title: Influence of laptop computer design and working position on physical exposure variables.
abstract: OBJECTIVE
  To evaluate the impact of two laptop designs (with or without palm rest) and two work situations (on desk or lap) on neck and upper limb posture, muscle activity and productivity.
  
  
  METHODS
  Eight healthy subjects performed a standardized typing task of 15 min duration. During the last 5 min of each test, the neck, upper arm and trunk postures were captured by a three-dimensional video system, wrist motion was measured by a biaxial electrogoniometer and muscle activity of four neck and upper limb muscles was recorded.
  
  
  RESULTS
  Only minor differences in postures, wrist positions and productivity were observed when comparing the two laptop designs in the same situation. Larger differences were found when comparing the two situations (desk or lap). In the desk situation, the subjects bent their heads forward less, had less backward trunk inclination and wrist extension, but more elevation of the upper arm. Higher electromyographic (EMG) levels in the trapezius and deltoid muscles and lower EMG levels in the wrist extensors were also found in the desk situation.
  
  
  CONCLUSIONS
  Our findings do not favor one particular laptop design because only small differences in physical exposure were found. However, the workstation set up influenced the physical exposure variables, and was pinpointed as the main determinant to be considered when doing laptop work even-though no ideal situation was found. Greater physical (muscular and articular) constraints seem to be imposed to the shoulder region in the desk situation whereas the head-neck and wrist segments appear to be more stressed in the lap situation.
  
  
  CONCLUSIONS
  Laptop computers are often used although the physical exposure in laptop work and the impact of different laptop designs have not been systematically assessed. A better understanding of these factors may help formulate some recommendations for laptop users.
authors.affiliation: Department of Rehabilitation, Faculty of Medicine, Laval University and Center for Interdisciplinary Research in Rehabilitation and Social Integration, 525, Blvd Hamel, B-77, Que., Canada G1M 2S8. helene.moffet@rea.ulaval.ca
authors.forename: H
authors.initials: H
authors.lastname: Moffet
authors.forename: M
authors.initials: M
authors.lastname: Hagberg
authors.forename: E
authors.initials: E
authors.lastname: Hansson-Risberg
authors.forename: L
authors.initials: L
authors.lastname: Karlqvist
mesh_terms: D000328:Adult; D001132:Arm / Q000502:physiology; D001696:Biomechanical Phenomena; D003201:Computers; D004867:Equipment Design; D006804:Ergonomics; D005260:Female; D006801:Humans; D007374:Interior Design and Furnishings; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D009333:Neck / Q000502:physiology; D009784:Occupational Diseases / Q000517:prevention & control*; D011187:Posture / Q000502:physiology*; D011446:Prospective Studies; D016059:Range of Motion, Articular; D018570:Risk Assessment; D012494:Sampling Studies; D012680:Sensitivity and Specificity; D013314:Stress, Mechanical; D014955:Wrist Joint / Q000502:physiology