title: Aerobic training improves vagal reactivation regardless of resting vagal control.
abstract: OBJECTIVE
  Resting cardiac vagal modulation (RCVM) and postexercise vagal reactivation (PEVR) are markers of parasympathetic activity. We investigated whether adaptations in these markers to aerobic training are influenced by baseline autonomic control.
  
  
  METHODS
  Forty healthy men (19.2 ± 0.8 yr) of similar cardiorespiratory fitness (VO₂peak = 50.4 ± 5.7 mL·kg⁻¹·min⁻¹) completed the study, being matched for autonomic activity and randomized into four groups: training low-RCVM (TL; n = 11, high-frequency power component [HF] = 48.1 ± 8.2 normalized units [n.u.]) and high-RCVM (TH; n = 11, HF = 63.1 ± 5.9 n.u.) and nonexercise control low-RCVM (CL; n = 9, HF = 47.1 ± 7.5 n.u) and high-RCVM (CH; n = 9, HF = 65.5 ± 8.3 n.u.). Aerobic training groups exercised 3 d·wk⁻¹ for 40 min at 75%-85% HR reserve for 12 wk. Before and after the training period, sequences of 5-min R-R intervals were recorded at rest and immediately after maximal treadmill test to estimate (a) RCVM (HF) and (b) PEVR (root mean square of successive R-R differences-rMSSD(3-5min) = mean value from 3 to 5 min of recovery).
  
  
  RESULTS
  Training improved VO₂peak in TL (11.7% ± 5.4%, P < 0.01) and TH (7.0% ± 2.9%, P < 0.01), with no difference between groups (P = 0.70), but not in CL (0.8% ± 3.9%) and CH (1.8% ± 6.2%, P = 0.90). Only TL increased RCVM (56.6 ± 13.3 n.u., P = 0.03), approaching TH level (58.9 ± 12.3 n.u.; P = 0.60); rMSSD(3-5min) increased in both training groups (P < 0.01) but not in controls (P = 0.99). Relative changes in RCVM (ΔHF%) and PEVR (ΔrMSSD(3-5min)%) were significantly correlated in TL (r = 0.61, P = 0.04).
  
  
  CONCLUSIONS
  PEVR after exercise increased in both exercise training groups, whereas RCVM increased only in the group with low vagal activity at baseline. Vagal reactivation may be improved by aerobic training, even when basal activity remains unaltered.
authors.affiliation: 1Brazilian Army Research Institute of Physical Fitness, Rio de Janeiro, BRAZIL; 2Physical Education Graduate Program, Gama Filho University, Rio de Janeiro, BRAZIL; 3Department of Physiology and Pharmacology, Fluminense Federal University, Niterói, Rio de Janeiro, BRAZIL; 4Department of Kinesiology, University of Connecticut, Storrs, CT; and 5Physical Activity and Health Promotion Laboratory, Rio de Janeiro State University, Rio de Janeiro, BRAZIL.
authors.forename: Antonio
authors.initials: A
authors.lastname: Duarte
authors.forename: Pedro Paulo
authors.initials: PP
authors.lastname: Soares
authors.forename: Linda
authors.initials: L
authors.lastname: Pescatello
authors.forename: Paulo
authors.initials: P
authors.lastname: Farinatti
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D000293:Adolescent; D000886:Anthropometry; D004562:Electrocardiography; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D006801:Humans; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology; D010275:Parasympathetic Nervous System / Q000502:physiology*; D010806:Physical Education and Training; D012420:Running / Q000502:physiology*; D014630:Vagus Nerve / Q000502:physiology*; D055815:Young Adult