1. Department of Oncology, Addenbrooke's Hospital, Cambridge CB2 2QQ, UK
2. Departments of Urology and Epidemiology and Biostatistics, University of California at San Francisco, Mission Hall, Box 1695-550, 16th Street, 6th Floor, San Francisco, CA 9414, USA
3. Department of Medicine, Bedford Hospital, Kempston road, Bedford MK42 9DJ, UK
4. Exercise Medicine Research Institute, Edith Cowan University, 270 Joondalup Drive, Perth, WA 6027, Australia