extremities, stress fractures yield longer absences than traumatic fractures and young players have more stress fractures than old players. There is no difference in risk among players at different playing positions., Funding Agencies|UEFA; Swedish Football Association; Football Association Premier League Limited; Swedish National Centre for Research in Sports

Background There are limited data on the nature, type and incidence of illness in football. Previous studies indicate that gastrointestinal and respiratory tract illnesses are most common. Aim To describe the incidence and burden of illness in male professional football. Methods Over the 4-year study period, 2011-2014, 73 professional football teams in Europe participated, with a total of 1 261 367 player-days recorded. All time-loss illnesses were recorded by the medical staff of each club. A recordable illness episode was any physical or psychological symptom (not related to injury) that resulted in the player being unable to participate fully in training or match play. Results A total of 1914 illness episodes were recorded. The illness incidence was 1.5 per 1000 player-days, meaning that, on average, a player experienced an illness episode every second season, with a median of 3 days absence per illness episode. Severe illness (absence amp;gt;4 weeks) constituted 2% of all illnesses. Respiratory tract illness was the most common (58%), followed by gastrointestinal illness (38%). Respiratory tract illness, gastrointestinal illness and cardiovascular illness caused the highest illness burden. Conclusions The illness incidence among male professional football players is low compared with the injury incidence. We found that the highest illness burden was caused by illness to the respiratory tract, gastrointestinal tract and cardiovascular system., Funding Agencies|UEFA; Swedish Football Association; Football Association Premier League Limited; Swedish National Centre for Research in Sports; Royal Norwegian Ministry of Culture and Church Affairs; South-Eastern Norway Regional Health Authority; IOC; Norwegian Olympic Committee & Confederation of Sport; Norsk Tipping AS

Background Heterogeneous taxonomy of groin injuries in athletes adds confusion to this complicated area. Aim The Doha agreement meeting on terminology and definitions in groin pain in athletes was convened to attempt to resolve this problem. Our aim was to agree on a standard terminology, along with accompanying definitions. Methods A one-day agreement meeting was held on 4 November 2014. Twenty-four international experts from 14 different countries participated. Systematic reviews were performed to give an up-to-date synthesis of the current evidence on major topics concerning groin pain in athletes. All members participated in a Delphi questionnaire prior to the meeting. Results Unanimous agreement was reached on the following terminology. The classification system has three major subheadings of groin pain in athletes: 1. Defined clinical entities for groin pain: Adductor-related, iliopsoas-related, inguinal-related and pubic-related groin pain. 2. Hip-related groin pain. 3. Other causes of groin pain in athletes. The definitions are included in this paper. Conclusions The Doha agreement meeting on terminology and definitions in groin pain in athletes reached a consensus on a clinically based taxonomy using three major categories. These definitions and terminology are based on history and physical examination to categorise athletes, making it simple and suitable for both clinical practice and research.

Background Groin injuries are troublesome in mens and womens football. Aim To review the literature on the epidemiology of groin injury in senior football and compare injury occurrence between sexes. Methods Studies were identified through a search of PubMed, EMBASE, CINAHL and Web of Science, in the reference lists of the selected articles and the authors bibliographies. The number of injuries, percentage of groin injury from all injuries and rate of groin injury per 1000 h were extracted. Exposure and injury data were aggregated across included studies and the absolute differences in groin injury proportion and rate of groin injury were compared between sexes. Risk of bias was assessed using a 5-item checklist. Results 34 articles met the study criteria and were included. The proportion of groin injury in club-seasonal football was 4-19% in men and 2-14% in women. Aggregated data analysis (29 studies) showed a higher relative proportion of groin injury in men than in women (12.8% vs 6.9%, absolute difference 5.9%, 95% CI 4.6% to 7.1%). The rate of groin injury varied from 0.2 to 2.1/1000 h in men and 0.1 to 0.6/1000 h in womens club football, and aggregated analysis (23 studies) showed a more than two-fold higher rate in men (0.83/1000 h vs 0.35/1000 h, rate ratio 2.4, 95% CI 2.0 to 2.9). High risk of bias was identified for participant selection (18 studies), exposure (17 studies) and precision estimate (16 studies). Conclusions Groin injuries are frequent in senior football and are more common in men than women. Future research needs to be of higher quality., Funding Agencies|Union of European Football Associations; Swedish Football Association; Football Association Premier League Limited; Swedish National Centre for Research in Sports

