PMC

Lomb-Scargle PSD estimates for a single participant for the three time windows , and at moderate (a) and vigorous (b) intensities. The vertical dashed lines delineate the ultra-low frequency (ULF), very-low frequency (VLF) and low-frequency bands

Data records for a single participant at the three intensity levels. r rest, m moderate, v vigorous. (a) Raw RR intervals. The horizontal dashed line depicts the border between moderate and vigorous intensity (60% of HRR) for this participant: HR = 143 bpm, RR interval = 420 ms. (b) Lomb-Scargle PSD estimates. The vertical dashed lines delineate the ultra-low frequency (ULF), very-low frequency (VLF) and low-frequency bands

Mean power in the ULF (top row) and VLF (bottom row) frequency bands; the corresponding numerical values are given for intensity dependence (figure parts a and b) in Table  and for time dependence (figure parts c–f) in Table . The main bars depict mean power and error bars show 95% confidence intervals for the means. Values are given as . , , . ULF ultra-low frequency, VLF very-low frequency, r rest, m moderate, v vigorous. , and : first, second and third time windows. a Intensity dependence, ULF, b Intensity dependence, VLF, c Time dependence, m, ULF, d Time dependence, m, VLF, e Time dependence, v, ULF and f Time dependence, v, VLF