| Hi-index | 0.00 |
1. Background: The post-exercise period is associated with a profound decrease in sympathetic activity and arterial pressure. We have recently shown that endurance exercise training in rate is associated with highly significant decreases of low frequency (LF: 0.19-0.61 Hz) power of blood pressure (BP). In this study, we measured cardiac output (CO) and systolic blood pressure (SBP) continuously for at least 5 min in rats before (n = 5) and after (n = 4) exercise. The purpose of this study was to determine if acute exercise produces post-exercise changes in the low frequency power (LF: 0.19-0.61 Hz) of CO as the decrease in this band of BP appears to be mediated by the sympathetic nervous system.2. Methods: The data were sampled at 200 Hz and the HR time series were derived from the SBP signal. The signals were sampled at 16 Hz and the spectral powers were obtained in the following bands; total power (TP: 0-2.5 Hz), very low frequency power (VLF: 0-0.19 Hz), low frequency power (LF: 0.19-0.61 Hz) and high frequency power (HF: 1.2-2.5 Hz). We also obtained the transfer magnitude and coherence between HR and CO. Finally, largest Lyapunov exponent (LLE) was obtained as a measure of chaos for HR and CO before and after exercise.3. Results: There was a significant decrease in LLE of CO (p 0.05) after exercise.4. Conclusions: These results suggest that the CO time series appear to be chaotic in nature and the decrease in LLE after exercise, especially in relation to HR appears to be due to a decrease in sympathetic activity. These new nonlinear techniques may prove to be of additional value to the linear measures such as spectral analysis.