Table 2.

Associations between allostatic load and heart rate variability indicators based on frequency domain, time domain and Poincaré analyses (n=27)

	Frequency domain (FFT)		Frequency domain (AR)		Time domain		Poincaré
	Total HRV		Total HRV		Total HRV (SDNN)		Total HRV (SD2)
	r	p	r	p	r	p	r	p
Ph0	−0.670	<0.001	−0.667	<0.001	−0.658	<0.001	−0.562	0.002
Ph1	−0.569	0.002	−0.565	0.003	−0.530	0.004	−0.451	0.018
Ph2	−0.558	0.002	−0.551	0.003	−0.561	0.002	−0.423	0.028
Ph3	−0.469	0.014	−0.497	0.008	−0.484	0.010	−0.499	0.008
	Vagal measure (HF)		Vagal measure (HF)		Vagal measure (RMSSD)		Vagal measure (SD1)
	r	p	r	p	r	p	r	p
Ph0	−0.592	0.001	−0.584	0.001	−0.594	0.001	−0.590	0.001
Ph1	−0.458	0.016	−0.368	0.059	−0.323	0.100	−0.323	0.10
Ph2	−0.443	0.021	−0.412	0.033	−0.411	0.033	−0.407	0.035
Ph3	−0.327	0.096	−0.369	0.058	−0.296	0.134	−0.303	0.124

FFT = Fast Fourier Transformation; AR = Autoregression; HRV = heart rate variability; Ph0 = Phase 0 recording

(5 min baseline, supine); Ph1 = Phase 1 recording (getting up from supine to standing and remain standing for 5 min); Ph2 = Phase 2 recording (5 min standing, following Ph1); Ph3 = Phase 3 recording (5min standing, following Ph2); HF = High frequency band, represents predominantly vagal activity; SDNN = Standard deviation of all normal RR intervals, estimate of overall HRV; RMSSD = Root mean square of the differences between successive RR intervals, estimation of vagal power; SD1 = Standard deviation of the immediate or short-term RR variability as a result of vagal influence; SD2 = Indicator of long-term or slow variability of heart rate, representative of the global HRV.