Table 2.

Results of trend tests between heart rate variability items and occupational physical activity according to age and exercise frequency

			SDNN				rMSSD				LF				HF				LF:HF
			low		normal		low		normal		low		normal		low		normal		low		normal
			n	%	n	%	n	%	n	%	n	%	n	%	n	%	n	%	n	%	n	%
Age (years)		OPA
	< 45	Low	16	20.3	63	79.8	5	6.3	74	93.7	18	22.8	61	77.2	8	10.1	71	89.9	23	29.1	56	70.9
		High	8	23.5	26	76.5	2	5.9	32	94.1	11	32.4	23	67.7	4	11.8	30	88.2	12	35.3	22	64.7
		p-value	0.3481				0.464				0.1428				0.3977				0.2573
	≥45	Low	4	30.8	9	69.2	0	0.0	13	100.0	5	38.5	8	61.5	1	7.7	12	92.3	9	69.2	4	30.8
		High	4	80.0	1	20.0	3	60.0	2	40.0	4	80.0	1	20.0	3	60.0	2	40.0	1	20.0	4	80.0
		p-value	0.0299				0.0011				0.0572				0.0084				0.0299
Exercise (times/ week)
	≥ 3	Low	6	24.0	19	76.0	0	0.0	25	100.0	8	32.0	17	68.0	2	8.0	23	92.0	10	40.0	15	60.0
		High	3	25.0	9	75.0	2	16.7	10	83.3	4	33.3	8	66.7	2	16.7	10	83.3	6	50.0	6	50.0
		p-value	0.4735				0.0179				0.4677				0.2134				0.2827
	1–2	Low	9	20.9	34	79.1	3	7.0	40	93.0	11	25.6	32	74.4	5	11.6	38	88.4	15	34.9	28	65.1
		High	5	29.4	12	70.6	1	5.9	16	94.1	5	29.4	12	70.6	1	5.9	16	94.1	6	35.3	11	64.7
		p-value	0.2420				0.4391				0.3812				0.2519				0.4880
	0	Low	4	25.0	12	75.0	2	12.5	14	87.5	4	25.0	12	75.0	1	6.3	15	93.8	6	37.5	10	62.5
		High	2	33.3	4	66.7	2	33.3	4	66.7	4	66.7	2	33.3	3	50.0	3	50.0	0	0.0	6	100.0
		p-value	0.3479				0.1296				0.0352				0.0089				0.0393

SDNN the standard deviation of normal-to-normal intervals, rMSSD the root-mean square of the difference of successive normal R-R intervals, LF low frequency band power, HF high frequency band power, LF:HF ratio of low-frequency power to high-frequency power, OPA occupational physical activity