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Context: It is unclear whether playing position influences injury in male academy soccer players (ASP). Objective: To determine if playing position is associated with injury in ASP. Design: Descriptive Epidemiology Study. Setting: English, Spanish, Uruguayan and Brazilian soccer academies. Participants: 369 ASP from Under 14 (U14) to U23 age groups, classified as ‘post-peak height velocity' using maturity offset, and grouped as goalkeepers (GK), lateral defenders (LD), central defenders (CD), lateral midfielders (LM), central midfielders (CM) and forwards (FWD). Additional analysis compared central (CENT) with lateral/forward (LAT/FWD) positions. Main Outcome Measures: Injuries were recorded prospectively over one season. Injury prevalence proportion (IPP), days missed and injury incidence rate (IIR, injuries per 1000 training/match hours, n=116) were analysed according to playing position. Results: No association with playing position was observed for any injury type/location regarding IPP (P≥0.089) or days missed (P≥0.235). The IIR was higher in CD than LD for general (9.30 vs. 4.18 injuries/1000h, P=0.009), soft-tissue (5.14 vs. 1.95 injuries/1000h, P=0.026) and ligament/tendon injuries (2.69 vs. 0.56 injuries/1000h, P=0.040). Regarding CENT vs. LAT/FWD, there were no associations with IPP (P≥0.051) or days missed (P≥0.083), but general IIR was greater in CENT than LAT/FWD (8.67 vs. 6.12 injuries/1000h, P=0.047). Conclusions: ASP playing position was not associated with IPP or days missed but the higher general, soft-tissue and ligament/tendon IIR in CD suggests this position warrants specific attention regarding injury prevention strategies. These novel findings highlight the importance of including training/match exposure when investigating the influence of playing position on injury in ASP.

Objectives: To investigate if maturity status was associated with injury risk in male academy soccer players. Design: Prospective cohort surveillance study. Setting: Professional soccer academies. Participants: 501 players (aged 9-23 years) from eight academies in England, Spain, Uruguay and Brazil. Main outcome measures: Players were grouped by maturity offset as pre-peak height velocity (PHV), circa-PHV, post-PHV or adult. Injury prevalence proportion (IPP) and days missed were recorded for one season per player, with training/match exposure recorded in a sub-sample (n = 166). Results: IPP for all injuries combined increased with advancing maturity, with circa-PHV (p = 0.032), post-PHV (p < 0.001) and adult (p < 0.001) higher than pre-PHV. IPP was higher in post-PHV and adult than pre-PHV for non-contact (p = 0.001 and p = 0.012), soft-tissue (both p < 0.001), non-contact soft tissue (p < 0.001 and p = 0.005), muscle (both p < 0.001), thigh (both p < 0.001), ankle (p = 0.035 and p = 0.007) and hamstring injuries (p = 0.041 and p = 0.017). Ligament/tendon IPP was greater in adult versus pre-PHV (p = 0.002). IPP for growth-related injuries was lower in post-PHV than pre-PHV (p = 0.039). Injury incidence rates (n = 166) exhibited similar patterns to IPP in the full cohort. Conclusions: Injury patterns were similar between post-PHV and adult academy players but, crucially, relatively more of these groups suffered injuries compared to pre-and circa-PHV (except growth-related injuries).

Objectives To investigate if maturity status was associated with injury risk in male academy soccer players. Design Prospective cohort surveillance study. Setting Professional soccer academies. Participants 501 players (aged 9–23 years) from eight academies in England, Spain, Uruguay and Brazil. Main outcome measures Players were grouped by maturity offset as pre-peak height velocity (PHV), circa-PHV, post-PHV or adult. Injury prevalence proportion (IPP) and days missed were recorded for one season per player, with training/match exposure recorded in a sub-sample (n = 166). Results IPP for all injuries combined increased with advancing maturity, with circa-PHV (p = 0.032), post-PHV (p < 0.001) and adult (p < 0.001) higher than pre-PHV. IPP was higher in post-PHV and adult than pre-PHV for non-contact (p = 0.001 and p = 0.012), soft-tissue (both p < 0.001), non-contact soft-tissue (p < 0.001 and p = 0.005), muscle (both p < 0.001), thigh (both p < 0.001), ankle (p = 0.035 and p = 0.007) and hamstring injuries (p = 0.041 and p = 0.017). Ligament/tendon IPP was greater in adult versus pre-PHV (p = 0.002). IPP for growth-related injuries was lower in post-PHV than pre-PHV (p = 0.039). Injury incidence rates (n = 166) exhibited similar patterns to IPP in the full cohort. Conclusions Injury patterns were similar between post-PHV and adult academy players but, crucially, relatively more of these groups suffered injuries compared to pre- and circa-PHV (except growth-related injuries).

It is currently unknown if injury risk is associated with genetic variation in academy soccer players (ASP). We investigated whether nine candidate single nucleotide polymorphisms were associated (individually and in combination) with injury in ASP at different stages of maturation. Saliva samples and one season's injury records were collected from 402 Caucasian male ASP from England, Spain, Uruguay and Brazil, whose maturity status was defined as pre- or post-peak height velocity (PHV). Pre-PHV COL5A1 rs12722 CC homozygotes had relatively higher prevalence of any musculoskeletal soft-tissue (22.4% vs. 3.0%, P=0.018) and ligament (18.8% vs. 11.8%, P=0.029) injury than T-allele carriers, while VEGFA rs2010963 CC homozygotes had greater risk of ligament/tendon injury than G-allele carriers. Post-PHV IL6 rs1800795 CC homozygotes had a relatively higher prevalence of any (67.6% vs. 40.6%, P=0.003) and muscle (38.2% vs. 19.2%, P=0.013) injuries than G-allele carriers. Relatively more post-PHV EMILIN1 rs2289360 CC homozygotes suffered any injury than CT and TT genotypes (56.4% vs. 40.3% and 32.8%, P=0.007), while the 'protective' EMILIN1 TT genotype was more frequent in post- than pre-PHV ASP (22.3 vs. 10.0%, P=0.008). Regardless of maturity status, T-alleles of ACTN3 rs1815739 and EMILIN1 rs2289360 were associated with greater absence following ankle injury, while the MMP3 rs679620 T-allele and MYLK rs28497577 GT genotype were associated with greater absence following knee injury. The combination of injury-associated genotypes was greater in injured vs. non-injured ASP. This study is the first to demonstrate that a genetic association exists with injury prevalence in ASP, which differs according to maturity status.

To identify the most common injury types/locations in high-level male youth soccer players (YSP). Design Prospective cohort surveillance study. Setting Professional soccer club academies. Participants Six hundred and twenty-four high-level male YSP [Under 9 (U9) to U23 year-old age groups] from academies in England, Spain, Uruguay and Brazil. Main outcome measures Injury type, location and severity were recorded during one season. Injury severity was compared between age groups, while injury type and location were compared between nations. Results Four hundred and forty-three training or match injuries were recorded, giving an injury rate of 0.71 per player. Non-contact injuries were most common (58.5%), with most (44.2%) resolved between 8 and 28 days. Most injuries (75.4%) occurred in the lower limbs, with muscle (29.6%) the most commonly injured tissue. U14 and U16 suffered a greater number of severe injuries relative to U12 and U19/U20/U23/Reserves. Tendon injury rate was higher in Brazil vs. Spain (p < 0.05), with low back/sacrum/pelvis injury rate highest in Spain (p < 0.05). Conclusions The proportion of severe injuries in U14 and U16 suggests YSP injury risk is maturation-dependent. Minimal differences in type and location between high-level YSP from four different countries suggest injury rates in this population are geographically similar.