Injuries in elite male youth football and athletics: Growth and maturation as potential risk factors

Background: Elite youth athletes participate in intense and structured training programmes to realise their performance potential, but their development may be interrupted by injuries. To reduce the impact of injuries we first need to know which injuries affect participation the most and what the risk factors are. Growth and maturation represent two potential non-modifiable intrinsic risk factors that are unique to adolescent athletes. The literature published on this topic is, however, considered of low quality and findings in earlier studies are inconsistent. The aim of this thesis was therefore to identify the most common and burdensome injuries in elite male youth athletes participating in football (soccer) and athletics (track and field) and to explore growth and maturation as risk factors. Methods: All studies were based on data from routine monitoring of athletes at Aspire Academy, a national elite sports academy in Doha, Qatar. Participants were males aged 11 to 18 years participating in the football or athletics programmes. The first study (Paper I) was a methodological study where we investigated the effect on injury incidence when a broad medical-attention definition was used and recorders/supervisors were invested in research projects relying on the data. This study was based on injury data for the U16 through U18 squads from 2012/13 through 2016/17 (211 players). Papers II and III were descriptive epidemiological studies in athletics and football, respectively. Time-loss injuries were collected prospectively over five seasons in athletics (2014/15 through 2018/19, 179 athletes) and four seasons in football (2016/17 through 2019/20, 301 players) by physiotherapists. The most common (injury incidence) and burdensome (injury burden) combinations of injury location and type were identified, and injury patterns were examined for event groups (athletics; non-specialised, endurance, sprints, jumps, throws) and age groups (football; U13 through U18). In Papers IV and V, subsamples of athletes (74 in athletics, 103 in football) from the epidemiological studies with complete growth (anthropometric measures, i.e. height, leg length and body mass) and maturity (skeletal age, using the Fels method) assessments were included. Growth rates, maturity status and maturity tempo were then examined as risk factors for specific injury types. Main results: The level of investment in the injury surveillance programme by the injury recorder (team physiotherapist) or supervisor had a large impact on the incidence of non-time-loss injuries and injuries with a minimal day loss (1-3 days), while time-loss injuries overall were unaffected (Paper I). In athletics (Paper II), the main concerns were bone and muscle injuries, with thigh muscle strains/ruptures, lumbar spine stress fractures and lower leg bone stress injuries as the most burdensome location-type combinations. Injury patterns were, however, specific to each event group. In football (Paper III), typical “football injuries” (knee sprains, thigh strains and ankle sprains) were the most burdensome, followed by lumbosacral bone stress injuries and physis injuries to the hip/groin. Older athletes sustained more injuries relative to exposure (hours); muscle injuries were increasingly common and physis injuries less common with age. In Paper IV, younger skeletal age and greater changes in height, leg length and skeletal age over a season were associated with a greater incidence of bone and growth plate injuries in athletics. No associations with injury risk were found for changes in body mass, trunk height or body mass index. In football (Paper V), growth rates over shorter periods were not related to injury risk when accounting for age (chronological age or skeletal age) and load (weekly exposure). Older skeletal age was associated with significantly greater overall, sudden onset, muscle and joint sprain injury risk. The associations could, however, not be considered practically relevant due to the uncertain estimates for the odds ratios. Conclusion: Based on our findings, time-loss incidence should be used when multiple medical staff recorders are involved in the data collection. Injuries patterns in elite male youth athletes are specific to the sport, event group and age group; tailoring injury reduction programmes may therefore be possible. A large proportion of lost training and competition days were attributed to bone injuries; these should be targeted to a larger degree in risk factor studies and in injury reduction programmes. Skeletal maturity appears to affect the risk of sustaining certain injury types in football and athletics, while growth rates were only related to injury risk in athletics. Practitioners and researchers may need to consider the full growth and maturity process, rather than analysing short isolated periods, to better understand the relationship between growth, maturation and injury risk