title: A prospective study of computer users: II. Postural risk factors for musculoskeletal symptoms and disorders.
abstract: BACKGROUND
  Despite widespread recommendations regarding posture during computer use, associations between specific postures and musculoskeletal health are not well characterized.
  
  
  METHODS
  Six hundred and thirty-two newly hired computer users were followed prospectively to evaluate associations between posture and neck or shoulder (N/S) and hand or arm (H/A) musculoskeletal symptoms and musculoskeletal disorders. Participants' postures were measured at entry and they reported symptoms on weekly diaries. Participants reporting symptoms were examined for specific disorders. Multivariate Cox regression models were used to estimate associations between postural variables and risk of symptoms and disorders, controlling for confounding variables.
  
  
  RESULTS
  Keying with an inner elbow angle > 121 degrees, greater downward head tilt, and presence of armrests on the participants chair were associated with lower risk of N/S symptoms or N/S disorders. Keying with elbow height below the height of the "J" key and the presence of a telephone shoulder rest were associated with a greater risk of N/S symptoms or N/S disorders. Horizontal location of the "J" key > 12 cm from the edge of the desk was associated with a lower risk of H/A symptoms and H/A disorders. Use of a keyboard with the "J" key > 3.5 cm above the table surface, key activation force > 48 g, and radial wrist deviation of > 5 degrees while using a mouse was associated with a greater risk of H/A symptoms or H/A disorders. The number of hours keying/week was associated with H/A symptoms and disorders.
  
  
  CONCLUSIONS
  The results suggest that the risk of musculoskeletal symptoms and musculoskeletal disorders may be reduced by encouraging specific seated postures.
authors.affiliation: Department of Epidemiology, Rollins School of Public Health, Emory University, Atlanta, Georgia 30322, USA. mmarcus@sph.emory.edu
authors.forename: Michele
authors.initials: M
authors.lastname: Marcus
authors.forename: Fredric
authors.initials: F
authors.lastname: Gerr
authors.forename: Carolyn
authors.initials: C
authors.lastname: Monteilh
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Ortiz
authors.forename: Eileen
authors.initials: E
authors.lastname: Gentry
authors.forename: Susan
authors.initials: S
authors.lastname: Cohen
authors.forename: Alicia
authors.initials: A
authors.lastname: Edwards
authors.forename: Cindy
authors.initials: C
authors.lastname: Ensor
authors.forename: David
authors.initials: D
authors.lastname: Kleinbaum
mesh_terms: D001132:Arm; D003201:Computers; D006225:Hand; D006801:Humans; D009140:Musculoskeletal Diseases / Q000209:etiology*; D009333:Neck; D009784:Occupational Diseases / Q000209:etiology*; D011187:Posture; D011446:Prospective Studies; D012044:Regression Analysis; D012107:Research Design; D012307:Risk Factors; D012782:Shoulder