title: Heart rate variability in athletes and nonathletes at rest and during head-up tilt.
abstract: The purpose of the present study was to determine if autonomic heart rate modulation, indicated by heart rate variability (HRV), differs during supine rest and head-up tilt (HUT) when sedentary and endurance-trained cyclists are compared. Eleven sedentary young men (S) and 10 trained cyclists (C) were studied. The volunteers were submitted to a dynamic ECG Holter to calculate HRV at rest and during a 70 masculine HUT. The major aerobic capacity of athletes was expressed by higher values of VO2 at anaerobic threshold and peak conditions (P < 0.05). At rest the athletes had lower heart rates (P < 0.05) and higher values in the time domain of HRV compared with controls (SD of normal RR interval, SDNN, medians): 59.1 ms (S) vs 89.9 ms (C), P < 0.05. During tilt athletes also had higher values in the time domain of HRV compared with controls (SDNN, medians): 55.7 ms (S) vs 69.7 ms (C), P < 0.05. No differences in power spectral components of HRV at rest or during HUT were detected between groups. Based on the analysis of data by the frequency domain method, we conclude that in athletes the resting bradycardia seems to be much more related to changes in intrinsic mechanisms than to modifications in autonomic control. Also, HUT caused comparable changes in sympathetic and parasympathetic modulation of the sinus node in both groups.
authors.affiliation: Laboratório de Fisiologia do Exercício, Faculdade de Educação Física, Universidade Estadual de Campinas, Brasil.chezfab@terra.com.br
authors.forename: F S
authors.initials: FS
authors.lastname: Martinelli
authors.forename: M P T
authors.initials: MP
authors.lastname: Chacon-Mikahil
authors.forename: L E B
authors.initials: LE
authors.lastname: Martins
authors.forename: E C
authors.initials: EC
authors.lastname: Lima-Filho
authors.forename: R
authors.initials: R
authors.lastname: Golfetti
authors.forename: M A
authors.initials: MA
authors.lastname: Paschoal
authors.forename: L
authors.initials: L
authors.lastname: Gallo-Junior
mesh_terms: D000328:Adult; D001341:Autonomic Nervous System / Q000502:physiology*; D003430:Cross-Sectional Studies; D015716:Electrocardiography, Ambulatory; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test / Q000379:methods; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology; D010807:Physical Endurance / Q000502:physiology; D012146:Rest / Q000502:physiology*; D012849:Sinoatrial Node / Q000502:physiology; D013177:Sports / Q000502:physiology; D016683:Supine Position / Q000502:physiology; D018667:Tilt-Table Test