“…The estimated muscle mass for the designed regression formulas promote the specific knowledge of the muscle component and allow comparing the differences between rugby and soccer players, for example, where significant differences in the muscle mass of the upper limb may be found, assuming the rugby player needs better muscle development in his arms and forearm than an average soccer player (Barraza et al, 2009) or compared to other collective sports, such as basketball, volleyball or handball (Bayios et al, 2006;Carvajal et al, 2009;Gholami & Rad, 2010, Papadopoulou & Papadopoulou, 2010, individual sports (Sanchez-Muñoz et al, 2006;Kong & Heer, 2008;Knechtle et al, 2010a;Knechtle et al, 2010b;Bejan, 2010;Borgard, 2010) or between collective and individual sports. These formulas also allow establishing differences in the athlete himself, in different temporal moments, trained or untrained, injured or under normal performance conditions, etc.…”