Aerobic training improves vagal reactivation regardless of resting vagal control.

AB Purpose: 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 (V[spacing dot above]O2peak = 50.4 +/- 5.7 mL[middle dot]kg-1[middle dot]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[middle dot]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-rMSSD3-5min = mean value from 3 to 5 min of recovery). Results: Training improved V[spacing dot above]O2peak 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); rMSSD3-5min increased in both training groups (P < 0.01) but not in controls (P = 0.99). Relative changes in RCVM ([DELTA]HF%) and PEVR ([DELTA]rMSSD3-5min%) 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.