Table 1. Sample size, mean, correlation, agreement between device and reference methods and Bland-Altman outcomes for heart rate (bpm) and energy expenditure (kcal).

		Apple Watch	Fitbit Charge HR	Samsung Gear S	Mio ALPHA
Heart rate	N	22	22	22	22
(bpm)	Device mean ± SD	100.7 ±14.0	92.7 ± 11.5	93.4 ± 13.9	97.7 ± 14.6
	ECG mean ± SD	102.0 ± 14.4	102.0 ± 14.5	100.5 ± 14.6	102.0 ± 13.4
	r/Rho (95% CI)	0.95 (0.88 to 0.98)	0.81 (0.59 to 0.92)	0.67* (0.35 to 0.85)	0.87 (0.71 to 0.94)
	ICC (95% CI)	0.98 (0.94 to 0.99)	0.78 (-0.02 to 0.93)	0.80 (0.40 to 0.93)	0.91 (0.72 to 0.97)
	Mean difference ± SD	-1.3 ± 4.4	-9.3 ± 8.5	-7.1 ± 10.3	-4.3 ± 7.2
	Upper LoA	7.3	7.4	13.1	-0.44.avg + 52.69†
	Lower LoA	-9.9	-26.0	-27.3	0.4.avg—61.2†
Energy Expenditure	N	22	22	19⌃	22
(kcal)	Device mean ± SD	162.6 ± 33.0	236.8 ± 77.0	261.4 ± 47.5	189.5 ± 95.3
	Indirect calorimetry mean ± SD	285.7 ± 50.2	299.1 ± 46.0	287.5 ± 45.1	290.3 ± 46.3
	r/Rho (95% CI)	0.16 (-0.28 to 0.54)	0.64 (0.30 to 0.84)	0.86 (0.67 to 0.95)	0.46* (0.05 to 0.74)
	ICC (95% CI)	0.05 (-0.05 to 0.17)	0.56 (-0.18 to 0.83)	0.86 (0.15 to 0.96)	0.32 (-0.24 to 0.68)
	Mean difference ± SD	-123.1 ± 55.6	0.61.avg–224.6 ± 59.1†	-26.1 ± 24.2	0.91.avg -318.77 ± 84.8†
	Upper LoA	-14.1	1.3.avg–334.28†	21.3	0.91.avg -318.77 + 166.2†
	Lower LoA	-232.1	-0.11.avg–114.92†	-73.5	0.91.avg -318.77–166.2†

Notes: ICC = intraclass correlation coefficient, CI = confidence interval, kcal = kilocalories, ECG = electrocardiography, bpm = beats per minute, SD = standard deviation, avg = average. Correlations r/Rho are Pearson’s correlation coefficient (r) except where indicated by * where they are Spearman rank correlation coefficients (Rho) due to non-normally distributed data.

^† Where Bland-Altman parameters were systematically biased (mean difference/limits of agreement), values are presented as linear equations rather than point estimates.

^⌃ Missing values (n = 3) due to a data recording error.