title: Preexercise carbohydrate feeding and high-intensity exercise capacity: effects of timing of intake and carbohydrate concentration.
abstract: The present study aimed to investigate the influence of timing of preexercise carbohydrate feeding (Part A) and carbohydrate concentration (Part B) on short-duration high-intensity exercise capacity. In Part A, 17 males, and in Part B 10 males, performed a peak power output (PPO) test, two familiarization trials at 90% of PPO, and 4 (for Part A) or 3 (for Part B) experimental trials involving exercise capacity tests at 90% PPO. In Part A, the 4 trials were conducted following ingestion of a 6.4% carbohydrate/electrolyte sports drink ingested 30 (C30) or 120 (C120) minutes before exercise, or a flavor-matched placebo administered either 30 (P30) or 120 (P120) minutes before exercise. In Part B, the 3 trials were performed 30 min after ingestion of 0%, 2% or 12% carbohydrate solutions. All trials were performed in a double-blind cross-over design following and overnight fast. Dietary intake and activity in the 2 days before trials was recorded and replicated on each visit. Glucose, lactate, heart rate, and mood/arousal were recorded at intervals during the trials. In Part A, C30 produced the greatest exercise capacity (mean ± SD; 9.0 ± 1.9 min, p < .01) compared with all other trials (7.7 ± 1.5 min P30, 8.0 ± 1.7 min P120, 7.9 ± 1.9 min C120). In Part B, exercise capacity (min) following ingestion of the 2% solution (9.2 ± 2.1) compared with 0% (8.2 ± 0.7) and 12% (8.0 ± 1.3) solutions approached significance (p = .09). This study provides new evidence to suggest that timing of carbohydrate intake is important in short duration high-intensity exercise tasks, but a concentration effect requires further exploration.
authors.affiliation: Health and Exercise Sciences Research Group, School of Sport, University of Stirling, Scotland, UK.
authors.forename: Stuart D R
authors.initials: SD
authors.lastname: Galloway
authors.forename: Matthew J E
authors.initials: MJ
authors.lastname: Lott
authors.forename: Lindsay C
authors.initials: LC
authors.lastname: Toulouse
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D004032:Diet; D004040:Dietary Carbohydrates / Q000008:administration & dosage* / Q000097:blood / Q000494:pharmacology; D004311:Double-Blind Method; D004573:Electrolytes / Q000008:administration & dosage; D005247:Feeding Behavior; D006339:Heart Rate; D006801:Humans; D019344:Lactic Acid / Q000097:blood; D008297:Male; D010101:Oxygen Consumption; D010807:Physical Endurance / Q000187:drug effects*; D005082:Physical Exertion / Q000187:drug effects*; D010809:Physical Fitness / Q000502:physiology*; D012420:Running / Q000502:physiology*; D064133:Sports Nutritional Physiological Phenomena; D055815:Young Adult
chemical_list: D001786:Blood Glucose; D004040:Dietary Carbohydrates; D004573:Electrolytes; D019344:Lactic Acid