Background Data regarding direct athletic muscle injuries (caused by a direct blunt or sharp external force) compared to indirect ones (without the influence of a direct external trauma) are missing in the current literature-this distinction has clinical implications. Aim To compare incidence, duration of absence and characteristics of indirect and direct anterior (quadriceps) and posterior thigh (hamstring) muscle injuries. Methods 30 football teams and 1981 players were followed prospectively from 2001 until 2013. The team medical staff recorded individual player exposure and time-loss injuries. Muscle injuries were defined as indirect or direct according to their injury mechanism. Results In total, 2287 thigh muscle injuries were found, representing 25% of all injuries. Two thousand and three were valid for further analysis, of which 88% were indirect and 12% direct. The incidence was eight times higher for indirect injuries (1.48/1000 h) compared to direct muscle injuries (0.19/1000 h) (p<0.01). Indirect muscle injuries caused 19% of total absence, and direct injuries 1%. The mean lay-off time for indirect injuries amounted to 18.5 days and differed significantly from direct injuries which accounted for 7 days (p<0.001). 60% of indirect injuries and 76% of direct injuries occurred in match situations. Foul play was involved in 7% of all thigh muscle injuries, as well as in 2% of indirect injuries and 42% of direct injuries. Summary Muscle anterior and posterior thigh injuries in elite football are more frequent than have been previously described. Direct injuries causing time loss are less frequent than indirect ones, and players can usually return to full activity in under half the average time for an indirect injury. Foul play is involved in 7.5% of all thigh muscle injuries., Funding Agencies|UEFA

Background The Nordic hamstring (NH) exercise programme was introduced in 2001 and has been shown to reduce the risk of acute hamstring injuries in football by at least 50%. Despite this, the rate of hamstring injuries has not decreased over the past decade in male elite football. Aim To examine the implementation of the NH exercise programme at the highest level of male football in Europe, the UEFA Champions League (UCL), and to compare this to the Norwegian Premier League, Tippeligaen, where the pioneer research on the NH programme was conducted. Design Retrospective survey. Setting/participants 50 professional football teams, 32 from the UCL and 18 from Tippeligaen. Methods A questionnaire, based on the Reach, Efficacy, Adoption, Implementation and Maintenance framework, addressing key issues related to the implementation of the NH programme during three seasons from 2012 through 2014, was distributed to team medical staff using electronic survey software. Results The response rate was 100%. Of the 150 club-seasons covered by the study, the NH programme was completed in full in 16 (10.7%) and in part in an additional 9 (6%) seasons. Consequently, 125 (83.3%) club-seasons were classified as non-compliant. There was no difference in compliance between the UCL and Tippeligaen in any season (chi(2): 0.41 to 0.52). Conclusions Adoption and implementation of the NH exercise programme at the highest levels of male football in Europe is low; too low to expect any overall effect on acute hamstring injury rates., Funding Agencies|Royal Norwegian Ministry of Culture; South-Eastern Norway Regional Health Authority; International Olympic Committee; Norwegian Olympic Committee & Confederation of Sport; Norsk Tipping AS; UEFA; Swedish National Centre for Research in Sports

