Increased exogenous but unaltered endogenous carbohydrate oxidation with combined fructose-maltodextrin ingested at 120 g h−1 versus 90 g h−1 at different ratios

Abstract

Purpose This study aimed to investigate whether carbohydrate ingestion during 3 h long endurance exercise in highly trained cyclists at a rate of 120 g h−1 in 0.8:1 ratio between fructose and glucose-based carbohydrates would result in higher exogenous and lower endogenous carbohydrate oxidation rates as compared to ingestion of 90 g h−1 in 1:2 ratio, which is the currently recommended approach for exercise of this duration. Methods Eleven male participants (V̇O2peak 62.6 ± 7 mL kg−1 min−1, gas exchange threshold (GET) 270 ± 17 W and Respiratory compensation point 328 ± 32 W) completed the study involving 4 experimental visits consisting of 3 h cycling commencing after an overnight fast at an intensity equivalent to 95% GET. During the trials they received carbohydrates at an average rate of 120 or 90 g h−1 in 0.8:1 or 1:2 fructose-maltodextrin ratio, respectively. Carbohydrates were naturally high or low in 13C stable isotopes enabling subsequent calculations of exogenous and endogenous carbohydrate oxidation rates. Results Exogenous carbohydrate oxidation rates were higher in the 120 g h−1 condition (120–180 min: 1.51 ± 0.22 g min−1) as compared to the 90 g h−1 condition (1.29 ± 0.16 g min−1; p = 0.026). Endogenous carbohydrate oxidation rates did not differ between conditions (2.15 ± 0.30 and 2.20 ± 0.33 g min−1 for 120 and 90 g h−1 conditions, respectively; p = 0.786). Conclusions The results suggest that carbohydrate ingestion at 120 g h−1 in 0.8:1 fructose-maltodextrin ratio as compared with 90 g h−1 in 1:2 ratio offers higher exogenous carbohydrate oxidation rates but no additional sparing of endogenous carbohydrates. Further studies should investigate potential performance effects of such carbohydrate ingestion strategies.

Substrate utilization and durability during prolonged intermittent exercise in elite road cyclists

“…Therefore, continuous CHO supplementation is recommended during prolonged exercise at moderate-to-high intensities to maintain stable blood sugar levels and CHO oxidation (Stellingwerff and Cox 2014 ; Thomas et al 2016 ). Currently elite endurance athletes generally consume higher amounts of CHO during competitions (i.e., 90–120 g h −1 of multiple transportable CHO) compared to previous practices (Podlogar et al 2022 ; Podlogar and Wallis 2022 ). Another way to conserve CHO sources during prolonged exercise would be a shift towards a greater reliance on fat as a fuel source, since the utilization of CHO is inversely related to the oxidation of fatty acids. Consequently, possessing the ability to effectively utilize fat as an energy source alongside a high CHO intake could enhance durability during prolonged intermittent exercise.…”

Mass Sportrometry: An annual look back at applications of mass spectrometry in sport and exercise science

“…123 Over the past year, a total of 18 studies have been published using IR/elemental approaches in SES. These studies varied across the investigation of carbohydrate (CHO) utilization/oxidation, 20,113,[124][125][126][127][128] pro-tein synthesis/turnover, 50,64,[129][130][131][132] mineral absorption/status, [133][134][135] energy expenditure, 136 and environmental exposure. this study as the first occasion in which exogenous CHO oxidation has been assessed using IRMS techniques across different feeding strategies.…”

“… 123 Over the past year, a total of 18 studies have been published using IR/elemental approaches in SES. These studies varied across the investigation of carbohydrate (CHO) utilization/oxidation, 20 , 113 , 124 , 125 , 126 , 127 , 128 protein synthesis/turnover, 50 , 64 , 129 , 130 , 131 , 132 mineral absorption/status, 133 , 134 , 135 energy expenditure, 136 and environmental exposure. 137 …”

New Horizons in Carbohydrate Research and Application for Endurance Athletes

“…However, there is a relationship between exogenous carbohydrate oxidation rates and ingestion rates, and evidence shows that ingestion rates higher than 90 g•h −1 are feasible and that this results in very high exogenous carbohydrate oxidation rates [66,[76][77][78][79]]. Yet, evidence for recommending such high ingestion rates (i.e., > 90 g•h −1 ) remains inconclusive, as there appears to be no further improvement in performance [80], no sparing of endogenous carbohydrate stores [71] and, in some cases, aggressive carbohydrate feeding during exercise can result in increased muscle glycogen utilization [81,82]. It could be that athletes whose energy turnover rates during exercise are very high and thus have a high glucose flux to muscle due to increased blood flow proportional to absolute exercise intensity [83] could benefit from carbohydrate ingestion rates that are higher than currently recommended, but this requires further evaluation.…”

“…It has been reported that elite cyclists can tolerate more than 90 g·h −1 of carbohydrates mostly from glucose-based carbohydrates [ 70 ]. We have recently shown higher exogenous carbohydrate oxidation during prolonged endurance exercise in highly trained athletes with carbohydrate ingestion at 120 g·h −1 as compared to 90 g·h −1 [ 71 ]. However, endogenous carbohydrate oxidation was not further spared by the higher carbohydrate dose, and thus whether there would be an additional performance benefit requires clarification.…”