The purpose of this study is to ascertain whether there are differences in the physiological profiles of young athletes according to their sports specialty and age group. The sample is comprised of 400 athletes of both sexes from the Cheste Technification Centre (Valencia) classified into 3 age groups: <12-13, 14-16 and 17-20, and three endurance sports specialties: track and field, swimming and triathlon (n<\/em>=134, n<\/em>=135 and n<\/em>=131, respectively). The physiological profile is analyzed based on the values of maximum oxygen consumption (V.O2max) and the anaerobic threshold (AnT) based on total body mass (kg); muscle mass and fat-free mass, as well as logarithmic oxygen consumption (logV.O2), in order to nullify the effect of body size. The data were obtained from an incremental ergospirometric test on a ramp following the Wasserman protocol. The results stemming from the analysis of variance (Anova) in the sports specialties indicate that there are significant differences in all the variables measured between the athletes in track and field and swimming (p<\/em><0.05), and between those in triathlon and swimming (p<\/em><0.05). In contrast, no significant differences were found between the track and field athletes and triathletes (p<\/em>>0.05). Regarding the age groups, significant differences were found in all the variables measured between the 0.05).\u00a0<\/p>\n\n