Validation of Maximal, Submaximal, and Nonexercise Indirect V ˙ O2max Estimations at 2600 m Altitude

Abstract

Aim: To study the criterion validity of three indirect maximal oxygen uptake ($\dot{\text{V}}$O₂max) assessment equations at altitude. Methods: We studied 64 young adults (53% men) at Bogota, Colombia (2600 m altitude). Direct $\dot{\text{V}}$O₂max was measured by indirect calorimetry using a maximal incremental treadmill protocol. Indirect $\dot{\text{V}}$O₂max was estimated by two exercise field tests (the 20-m shuttle-run test [20-MST] and the 2-km walking test (UKK)) and one nonexercise method (the perceived functional ability-physical activity rating questionnaire [PFA-PAR]). Altitude-adjusted PFA-PAR was estimated as a 13% linear reduction in PFA-PAR. We calculated Lin concordance coefficients (LCC) and standard error of the estimates (SEEs), and we performed Bland-Altman analyses for each indirect method. Results: Mean $\dot{\text{V}}$O₂max was 41.2 ± 5.8 mL/kg/min in men and 32.2 ± 3.6 mL/kg/min in women. We found the highest agreement with direct $\dot{\text{V}}$O₂max for the 20-MST (LCC = 0.79, SEE = 3.91 mL/kg/min), followed in order by the altitude-adjusted PFA-PAR (LCC = 0.71, SEE = 4.12 mL/kg/min), the UKK (LCC = 0.67, SEE = 5.48 mL/kg/min), and the unadjusted PFA-PAR (LCC = 0.57, SEE = 4.75 mL/kg/min). The unadjusted PFA-PAR tended to overestimate $\dot{\text{V}}$O₂max, but Bland-Altman analysis showed that this bias disappeared after altitude adjustment. Conclusion: Several maximal, submaximal, and nonexercise methods provide estimates of $\dot{\text{V}}$O₂max with acceptable validity for use in epidemiological studies of populations living at moderate altitude.

Keywords: altitude; cardiorespiratory fitness; field test; maximal oxygen consumption; nonexercise testing; young adults.