Bio-energetic profile in 144 boys aged from 6 to 15 years with special reference to sexual maturation.

The effects of growth and pubertal development on bio-energetic characteristics were studied in boys aged 6-15 years (n = 144; transverse study). Maximal oxygen consumption (VO2max, direct method), mechanical power at VO2max (PVO2max), maximal anaerobic power (Pmax; force-velocity test), mean power in 30-s sprint (P30s; Wingate test) were evaluated and the ratios between Pmax, P30s and PVO2max were calculated. Sexual maturation was determined using salivary testosterone as an objective indicator. Normalized for body mass VO2max remained constant from 6 to 15 years (49 ml.min-1.kg-1, SD 6), whilst Pmax and P30s increased from 6-8 to 14-15 years, from 6.2 W.kg-1, SD 1.1 to 10.8 W.kg-1, SD 1.4 and from 4.7 W.kg-1, SD 1.0 to 7.6 W.kg-1, SD 1.0, respectively, (P less than 0.001). The ratio Pmax:PVO2max was 1.7 SD 3.0 at 6-8 years and reached 2.8 SD 0.5 at 14-15 years and the ratio P30s:PVO2max changed similarly from 1.3 SD 0.3 to 1.9 SD 0.3. In contrast, the ratio Pmax:P30s remained unchanged (1.4 SD 0.2). Significant relationships (P less than 0.001) were observed between Pmax (W.kg-1), P30s (W.kg-1), blood lactate concentrations after the Wingate test, and age, height, mass and salivary testosterone concentration. This indicates that growth and maturation have together an important role in the development of anaerobic metabolism.