Whole-body volume of oxygen consumption while walking: Agreement between measured and estimated values.

Predictive equations are widely employed for estimating the volume of oxygen consumption (VO) while walking, which is ultimately employed to determine energy expenditure and tailor exercise prescription. This study aimed to test the agreement between the measured VO and estimated VO during a walking protocol on a treadmill at 3.5, 4.5, 5.5, and 6.5 km/h. Thirty-eight young adults (50% women) participated in this cross-sectional study. The Omnical (Maastricht Instruments, Maastricht, The Netherlands) and K5 (Cosmed, Rome, Italy) metabolic systems were used to measure VO. To determine the predictive equations, a comprehensive literature search was conducted using the MEDLINE database from May 2022 to July 2023. Seven predictive equations were found and included for estimating VO values. We calculated the mean bias (mean difference between measured VO and estimated VO) obtained at each speed using one-sample t-tests. We compared the VO measured and estimated values using repeated measures analysis of variance and the Bland-Altman method. One-sample t-tests showed that all score errors were different from zero (ranging from 1.1 to 5.4 mL/kg/min). Thus, no predictive equation estimated similar VO values in comparison with the Omnical and K5 metabolic systems at all intensities. However, the Weyand equation showed the lowest bias across all intensities (score error of 1.1 mL/kg/min). This study showed a lack of agreement between the Omnical and K5 systems compared to diverse predictive equations specially designed to estimate VO during walking. Nevertheless, based on our results, the Weyand equation should be the preferred option.