Background Little is known about the short-term and long-term sequelae of concussion, and about when athletes who have sustained such injuries can safely return to play. Purpose To examine whether sports-related concussion increases the risk of subsequent injury in elite male football players. Study design Prospective cohort study. Methods Injuries were registered for 46 male elite football teams in 10 European countries in the 2001/ 2002-2011/ 2102 seasons. Two survival models were used to analyse whether concussion increased the subsequent risk of an injury in the first year. Results During the follow-up period, 66 players sustained concussions and 1599 players sustained other injuries. Compared with the risk following other injuries, concussion was associated with a progressively increased risk of a subsequent injury in the first year (0 to <3 months, HR=1.56, 95% CI 1.09 to 2.23; 3 to <6 months, HR=2.78, 95% CI 1.58 to 4.89; 6-12 months, HR=4.07, 95% CI 2.14 to 7.76). In the second model, after adjustment for the number of injuries in the year preceding the concussion, this injury remained significantly associated with the risk of subsequent injury in the first year (HR=1.47, 95% CI 1.05 to 2.05). Conclusions Concussion was a risk factor for sustaining subsequent injury within the following year. In-depth medical evaluation, which includes neurological and cognitive assessment, is warranted within the concussion management and return-to-play process.

Objective To provide a clear terminology and classification of muscle injuries in order to facilitate effective communication among medical practitioners and development of systematic treatment strategies. less thanbrgreater than less thanbrgreater thanMethods Thirty native English-speaking scientists and team doctors of national and first division professional sports teams were asked to complete a questionnaire on muscle injuries to evaluate the currently used terminology of athletic muscle injury. In addition, a consensus meeting of international sports medicine experts was established to develop practical and scientific definitions of muscle injuries as well as a new and comprehensive classification system. less thanbrgreater than less thanbrgreater thanResults The response rate of the survey was 63%. The responses confirmed the marked variability in the use of the terminology relating to muscle injury, with the most obvious inconsistencies for the term strain. In the consensus meeting, practical and systematic terms were defined and established. In addition, a new comprehensive classification system was developed, which differentiates between four types: functional muscle disorders (type 1: overexertion-related and type 2: neuromuscular muscle disorders) describing disorders without macroscopic evidence of fibre tear and structural muscle injuries (type 3: partial tears and type 4: (sub) total tears/tendinous avulsions) with macroscopic evidence of fibre tear, that is, structural damage. Subclassifications are presented for each type. less thanbrgreater than less thanbrgreater thanConclusions A consistent English terminology as well as a comprehensive classification system for athletic muscle injuries which is proven in the daily practice are presented. This will help to improve clarity of communication for diagnostic and therapeutic purposes and can serve as the basis for future comparative studies to address the continued lack of systematic information on musc, Funding Agencies|FC Bayern Munich, Adidas||Audi

Background Previously, no difference in acute injury rate has been found when playing football on artificial turf (AT) compared with natural grass (NG). Aim To compare acute injury rates in professional football played on AT and NG at the individual player level; and to compare, at club level, acute and overuse injury rates between clubs that have AT at their home venue (AT clubs) and clubs that have NG (NG clubs). Methods 32 clubs (AT, n=11; NG, n=21) in the male Swedish and Norwegian premier leagues were followed prospectively during the 2010 and 2011 seasons. Injury rate was expressed as the number of time loss injuries/1000 h and compared with rate ratio (RR) and 99% CI. Results No statistically significant differences were found in acute injury rates on AT compared with NG during match play (RR 0.98, 99% CI 0.79 to 1.22) or training (RR 1.14, 99% CI 0.86 to 1.50) when analysing at the individual player level. When analysing at the club level, however, AT clubs had a significantly higher acute training injury rate (RR 1.31, 99% CI 1.04 to 1.63) and overuse injury rate (RR 1.38, 99% CI 1.14 to 1.65) compared with NG clubs. Conclusions At the individual player level, no significant differences were found in acute injury rates when playing on AT compared with NG. However, clubs with AT at their home venue had higher rates of acute training injuries and overuse injuries compared with clubs that played home matches on NG., Funding Agencies|Swedish National Centre for Research in Sports||Swedish Football Association||Praktikertjanst AB||County Council of Ostergotland||Royal Norwegian Ministry of Culture and Church Affairs||South-Eastern Norway Regional Health Authority||International Olympic Committee||Norwegian Olympic Committee & Confederation of Sport||Norsk Tipping AS

