Graded Carbohydrate Ingestion up to 120 g·h ⁻¹ Attenuates the Reduction in Critical Power Following 3 h of Moderate‐Intensity Exercise in a Dose‐Dependent Manner

This study examined the effects of graded carbohydrate (CHO) ingestion at rates of 0 (water only), 60 and 120 g·h −1 (1:0.8 ratio of maltodextrin‐to‐fructose) on changes in critical power following 3‐h of moderate‐intensity cycling in endurance‐trained cyclists/triathletes ( n = 16; V̇O 2max 51.8 ± 6.8 mL·kg −1 ·min −1 ). Following a standardized 24‐h CHO loading protocol (8 g·kg −1 ) and pre‐exercise meal (2 g·kg −1 ), participants completed a 3‐min critical power (CP) test, with end‐test power (EP) and work done above EP used as estimates of CP and W ′ , respectively, in a non‐fatigued state and after 3‐h of cycling at 95% gas exchange threshold (‘fatigued’ state). CP was significantly reduced ( p < 0.001) after the 3‐h exercise in all experimental conditions (water: 236 ± 30 W; 60 g·h −1 : 257 ± 28 W; 120 g·h −1 : 266 ± 29 W) compared to the non‐fatigued state (277 ± 27 W). However, this reduction in CP was attenuated with increasing CHO intake during exercise in a dose‐dependent manner, such that CP after 3‐h was greater in the 120 g·h −1 vs. 60 g·h −1 vs. water condition ( p < 0.05). W ′ declined over time, with no differences between fatigued conditions ( p > 0.05). Mean whole‐body CHO oxidation rates were significantly higher ( p < 0.001) with increasing CHO intake (water: 1.84 ± 0.28; 60 g·h −1 : 2.16 ± 0.15; 120 g·h −1 : 2.31 ± 0.14 g·min −1 ). These data suggest that CHO ingestion at 120 g·h −1 limits the reduction in CP following prolonged moderate‐intensity cycling, with no effect on W ′ . These findings demonstrate that the boundary between heavy‐ and severe‐intensity exercise shifts under fatigue, with CHO availability possibly acting as a key modulator of endurance durability.