Puhan MA, Busching G, Schunemann HJ, VanOort E, Zaugg C, Frey M
Ann Intern Med. 2006;145:816-825.
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.
Comment.
The use of high-intensity exercise protocols in the initiation of pulmonary rehabilitation is well established. However, the more severely impaired patient often has difficulty with sustained exercise at the requisite workload levels (>70% of maximal exercise capacity), and this may directly affect not only the short-term outcome of exercise training but also the longer-term adherence to recommendations made during participation in pulmonary rehabilitation. This study is a well-designed randomized trial seeking to show that interval exercise (brief high-intensity bursts alternating with low-intensity exercise) is not inferior to high-intensity continuous exercise. Forty-nine and 51 patients were randomized to interval and continuous exercise groups, respectively; all had severe chronic obstructive pulmonary disease (mean FEV1, approximately 35% predicted, GOLD stage 3 and 4). At the end of 5 weeks (12 to 15 sessions), the interval group did not show less benefit in both health-related quality-of-life measures and 6-minute walk distance. Not only did the interval exercise group do at least as well using standard outcome measures, adherence to the assigned protocol was also significantly higher in this group, suggesting a higher level of patient preference. Whether the benefits would carry over into maintenance exercise training is unestablished, but the 2 protocols, interval and continuous exercise, seem to be equivalent in the initiation of pulmonary rehabilitation and can be offered as such, especially to patients with severe chronic obstructive pulmonary disease who may find the interval protocol more acceptable.
SK