1. a Agricultural Ergonomics Research Center, Department of Biological and Agricultural Engineering , University of California , Davis, CA, USA
2. b Department of Biomedical Engineering , Jungwong University , Goesan-Gun, South Korea
3. c Department of Community Health and Epidemiology , Queen's University , Kingston, Ontario, Canada
4. d Marshfield Clinic Research Foundation , National Farm Medicine Center , Marshfield, WI, USA