Department of Cardiopulmonary Rehabilitation, Centre for Exercise & Health, University Hospitals Coventry & Warwickshire NHS Trust, Coventry, UK. gordon.mcgregor@uhcw.nhs.uk.Warwick Clinical Trials Unit, Warwick Medical School, University of Warwick, Coventry, UK. gordon.mcgregor@uhcw.nhs.uk.Centre for Sport, Exercise & Life Sciences, Coventry University, Coventry, UK. gordon.mcgregor@uhcw.nhs.uk.Warwick Clinical Trials Unit, Warwick Medical School, University of Warwick, Coventry, UK.Warwick Clinical Trials Unit, Warwick Medical School, University of Warwick, Coventry, UK.Coventry & Warwickshire Partnership Trust, Coventry, UK.Centre for Care Excellence, University Hospitals Coventry & Warwickshire NHS Trust, Coventry, UK.Warwick Clinical Trials Unit, Warwick Medical School, University of Warwick, Coventry, UK.Department of Anaesthesia and Critical Care, University Hospitals Birmingham NHS Foundation Trust, Birmingham, UK.ICUSteps, Kemp House, London, UK.Department of Respiratory Medicine, University Hospitals Coventry & Warwickshire NHS Trust, Coventry, UK.Warwick Clinical Trials Unit, Warwick Medical School, University of Warwick, Coventry, UK.Warwick Clinical Trials Unit, Warwick Medical School, University of Warwick, Coventry, UK.Patient & Public Involvement Representative, Coventry, UK.Department of Cardiopulmonary Rehabilitation, Centre for Exercise & Health, University Hospitals Coventry & Warwickshire NHS Trust, Coventry, UK.Warwick Clinical Trials Unit, Warwick Medical School, University of Warwick, Coventry, UK.Department of Cardiopulmonary Rehabilitation, Centre for Exercise & Health, University Hospitals Coventry & Warwickshire NHS Trust, Coventry, UK.Warwick Clinical Trials Unit, Warwick Medical School, University of Warwick, Coventry, UK.Warwick Clinical Trials Unit, Warwick Medical School, University of Warwick, Coventry, UK.Warwick Clinical Trials Unit, Warwick Medical School, University of Warwick, Coventry, UK.Warwick Clinical Trials Unit, Warwick Medical School, University of Warwick, Coventry, UK.Warwick Clinical Trials Unit, Warwick Medical School, University of Warwick, Coventry, UK.Centre for Health Economics at Warwick, Warwick Medical School, University of Warwick, Coventry, UK.Warwick Clinical Trials Unit, Warwick Medical School, University of Warwick, Coventry, UK.Warwick Research in Nursing, Warwick Medical School, University of Warwick, Coventry, UK.Warwick Clinical Trials Unit, Warwick Medical School, University of Warwick, Coventry, UK.