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Predictors of low endurance time in constant work rate cycle testing in COPD

The COPD Biomarker Qualification Consortium (CBQC) is a collaboration of industry and academia, managed by the COPD Foundation. CBQC seeks to qualify biomarkers and clinical outcome assessments through defined regulatory processes. Constant work rate (CWR) cycle ergometry is a sensitive method to discern responses to interventions. A patient-level database was developed from 23 published studies involving 5,853 COPD patients. CWR exercise was performed at an individualized work rate following an incremental exercise test (IET). Expert opinion holds that baseline tests of 3-8 min duration are desirable. A widely utilized strategy is to select baseline CWR at 75-80% of peak work rate (PWR) in the preceding IET. We sought to determine whether refinement of this procedure may increase likelihood of achieving desired exercise duration. Of 4,963 tests performed at 74-81% PWR, 19.6% had duration 8 min. By plotting the mean value (±SD) of several baseline variables as a function of baseline CWR duration, we determined that duration 8 min emerged. Adjustment to reduce baseline work rate in subjects with these characteristics may increase likelihood of eliciting exercise durations within the desired 3-8 min range.