1 Program in Physical Therapy, Washington University School of Medicine in St. Louis, 4444 Forest Park Avenue, St. Louis, MO, 63108, USA.
2 Department of Mechanical and Materials Engineering, Queen's University, McLaughlin Hall, 130 Stuart Street, Kingston, Ontario, Canada.
3 Mallinckrodt Institute of Radiology, Washington University School of Medicine, 1 Barnes Jewish Hospital Plaza, St Louis, MO, 63110, USA.
4 Program in Physical Therapy, Washington University School of Medicine in St. Louis, 4444 Forest Park Avenue, St. Louis, MO, 63108, USA. r.lawrence@wustl.edu.