This study aimed to establish normative record power profile (RPP) values for male under-23 (U23) cyclists and to quantify fatigue effects on mean maximal power (MMP) after accumulated total work and work performed above critical power (CP). Power output (PO) data from 90 elite U23 cyclists competing in major 2025 races (Giro Next Gen, Tour de l'Avenir, Orlen Nations Grand Prix, Tour de la Paix) were retrospectively analyzed. MMP was determined for 5, 30 s, 1, 5, and 20 min in fresh conditions and after predefined fatigue levels (total work: 1000-3000 kJ absolute or 20-60 kJ·kg-1 relative; work above CP: 100-300 kJ absolute or 2-6 kJ·kg-1 relative). In fresh conditions, relative MMP ranged from 16.0 ± 1.9 W·kg-1 (5 s) to 5.5 ± 0.5 W·kg-1 (20 min; n = 48). Fatigue induced significant declines in MMP (p < 0.05). PO reductions were greater ßat shorter durations (-53.8% for 5 s after 60 kJ·kg-1 of total work) than at longer durations (-13.6% for 20 min after 6 kJ·kg-1 of work above CP). At the examined accumulated-work levels, total work produced larger absolute percentage reductions, whereas energy-normalized comparisons indicate that supra-CP work carries a higher decrement per unit of accumulated energy. These findings highlight durability as a performance marker in U23 cycling and provide benchmarks to improve talent identification and training decisions prior to World Tour transition.
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