Interval versus continuous high-intensity exercise in chronic obstructive pulmonary disease: A randomized trial

Background: Guidelines recommend high-intensity continuous exercise to reduce peripheral muscle dysfunction in patients with chronic obstructive pulmonary disease but acknowledge that interval exercise might be an equally effective alternative that is better tolerated by patients. Objective: To assess whether interval exercise is no less effective than high-intensity continuous exercise and whether it is tolerated better by patients with severe chronic obstructive pulmonary disease. Design: Randomized, noninferiority trial. Setting: Publicly funded rehabilitation hospital in Switzerland. Patients: 98 patients with severe chronic obstructive pulmonary disease, with or without recent exacerbations. Intervention: 12 to 15 supervised interval or high-intensity continuous exercise sessions (over 3 weeks) followed by exercise at home. Measurements: Health-related quality of life determined by using the Chronic Respiratory Questionnaire (CRQ) (scores from 1 [most severe impairment] to 7 [no impairment]) after 5 weeks and number of unintended breaks during supervised exercise. Results: Both groups experienced large improvements in health-related quality of life (increase of CRQ total scores of 1.00 [SD, 0.98] for the interval exercise group and 1.02 [SD, 1.05] for the continuous exercise group). Adjusted between-group differences between the interval exercise group and the continuous exercise group (-0.05 [95% CI, -0.42 to -0.32] for CRQ and 1.1 meters [CI, -25.4 to 27.6 meters] for 6-minute walking distance) were within the a priori defined boundaries of noninferiority (0.5 for CRQ and 45 meters for 6-minute walking distance). Twenty-one (47.9%) patients using interval exercise and 11 (24.0%) patients using continuous exercise were able to adhere to the protocol (difference, 23.9 percentage points [CI, 5.0 to 42.8 percentage points]; P = 0.014). The median number of unintended breaks lasting 1 minute or more was 2 (interquartile range, 0 to 16) for patients in the interval exercise group and 11 (interquartile range, 2 to 26) for patients in the continuous exercise group (P = 0.023). Limitations: The study focused on initiation of exercise and not on outpatient or home-based maintenance of exercise. Conclusions: Clinicians and patients can choose either of the 2 exercise plans to initiate physical exercise.