The aim of this systematic review was to assess functional improvement, measured by the 6-minute walk test (6MWT) after the application of a resistance training (RT) protocol in people with chronic obstructive pulmonary disease (COPD).

The search involved the databases ClinicalTrials.gov, Cochrane Central Register of Controlled Trials, EMBASE, PubMed and Scopus from the beginning of inception to September 1, 2019. Randomized controlled trials evaluating the functional impact of RT were included. The quality of the trials was assessed with the Physiotherapy Evidence Database (PEDro) scale. Calculations were performed according to mean difference (MD) for differences between pre- and post-intervention in 6MWT distance and according to the standardized mean difference (SMD) for post-treatment results of the 6MWT and quadriceps muscle strength (QMS) improvement.

In total, 23 studies (690 patients) met the inclusion criteria. Meta-analysis was used to compute the best improvement on the 6MWT with an analysis of improvement pre- versus post-treatment (MD 37.3, 95% confidence interval [CI] 9.8; 64.8, I² = 86%, p = 0.008) versus post-treatment alone, intervention versus control group (MD 15.5, 95% CI -7.7; 38.6, I^2 = 71%, p = 0.19). QMS was significantly improved (SMD 2.9, 95% CI 1.1; 4.7, I^2 = 91%, p = 0.002).

The results of the meta-analysis show a significant improvement in walking ability and performance measured by the 6MWT and an improvement in QMS for people with COPD responding to the therapy. The main limitation of this review is the significant heterogeneity across the study results. Furthermore, the statistical significance does not totally coincide with the clinical significance. RT is recommended to reduce muscle dysfunction and seems useful when combined with endurance training.