1. Comparative Neuromuscular Diseases Laboratory, Department of Clinical Science and Services, Royal Veterinary College, London NW1 0TU, UK
2. Structure and Motion Laboratory, Department of Comparative Biological Sciences, Royal Veterinary College, Hawkshead Lane, Hatfield AL9 7TA, UK
3. Neuromechanics Laboratory, Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697, USA