title: Effects of elevated plasma adrenaline levels on substrate metabolism, effort perception and muscle activation during low-to-moderate intensity exercise.
abstract: The aim of this study was to differentiate the role of raised plasma adrenaline (Adr) concentrations from sympathoadrenal activation associated with moderate-intensity exercise, on muscle activation, cardiopulmonary responses, fuel metabolism, and ratings of perceived exertion (RPE) during low-intensity exercise. Two groups of subjects (MOD, n=6; LOW, n=7) cycled on two occasions for 90 min. MOD cycled at 68% VO(2max) with saline infusion, and at 34% VO(2max) with Adr infusion. LOW cycled twice at 34% VO(2max), with either Adr or saline infusion. Infusions (0.015 g Adr/kg/min) started at 15 min and increased plasma [Adr] somewhat higher than during exercise at 68% VO(2max) (approximately 1.9 vs. 1.4 nM, at 75 min). Mean plasma glucose and lactate concentrations during LOW were significantly higher with Adr than saline infusion (5.1+/-0.6 vs. 4.4+/-0.3 mmol/l, P<0.01 and 2.1+/-0.8 vs. 1.3+/-0.5 mmol/l, P<0.01, respectively). Elevated [Adr], without increased exercise intensity, did not alter glycogenolysis. There were also no effects of Adr infusion at 34% VO(2max) on heart rate, oxygen consumption, [FFA], respiratory exchange ratio, intramuscular triglyceride utilization, muscle activation or RPE. In conclusion, elevated [Adr] similar to those found during moderate-intensity exercise increased plasma glucose and lactate availability, but did not alter intramuscular fuel utilization, effort perception or muscle activation.
authors.affiliation: Department of Human Biology, UCT/MRC Research Unit for Exercise Science and Sports Medicine, University of Cape Town, P.O. Box 115, 7725 Newlands, South Africa.
authors.forename: Sacha J
authors.initials: SJ
authors.lastname: West
authors.forename: Julia H
authors.initials: JH
authors.lastname: Goedecke
authors.forename: Lizl
authors.initials: L
authors.lastname: van Niekerk
authors.forename: Malcolm
authors.initials: M
authors.lastname: Collins
authors.forename: Alan
authors.initials: A
authors.lastname: St Clair Gibson
authors.forename: Ian A
authors.initials: IA
authors.lastname: Macdonald
authors.forename: Timothy D
authors.initials: TD
authors.lastname: Noakes
authors.forename: Estelle V
authors.initials: EV
authors.lastname: Lambert
mesh_terms: D000293:Adolescent; D000328:Adult; D001786:Blood Glucose; D004576:Electromyography; D004837:Epinephrine / Q000097:blood* / Q000494:pharmacology*; D015444:Exercise / Q000502:physiology*; D005947:Glucose / Q000378:metabolism; D006003:Glycogen / Q000378:metabolism; D006339:Heart Rate; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D009638:Norepinephrine / Q000097:blood / Q000378:metabolism; D011659:Pulmonary Gas Exchange; D013566:Sympathomimetics / Q000097:blood* / Q000494:pharmacology*; D014280:Triglycerides / Q000378:metabolism; D055815:Young Adult
chemical_list: D001786:Blood Glucose; D013566:Sympathomimetics; D014280:Triglycerides; D006003:Glycogen; D005947:Glucose; D009638:Norepinephrine; D004837:Epinephrine