Eight-week high-intensity inspiratory muscle training improves cardiac autonomic function in COPD: a randomized controlled trial
A randomized trial in 39 stable COPD patients found that eight weeks of 30 inspiratory breaths twice daily at the highest tolerable intensity shifted heart-rate variability toward greater parasympathetic activity and improved six-minute walk distance and health scores versus control. The trial was small, lacked sham training, and did not measure long-term cardiac events or exacerbations.