Longitudinal changes in maximal oxygen uptake in adolescent girls and boys with different training backgrounds.

The purpose of this study was to investigate the effects of high-volume endurance training on the development of maximal oxygen uptake (VO ) in physically active boys and girls between the ages of 12 and 15 years, using a longitudinal design. The children participated in organized training in sports clubs for an average of 7-10 hours per week, with one group undertaking a high volume of endurance training (~7 hours per week; End boys, n = 23 and End girls, n = 17) and the other group having a primary focus on technical and tactical skill development, undertaking low volumes of endurance training (~1.6 hours per week; non-End boys, n = 29 and non-End girls, n = 9).

Longitudinal Training-related Hematological Changes in Boys and Girls from Ages 12 to 15 yr.

Purpose: Natural growth and maturation cause hemoglobin mass (Hbmass) and blood volume (BV) to increase during childhood and adolescence. Whether endurance training during the same period can cause further increases in these variables is not clear. Also, body composition develops differently in girls and boys during puberty, and the effect of these differences on hematological variables has not been previously studied.