1. Centre for Health, Activity and Rehabilitation Research, School of Physiotherapy, University of Otago, P.O. Box 56, 325 Great King Street, Dunedin 9054, New Zealand
2. Centre for Health and Rehabilitation Technologies, Institute of Nursing and Health Research, School of Health Sciences, University of Ulster, Shore Road, Newtownabbey, County Antrim BT37 0QB, UK