Background Ankle injury is common in football, but the circumstances surrounding them are not well characterised. Aim To investigate the rates, especially time-trends, and circumstances of ankle injuries in male professional football. Methods 27 European clubs with 1743 players were followed prospectively between 2001/2002 and 2011/2012. Time loss injuries and individual-player exposure during training sessions and matches were recorded. Injury rate was defined as the number of injuries/1000 h. Results A total of 1080 ankle injuries were recorded (13% of all injuries) with lateral ligament ankle sprain being the most common injury subtype (51% of all ankle injuries). The rates of ankle injury and ankle sprain were 1/1000 h and 0.7/1000 h, respectively. The ankle sprain rate declined slightly over time during the 11-year study period (on average 3.1%/season) with a statistically significant seasonal trend (p=0.041). Foul play according to the referee was involved in 40% of the match-related ankle sprains. Syndesmotic sprains and ankle impingement were uncommon causes of time loss (3% each of all ankle injuries). Conclusions Lateral ligament ankle sprain constituted half of all ankle injuries in male professional football, whereas ankle impingement syndromes were uncommon. The ankle sprain rate decreased slightly over time, but many ankle sprains were associated with foul play. Our data extend the body of literature that provides football policy makers with a foundation to review existing rules and their enforcement., Funding Agencies|Union of European Football Associations (UEFA)||Swedish National Centre for Research in Sports, and Praktikertjanst AB

Background Owing to the complexity and heterogeneity of muscle injuries, a generally accepted classification system is still lacking. less thanbrgreater than less thanbrgreater thanAims To prospectively implement and validate a novel muscle injury classification and to evaluate its predictive value for return to professional football. less thanbrgreater than less thanbrgreater thanMethods The recently described Munich muscle injury classification was prospectively evaluated in 31 European professional male football teams during the 2011/2012 season. Thigh muscle injury types were recorded by team medical staff and correlated to individual player exposure and resultant time-loss. less thanbrgreater than less thanbrgreater thanResults In total, 393 thigh muscle injuries occurred. The muscle classification system was well received with a 100% response rate. Two-thirds of thigh muscle injuries were classified as structural and were associated with longer lay-off times compared to functional muscle disorders (pandlt;0.001). Significant differences were observed between structural injury subgroups (minor partial, moderate partial and complete injuries) with increasing lay-off time associated with more severe structural injury. Median lay-off time of functional disorders was 5-8 days without significant differences between subgroups. There was no significant difference in the absence time between anterior and posterior thigh injuries. less thanbrgreater than less thanbrgreater thanConclusions The Munich muscle classification demonstrates a positive prognostic validity for return to play after thigh muscle injury in professional male football players. Structural injuries are associated with longer average lay-off times than functional muscle disorders. Subclassification of structural injuries correlates with return to play, while subgrouping of functional disorders shows less prognostic relevance. Functional disorders are often underestimated clinically and require further

Background The influence of fixture congestion on injury rates and team performance has only been scarcely investigated. Aim To study associations between recovery time and match load and injury rates and team performance in professional football. Methods Exposure and time loss injuries were registered prospectively from 27 teams over 11 seasons. Matches were grouped according to recovery days before each match (≤3 vs >3 days, and ≤4 vs ≥6 days). Injury rates and team performance were compared between groups. Match load in match sequences containing five consecutive matches was determined by the number of days separating the first match and the last training session during that match sequence. Linear regression was used to study associations between match load and injury rates and team performance. Results Team performance showed no association with match load, or recovery days prior to matches, except for Europa League matches that indicated more matches lost with short recovery (≤3 days) (p=0.048). Total injury rates and muscle injury rates were increased in league matches with ≤4 days compared with ≥6 days’ recovery (RR 1.09, 95% CI 1.00 to 1.18, and RR 1.32, 95% CI 1.15 to 1.51, respectively), specifically hamstring and quadriceps injuries. High match load was associated with increase in muscle injury rate in matches in the same match sequence (p=0.012), and increase in ligament injury rate in training in the subsequent match sequence (p=0.003). Conclusions Fixture congestion was associated with increased muscle injury rates but had no, or very limited, influence on team performance., Funding Agencies|Union of European Football Associations (UEFA)||Swedish National Centre for Research in Sports, and Praktikertjanst AB

