Abstract
Walking tests, such as the 6-min walk test (6MWT), are popular methods of estimating peak oxygen uptake (VO2peak) in clinical populations. However, the strength of the distance vs. VO2peak relationship is not strong, and there are no equations for estimating ventilatory threshold (VT), which is important for training prescription and prognosis. Since the 6MWT is often limited by walking mechanics, prediction equations that include simple additional predictors, such as the terminal rating of perceived exertion (RPE), hold the potential for improving the prediction of VO2max and VT. Therefore, this study was designed to develop equations for predicting VO2peak and VT from performance during the 6MWT, on the basis of walking performance and terminal RPE. Clinically stable patients in a cardiac rehabilitation program (N = 63) performed the 6MWT according to the American Thoracic Society guidelines. At the end of each walk, the subject provided their terminal RPE on a 6–20 Borg scale. Each patient also performed a maximal incremental treadmill test with respiratory gas exchange to measure VO2peak and VT. There was a good correlation between VO2peak and 6MWT distance (r = 0.80) which was improved by adding the terminal RPE in a multiple regression formula (6MWT + RPE, R2 = 0.71, standard error of estimate, SEE = 1.3 Metabolic Equivalents (METs). The VT was also well correlated with walking performance, 6MWT distance (r = 0.80), and was improved by the addition of terminal RPE (6MWT + RPE, R2 = 0.69, SEE = 0.95 METs). The addition of terminal RPE to 6MWT distance improved the prediction of maximal METs and METs at VT, which may have practical applications for exercise prescription.
Highlights
Exercise capacity is an important quantitative expression of the ability to perform muscular activity
When the 6-min walk test (6MWT) distance and terminal rating of perceived exertion (RPE) were combined in a multiple regression equation to predict Max Metabolic Equivalents (METs), the R2 increased from 0.63 to 0.71, with a SEE of 1.3 METs and a standardized residual of 1.0 METs
Unique to this study was the ability of 6MWT distance + terminal RPE to predict the METs@ventilatory threshold (VT), which is a better measure of sustainable exercise capacity [2,9], a powerful emerging measure of prognosis [10,11] and a very useful measure for prescribing exercise [3]
Summary
Exercise capacity is an important quantitative expression of the ability to perform muscular activity. VT, a physiologically complex concept [9], has come to be recognized as a better measure of exercise capacity than VO2peak relative to the ability to carry out daily activities [2,3]. Cardiopulmonary exercise testing (which is technically demanding) [12] is required to measure VO2peak and VT. Directly cardiopulmonary exercise testing is normally only conducted for the purpose of exploring the differential diagnosis of dyspnea or to determine if there is a multi-organ system explanation of exercise intolerance Cardiopulmonary exercise testing (which is technically demanding) [12] is required to measure VO2peak and VT. directly cardiopulmonary exercise testing is normally only conducted for the purpose of exploring the differential diagnosis of dyspnea or to determine if there is a multi-organ system explanation of exercise intolerance
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