Abstract
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 [FEV(1)] standard deviation [SD ]=43 [25] %predicted; FEV(1) 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.