Background The influence of injuries on team performance in football has only been scarcely investigated. Aim To study the association between injury rates and team performance in the domestic league play, and in European cups, in male professional football. Methods 24 football teams from nine European countries were followed prospectively for 11 seasons (2001–2012), including 155 team-seasons. Individual training and match exposure and time-loss injuries were registered. To analyse the effect of injury rates on performance, a Generalised Estimating Equation was used to fit a linear regression on team-level data. Each team's season injury rate and performance were evaluated using its own preceding season data for comparison in the analyses. Results 7792 injuries were reported during 1 026 104 exposure hours. The total injury incidence was 7.7 injuries/1000 h, injury burden 130 injury days lost/1000 h and player match availability 86%. Lower injury burden (p=0.011) and higher match availability (p=0.031) were associated with higher final league ranking. Similarly, lower injury incidence (p=0.035), lower injury burden (p<0.001) and higher match availability (p<0.001) were associated with increased points per league match. Finally, lower injury burden (p=0.043) and higher match availability (p=0.048) were associated with an increase in the Union of European Football Association (UEFA) Season Club Coefficient, reflecting success in the UEFA Champions League or Europa League. Conclusions Injuries had a significant influence on performance in the league play and in European cups in male professional football. The findings stress the importance of injury prevention to increase a team's chances of success., Funding Agencies|Union of European Football Associations (UEFA)||Swedish National Centre for Research in Sports and Praktikertjanst AB

Background less thanbrgreater than less thanbrgreater thanThere is little information about Metatarsal Five (MT-5) fractures for specific sports. less thanbrgreater than less thanbrgreater thanObjective less thanbrgreater than less thanbrgreater thanTo study the occurrence, the imaging characteristics, the lay-off times and healing problems of MT-5 fractures among male footballers. less thanbrgreater than less thanbrgreater thanMethods less thanbrgreater than less thanbrgreater thanSixty-four European elite teams were monitored from 2001 to 2012. x-Rays were collected and classified by the Torg criteria. less thanbrgreater than less thanbrgreater thanResults less thanbrgreater than less thanbrgreater thanOf 13754 injuries, 0.5% (67) proved to be MT-5 fractures. Their incidence was 0.04 injuries/1000h of exposure. A team of 25 players might thus expect an MT-5 fracture every fifth season. Of these fractures, 67% (38) were primary and 33% were refractures. One of the 38 primary fractures was an avulsion of the tuberosity; all the others (97%) located towards the base. In total, 32% of the players with MT-5 fracture were younger than 21years, 40% of the fractures occurred during the preseason and 45% of the players had prodromal symptoms. In total, 54% of the initial x-rays were classified as Torg type II (stress fractures), and 46% were classified as Torg type I (acute type). After surgical treatment the fractures healed faster, compared with conservative treatment (75% vs 33%, pandlt;0.05). There was no significant difference in lay-off days between players that had been operated, and those that had not (80 vs 74days, p=0.67). less thanbrgreater than less thanbrgreater thanConclusions less thanbrgreater than less thanbrgreater thanThe majority of MT-5 fractures are stress fractures, and mainly occur among young players. There are frequent healing problems, which might be explained by the stress nature of the injury. After surgery there are less healing problems, comp, Funding Agencies|UEFA||Swedish Centre for Research in Sports, and Praktikertjanst AB

