title: Keyboard use and musculoskeletal outcomes among computer users.
abstract: BACKGROUND
  In this review, the epidemiological evidence examining associations between upper extremity musculoskeletal symptoms and disorders and keyboard use intensity (hours of computer use-per day or per-week) and computer user posture was explored.
  
  
  METHODS
  An OVID Medline literature search was conducted to identify papers published in the peer-reviewed medical literature between 1966 and November, 2005. A total of 558 citations were found and reviewed. Those papers in which associations between musculoskeletal outcomes and (1) posture (ascertained by a study investigator) or (2) computer use, in units of hours-per-day, hours-per-week, or as a percent of work-time, were included in the review.
  
  
  RESULTS
  Thirty-nine epidemiological studies examining associations between computer use and MSD outcomes were identified. While the observational epidemiological literature was heterogeneous, some trends did emerge. It appears that the most consistent finding was the association observed between hours keying and hand/arm outcomes. Associations between some postural effects and musculoskeletal outcomes may also be inferred from the literature. In particular, placing the keyboard below the elbow, limiting head rotation, and resting the arms appears to result in reduced risk of neck/shoulder outcomes. Minimizing ulnar deviation and keyboard thickness appears to result in reduced risk of hand/arm outcomes.
  
  
  CONCLUSIONS
  Several methodological limitations, including non-representative samples, imprecise or biased measures of exposure and health outcome, incomplete control of confounding, and reversal of cause and effect, may contribute to the heterogeneity of observed results. Suggestions are made for improving the validity of future investigations.
authors.affiliation: Department of Occupational and Environmental Health, College of Public Health, University of Iowa, 100 Oakdale Campus, Iowa City, IA 52242, USA. fred-gerr@uiowa.edu
authors.forename: Fred
authors.initials: F
authors.lastname: Gerr
authors.forename: Carolyn P
authors.initials: CP
authors.lastname: Monteilh
authors.forename: Michele
authors.initials: M
authors.lastname: Marcus
mesh_terms: D016287:Computer Peripherals; D012090:Cumulative Trauma Disorders / Q000453:epidemiology* / Q000209:etiology; D006804:Ergonomics; D006801:Humans; D016239:MEDLINE; D009140:Musculoskeletal Diseases / Q000453:epidemiology* / Q000209:etiology; D009784:Occupational Diseases / Q000453:epidemiology* / Q000209:etiology; D011187:Posture; D034941:Upper Extremity / Q000503:physiopathology*