Short-term correlation properties of R-R interval dynamics at different exercise intensity levels

Summary Methods based on non‐linear heart rate (HR) dynamics have been suggested to probe features in HR behaviour that are not easily detected by the traditional HR variability indices. This study tested the hypothesis that analysis of correlation properties of R–R intervals provides useful information on HR fluctuation during exercise. High‐ (HF) and low‐frequency (LF) spectral components and a short‐term scaling exponent (α1) of HR variability, were analysed for nine healthy subjects at rest, during incremental and steady‐state exercise, during atropine infusion and during incremental exercise after atropine administration. During the incremental exercise test α1 increased from rest to an intensity level of ∼40% of (from 1·07 ± 0·24 to 1·50 ± 0·25, P