. 2021 Mar 25;9(3):e25313. doi: 10.2196/25313

Table 2.

Validity of measuring heart rate with Polar OH1 and Fitbit Charge 3 devices. Data are aggregated to a single data point for each of the activity domains. Data are analyzed for all data points (column “Overall”) and for each of the activity domains.

Device			Overall (n=111^a)		Rest (n=19^a)		Cycling light (n=19^a)		Cycling hard (n=19^a)		Treadmill (n=19^a)		Sprint cycling (n=18^a)		Sprint running (n=17^a)
Polar H10
	Heart rate (beats·min^-1), mean (SD)	106 (27)		62 (9)		89 (11)		119 (12)		124 (14)		128 (17)		120 (12)
Polar OH1
	Heart rate (beats·min^-1), mean (SD)	105 (27)		62 (9)		89 (10)		118 (12)		124 (14)		122 (17)		121 (15)
	Mean bias (beats·min^-1)	1		0		0		1		0		5		1
	Limits of agreement (beats·min^-1)	−8 to 10		0 to 1		−3 to 2		−2 to 4		−1 to 2		−8 to 18		−16 to 15
	MAPE^b (%)	0.6		0.2		0.7		−0.8		0.2		−4.1		0.5
	Correlation coefficient	0.954		0.983		0.974		0.985		0.992		0.807		0.67
	95% CI of correlation coefficient	0.953 to 0.955		0.982 to 0.984		0.971 to 0.977		0.083 to 0.987		0.992 to 0.993		0.795 to 0.819		0.651 to 0.687
Fitbit Charge 3
	Heart rate (beats·min^-1), mean (SD)	97 (26)		61 (9)		81 (10)		100 (21)		123 (10)		109 (23)		112 (11)
	Mean bias (beats·min^-1)	−9		−1		−7		−19		−2		−18		−8
	Limits of agreement (beats·min^-1)	−41 to 23		−2 to 0		−36 to 22		−63 to 26		−13 to 10		−63 to 26		−28 to 12
	MAPE (%)	7.37		−1.5		−7		−15		−1		−13.9		−6
	Correlation coefficient	0.888		0.884		−0.056		0.183		0.924		0.771		0.496
	95% CI of correlation coefficient	0.885 to 0.890		0.876 to 0.891		−0.113 to 0.002		0.127 to 0.238		0.921 to 0.927		0.756 to 0.784		0.471 to 0.520

^an: number of data points analyzed for each domain.

^bMAPE: mean absolute percentage error.