Table 3.

Accuracy of measuring heart rate (HR) using Cardiio smartphone app compared with reference electrocardiogram.

Statistic		Resting HR	Postmoderate-intensity exercise HR	Postvigorous intensity-exercise HR
Fingertip PPGadetection
	Coefficient of determination	.993	.988	.990
	RMSEb (beats/min)	1.03	2.15	2.01
	RMSE (%)	1.40	2.53	1.93
	Wilcoxon signed rank test, P value	.53	.09	.60
	Paired Student t test, P value	.69	.03	.19
	Mean (SD) difference (beats/min)	–0.05 (1.03)	–0.36 (2.14)	–0.18 (2.02)
	Median difference (beats/min)	0.500	0	0
Facial PPG detection
	Coefficient of determination	.994	.965	.960
	RMSE (beats/min)	1.02	3.68	3.84
	RMSE (%)	1.44	4.11	3.73
	Wilcoxon signed rank test, P value	.02	<.001	.08
	Paired Student t test, P value	.01	<.001	.001
	Mean (SD) difference (beats/min)	–0.29 (1.03)	–1.09 (3.67)	–0.93 (3.84)
	Median difference (beats/min)	–1.166	–2.000	–1.000

^aPPG: photoplethysmography.

^bRMSE: root mean square error.