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Nutrients
Jan 03, 2018;10 (1):

Metabolic Responses to Carbohydrate Ingestion during Exercise: Associations between Carbohydrate Dose and Endurance Performance.

Michael L Newell, Gareth A Wallis, Angus M Hunter, Kevin D Tipton, Stuart D R Galloway
Author Information
  1. Michael L Newell: Department of Life Sciences, Faculty of Science and Technology University of Westminster, London W1W 6UW, UK. m.newell@westminster.ac.uk.
  2. Gareth A Wallis: School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham B15 2TT, UK. g.a.wallis@bham.ac.uk. ORCID
  3. Angus M Hunter: Physiology, Exercise and Nutrition Research Group, Faculty of Health Sciences and Sport, University of Stirling, Stirling FK9 4LA, UK. a.m.hunter1@stir.ac.uk.
  4. Kevin D Tipton: Physiology, Exercise and Nutrition Research Group, Faculty of Health Sciences and Sport, University of Stirling, Stirling FK9 4LA, UK. k.d.tipton@stir.ac.uk.
  5. Stuart D R Galloway: Physiology, Exercise and Nutrition Research Group, Faculty of Health Sciences and Sport, University of Stirling, Stirling FK9 4LA, UK. s.d.r.galloway@stir.ac.uk. ORCID
PMID: 29301367 DOI: 10.3390/nu10010037

Abstract

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 range, and to determine the association with performance outcome. In a double-blind, randomized cross-over design, male cyclists ( = 20, mean ± SD, age 34 ± 10 years, mass 75.8 ± 9 kg, peak power output 394 ± 36 W, VO 62 ± 9 mL·kg·min) 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. 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 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. Further work is required to explore dose-response effects of CHO feeding and associations between multiple metabolic parameters and subsequent performance outcome.

Keywords

exogenous fat oxidation fatty acids glucose hepatic glucose output

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MeSH Term

Administration, Oral
Adult
Beverages
Bicycling
Biomarkers
Blood Glucose
Cross-Over Studies
Dietary Sugars
Double-Blind Method
Drug Administration Schedule
Energy Metabolism
England
Exercise
Fatty Acids, Nonesterified
Glucose
Humans
Insulin
Male
Muscle Contraction
Muscle, Skeletal
Oxidation-Reduction
Physical Endurance
Young Adult

Chemicals

Biomarkers
Blood Glucose
Dietary Sugars
Fatty Acids, Nonesterified
Insulin
Glucose
Journal Article Randomized Controlled Trial
Article has an altmetric score of 89

Word Cloud

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