Design
This was a mono-center, 1:1 prospective RCT (details of randomization outlined in additional file 1). At three months of the 6 months PR-program, eligible patients were included in the study after signing a written informed consent. The trial was registered at clinicaltrials.gov (NCT02702791) and was approved by the local ethics committee (S57963). It consisted of four visits: (1) a visit at randomization, upon completion of 3 months of PR (i.e. start of the study – V0), (2) a visit at the end of PR (i.e. upon completion of 6 months of PR and 3 months after randomization – V1), (3) a visit 3 months after discharge from PR and 6 months after randomization (V2) and (4) a visit 6 months after discharge from PR and 9 months after randomization (V3) (Fig. 
Study design. Four study visits: a visit at randomization (i.e. after 3 months of PR; V0), a visit at the end of PR (i.e. after 6 months of PR; V1), a visit after 3 months of follow-up from PR (V2) and a visit after 6 months of follow-up from PR (V3). Data at the start of PR (i.e. 3 months before randomization) were also used for analysis (V-1). Patients were followed up for 9 months after initiation of the PA telecoaching program. PR, pulmonary rehabilitation; V, visit; UCG, usual care group; IG, intervention groupThe first randomization visit for the first patient took place on October 2015. Last patient last visit took place on September 2019.