Purpose: Maximizing carbohydrate availability is important for many endurance events. Combining pectin and sodium alginate with ingested maltodextrin-fructose (MAL+FRU+PEC+ALG) has been suggested to enhance carbohydrate delivery via hydrogel formation but the influence on exogenous carbohydrate oxidation remains unknown. The primary aim of this study was to assess the effects of MAL+FRU+PEC+ALG on exogenous carbohydrate oxidation during exercise compared to a maltodextrin-fructose mixture (MAL+FRU). MAL+FRU has been well established to increase exogenous carbohydrate oxidation during cycling, compared to glucose-based carbohydrates (MAL+GLU). However, much evidence focuses on cycling, and direct evidence in running is lacking. Therefore, a secondary aim was to compare exogenous carbohydrate oxidation rates with MAL+FRU versus MAL+GLU during running.
Methods: Nine trained runners completed two trials (MAL+FRU and MAL+FRU+PEC+ALG) in a double-blind, randomised crossover design. A subset (n=7) also completed a MAL+GLU trial to address the secondary aim, and a water trial to establish background expired CO2 enrichment. Participants ran at 60% V˙O2peak for 120 min while ingesting either water only, or carbohydrate solutions at a rate of 1.5 g carbohydrate·min.
Results: At the end of 120 min of exercise, exogenous carbohydrate oxidation rates were 0.9 (SD 0.5) g·min with MAL+GLU ingestion. MAL+FRU ingestion increased exogenous carbohydrate oxidation rates to 1.1 (SD 0.3) g·min (p=0.038), with no further increase with MAL+FRU+PEC+ALG ingestion (1.1 (SD 0.3) g·min; p=1.0). No time x treatment interaction effects were observed for plasma glucose, lactate, insulin or non-esterified fatty acids, nor for ratings of perceived exertion or gastrointestinal symptoms (all p>0.05).
Conclusion: To maximise exogenous carbohydrate oxidation during moderate-intensity running, athletes may benefit from consuming glucose(polymer)-fructose mixtures over glucose-based carbohydrates alone, but the addition of pectin and sodium alginate offers no further benefit.
Postexercise Fructose-Maltodextrin Ingestion Enhances Subsequent Endurance CapacityE Maunder et al. Med Sci Sports Exerc 50 (5), 1039-1045. PMID 29232314. - Randomized Controlled TrialShort-term recovery of endurance capacity was significantly enhanced with FRU + MAL versus GLU + MAL ingestion during recovery.
Fructose and Sucrose Intake Increase Exogenous Carbohydrate Oxidation During ExerciseJ Trommelen et al. Nutrients 9 (2). PMID 28230742. - Randomized Controlled TrialPeak exogenous carbohydrate oxidation rates typically reach ~1 g∙min-1 during exercise when ample glucose or glucose polymers are ingested. Fructose co-ingestion has been …
Exogenous CHO Oxidation With Glucose Plus Fructose Intake During ExerciseCJ Hulston et al. Med Sci Sports Exerc 41 (2), 357-63. PMID 19127189.The present study demonstrates that ingesting moderate amounts of glucose plus fructose does not increase exogenous CHO oxidation above that of an isocaloric amount of gl …
Fructose-Glucose Composite Carbohydrates and Endurance Performance: Critical Review and Future PerspectivesDS Rowlands et al. Sports Med 45 (11), 1561-76. PMID 26373645. - ReviewSports beverages formulated with fructose and glucose composites enhance exogenous carbohydrate oxidation, gut comfort, and endurance performance, relative to single-sacc …
The Use of Carbohydrates During Exercise as an Ergogenic AidNM Cermak et al. Sports Med 43 (11), 1139-55. PMID 23846824. - ReviewCarbohydrate and fat are the two primary fuel sources oxidized by skeletal muscle tissue during prolonged (endurance-type) exercise. The relative contribution of these fu …