Table 2.

HR responses during the sitting test and the head-up tilt test (HUTT) at different time intervals ($\overline{x}\pm S$).

Items	Sitting test	HUTT	t value	P-value
Control
ΔHRmax, bpm	16.2 ± 8.6	23.4 ± 5.9	−4.238	<0.001*
ΔHR 1 min, bpm	13.8 ± 8.7	11.1 ± 7.7	1.360	0.184
ΔHR 3 min, bpm	12.4 ± 9.4	17.8 ± 7.6	−2.756	0.010*
ΔHR 5 min, bpm	13.1 ± 7.5	20.2 ± 5.6	−4.408	<0.001*
ΔHR 10 min, bpm	14.4 ± 9.6	21.1 ± 6.7	−3.469	0.002*
POTS
ΔHRmax, bpm	30.5 ± 11.4‡	46.2 ± 8.9‡	−7.464	<0.001*
ΔHR 1 min, bpm	24.4 ± 10.1‡	21.6 ± 8.6‡	1.477	0.151
ΔHR 3 min, bpm	25.2 ± 8.9‡	37.0 ± 9.8‡	−6.730	<0.001*
ΔHR 5 min, bpm	26.9 ± 10.3‡	41.7 ± 9.4‡	−6.436	<0.001*
ΔHR 10 min, bpm	26.4 ± 12.8‡	44.3 ± 10.5‡	−7.523	<0.001*

Data are the mean ± standard deviation.

HR, heart rate; ΔHR 1/3/5/10 min, change of HR from supine to sitting or tilting at 1, 3, 5, and 10 min; ΔHR_max, maximum change of HR during the 10 min of the sitting test or the HUTT.

^*p < 0.05 (statistically significant);

^‡p < 0.001 (significantly different compared with that measured in the control group).