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_2max ) 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). VO_2max and anthropometrics were assessed at age 12, 13, and 15. At age 12, VO_2max was 58.9 (5.6), 65.5 (7.2), 56.5 (6.5), and 58.8 (7.9) mL·kg^-1 ·min^-1 in End girls, End boys, non-End girls, and non-End boys, respectively. Over the three years, there was no difference between the training groups in the development of VO_2max independent of scaling. In boys, VO_2max relative to body mass (BM) did not change from age 12 to 15, while VO_2max tended to decrease relative to fat-free mass (FFM). In girls, VO_2max relative to BM decreased slightly from age 12 to 15, with no changes over the years relative to FFM. The present longitudinal study suggests that in growing active children during puberty, high volumes of systematic endurance training do not have an additional effect on VO_2max compared with similar volume of training mainly aiming at developing motor skills.