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

Source: PubMed Central Open Access, NCBI / U.S. National Library of Medicine

ABSTRACT This study examined the effects of graded carbohydrate (CHO) ingestion at rates of 0 (water only), 60 and 120 g·h(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 (= 16; V̇O51.8 ± 6.8 mL·kg·min). Following a standardized 24‐h CHO loading protocol (8 g·kg) and pre‐exercise meal (2 g·kg), 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 ( 0.05). Mean whole‐body CHO oxidation rates were significantly higher (< 0.001) with increasing CHO intake (water: 1.84 ± 0.28; 60 g·h: 2.16 ± 0.15; 120 g·h: 2.31 ± 0.14 g·min). These data suggest that CHO ingestion at 120 g·hlimits 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.