Intensity of physical exercise and its effect on functional capacity in COPD: systematic review and meta-analysis

OBJECTIVE: To evaluate the effects of high-intensity interval training (HIIT), in comparison with those of continuous exercise, on functional capacity and cardiovascular variables in patients with COPD, through a systematic review and meta-analysis of randomized controlled trials. METHODS: We searched PubMed, the Physiotherapy Evidence Database, the Cochrane Central Register of Controlled Trials, and EMBASE, as well as performing hand searches, for articles published up through January of 2017. We included studies comparing exercise regimens of different intensities, in terms of their effects on functional capacity and cardiovascular variables in patients with COPD. RESULTS: Of the 78 articles identified, 6 were included in the systematic review and meta-analysis. Maximal oxygen consumption (VO(2max)) did not differ significantly between HIIT and control interventions. That was true for relative VO(2max) (0.03 mL/kg/min; 95% CI: −3.05 to 3.10) and absolute VO(2max) (0.03 L/min, 95% CI: −0.02 to 0.08). CONCLUSIONS: The effects of HIIT appear to be comparable to those of continuous exercise in relation to functional and cardiovascular responses. However, our findings should be interpreted with caution because the studies evaluated present a high risk of bias, which could have a direct influence on the results.