Aim: This study investigated the development of power profiles and performance-related measures from the junior level (<19 years) via U23 (19-23 years) to senior level (>23 years) in 19 female and 100 male Norwegian national team cyclists.

Methods: A total of 285 tests were performed in a 3-day laboratory-standardized testing regime. The tests included power profiles with shorter duration (6-60 s) and longer durations (12-30 min) together with performance-related measures: Critical power (CP), work capacity above CP (W'), power output at 4 and 2 mmol·L^-1 [BLa^-] (L₄ and L₂), maximal aerobic power (W_max), and maximal oxygen uptake (VO_2max), gross efficiency (GE), and pedalling efficiency.

Results: Females and males evolve similarly when maturing from junior via U23 to senior categories (all p > 0.07), except for VO_2max which increased in females (but not males) from junior to senior level (534 ± 436 ml·min^-1, p = 0.013). In general, only performances of longer durations improved with age (12-min and 30-min, p = 0.028, and p = 0.042, respectively). Performance-related measures like W_max, VO_2max, CP, L₄, L₂, and pedalling efficiency in the fresh state improved with age (all p ≤ 0.025). Importantly, performance in the semi-fatigued state during a 5-min maximal test, was also improved with age (p = 0.045) despite a higher external energy expenditure prior to the test (p = 0.026).

Conclusions: Junior cyclists show highly developed sprint-abilities, and the primary improvements of absolute power outputs and performance-related measures are seen for durations >60 s when maturing to U23 and senior categories. However, the durability, i.e., the capacity to maintain performance in a semi-fatigued state is improved with age.