Article Variation in body composition in professional soccer players: inter- and intra-seasonal changes and the effects of exposure time and player position

The aim of this study was to examine variations in measures of body composition in elite soccer players. Skinfolds and measures of body mass (BM) recorded on a monthly basis across an entire competitive season in a group of senior professional players (N=26) were used to estimate body fat (%BF) and provide fat-free body mass values (FFBM). Mean values in players were compared between six specific positional roles (goalkeepers, central and lateral defenders/midfielders and centre-forwards). In-season variations in measures were studied by comparing values at 5 separate points across the season. The effects of positional group (goalkeepers, defenders, midfielders and forwards) and exposure time to play (participation time in training and matches) in relation to in-season variations were also examined. To investigate inter-seasonal changes, repeated measures were taken in players (N=9) over three consecutive seasons. In relation to positional role, a difference in average %BF and BM values was observed (p<0.001) with substantial differences observed in goalkeepers, lateral midfielders and forwards. Across all players, there were significant in-season variations in %BF (between startand mid-season and midand end-season, p<0.001) and FFBM (between startand mid-season and startand end-season, p<0.001) while BM remained unchanged. Further analysis of these fluctuations in %BF and FFBM at different points of the season showed that variations differed across the positional groups (p<0.01), especially in defenders and midfielders. In contrast, no association was observed between measures and exposure time and no differences were reported across seasons. Practitioners should consider individual positional role when interpreting mean body composition data. They should also take into account positional groups when in-season variations in body composition are identified. Variations in body composition 3