title: Is autonomic support of arterial blood pressure related to habitual exercise status in healthy men?
abstract: We determined if the tonic autonomic nervous system (ANS) contribution to arterial blood pressure (BP) maintenance in humans is related to habitual endurance exercise status. Twenty-three healthy young (age 18-31 years) males, 11 endurance exercise-trained and 12 untrained, were studied. Maximal oxygen consumption was higher (P < 0.001) and resting heart rate and body fatness were lower (P < 0.05) in the exercise-trained men. Plasma noradrenaline concentrations and BP decreased from baseline levels in response to ganglionic blockade (intravenous trimethaphan) in both groups (all P < 0.001). The absolute (Delta mmHg: systolic = -35 +/- 2 vs. -32 +/- 4; diastolic = -13 +/- 2 vs. -10 +/- 2; mean = -21 +/- 2 vs. -17 +/- 3) and relative (Delta%: systolic = -35 +/- 2 vs. -31 +/- 3; diastolic = -26 +/- 3 vs. -20 +/- 3; mean = -31 +/- 2 vs. -26 +/- 3) decreases in BP were not significantly different between the endurance-trained and untrained men. There were no significant group differences in the heart rate, stroke volume, cardiac output or systemic vascular resistance (conductance) responses to trimethaphan. Systemic vascular alpha-adrenergic sensitivity (slope of the increase in mean BP with incremental phenylephrine infusion during ganglionic blockade) also did not differ in the two groups (endurance-trained: 3.2 +/- 0.5; untrained: 3.2 +/- 0.7 mmHg (ng phenylephrine)(-1) (ml plasma)(-1)). In the pooled sample, the decrease in mean BP during trimethaphan was related to baseline and changes in plasma noradrenaline concentrations (r = 0.58-0.65, P < 0.001) and alpha-adrenergic sensitivity (r = 0.49, P < 0.02). Our results suggest that the endurance exercise-trained state is not obviously associated with altered ANS support of BP in healthy young men. Basal sympathetic nervous system (SNS) activity and alpha-adrenergic vascular sensitivity are significant physiological correlates of ANS support of BP in this population.
authors.affiliation: Department of Kinesiology and Applied Physiology, University of Colorado at Boulder, Boulder, CO 80309, USA. pamela@spot.colorado.edu
authors.forename: Pamela Parker
authors.initials: PP
authors.lastname: Jones
authors.forename: Linda F
authors.initials: LF
authors.lastname: Shapiro
authors.forename: Gretchen A
authors.initials: GA
authors.lastname: Keisling
authors.forename: Robert A
authors.initials: RA
authors.lastname: Quaife
authors.forename: Douglas R
authors.initials: DR
authors.lastname: Seals
mesh_terms: D000293:Adolescent; D000328:Adult; D001341:Autonomic Nervous System / Q000502:physiology*; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology*; D005070:Evans Blue; D015444:Exercise / Q000502:physiology*; D005730:Ganglionic Blockers / Q000494:pharmacology; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D006728:Hormones / Q000097:blood; D006801:Humans; D010101:Oxygen Consumption / Q000502:physiology; D010953:Plasma Volume; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000502:physiology
chemical_list: D005730:Ganglionic Blockers; D006728:Hormones; D011942:Receptors, Adrenergic, alpha; D005070:Evans Blue