Table 2. Cardiac autonomic nervous system measures in boys and girls, by posture (N = 2,624).

	Boys						Girls
	Lying down			Sitting up			Lying down		Sitting up
	Mean	SD		Mean	SD		Mean	SD	Mean	SD
Heart rate (bpm)	83.7	9.3	*	89.3	9.9	* †	86.7	9.8	92.4	10.2	†
Pre-ejection period (msec)	76.6	11.6	*	78.5	12.2	* †	77.6	10.1	81.1	11.6	†
Respiratory sinus arrythmia (msec)	127.8	59.5	*	114.9	53.9	* †	121.6	56.3	108.2	51.0	†
Cardiac Autonomic Balance	−0.01	1.46		−0.06	1.39		−0.03	1.36	0.03	1.33	†

*p<0.05 for one sample T-test on sex difference.

^†p<0.05 for paired samples T-test on posture difference.