Injury incidence in male elite youth football players is associated with preceding levels and changes in training load.

Objectives: Elite youth football players miss out on a large part of seasonal training due to injury. Limited research suggests an association between external and internal training load (TL) and injury incidence in elite youth football. This study analysed external and internal TL variables and their association with injury incidence in a group of male elite youth football players over four seasons. Methods: Measures of external and internal TL and injury incidence of 56 male elite youth football players (age 17-19 years) were collected throughout four seasons. Heart rate, session rating of perceived exertion andGlobal Positioning System (GPS) variables were analysed. Individual players' TL during the 30 days leading up to injury was compared with 30-day injury-free control periods. Change in TL through the periods was also analysed. Results: Eighty-five injuries were included for analysis, showing that for most TL variables, the average levels were significantly lower during the period leading up to injury. Significant increases for the majority of TL variables were also found during the periods leading up to injury, while the control periods did not show any significant change. Conclusion: A lower and/or increasing average TL volume over 30 days might increase the risk of injury in male elite youth football players. Avoiding long-term drops in TL and balance increases in TL might be beneficial to reduce injury risk.

ACTN3's R577X Single Nucleotide Polymorphism Allele Distribution Differs Significantly in Professional Football Players according to Their Field Position.

INTRODUCTION: Football is characterised by intermittent high-intensity efforts varying according to the field position of a player. We aimed to ascertain whether polymorphisms in the ACTN3 gene are associated with different playing positions in elite professional football players. SUBJECTS AND METHODS: Genotyping of the ACTN3 gene was conducted in 43 elite professional football players of a single team. Playing position was recorded based on the player's most frequent position. RESULTS: The genotype distribution was not significant between positions (p = 0.057), while the allele distribution differed significantly (p = 0.035). Goalkeepers (p = 0.04, p = 0.03), central defenders (p = 0.03, p = 0.01), and central midfielders (p = 0.01, p = 0.00) had a significantly different allele distribution compared with wide midfielders and forward players. CONCLUSIONS: Genetic biomarkers may be important when analysing performance capability in elite professional football. Identifying the genetic characteristics of a player to adapt his playing position may lead to orientation of positions based on physical capabilities and tissue quality in young football players, and also to performance enhancement in those who are already playing in professional teams.

Epidemiological Data on LCL and PCL Injuries Over 17 Seasons in Men's Professional Soccer: The UEFA Elite Club Injury Study.

BACKGROUND: There is limited epidemiological information on injury rates and injury mechanisms for lateral collateral ligament (LCL) and posterior cruciate ligament (PCL) injuries in male professional soccer. In addition, time trends and lay-off times for these injuries have not yet been determined. AIM: To determine injury rates and circumstances of LCL and PCL injuries over 17 seasons in men's professional soccer. METHODS: A prospective cohort study, in which 68 professional European soccer teams were followed over 17 consecutive seasons (2001/2002 to 2017/2018). The teams' medical staff recorded player exposure and time-loss injuries. Lay-off time was reported as the median and the first and third quartile. Injury rate was defined as the number of injuries per 1000 player-hours. RESULTS: One hundred and twenty-eight LCL and 28 PCL injuries occurred during 2,554,686 h of exposure (rate 0.05 and 0.01/1000 h, respectively). The median lay-off time for LCL injuries was 15 (Q1=7, Q3=32) days, while it was 31 days for PCL injuries (Q1=15, Q3=74). The match injury rate for LCL injuries was 11 times higher than the training injury rate (0.21 vs 0.02/1000 h, rate ratio [RR] 10.5, 95% CI 7.3 to 15.1 p<0.001) and the match injury rate for PCL injuries was 20 times higher than the training injury rate (0.056 vs 0.003/1000 h, RR 20.1, 95% CI 8.2 to 49.6, p<0.001). LCL injuries saw a significant annual decrease of approximately 3.5% (p=0.006). In total, 58% (63/108) of all LCL injuries and 54% (14/26) of all PCL injuries were related to contact mechanism. CONCLUSION: This study with prospectively registered data on LCL and PCL injuries in men's professional soccer shows that the median lay-off from soccer for LCL and PCL injuries is approximately 2 and 4 weeks respectively. These rare knee ligament injuries typically occur during matches and are associated with a contact injury mechanism.

Medial collateral ligament injuries of the knee in male professional football players: a prospective three-season study of 130 cases from the UEFA Elite Club Injury Study.