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Background less thanbrgreater than less thanbrgreater thanLimited information is available on the variation in injury rates over multiple seasons of professional football. less thanbrgreater than less thanbrgreater thanAim less thanbrgreater than less thanbrgreater thanTo analyse time-trends in injury characteristics of male professional football players over 11 consecutive seasons. less thanbrgreater than less thanbrgreater thanMethods less thanbrgreater than less thanbrgreater thanA total of 1743 players comprising 27 teams from 10 countries were followed prospectively between 2001 and 2012. Team medical staff recorded individual player exposure and time loss injuries. less thanbrgreater than less thanbrgreater thanResults less thanbrgreater than less thanbrgreater thanA total of 8029 time loss injuries were recorded. The match unavailability due to injury was 14% and constant over the study period. On average, a player sustained two injuries per season, resulting in approximately 50 injuries per team and season. The ligament injury rate decreased during the study period (R-2=0.608, b=-0.040, 95% CI -0.065 to -0.016, p=0.005), whereas the rate of muscle injury (R-2=0.228, b=-0.013, 95% CI -0.032 to 0.005, p=0.138) and severe injury (R-2=0.141, b=0.015, 95% CI -0.013 to 0.043, p=0.255) did not change over the study period. In addition, no changes in injury rates over the 11-year period were found for either training (R-2=0.000, b=0.000, 95% CI -0.035 to 0.034, p=0.988) or match play (R-2=0.282, b=-0.015, 95% CI -0.032 to 0.003, p=0.093). less thanbrgreater than less thanbrgreater thanConclusions less thanbrgreater than less thanbrgreater thanThe injury rate has decreased for ligament injuries over the last 11years, but overall training, match injury rates and the rates of muscle injury and severe injury remain high., Funding Agencies|UEFA||Swedish National Centre for Research in Sports and Praktikertjanst AB

Background Medial collateral ligament (MCL) injury is the most common knee ligament injury in professional football. less thanbrgreater than less thanbrgreater thanAim To investigate the rate and circumstances of MCL injuries and development over the past decade. less thanbrgreater than less thanbrgreater thanMethods Prospective cohort study, in which 27 professional European teams were followed over 11 seasons (2001/2002 to 2011/2012). Team medical staffs recorded player exposure and time loss injuries. MCL injuries were classified into four severity categories. Injury rate was defined as the number of injuries per 1000 player-hours. less thanbrgreater than less thanbrgreater thanResults 346 MCL injuries occurred during 1057 201 h (rate 0.33/1000 h). The match injury rate was nine times higher than the training injury rate (1.31 vs 0.14/1000 h, rate ratio 9.3, 95% CI 7.5 to 11.6, pandlt;0.001). There was a significant average annual decrease of approximately 7% (p=0.023). The average lay-off was 23 days, and there was no difference in median lay-off between index injuries and reinjuries (18 vs 13, p=0.20). Almost 70% of all MCL injuries were contact-related, and there was no difference in median lay-off between contact and non-contact injuries (16 vs 16, p=0.74). less thanbrgreater than less thanbrgreater thanConclusions This largest series of MCL injuries in professional football suggests that the time loss from football for MCL injury is 23 days. Also, the MCL injury rate decreased significantly during the 11-year study period., Funding Agencies|UEFA||Swedish Centre for Research in Sports||Praktikertjanst AB

Background There is limited information about Achilles tendon disorders in professional football. less thanbrgreater than less thanbrgreater thanAims To investigate the incidence, injury circumstances, lay-off times and reinjury rates of Achilles tendon disorders in male professional football. less thanbrgreater than less thanbrgreater thanMethods A total of 27 clubs from 10 countries and 1743 players have been followed prospectively during 11 seasons between 2001 and 2012. The team medical staff recorded individual player exposure and time-loss injuries. less thanbrgreater than less thanbrgreater thanResults A total of 203 (2.5% of all injuries) Achilles tendon disorders were registered. A majority (96%) of the disorders were tendinopathies, and nine were partial or total ruptures. A higher injury rate was found during the preseason compared with the competitive season, 0.25 vs 0.18/1000 h (rate ratio (RR) 1.4, 95% CI 1.1 to 2.0; p=0.027). The mean lay-off time for Achilles tendinopathies was 23 +/- 37 (median=10, Q(1)=4 and Q(3)=24) days, while a rupture of the Achilles tendon, on average, caused 161 +/- 65 (median=169, Q(1)=110 and Q(3)=189) days of absence. Players with Achilles tendon disorders were significantly older than the rest of the cohort, with a mean age of 27.2 +/- 4 years vs 25.6 +/- 4.6 years (pandlt;0.001). 27% of all Achilles tendinopathies were reinjuries. A higher reinjury risk was found after short recovery periods (31%) compared with longer recovery periods (13%) (RR 2.4, 95% CI 2.1 to 2.8; pandlt;0.001). less thanbrgreater than less thanbrgreater thanConclusions Achilles tendon disorders account for 3.8% of the total lay-off time and are more common in older players. Recurrence is common after Achilles tendinopathies and the reinjury risk is higher after short recovery periods., Funding Agencies|Union of European Football Associations (UEFA)||Swedish National Centre for Research in Sports||Praktikertjanst AB

