The 6-min walking test (6-MWT) is probably the most widely used test to measure the functional capacity in cardiac rehabilitation. Although the American Thoracic Society recommends testing on a flat surface, treadmills are also used for testing. Therefore, this study investigated the interchangeability of results of treadmill and hallway 6-MWT in a population of patients participating in a cardiac rehabilitation programme. Agreement in 6-min walking distance between the hallway and treadmill test results were calculated by taking the mean difference between the two methods and the 95% confidence interval of the difference and plotting this against the average of the two test results. A Bland and Altman plot was constructed, showing the mean difference and the 95% limits of agreement between the two methods. Sixty-nine patients participated in this study. Mean difference between walking on a treadmill and walking in a hallway was 9 m in favour of the hallway test. The 95% limits of agreement were+/-118 m.
Results of the 6-MWT conducted in a hallway or on a treadmill are not interchangeable, because of large between-test variations in the distances walked by individual participants.