1. Carver College of Medicine; The University of Iowa; Iowa City Iowa
2. Department of Kinesiology; Iowa State University; Ames Iowa
3. Department of Orthopaedics and Rehabilitation; The University of Vermont; Burlington Vermont
4. Department of Epidemiology, The University of Iowa, Iowa City, IA
5. Department of Rehabilitation Medicine; University of Kansas Medical Center; 3901 Rainbow Blvd, Mailstop 1046 Kansas City, KS 66160