title: Exercise metabolism at different time intervals after a meal.
abstract: To determine how long a meal will affect the metabolic response to exercise, nine endurance-trained and nine untrained subjects cycled for 30 min at 70% of peak O2 consumption (VO2 peak) 2, 4, 6, 8, and 12 h after eating 2 g carbohydrate/kg body wt. In addition, each subject completed 30 min of cycling 4 h after the meal at an intensity that elicited a respiratory exchange ratio (RER) of 0.94-0.95. During exercise after 2 and 4 h of fasting, carbohydrate oxidation was elevated 13-15% compared with the response to exercise after an 8- and 12-h fast (P less than 0.01). The increase in blood glycerol concentration during exercise (30 to 0 min) was linearly related to the length of fasting (r = 0.99; P less than 0.01). In all subjects, plasma glucose concentration declined 17-21% during exercise after 2 h of fasting (P less than 0.01). Plasma glucose concentration also declined (15-25%) during exercise in the trained subjects after 4 and 6 h of fasting (P less than 0.05) but did not change in the untrained subjects. However, the decline in plasma glucose concentration was similar (14%) in the two groups when the exercise intensity was increased in the trained subjects (i.e., 78 +/- 1% VO2 peak) and decreased in the untrained subjects (i.e., 65 +/- 3% VO2 peak) to elicit a similar RER.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Kinesiology and Health, University of Texas, Austin 78712.
authors.forename: S J
authors.initials: SJ
authors.lastname: Montain
authors.forename: M K
authors.initials: MK
authors.lastname: Hopper
authors.forename: A R
authors.initials: AR
authors.lastname: Coggan
authors.forename: E F
authors.initials: EF
authors.lastname: Coyle
mesh_terms: D001786:Blood Glucose / Q000378:metabolism; D050260:Carbohydrate Metabolism; D004435:Eating / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D005215:Fasting; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005990:Glycerol / Q000097:blood; D006801:Humans; D007328:Insulin / Q000097:blood; D008297:Male; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D010807:Physical Endurance / Q000502:physiology; D011659:Pulmonary Gas Exchange / Q000502:physiology; D013997:Time Factors
chemical_list: D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D005990:Glycerol