Background Hamstring injury is the single most common injury in professional football. MRI is commonly used to confirm the diagnosis and provide a prognosis of lay-off time. less thanbrgreater than less thanbrgreater thanObjective To evaluate the use of MRI as a prognostic tool for lay-off after hamstring injuries in professional football players and to study the association between MRI findings and injury circumstances. less thanbrgreater than less thanbrgreater thanMethods Prospective cohort study where 23 European professional teams, were followed between 2007 and 2011. Team medical staffs recorded individual player exposure and time-loss injuries. Radiological grading was performed using a modified Peetrons classification into four grades where grades 2 and 3 represent fibre disruption. less thanbrgreater than less thanbrgreater thanResults In total, 516 hamstring injuries occurred and 58% of these were examined by MRI. Thirteen per cent were grade 0 injuries, 57% grade 1, 27% of grade 2 and 3% of grade 3. Grade 0 and 1 injuries accounted for 56% (2141/3830 days) of the total lay-off. The layoff time differed between all four radiological grades of injury (8 +/- 3, 17 +/- 10, 22 +/- 11 and 73 +/- 60 days, p andlt; 0.0001). Eighty-three per cent of injuries affected the biceps femoris while 11% and 5% occurred to the semimembranosus and semitendinosus, respectively. Re-injuries (N=34/207) constituted 16% of injuries. All re-injuries occurred to the biceps femoris. less thanbrgreater than less thanbrgreater thanConclusion MRI can be helpful in verifying the diagnosis of a hamstring injury and to prognosticate layoff time. Radiological grading is associated with lay-off times after injury. Seventy per cent of hamstring injuries seen in professional football are of radiological grade 0 or 1, meaning no signs of fibre disruption on MRI, but still cause the majority of absence days., Funding Agencies|UEFA, Swedish Centre for Research in sport and Praktikertjanst AB

Background Football turf is increasingly used in European soccer competition. Little is known on the rotational torque that players experience on these fields. High rotational torques between the shoe outsole and the sports surface has been correlated with torsional injuries of the lower limb and knee. less thanbrgreater than less thanbrgreater thanPurpose To evaluate the effect of six parameters that could influence the rotational torque between the shoe outsole and the latest generation football turf. less thanbrgreater than less thanbrgreater thanStudy design Controlled laboratory study. less thanbrgreater than less thanbrgreater thanMethods A testing apparatus was constructed to measure the peak torque generated during a controlled rotation of the foot. Six parameters that could potentially influence the frictional forces, were considered: (1) the sports surface, (2) the shoe outsole cleat design, (3) the weather conditions, (4) the weight, (5) the presence of an impact and (6) the direction of rotation. less thanbrgreater than less thanbrgreater thanResults The football turf without infill showed significantly lower frictional torques than natural grass whereas a football turf with sand/rubber infill had significantly higher torques. Blades were associated with significantly higher torques than studs on natural grass and on one football turf with sand/rubber infill. Dry weather was associated with higher torques only for the football turf without infill. The torque increased linearly and significantly with an increasing vertical load. The rotational torque increased significantly following an impact. Torques on external rotational movements were significantly higher with blades. less thanbrgreater than less thanbrgreater thanConclusions Important differences in rotational torques are found and could be seen as potential risk factors for torsional injuries of the lower limb.