1University of California Davis Medical Center, Orthopaedics Research Laboratories, Research Building I, 4625 Second Avenue, Sacramento, CA 95817, USA
2Indiana University School of Medicine, Department of Anatomy, MS 259, 635 Barnhill Drive, Indianapolis, IN 46202, USA
3The Pennsylvania State University, Center for Locomotion Studies, 29 Recreation Building, University Partk, PA 16802-5702, USA