Taking a breather: Do physiological changes induced by growth during puberty outweigh those induced by endurance training in youth athletes?

Abstract

This dissertation is based on one prospective study, including one controlled trial, divided into four papers. The primary objective was to enhance our knowledge regarding the influence of endurance training on maximal oxygen uptake (V̇O2max) and cardiorespiratory functions in youth endurance athletes throughout puberty. We also aimed to evaluate the reliability and accuracy in rating bone age from DXA scans through self-practice as a marker of maturity level.

Seventy-eight males and females from a local cross-country ski club (n = 49, aged: 12.4 ± 0.5) and an elementary school in the greater Oslo area (n = 29, aged: 12.3 ± 0.3) were recruited and followed over 14 months. The two cohorts were chosen based on their large disparities in level of physical activity and training regime. The cross-country skiers averaged 7.0 ± 2.3 hours of weekly training throughout the 14 months, and their training mainly consisted of cross-country skiing but also included other sports. On the other hand, the elementary school children, who served as a control group for growth and maturation, averaged 2.5 ± 2.4 hours of weekly training throughout the 14 months. This group did not participate in endurance sports, and many of them did very little training and were habitually less physically active than the crosscountry skiers.

In conclusion, this 14-month prospective study, including an 8-week training intervention, suggests that endurance training during puberty in youth athletes does not result in superior changes in V̇O2max and cardiorespiratory functions beyond the changes from growth and maturation.