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

Figures & data

Figure 1.  Photography (A: side view, B: top view, and C: back view) of the stepper (Go Sport®, Grenoble, France).

Table 1.   Anthropometric and spirometric data of the chronic obstructive pulmonary disease patients

Variable (units)
Women (%)	40.0
Age (years)	60.8 ± 8.9
Height (cm)	167 ± 10
Body mass (kg)	74.0 ± 15.3
Body mass index (kg.m^−2)	26.5 ± 5.3
FEV1 (L)	1.7 ± 0.6
FEV1 (%)	63.4 ± 20.5
FVC (L)	2.7 ± 0.8
FVC (%)	74.2 ± 21.2
FEV1/FVC (%)	62.4 ± 4.1

FEV₁: forced expiratory volume in one second; FVC, forced vital capacity.

Table 2.   Perceptual and physiological data (mean ± standard error of measurement) obtained during the 6-minute stepper tests before and after pulmonary rehabilitation

	6MST1	6MST2	Mean	6MST3	6MST4	Mean
Mean muscular CR10	4.1 (0.3)	4.0 (0.4)	4.1 (0.7)	3.7 (0.5)	3.8 (0.5)	3.7 (0.5)*
Mean dyspnea CR10	3.9 (0.4)	3.6 (0.3)	3.8 (0.6)	3.3 (0.5)	3.3 (0.5)	3.3 (0.5)*
Mean SpO2 (%)	94.7 (0.4)	94.5 (0.4)	94.6 (0.8)	94.5 (0.9)	94.1 (1.0)	94.3 (0.9)
Fall of SpO2 (%)	3.1 (0.5)	3.3 (0.3)	3.2 (0.8)	3.7 (0.9)	3.1 (0.7)	3.4 (0.8)
Mean HR (% maximal HR)	68.5 (1.8)	71.1 (1.8)	69.8 (3.2)	65.6 (2.5)	67.9 (2.7)	66.7 (2.6)^#
HR at the exercise end (% maximal HR)	69.8 (2.0)	75.0 (3.2)	72.4 (3.4)	69.0 (3.0)	71.8 (3.7)	70.4 (3.3)

6MST₁: first 6-minute stepper test before pulmonary rehabilitation; 6MST₂: second 6-minute stepper test before pulmonary rehabilitation; 6MST₃: first 6-minute stepper test after pulmonary rehabilitation; 6MST₄: second 6-minute stepper test after pulmonary rehabilitation; CR10: (muscular or dyspnea) perceived exertion from the Borg 10-point category-ratio scale; SpO₂: arterial oxygen saturation; HR: heart rate; *significant difference between before and after pulmonary rehabilitation (P < 0.02); #significant difference between before and after pulmonary rehabilitation (P < 0.01).

Table 3.  Mean (standard error of measurement) of the performances obtained during the six-minute stepper tests before and after the pulmonary rehabilitation

Performance (units)	Mean (standard error of measurement)
Before pulmonary program
6MST1 (strokes)	473 (37.1)
6MST2 (strokes)	514 (40.4)
Mean (6MST1 + 6MST2 / 2; strokes)	494 (37.8)
Difference (6MST2 − 6MST1; strokes)	42 (15.6)
After pulmonary program
6MST3 (strokes)	508 (40.8)
6MST4 (strokes)	559 (47.1)
Mean (6MST3 + 6MST4 / 2; strokes)	533 (43.4)^#
Difference (6MST4 − 6MST3; strokes)	52 (17.9)
Before and after pulmonary program
Mean (6MST1 + 6MST3 / 2)	489 (39.1)
Mean (6MST2 + 6MST4 / 2)	535 (43.8)*
Difference (6MST3 − 6MST1)	34 (22.5)
Difference (6MST4 − 6MST2)	45 (25.9)

6MST₁: first 6-minute stepper test before pulmonary rehabilitation; 6MST₂: second 6-minute stepper test before pulmonary rehabilitation; 6MST₃: first 6-minute stepper test after pulmonary rehabilitation; 6MST₄: second 6-minute stepper test after pulmonary rehabilitation; *significant difference between the first and second tests (P < 0.05); ^#significant difference between before and after pulmonary rehabilitation (P < 0.01).

Figure 2.  Bland and Altman plots for the comparison between the performances measured from the first (6MST₁ or 6MST₃) and second (6MST₂ vs 6MST₄) 6-minute stepper tests before (left panel) and after (right panel) pulmonary rehabilitation. The dashed line is the bias and the solid lines are the 95% limits of agreement (95% LoA).