title: Tricarboxylic-acid-cycle intermediates and cycle endurance capacity.
abstract: The purpose of this study was to determine whether ingestion of a multinutrient supplement containing 3 tricarboxylic-acid-cycle intermediates (TCAIs; pyridoxine-alpha-ketoglutarate, malate, and succinate) and other substances potentially supporting the TCA cycle (such as aspartate and glutamate) would improve cyclists' time to exhaustion during a submaximal endurance-exercise test (approximately 70 % to 75 % VO2peak) and rate of recovery. Seven well-trained male cyclists (VO2max 67.4 2.1 mL x kg(-1) x in(-1), 28.6 +/- 2.4 y) participated in a randomized, double-blind crossover study for 7 wk. Each took either the treatment or a placebo 30 min before and after their normal training sessions for 3 wk and before submaximal exercise tests. There were no significant differences between the TCAI group (KI) and placebo group (P) in time to exhaustion during cycling (KI = 105 +/- 18, P = 113 +/- 11 min); respiratory-exchange ratio at 20-min intervals; blood lactate and plasma glucose before, after, and at 30-min intervals during exercise; perceived exertion at 20-min intervals during exercise; or time to fatigue after the 30-min recovery (KI = 16.1 +/- 3.2, P = 15 +/- 2 min). Taking a dietary sport supplement containing several TCAIs and supporting substances for 3 wk does not improve cycling performance at 75 % VO2peak or speed recovery from previously fatiguing exercise.
authors.affiliation: Dept of Human Nutrition, Food and Animal Sciences, University of Hawaii at Manoa, Honolulu, HI 96822, USA.
authors.forename: Amy C
authors.initials: AC
authors.lastname: Brown
authors.forename: Holden S H
authors.initials: HS
authors.lastname: Macrae
authors.forename: Nathan S
authors.initials: NS
authors.lastname: Turner
mesh_terms: D000328:Adult; D000596:Amino Acids / Q000008:administration & dosage* / Q000378:metabolism; D001642:Bicycling / Q000502:physiology*; D002952:Citric Acid Cycle / Q000502:physiology*; D018592:Cross-Over Studies; D019587:Dietary Supplements; D004311:Double-Blind Method; D005080:Exercise Test; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D006801:Humans; D008297:Male; D010101:Oxygen Consumption; D010807:Physical Endurance / Q000187:drug effects / Q000502:physiology*; D005082:Physical Exertion / Q000187:drug effects / Q000502:physiology; D013997:Time Factors
chemical_list: D000596:Amino Acids