1. a Labor Education and Research Center, 1289 University of Oregon , Eugene , OR , USA
2. b School of Physical Therapy & Rehabilitation Science, University of Montana , 32 Campus Drive, Missoula , MT , USA
3. c College of Public Health and Human Sciences, Oregon State University , 401 Waldo Hall, Corvallis , OR , USA
4. d Department of Physical Therapy , Eastern Washington University , 310 N. Riverpoint Blvd., Box T, Spokane , WA , USA