Agreement between VO2max estimated from six-minute walk test and Chester step test in normal adults

Background: Cardiorespiratory fitness is a health-related component of overall physical fitness assessed as maximal oxygen uptake (VO2max) during any physical activity. The six-minute walk test (6MWT) and Chester step test (CST) are two submaximal exercise tests routinely administered to estimate the VO2max of an individual. Thus, the aim of this study was to assess whether an agreement exists between the VO2max estimated by 6MWT and CST in normal adults.
Method: This crossover study was conducted with 80 healthy adults aged 18-40 years. All participants performed the 6MWT and CST on consecutive days. VO2max from the 6MWTwas estimated using a prediction equation whereas from the CST using the graphical plot method.
Results: The mean VO2max-6MWT and VO2max-CST were 43.53 ± 4.65 ml/kg/min and 38.34 ± 4.94 ml/kg/min respectively. The Bland and Altman analysis revealed that the mean difference between VO2max-6MWT and VO2max-CST was 5.19 ± 5.50 ml/kg/min which exceeded the maximum acceptable difference of 3 ml/kg/min decided a priori. The line of equality (X axis) did not fall within the confidence interval of the mean difference indicating that VO2max estimated using the two submaximal exercise tests significantly differ from each other. The standard error of mean was 0.61 ml/kg/min and the standard error of limits of agreement was 1.06 ml/kg/min.
Conclusion: VO2max estimated from the six-minute walk test and Chester step test show no agreement with each other.