title: Plasma catecholamines and heart rate at the beginning of muscular exercise in man.
abstract: The relationship between the time course of heart rate and venous blood norepinephrine (NE) and epinephrine (E) concentrations was studied in 7 sedentary young men before and during 3 bicycle exercises of 5 min each (respectively 23 +/- 2.8%, 45 +/- 2.6% and 65 +/- 2.4% VO2max, mean +/- SE). During the low level exercise the change in heart rate is monoexponential (tau = 5.7 +/- 1.2 s) and no increment above the resting level of NE (delta NE) or of E (delta E) occurs. At the medium and highest intensity of exercise: a) the change in heart rate is biexponential, tau for the fast and the slow component averaging about 3 and 80 s respectively; b) delta NE (but not delta E) increases continuously with time of exercise; c) at the 5th min of exercise heart rate increments are related to delta NE; d) between 20 s and 5 min, at corresponding sampling times, the heart rate of the slow component is linearly related to delta NE. At exercise levels higher than 33% VO2max the increase in heart rate described by the slow component of the biexponential kinetic could be due to an augmented sympathetic activity revealed by increased NE blood levels.
authors.affiliation: Department of Biomedical Sciences, University of Brescia, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Orizio
authors.forename: R
authors.initials: R
authors.lastname: Perini
authors.forename: A
authors.initials: A
authors.lastname: Comandè
authors.forename: M
authors.initials: M
authors.lastname: Castellano
authors.forename: M
authors.initials: M
authors.lastname: Beschi
authors.forename: A
authors.initials: A
authors.lastname: Veicsteinas
mesh_terms: D000328:Adult; D001481:Basal Metabolism; D004837:Epinephrine / Q000097:blood*; D006339:Heart Rate; D006801:Humans; D007700:Kinetics; D008297:Male; D009638:Norepinephrine / Q000097:blood*; D005082:Physical Exertion
chemical_list: D009638:Norepinephrine; D004837:Epinephrine