title: Slow-Absorbing Modified Starch before and during Prolonged Cycling Increases Fat Oxidation and Gastrointestinal Distress without Changing Performance.
abstract: While prior research reported altered fuel utilization stemming from pre-exercise modified starch ingestion, the practical value of this starch for endurance athletes who consume carbohydrates both before and during exercise is yet to be examined. The purpose of this study was to determine the effects of ingesting a hydrothermally-modified starch supplement (HMS) before and during cycling on performance, metabolism, and gastrointestinal comfort. In a crossover design, 10 male cyclists underwent three nutritional interventions: (1) a commercially available sucrose/glucose supplement (G) 30 min before (60 g carbohydrate) and every 15 min during exercise (60 g∙h(-1)); (2) HMS consumed at the same time points before and during exercise in isocaloric amounts to G (Iso HMS); and (3) HMS 30 min before (60 g carbohydrate) and every 60 min during exercise (30 g·h(-1); Low HMS). The exercise protocol (~3 h) consisted of 1 h at 50% Wmax, 8 × 2-min intervals at 80% Wmax, and 10 maximal sprints. There were no differences in sprint performance with Iso HMS vs. G, while both G and Iso HMS likely resulted in small performance enhancements (5.0%; 90% confidence interval = ±5.3% and 4.4%; ±3.2%, respectively) relative to Low HMS. Iso HMS and Low HMS enhanced fat oxidation (31.6%; ±20.1%; very likely (Iso); 20.9%; ±16.1%; likely (Low), and reduced carbohydrate oxidation (-19.2%; ±7.6%; most likely; -22.1%; ±12.9%; very likely) during exercise relative to G. However, nausea was increased during repeated sprints with ingestion of Iso HMS (17 scale units; ±18; likely) and Low HMS (18; ±14; likely) vs. G. Covariate analysis revealed that gastrointestinal distress was associated with reductions in performance with Low HMS vs. G (likely), but this relationship was unclear with Iso HMS vs. G. In conclusion, pre- and during-exercise ingestion of HMS increases fat oxidation relative to G. However, changes do not translate to performance improvements, possibly owing to HMS-associated increases in gastrointestinal distress, which is not attenuated by reducing the intake rate of HMS during exercise.
authors.affiliation: Institute of Sport Sciences and Medicine, Department of Nutrition, Food, and Exercise Sciences, Florida State University, Tallahassee, FL 32306, USA. dab13b@my.fsu.edu.
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Baur
authors.affiliation: Institute of Sport Sciences and Medicine, Department of Nutrition, Food, and Exercise Sciences, Florida State University, Tallahassee, FL 32306, USA. fd14c@my.fsu.edu.
authors.forename: Fernanda de C S
authors.initials: Fde C
authors.lastname: Vargas
authors.affiliation: Institute of Sport Sciences and Medicine, Department of Nutrition, Food, and Exercise Sciences, Florida State University, Tallahassee, FL 32306, USA. cwb12b@my.fsu.edu.
authors.forename: Christopher W
authors.initials: CW
authors.lastname: Bach
authors.affiliation: Institute of Sport Sciences and Medicine, Department of Nutrition, Food, and Exercise Sciences, Florida State University, Tallahassee, FL 32306, USA. jag12h@my.fsu.edu.
authors.forename: Jordan A
authors.initials: JA
authors.lastname: Garvey
authors.affiliation: Institute of Sport Sciences and Medicine, Department of Nutrition, Food, and Exercise Sciences, Florida State University, Tallahassee, FL 32306, USA. mormsbee@fsu.edu.|Department of Biokinetics, Exercise and Leisure Sciences, University of KwaZulu-Natal, Durban 4000, South Africa. mormsbee@fsu.edu.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Ormsbee
mesh_terms: D000293:Adolescent; D000328:Adult; D054874:Athletic Performance / Q000502:physiology*; D001642:Bicycling; D018592:Cross-Over Studies; D004311:Double-Blind Method; D004734:Energy Metabolism; D015444:Exercise; D005767:Gastrointestinal Diseases / Q000209:etiology / Q000503:physiopathology*; D005947:Glucose / Q000008:administration & dosage; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D050356:Lipid Metabolism / Q000187:drug effects*; D008297:Male; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D010807:Physical Endurance / Q000187:drug effects; D012146:Rest; D013213:Starch / Q000008:administration & dosage / Q000009:adverse effects / Q000494:pharmacology*; D013395:Sucrose / Q000008:administration & dosage
chemical_list: D013395:Sucrose; D013213:Starch; D005947:Glucose
keywords: blood glucose; carbohydrate; ergogenic aids; gastrointestinal distress; glycemic index