Background: Patients with severe chronic obstructive pulmonary disease (COPD) benefit from supervised exercise training. Current guidelines suggest that continuous, high-intensity exercise (equal to or greater than 70 percent of maximal exercise capacity) improves prognosis and quality of life of patients with severe COPD. However, many of these patients are unable to tolerate this level of continuous exercise. Interval exercise may be an alternative. Puhan and colleagues compared the short-term effectiveness of continuous exercise with interval exercise in patients with severe COPD.

The Study: This randomized trial was conducted at a public rehabilitation hospital in Switzerland. Ninety-eight patients, with an average age of 69 years, who had severe COPD were enrolled. Patients with a diagnosis of cancer in the preceding two years (excluding skin cancer) or who had medical conditions impairing their ability to exercise were excluded. All patients completed a three-week inpatient rehabilitation program that included 12 to 15 exercise sessions, breathing therapy, guided walking tours, relaxation therapy, and patient education.

Patients were randomized into continuous and interval exercise groups. The continuous group was assigned to work at 70 percent of normal maximal exercise capacity for the entire session. Meanwhile, the interval group alternated 20 seconds at 50 percent of short-term maximal exercise capacity with 40 seconds at 10 percent of short-term maximal exercise capacity.

Patients also were instructed to perform aerobic exercise at home for at least 20 minutes per day. Follow-up visits occurred at three, five, and 12 weeks; however, this article focused on five-week outcomes.

The primary outcome measure was health-related quality-of-life scores on the Chronic Respiratory Questionnaire. Secondary outcomes included improvements in exercise capacity, depression and anxiety scores, and numeric health state rating. Exercise tolerance was measured as the number of unintended breaks needed. Data were analyzed using predetermined statistical criteria for noninferiority of interval exercise.

Results: After five weeks, patients in the continuous and interval exercise groups had statistically similar improvements in questionnaire scores and exercise capacity. With regard to adherence, 47.9 percent of the interval group and 24.0 percent of the continuous group followed the exercise protocols. Additionally, patients in the continuous group took more unintended breaks than those in the interval group.

Conclusion: Interval exercise is as effective as continuous, high-intensity exercise for improving short-term quality of life and exercise capacity in patients with severe COPD; however, interval exercise was better tolerated. The authors suggest that family physicians offer both options to eligible patients and prescribe an exercise program based on patient preference.