Validity of simplified, calibration-less exercise intensity measurement using resting heart rate during sleep: a method-comparison study with respiratory gas analysis

Table 1 Fixed and proportional bias in the Bland-Altman analysis

	%VO₂R vs. %HRR based on	Fixed bias							Proportional bias
		Mean difference	95% CI	P	Lower	95% CI	Upper	95% CI	difference vs. mean
		Mean difference	95% CI	P	LOA	95% CI	LOA	95% CI	r	P
Treadmill testing with Bruce protocol	HR_sitting	10.8	8.8, 12.7	< 0.0001	−5.4	−13.4, 0.0	27.0	22.5, 35.0	−0.45	< 0.01
	HR_lying	7.7	5.4, 9.9	< 0.0001	−11.4	− 23.5, −4.9	26.8	20.3, 38.8	−0.18	0.14
	HR_sleeping	1.7	−0.2, 3.6	0.2552	−13.7	−25.3, −9.3	17.2	12.7, 25.3	0.24	0.06
Six minutes walking test	HR_sitting	12.7	10.0, 15.5	< 0.0001	−5.0	−16.0, 0.0	30.4	24.3, 41.4	0.00	0.98
	HR_lying	7.0	4.0, 10.0	< 0.0001	−11.6	−23.5, −5.0	25.6	18.9, 37.5	0.02	0.90
	HR_sleeping	−2.9	−5.0, −0.7	0.0492	−16.3	− 24.6, −11.6	10.5	5.9, 18.9	0.26	0.11

HR, heart rate; LOA, limit of agreement; CI, confidence interval; %VO₂R, percent oxygen consumption reserve; %HRR, percent heart rate reserve, HR_sitting; resting HR at sitting awake, HR_sitting; resting HR at sitting awake, HR_lying; resting HR at lying awake, HR_sleeping; resting HR during sleeping

ISSN: 2052-1847