Fig. 5.

Spectra for the signal RR versus residuals $r_t$ where the latter have been calculated from the original (‘noise’) and pre-processed (‘noise filtered’) signals PP, shown in red and green, respectively. The vertical lines show the frequency bands used in HRV analysis: LF between 0.04 and 0.15 Hz, and HF between 0.15 and 0.4 Hz