Influencers of the selection between heart-period and heart-rate on the spectral evaluation of heart rhythm variability during exercise

The aim of this study was to evaluate whether use of heart period (HP) or heart rate (HR) may influence the spectral estimate of changes in heart rhythm variability (HRV) induced by physical exercise. For this purpose, power spectra were derived from both HP and HR signals monitored in 8 subjects before, during and after cycling. Powers around 0.1 (LF) and 0.3 (HF) Hz were computed, along with their ratio (LF/HF). Results indicate that HP and HR spectra provide different descriptions of HRV changes in response to exercise. LF and HF powers differed markedly whenever significant changes in the mean heart rhythm occurred in some cases leading to opposite conclusions. A logarithmic transformation of HP and HR signals was proposed to obtain a univocal estimation of NRV spectra.<>