A Prospective Study on Maximal Oxygen Uptake and Cardiovascular Functions in 12-Year-Old Endurance Athletes and Their...

The maximal oxygen uptake (V̇O_2max) is typically higher in endurance-trained adolescents than in non-endurance-trained peers. However, the specific mechanisms contributing to this remain unclear, as well as the impact of training during this developmental stage. This study aims to compare V̇O_2max and cardiovascular functions between 12-year-old endurance athletes and non-endurance-trained over a 14-month period. Anthropometrics, V̇O_2max, hemoglobin mass (Hb_mass), blood volume (BV), and left-ventricular morphology were assessed four times over the 14 months in a group of young cross-country skiers (END, n = 42, age: 12.4 ± 0.5, girls: n = 27) and a group of controls (CON, n = 26, age: 12.3 ± 0.3, girls: n = 15). Throughout the 14-month follow-up, END did more weekly training than CON (7.0 ± 2.3 vs. 2.5 ± 2.4 h, p < 0.001), with only END conducting endurance training. END had ~18% higher V̇O_2max relative to fat-free mass (FFM) than CON (p < 0.001). Stroke volume (SV) and left ventricular end-diastolic volume (LV EDV) relative to FFM were also higher for END than CON (p < 0.001 and 0.004), while no significant differences were found for Hb_mass and BV. No significant interaction was seen for group and time for V̇O_2max (p = 0.352-0.767) or any cardiovascular parameters (p = 0.131-0.956) in absolute measures or relative to FFM. In conclusion, the END group exhibited higher V̇O_2max, LV EDV, and SV compared to the CON group, with no significant difference in BV and Hb_mass. Despite substantial differences in training volume, the progression of these variables over the 14-month period was similar in both groups.