Jon Cornwall1, James M Elliott2, David M Walton3, Peter G Osmotherly4. 1. Otago Medical School, University of Otago, P.O. Box 56, Dunedin 9016, New Zealand. 2. Department of Physical Therapy and Human Movement Sciences, Feinberg School of Medicine, Northwestern University, Chicago, Illinois; and Northern Sydney Local Health District, Faculty of Health Sciences, The University of Sydney, St. Leonards, Sydney, Australia. 3. School of Physical Therapy, Western University, London, Ontario, Canada. 4. Discipline of Physiotherapy, The University of Newcastle, New South Wales, Australia.