PURPOSE: Medial collateral ligament (MCL) injury is the single most common traumatic knee injury in football. The purpose of this study was to study the epidemiology and mechanisms of MCL injury in men's professional football and to evaluate the diagnostic and treatment methods used. METHODS: Fifty-one teams were followed prospectively between one and three full seasons (2013/2014-2015/2016). Individual player exposure and time-loss injuries were recorded by the teams' medical staffs. Moreover, details on clinical grading, imaging findings and specific treatments were recorded for all injuries with MCL injury of the knee as the main diagnosis. Agreement between magnetic resonance imaging (MRI) and clinical grading (grades I-III) was described by weighted kappa. RESULTS: One hundred and thirty of 4364 registered injuries (3%) were MCL injuries. Most MCL injuries (98 injuries, 75%) occurred with a contact mechanism, where the two most common playing situations were being tackled (38 injuries, 29%) and tackling (15 injuries, 12%). MRI was used in 88 (68%) of the injuries, while 33 (25%) were diagnosed by clinical examination alone. In the 88 cases in which both MRI and clinical examination were used to evaluate the grading of MCL injury, 80 (92% agreement) were equally evaluated with a weighted kappa of 0.87 (95% CI 0.77-0.96). Using a stabilising knee brace in players who sustained a grade II MCL injury was associated with a longer lay-off period compared with players who did not use a brace (41.5 (SD 13.2) vs. 31.5 (SD 20.3) days, p = 0.010). CONCLUSION: Three-quarter of the MCL injuries occurred with a contact mechanism. The clinical grading of MCL injuries showed almost perfect agreement with MRI grading, in cases where the MCL injury is the primary diagnosis. Not all grade II MCL injuries were treated with a brace and may thus indicate that routine bracing should not be necessary in milder cases. LEVEL OF EVIDENCE: Prospective cohort study, II.

ACTN3 single nucleotide polymorphism is associated with non-contact musculoskeletal soft-tissue injury incidence in elite professional football players.

PURPOSE: Muscle injuries are common in professional football, even though prevention protocols are being implemented. Genetics constitutes a novel field for studying intrinsic injury risks and performance. Since previous studies involving single nucleotide polymorphisms (SNPs) have shown that SNPs influence muscle injury rate, injury severity and recovery time, the aim was to study the association the SNP of ACTN3 has with those parameters in professional football players. METHODS: The medical staff team recorded non-contact musculoskeletal soft-tissue injuries in 43 professional football players in 7 different seasons (2007-2012 and 2015-2016). Injury rate, injury severity and injury recovery times were established. Players were genotyped by extracting DNA from a blood sample and using a polymerase chain reaction. RESULTS: Injury rate was associated with the SNP of ACTN3 (p = 0.003). The 577R allele was more frequent in subjects than in a normal population by showing presence in 93% of the subjects and suggesting that it could influence football performance. No statistically significant differences in injury severity and recovery time were associated with the SNP of ACTN3. CONCLUSIONS: Genetics is gaining in importance when assessing injury risk and performance in professional football. ACTN3 can be regarded as a biomarker of injury susceptibility in this discipline. Identifying those players with the highest injury susceptibility through genetics could lead football teams to individualise workloads and prevention protocols. LEVEL OF EVIDENCE: III.

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

PURPOSE: Damage to skeletal muscle necessitates regeneration to maintain proper muscle form and function. Interindividual differences in injury severity, recovery time, and injury rate could be explained by the presence of single nucleotide polymorphisms (SNPs) in genes involved in the reparation and regeneration of connective tissue . We wished to identify new genetic biomarkers that could help to prevent or minimize the risk of non-contact muscle injuries and are associated with a predisposition to developing muscle injuries. METHODS: Using allelic discrimination techniques, we analysed 12 SNPs in selected genes from the genomic DNA of 74 elite soccer players. RESULTS: SNPs in the hepatocyte growth factor (HGF) gene showed evidence of a statistically significant association with injury incidence, severity, and recovery time. SNPs in the SOX15 gene showed evidence of a statistically significant association with injury incidence. SNPs in the GEFT and LIF genes showed evidence of a statistically significant association with recovery time. CONCLUSIONS: Genetic profile could explain why some elite soccer players are predisposed to suffer more injuries than others and why they need more time to recover from a particular injury. SNPs in HGF genes have an important role as biomarkers of biological processes fragility within muscle injuries related to injury rate, severity, and long recovery time.

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

BACKGROUND: Studies have shown that previous injury, not necessarily anatomically related, is an important injury risk factor. However, it is not known whether a player runs an increased risk of anterior cruciate ligament (ACL) injury after returning to play from other injury types. PURPOSE: To analyze whether professional soccer players are more susceptible to ACL injury after returning to play from any previous injury. STUDY DESIGN: Case-control study; Level of evidence, 3. METHODS: A total of 101 elite male soccer players suffering a first-time complete ACL injury between 2001 and 2014 were included and matched according to team, age, and playing position with control players who did not have a current injury (1:1 match). For each injured player, the 90-day period prior to the ACL injury was analyzed for injuries and compared with that of control players by using odds ratios (ORs) and 95% CIs. RESULTS: The odds of a player with an ACL injury sustaining a previous injury in the 90-day period did not differ significantly from that of controls (OR, 1.20; 95% CI, 0.66-2.17; P = .65). Testing the frequency of absence periods due to injury between the groups revealed that the odds of a player with an ACL injury having a previous period of absence due to injury did not differ compared with controls (OR, 1.14; 95% CI, 0.64-2.01; P = .77). CONCLUSION: Players with ACL injury did not have a greater occurrence of absence due to injury in the 3 months preceding their ACL injury compared with matched controls. This indicates that previous injury of any type does not increase the risk of suffering an ACL injury.

The UEFA injury study: 11-year data concerning 346 MCL injuries and time to return to play.

BACKGROUND: Medial collateral ligament (MCL) injury is the most common knee ligament injury in professional football. AIM: To investigate the rate and circumstances of MCL injuries and development over the past decade. METHODS: 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. RESULTS: 346 MCL injuries occurred during 1 057 201 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, p<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). CONCLUSIONS: 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.