PHYSIOLOGICAL
BASIS OF HRV
The physiological basis of
HRV is the fluctuations of the activity in brain cardiovascular
vasoconstructory and vasodilatatory centers. Normally, these
fluctuations are a
result of blood pressure oscillation (baroreflex modulated);
respiration
(parasympathically mediated via thoracic stretch receptors);
thermoregulation
(sympathetically mediated via thermoregulatory peripheral blood flow
adjustments) and circadian biorhythm. All these factors can influence
the
length of beat-to-beat intervals, named cardiointervals or R-R
intervals. Their
values are an object of mathematical estimation yielding the amount of
HRV.
The increase or decrease of HRV is reflected by the difference of
cardiointervals length (expressed with a time-based measurements as
ms), and by
the difference of the spectral power (expressed with a frequency-based
measurement as Hz). Thus, there are two types of HRV measures –
time-domain
measures and frequency-domain measures, explained in details in the
Stress test
–> Summary section.
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