Repeatability of usual and fast walking speeds in patients with chronic obstructive pulmonary disease.

Rationale: Evaluation of the role of walking speeds in chronic obstructive pulmonary disease (COPD) should be preceded by an assessment of its repeatability. This study aimed to establish the repeatability of the usual (susual) and fast (sfast) walking speeds among patients with stable COPD and determine the accuracy of manual measurement.
Methods: Participants demonstrated their susual and sfast over 10 m with speed calculated using a stopwatch; the accuracy was confirmed with optical sensors. The walks were repeated after a 5-minute rest; the session was repeated on 2 subsequent days. The coefficient of repeatability (CR) was calculated for both speeds, and their stability over days was determined.
Results: A total of 29 participants (forced expiratory volume in 1 second (FEV1) = 43 ± 25% predicted; FEV1/forced vital capacity (FVC) = 41 ± 13%; susual = 60.3 ± 11 m·min; sfast = 74.3 ± 11.5 m·min) completed the study. The CRs for the susual and sfast were 7.5 (95% CI: 5.0-10.0) and 7.1 (95% CI: 4.8-9.4) m·min, respectively. There was a small increase in the susual (5%; P < .001) on the second trial of every day and between successive days (5%; P < .001); the sfast was not different between trials (P = .09) and increased only between day 1 and day 2 (4%; P < .0001). There was no difference between the stopwatch and the sensor determined susual (-0.5 [95% CI: -1.1 to 0.1] m·min; P = .12). The small difference (-2.1 [95% CI: -2.7 to -1.5] m·min; P = .0001) between the methods for sfast was within the CR of the sfast.
Conclusions: In patients with moderate to severe COPD, repeated measures of the susual and sfast using a stopwatch support the use of these tests for simple, quick assessments of disability.