We compared the effects of the active standing test (AST) on the variability of systolic and diastolic subintervals, which were estimated by measuring the electromechanical periods from the R wave peak (R) to the systolic peak (S) of the noninvasive arterial pressure waveform (RS), and from S to R (SR), respectively. The time courses of the low-frequency components (LFRR, LFSR, and LFRS) and the corresponding high-frequency components (HFRR, HFRS, HFSR) of the RR, RS, and SR time series of 24 healthy volunteers who performed AST were computed using the smoothed pseudo-Wigner-Ville time-frequency distribution. Correlations, coherences, and ratios between the spectral indexes were also obtained. During AST, the response patterns of the indexes showed the following changes, relative to their baseline. RR and SR exhibited an abrupt fall maintained until the end, followed by an overshoot during recovery. LFRR and LFSR showed overshoots -one at the beginning and the other at the end of AST. HFSR depicted an abrupt initial fall that was maintained until the end, followed by an overshoot during recovery. RS showed minuscule changes consisting of an initial increase followed by a decrease that recovered at the end. LFRS displayed very small overshoots at the beginning and the end. HFRS exhibited a tiny increment that was held until the end. During AST, the coherences and correlations of LFSR-LFRR and HFSR-HFRR relationships were very high (Table), with LFSR/LFRR ratio of 1.10±0.07 and HFSR/HFRR of 1.21±0.13. However, the corresponding values for LFRS-LFRR and HFRS-HFRR were smaller (Table), with LFRS/LFRR of 0.02±0.01 and HFRS/HFRR ratio of 0.05±0.06. Our findings strongly support that AST induces almost identical modulatory effects of sympathetic increase and vagal decrease in both SR (diastolic) and RR series variabilities. In contrast, the sympathetic and vagal modulatory effects of AST on RS (systolic) series variability are negligible.