Figure 2.

Linear regression plots between the estimated maximum oxygen consumption measured by smartwatch test and maximum oxygen consumption measured by cardiopulmonary exercise testing. Pearson correlation between the maximum oxygen consumption estimated by smartwatch and measured by cardiopulmonary exercise testing at low altitude (A) and at high altitude (B). The coefficient of determination (R2) and 95% CI bounds (dotted line) are depicted for the regression lines (solid). VO₂max-CPET: maximum oxygen consumption measured by cardiopulmonary exercise testing; VO₂max-SWT: estimated maximum oxygen consumption by smartwatch test.