Strengths and limitations of this study
This was a high quality multicentred randomised controlled trial. We followed Medical Research Council guidance to develop and evaluate the intervention.The intervention was systematically designed and refined over several years, including during the feasibly trial.The intervention was about as intensive as could be credibly delivered by a public health service. The funder, the National Institute for Health and Care Research on behalf of the UK NHS, was concerned that the intervention was unfeasibly intensive and requested the inclusion of a briefer and less expensive intervention in the feasibility study. The feasibility study, however, demonstrated the need for prolonged supervision.The patient population lacked diversity, being disproportionately well educated, white men. The study enrolled people willing to agree to take part in research and perform prolonged exercise who may already have had healthy lifestyles and therefore been the least likely to benefit. Motivation to take part in trials is unlikely to be independent of motivation to exercise.The trial was disrupted by the covid-19 pandemic and the associated lockdown and social distancing. Clinical delivery teams were quick to move to remote delivery of the intervention and in so doing demonstrated great flexibility and innovation,Blinding of participants was not possible, as is usual in rehabilitation trials, although both groups had an active intervention. In the feasibility study, we tried blinding the researchers who collected outcome data, but this proved impossible to maintain. Participants’ expectations of the outcome of intervention or usual care were not measured but were explored in qualitative interviews.