1 Department of Rehabilitation, University of Zimbabwe, College of Health Sciences, Harare, Zimbabwe, Department of Physiotherapy, School of Therapeutic Sciences, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
2 UCSF Pulmonary Rehabilitation and Sleep Disorders Center, University of California San Francisco, San Francisco, CA, USA.
3 Division of Pulmonary and Critical Care Medicine, University of California San Francisco, San Francisco, CA, USA <email></email>, Email: john.metcalfe@ucsf.edu.