Changes in body composition and aerobic fitness according to-chronological age and maturity offset in elite junior rugby players

OBJECTIVE Professional Rugby clubs are increasingly investing in young talent. Early maturing boys have a distinct physical advantage in a game not only reliant on skill and understanding but also size and power. There are no recent data reported on elite junior rugby players where playing position, chronological age and maturity have been taken into account. This study first aimed to provide descriptive, anthropometric and' aerobic fitness data in elite young players by age, maturity and position, and second to compare differences in boys composition and aerobic fitness by controlling for decimal age and maturity offset. METHODS 12 elite boys in season 2004-5 and 17 elite boys in 2005-6 had their body composition measured using DEXA, aerobic fitness using a discontinuous treadmill protocol. Maturity offset was also calculated (Mirwald et al., 2002). Differences in lean body mass (LBM), fat mass (FM) and VO2peak were compared by time and playing position whilst separately controlling for decimal age and maturity offset. RESULTS VO2peak was stable across time for both forwards and backs although backs had significantly higher aero-bic power than forwards even after controlling for decimal age of maturity offset. Forwards carried significantly more LBM than backs although increases were similar between time 1 and 2. Differences in LBM disappeared when control-ling for maturity but nor for decimal age. DISCUSSION Forwards had greater LBM and FM whereas backs had similar levels of LBM. Backs had significantly greater aerobic fitness than forwards. Forwards had greater amounts of LBM and FM than backs although the differ-ences in LBM disappeared after controlling for maturity offset. It was suggested that most differences in LBM were a result of more advanced maturity in forwards.