Strengths and limitations
PR-benefits
To the best of our knowledge, this trial is one of the first to test a long-term effect of a PA intervention and to investigate the causal relationship between PA and PR-benefits using an interventional design after 3 months of PR and 9 months of follow-up. It therefore helps to understand the importance of achieving the long-term goals of PR as described in the guidelines for PR by major respiratory Societies [Due to the nature of the intervention, patients could not be blinded for group allocation. PR-sessions were performed in group and contamination could not be prevented. This study was conducted in a 6-month outpatient PR setting. This needs to be considered for the external validity of our findings. However, the actual PA-telecoaching intervention started after 3 months of PR. The study by Spielmanns et al. is a first external validation that the concept of starting PA coaching after shorter PR may also be successful [