Recovery of Linear and Nonlinear Heart Rate Variability Metrics After Short-Term Moderate versus Vigorous Intensity Exercise: A Cross-Sectional Randomized Cross-Over Study.

The present study explored acute responses of heart rate (HR) variability (HRV) metrics, incorporating the nonlinear index alpha 1 of detrended fluctuation analysis (DFAa1) during passive recovery, providing information about correlation properties of HR time series during the regulation of recovery processes. Recreationally active female (n = 13) and male (n = 13) participants participated. In a first session, a graded exercise test was conducted to determine peak HR (HRPEAK) and peak oxygen consumption (VO2PEAK). In a second and third session, participants completed an endurance training with moderate intensity (MOD) on a treadmill and an exergaming training with vigorous intensity (VIG), randomized and counterbalanced. Before and up to 45 min after the respective exercise sessions, RR-interval and hemodynamic measurements (peripheral systolic, SBP; diastolic blood pressure, DBP; and pulse wave velocity, PWV) were conducted. Internal load analysis of MOD versus VIG revealed significant differences and appropriate prescription of intensity domains during exercise (%HRPEAK: ∼66% vs. 86% and %VO2PEAK: ∼48% vs. 66%). The present data showed significant main effects of time, intensity, and their interaction for all RR-interval outcomes, PWV, and SBP. DFAa1 demonstrated a stronger correlated reorganization and overcompensation after VIG, with higher values and therefore increased correlation properties throughout the recovery process. The present data suggest that VIG transiently delays the recovery of cardiac parasympathetic activity and the normalization of correlation properties of HR time series. Regarding acute early and delayed recovery processes, higher correlation properties may reflect more order (less complexity) and interaction of involved physiological subsystems, supporting the assumption of increased systemic control to process the demands of higher exercise intensity.