[1] McMaster Univ, Sch Rehabil Sci, Hamilton, ON L8S 1C7, Canada
[2] Canadian Mem Chiropract Coll, Toronto, ON, Canada
[3] McMaster Univ, Dept Clin Epidemiol & Biostat, Hamilton, ON L8S 1C7, Canada
[4] NW Hlth Sci Univ, Wolfe Harris Ctr Clin Studies, Bloomington, IN USA
[5] Univ Amsterdam, Acad Med Ctr, Coronel Inst Occupat Hlth, NL-1105 AZ Amsterdam, Netherlands