Cardiopulmonary adjustment and metabolic response to maximal and submaximal physical exercise of boys and girls at different stages of maturity

Cardiopulmonary and metabolic variables were investigated at maximal and submaximal bicycle ergometer exercises in 41 swimmers of both sexes, 8–18 years old. \(\dot V\)O₂ max and \(\dot V\)O₂ max·HR⁻¹ were higher in boys than in girls and increased with maturity, while \(\dot V\)O₂ max·kg⁻¹ and HVE were not influenced by this. The HV increased clearly during this growth period, the pubertal and postpubertal subjects showing 16 and 17% higher values for HV and HV·kg⁻¹ than those reported in normal schoolchildren populations. During the submaximal exercise at 70% \(\dot V\)O₂ max the highest HR values were found in the prepubertal group, whilst the lowest were observed in the postpubertal subjects. These findings suggest that a given percentage of \(\dot V\)O₂ max as a reference unit, is more reliable than a certain HR to obtain comparable results in subjects with different ages. Blood samples were collected before, during, and after the submaximal exercise. Blood glucose and FFA did not differ in relation to the stages of maturity. During exercise, insulin decreased in prepubertal children, did not alter in pubertal adolescents, and increased in postpubertal subjects. The lactate concentration, during exercise, increased in relation to maturity. The same results were found for HGH, but no differences were found with regard to sex. Since the pattern of HGH secretion during exercise is similar to that found after arginine and insulin administration it is assumed that the same mechanism (i.e., sex hormones) triggers the HGH release.