We all know that body dimensions affect athletic performance, especially in young players differing in maturation. However, how important is this effect is still unclear, and the available methods to account for differences in body dimensions have not been compared. In this study we compared the Aspire Qatari U15 players with the best french U15 players, and examined how their different body size affected their locomotor performance. The first interesting findings was to see how shorter (-7cm) and lighter (-10 kg) the Qatari are !! As you will also understand if you read all results in details, allometric scaling helps to account for these differences, but not always – body dimensions don’t explain everything ! Feedback appreciated, as always.