Table 2.

Correlations and differences between the estimated maximum oxygen consumption in the smartwatch test and the measured maximum oxygen consumption in the cardiopulmonary exercise test.

	VO2max-CPETa (mL·kg–1·min–1), mean (SD)	VO2max-SWTb (mL·kg–1·min–1), mean (SD)	CEc (mL·kg–1·min–1), mean (SD)	t (df)	r	Intraclass correlation coefficient	Mean absolute error (mL·kg–1·min–1)	Mean absolute percentage error (%)
Low altitude (n=46)	30.17 (5.01)	31.28 (5.17)	1.11 (1.73)	4.35 (45) (Pd<.001)	0.943 (P<.001)	0.942 (P<.001)	1.761	6
High altitude (n=41)	25.20 (6.46)	26.17 (6.71)	0.98 (1.54)	4.05 (40) (P<.001)	0.973 (P<.001)	0.973 (P<.001)	1.610	6.80

^aVO₂max-CPET: maximum oxygen consumption measured by the cardiopulmonary exercise test.

^bVO₂max-SWT: maximum oxygen consumption estimated by the smartwatch test.

^cCE: constant error (arithmetic mean of the difference between estimated and measured VO₂max).

^dDifferences were considered statistically significant if P<.05.