Walking is frequently used in the exercise rehabilitation of patients with COPD. Walking ability can be characterized by the two-parameter hyperbolic relationship between endurance and speed. One parameter, critical walk speed (s_critical), represents the maximum speed that can be endured indefinitely. The purpose of this study was to: (1) determine the effect of pulmonary rehabilitation on the critical speed and (2) compare the critical speed with the speed chosen during self-paced walking.
We estimated critical speed in patients with COPD before and after rehabilitation. Patients completed four high-intensity constant-speed walk tests to intolerance on a 30-m course. The parameters of the hyperbolic relationship were determined using nonlinear regression of endurance on speed. Participants also completed self-paced walks: (1) for as long as they could, (2) at their “usual” and “fast” speeds, and (3) as a 6-min walk test.
Twelve participants (FEV1 [SD], 41  % predicted; FEV1/FVC, 41 ) completed the study. At baseline, the critical speed (65  m/min) was not significantly different from the self-paced, usual, or 6-min walk speeds (65 , 67 , and 63  m/min, respectively). There was a significant increase in critical speed (6 [1-10] m/min) and 6-min speed (16 [10-21] m/min) after rehabilitation, without changes in the self-paced, usual, or fast speeds.
Patients with COPD increase their critical walk speed after pulmonary rehabilitation. The pace chosen during common walk tasks is closely related to critical speed; this relationship is altered after rehabilitation.
ClinicalTrials.gov; No.: NCT00781183; URL: www.clinicaltrials.gov