title: Effects of prolonged exercise at a similar percentage of maximal oxygen consumption in trained and untrained subjects.
abstract: Six trained male cyclists and six untrained but physically active men participated in this study to test the hypothesis that the use of percentage maximal oxygen consumption (%VO2max) as a normalising independent variable is valid despite significant differences in the absolute VO2max of trained and untrained subjects. The subjects underwent an exercise test to exhaustion on a cycle ergometer to determine VO2max and lactate threshold. The subjects were grouped as trained (T) if their VO2max exceeded 60 ml.kg-1.min-1, and untrained (UT) if their VO2max was less than 50 ml.kg-1.min-1. The subjects were required to exercise on the ergometer for up to 40 min at power outputs that corresponded to approximately 50% and 70% VO2max. The allocation of each exercise session (50% or 70% VO2max) was random and each session was separated by at least 5 days. During these tests venous blood was taken 10 min before exercise (- 10 min), just prior to the commencement of exercise (0 min), after 20 min of exercise (20 min), at the end of exercise and 10 min postexercise (+ 10 min) and analysed for concentrations of cortisol, [Na+], [K+], [Cl-], glucose, free fatty acid, lactate [la-], [NH3], haemoglobin [Hb] and for packed cell volume. The oxygen consumption (VO2) and related variables were measured at two time intervals (14-15 and 34-35 min) during the prolonged exercise tests. Rectal temperature was measured throughout both exercise sessions. There was a significant interaction effect between the level of training and exercise time at 50% VO2max for heart rate (fc) and venous [la-].(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Rehabilitation Research Centre, Cumberland College of Health Sciences, University of Sydney, Lidcombe, NSW, Australia.
authors.forename: G C
authors.initials: GC
authors.lastname: Gass
authors.forename: T M
authors.initials: TM
authors.lastname: McLellan
authors.forename: E M
authors.initials: EM
authors.lastname: Gass
mesh_terms: D000328:Adult; D000641:Ammonia / Q000097:blood; D015444:Exercise / Q000502:physiology*; D006339:Heart Rate; D006400:Hematocrit; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D007773:Lactates / Q000097:blood; D019344:Lactic Acid; D008297:Male; D010101:Oxygen Consumption; D010807:Physical Endurance / Q000502:physiology*; D013997:Time Factors
chemical_list: D006454:Hemoglobins; D007773:Lactates; D019344:Lactic Acid; D000641:Ammonia