Six-minute stepper test: a valid clinical exercise tolerance test for COPD patients

JM Grosbois,^1,2 C Riquier,³ B Chehere,⁴ J Coquart,⁵ H Béhal,⁶ F Bart,² B Wallaert,^2,3 C Chenivesse<sup>3

1</sup>FormAction Santé, Pérenchies, France; ²Department of Respiratory Medicine, Centre Hospitalier Germon et Gauthier, Béthune, France; ³Department of Respiratory Medicine Immunology and Allergy, Centre Hospitalier Universitaire de Lille, Competence Center for rare lung diseases, University Lille 2, Lille, France; ⁴EA 7369, URePSSS, Multidisciplinary Research Unit in Sport Health Society, University Lille 2, Lille, France; ⁵Faculty of Sport Sciences, Sports and Physical Activity, Center for Ecology and Transformation, University of Rouen, Mont Saint Aignan, France; ⁶Department of Statistical Methods and Biostatistics, Centre Hospitalier Universitaire de Lille, University of Lille Nord, Lille, France

Introduction: Exercise tolerance testing is an integral part of the pulmonary rehabilitation (PR) management of patients with chronic obstructive pulmonary disease (COPD). The 6-minute stepper test (6MST) is a new, well-tolerated, reproducible exercise test, which can be performed without any spatial constraints.
Objective: The aim of this study was to compare the results of the 6MST to those obtained during a 6-minute walk test (6MWT) and cardiopulmonary exercise testing (CPET) in a cohort of COPD patients.
Methods: Ninety-one COPD patients managed by outpatient PR and assessed by 6MST, 6MWT, and CPET were retrospectively included in this study. Correlations between the number of steps on the 6MST, the distance covered on the 6MWT, oxygen consumption, and power at the ventilatory threshold and at maximum effort during CPET were analyzed before starting PR, and the improvement on the 6MST and 6MWT was compared after PR.
Results: The number of steps on the 6MST was significantly correlated with the distance covered on the 6MWT (r=0.56; P<0.0001), the power at maximum effort (r=0.46; P<0.0001), and oxygen consumption at maximum effort (r=0.39; P<0.005). Performances on the 6MST and 6MWT were significantly improved after PR (570 vs 488 steps, P=0.001 and 448 vs 406 m, respectively; P<0.0001). Improvements of the 6MST and 6MWT after PR were significantly correlated (r=0.34; P=0.03).
Conclusion: The results of this study show that the 6MST is a valid test to evaluate exercise tolerance in COPD patients. The use of this test in clinical practice appears to be particularly relevant for the assessment of patients managed by home PR.

Keywords: 6-minute stepper test, 6-minute walk test, exercise tolerance, pulmonary rehabilitation, cardiopulmonary exercise testing, validity