Reproducibility and Sensitivity of the 6-Minute Stepper Test in Patients with COPD

Abstract

The aims of this study were to test the reproducibility of the 6-minute stepper test (6MST), and evaluate its accuracy in detecting improved functional capacity after pulmonary rehabilitation (PR) in patients with chronic obstructive pulmonary disease (COPD). Thirty-five COPD outpatients performed two 6MSTs in the same session, before (6MST₁ and 6MST₂) and after (6MST₃ and 6MST₄) PR. The performance, perceived exertion, heart rate and arterial oxygen saturation were measured during each 6MST. The performance was higher during the second 6MST of the same session (before PR: 514 strokes during the 6MST₂ > 471 strokes during the 6MST1, and after PR: 559 strokes during the 6MST₄ > 508 strokes during the 6MST₃; p = 0.04). After PR, 6MST performance was higher than before PR (6MST₃ > 6MST₁ and 6MST₄ > 6MST₂; P < 0.01). The bias (the difference in the number of strokes) between the two 6MSTs from the same session (before PR: 6MST₂-6MST₁ = 42 strokes vs after PR: 6MST₄-6MST₃ = 52 strokes) was not different (P = 0.34). However, both bias were greater than 0 (P < 0.001). The mean performances for the two 6MSTs of the same session (before PR: 6MST₁ and 6MST₂ and after PR: 6MST₃ and 6MST₄) were correlated with the bias between these performances (P < 0.01; r = 0.32). The perceived exertions were lower after PR (P < 0.02). The systematic improvement of performance (8–10%) during the second 6MST of the each session may be explained from the warming of hydraulic jacks of the stepper and/or learning effect. On the other hand, the 6MST seems sufficiently sensitive to detect functional capacity improvements after PR in patients with COPD.

Keywords:

• exercise text
• field test
• functional capacity
• pulmonary rehabilitation
• reliability