Background:Power spectrum analysis of heart rate variability (HRV) can be used to assess the state of sympathovagal balance-modulating sinus node activity. Stroke volume variability (SVV) probably reflects the dynamics of physiological control mechanisms over time.Material/Methods: Power spectrum HRV and SVV were simultaneously measured in 44 healthy men. The values of the HRV and SVV parameters were compared for the supine and upright body positions in three age groups (I: 20–40; II: 40–60; III: >60 years old). The total power (TP) of the very low (VLF:<0.05 Hz), low (LF: 0.05–0.15 Hz) and high (HF: 0.15–0.5 Hz) HRV and SVV frequency bands were measured. The LF/HF and lnLF/lnHF ratios for HRV and SVV were calculated.
Results: The upright position caused a significant decrease in HRV in the HF and lnHF bands and an increase in the LF/HF and lnLF/HF ratios in all groups. SVV analysis for the supine position revealed significant differences in lnTP and HF values (between groups I and II) and in lnHF values (between groups I and II and I and III). SVV analysis for the upright position revealed differences in lnTP (between groups I and II and I and III), lnVLF (between groups I and III and I and III), lnLF (between groups I and II and I and III) and lnHF (between groups I and II and I and III).
Conclusions: The combined analysis of HRV and SVV revealed different cardiovascular responses to postural stress in the three age groups considered.

Keywords: Analysis of Variance, Electrocardiography - methods, Heart Rate - physiology, Posture - physiology, Signal Processing, Computer-Assisted, Stroke Volume - physiology, Analysis of Variance, Electrocardiography - methods, Heart Rate - physiology, Posture - physiology, Signal Processing, Computer-Assisted, Stroke Volume - physiology