Saving Time for Patients with Moderate to Severe COPD: Endurance Test Speed Set Using Usual and Fast Walk Speeds

Background: For assessing the effects of interventions on exercise tolerance, the tolerable duration (t_limit) of a high-intensity constant-speed endurance test is recommended. The test intensity is determined by the test speed (s_test) which should be individualized to target a t_limit of 3 to 15 minutes. We determined the accuracy of setting the s_test to achieve a targeted t_limit of 3 to 15 minutes using the participant's easily measured and non-fatiguing usual (s_usual) and fast (s_fast) walk speeds. Methods: Participants with COPD were asked to walk at their usual and fast walk speeds to establish their s_usual and s_fast. This required that they walk for less than 1 minute. The individualized s_test was calculated from a previously developed equation (0.57 x [s_fast - s_usual]) + s_usual. Participants then completed a constant-speed endurance test, walking at this calculated s_test to intolerance, to determine if the resultant t_limit occurred within 3 to 15 minutes. Results: Twenty-nine participants (forced expiratory volume in 1 second [FEV₁] standard deviation [SD ]=43 [25] %predicted; FEV₁ to forced vital capacity [FVC]ratio= 41 [13]%; s_usual = 57.3 [10.4] meters per minute (m·min^-1 ); s_fast = 71.7 [10.7] m·min^-1) completed the study. During testing, 24 (83%) participants used supplemental oxygen and 16 (55%) used a walking aid. The derived s_test was 65.6 [10.3] m·min^-1 with the observed t_limit of 6.0 [5.0] minute. Twenty-four of 29 (83 %) endurance tests were within 3 to 15 minutes. Conclusion: Using the usual and fast walk speeds provides a simple, quick, inexpensive method for clinicians to set an acceptable endurance walk speed.