Reducing the risk of injury in young footballers.

The risks and benefits of children and adolescents par‐ ticipating in elite sports have long been debated. Reports of growth retardation in elite gymnasts and degenerative joint disease in the elbows of young baseball players have caused anxiety among parents and sporting bodies. In contrast, Ericsson’s theory of deliberate practice dictates the need for high volumes of training at a young age to reach expert level in skilled tasks including sport.1 Health and sports professionals need answers to help with the understandable confusion confronting the parents of our next generation of athletes. In the linked study, Johnson and colleagues assess growth, development, and factors associated with injury in elite schoolboy footballers.2 The evidence base shows common themes in different sports. The incidence of injury increases with chrono‐ logical age and pubertal stage.3‐5 Despite weight for age competitions in several youth sports—including Ameri‐ can football, rugby union, and wrestling—the evidence on whether height or weight is associated with the risk of injury is conflicting. Weight for age classification was popular in the past, but its accuracy in matching oppo‐ nents of equivalent maturity today may be compromised by high rates of childhood obesity. Many aspects of sports performance, including aerobic capacity, strength, and power, are related to biological maturity. Studies have shown a preponderance of early maturers in adolescent sports that require strength and speed such as tennis, football, and swimming, whereas sports such as gymnastics tend to favour late maturers.6 7 A normal maturer who plays against an early maturer may therefore be disadvantaged, and late maturers may have an increased risk of injury when playing against stronger and fitter opponents. Johnson and colleagues investigate the association between maturity status and other factors, including training volume and playing load, and risk of injury in elite schoolboy footballers.2 Maturity status was defined as the difference between skeletal age and chronological age. The investigators found that maturity status together with playing and training time collectively explained 48% of the variation in injury rates. The study also con‐ firms previously identified research findings in football and other sports that injury rates are higher during match play than during training.5 8 Few studies have examined the association between maturity status and the risk of injury. One previous study found no significant difference in the incidence of injury in elite footballers who were early, normal, and late maturers, although the three groups showed different patterns and severities of injury.9 Another study found no association between maturity status—measured by percentage of predicted mature height—and injury risk in young American footballers.5 The linked study is the first to show that maturity status combined with other factors may influence the risk of injury. Childhood and adolescence are times of skeletal vul‐ nerability. The peak incidence of fracture coincides with the time of peak height velocity in both boys and girls.10 The presence of growth plates and apophyses (tendon‐ growth plate interfaces) produces a unique pattern of injury in this population. During adolescence, apophyses are susceptible to traction forces, both acute and chronic, which account for the avulsion fractures and traction apophysitis seen in this age group. “How much is too much?” is a question often asked in relation to children’s participation in sport. Evidence based guidelines to answer this question are lacking in most youth sports. The risk of elbow and shoulder injury in adolescent pitchers in Little League baseball increases with increasing pitch counts.11 This finding has resulted in guidelines that limit competition and training loads in young pitchers, but these guidelines should be regarded as best practice rather than evidence based. The opti‐ mum number of pitches per game and per season is unknown. Although reducing training and competition loads seems to be an appropriate response, there is no clear evidence that such policies reduce injury rates. Most youth sports around the world are classified on the basis of chronological age. However, the matura‐ tional status of children of the same age differs signifi‐ cantly during adolescence. Nearly half of the footballers in the linked study were early or late maturers, which questions the validity of forming teams and designing training programmes on the basis of chronological age. Matching for skeletal age on the basis of radiography may not be practical except in elite sports. Proxies of skeletal maturity such as Tanner staging could be con‐ sidered, although this raises privacy concerns, and self reported Tanner staging is not very reliable.12 Johnson and colleagues’ study is an important study of a highly specialised population. Although it is valu‐ able, we cannot extrapolate their findings to non‐elite athletes or young athletes participating in other sports. Larger studies are needed to identify predictors of injury in community based children’s sport. Elite sporting pro‐ grammes should consider matching players for skeletal age and regulating training and competition loads, and all coaches working in youth sport should be made aware of the potential hazards of overtraining during vulnerable periods of growth. ReseaRch, p 694