Purpose
Pulmonary rehabilitation (PR) programs are important in the treatment of patients with chronic obstructive pulmonary disease (COPD) but vary widely in type, duration, and efficacy. This meta-analysis investigated the effect of PR programs on respiratory muscle strength in patients with COPD.

Methods
PubMed, Embase, and CINAHL were searched. The primary outcome variables were maximal expiratory pressure (MEP) and maximal inspiratory pressure (MIP). The secondary outcome variables were the modified Borg score after the 6-min walking test, percent predicted forced expiratory volume in 1 second (FEV1%pred), and percent FEV1/forced volume capacity (FVC). Comprehensive Meta-Analysis, version 3.0, was used to analyze the data. The effect size was calculated using the standardized mean difference (SMD) and 95% confidence interval (CI).

Results
Twenty randomized controlled trials (with 992 participants) were included in the analysis. The PR programs had a significant effect on the MEP (SMD, 0.87; 95% CI, 0.42–1.32; p < .001), MIP (SMD, 0.53; 95% CI, 0.13–0.93; p = .009), and modified Borg score (SMD, −0.37; 95% CI, −0.52 to −0.22; p < .001) in patients with COPD. There was no effect on FEV1%pred (SMD, 0.09; 95% CI, −0.12 to 0.30; p = .406) or FEV1/FVC% (SMD, 0.04; 95% CI, −0.17 to 0.26; p = .702).

Conclusion
PR programs improve respiratory muscle strength in patients with COPD. Strategies for selecting a suitable PR program need to be developed, and future studies should evaluate the long-term effects of such programs on pulmonary function.