This paper reports temporal changes in physiological measurements of exercise performance in a young man transitioning from alpine skiing until he became a world junior champion time trial cyclist after only 3 yr of bike-specific training. At the time he became World Champion he also achieved among the highest reported maximal oxygen uptake (V̇o2max) value, 96.7 ml·min-1·kg-1, or 7,397 ml/min in absolute terms at 76.5 kg, which had increased by 29.6% from 74.6 ml·min-1·kg-1 pre-bike-specific training. After 15 mo with almost no structured exercise training, V̇o2max returned to 77.0 mL·min-1·kg-1 and was similar to the value reported before specific bike training, albeit with absolute term (6,205 ml/min) still being 11.3% higher. Part of the explanation for his athletic achievements is likely also related to the up to 20.9% improvement in Power@4 mmol/l (W). Although genetic profiles of endurance athletes have not generated data suggesting a shared genetic signature associated with elite endurance performance, this case study highlights the importance of intrinsic biological factors in elite endurance performance.NEW & NOTEWORTHY This study shows that very high V̇o2max values (>70 ml·min-1·kg-1) can be found in individuals not previously specializing in aerobic training and that values of >90 ml·min-1·kg-1, as well as a cycling world junior champion title, can be achieved in such individuals with just 3 yr of dedicated exercise training.