Metabolic responses to carbohydrate ingestion during exercise: associations between carbohydrate dose and endurance performance
Issue Date
2018-01-03Subjects
exogenousfat oxidation
fatty acids
hepatic glucose output
glucose
Subject Categories::C730 Metabolic Biochemistry
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Carbohydrate (CHO) ingestion during exercise lasting less than three hours improves endurance exercise performance but there is still debate about the optimal dose. We utilised stable isotopes and blood metabolite profiles to further examine metabolic responses to CHO (glucose only) ingestion in the 20–64 g·h−1 range, and to determine the association with performance outcome. In a double-blind, randomized cross-over design, male cyclists (n = 20, mean ± SD, age 34 ± 10 years, mass 75.8 ± 9 kg, peak power output 394 ± 36 W, VO2max 62 ± 9 mL·kg−1·min−1) completed four main experimental trials. Each trial involved a two-hour constant load ride (185 ± 25 W) followed by a time trial, where one of three CHO beverages, or a control (water), were administered every 15 min, providing 0, 20, 39 or 64 g CHO·h−1. Dual glucose tracer techniques, indirect calorimetry and blood analyses were used to determine glucose kinetics, exogenous CHO oxidation (EXO), endogenous CHO and fat oxidation; and metabolite responses. Regression analysis revealed that total exogenous CHO oxidised in the second hour of exercise, and suppression of serum NEFA concentration provided the best prediction model of performance outcome. However, the model could only explain ~19% of the variance in performance outcome. The present data demonstrate that consuming ~40 g·h−1 of CHO appears to be the minimum ingestion rate required to induce metabolic effects that are sufficient to impact upon performance outcome. These data highlight a lack of performance benefit and few changes in metabolic outcomes beyond an ingestion rate of 39 g·h−1. Further work is required to explore dose-response effects of CHO feeding and associations between multiple metabolic parameters and subsequent performance outcome.Citation
Newell M, Wallis G, Hunter A, Tipton K, Galloway S (2018) 'Metabolic responses to carbohydrate ingestion during exercise: associations between carbohydrate dose and endurance performance', Nutrients, 10 (1)Publisher
MDPIJournal
NutrientsPubMed ID
29301367PubMed Central ID
PMC5793265Additional Links
https://www.mdpi.com/2072-6643/10/1/37Type
ArticleLanguage
enEISSN
2072-6643ae974a485f413a2113503eed53cd6c53
10.3390/nu10010037
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