Does elevating and tilting the input device support surface affect typing force and postural exposures of the wrist?
Asundi-K; Johnson-PW; Dennerlein-JT
Work 2011 Jun; 39(2):187-193
OBJECTIVE: Compare wrist kinematics and typing force during computer work across two workstations, one configured according to recommended guidelines with the keyboard support surface flat and near resting elbow height, the other according to users' actual setup and preference, with an elevated, and positively tilted support surface. PARTICIPANTS: Twenty participants completed a standard computer task at the two workstation configurations. METHODS: A thin profile force plate, placed under the keyboard recorded keyboard reaction forces. Twin axis electro-goniometers (SG65 Biometrics Ltd, London, UK) affixed to the back of the right and left hand of each subject continuously measured wrist extension/flexion and ulnar/radial deviation. RESULTS: Typing force and wrist kinematics were similar between the two configurations with only 10th percentile ulnar deviation for the right hand showing a borderline significant difference of 1 degree between the two configurations. CONCLUSION: Elevating and tilting the input device support surface does not necessarily affect typing force and kinematics of the wrist. The combination of the input device support surface and user upper extremities form a complex kinematic system with several degrees of freedom. Wrist postures during computer use are a function of multiple factors other than simply keyboard tilt.
Humans; Men; Women; Age-groups; Biomechanics; Musculoskeletal-system; Physiology; Posture; Risk-factors; Task-performance; Musculoskeletal-system-disorders;
Author Keywords: Computer workstation; physical risk factors; musculoskeletal disorders
Jack T. Dennerlein, Ph.D., Department of Environmental Health, Harvard School of Public Health, 665 Huntington Avenue, Boston, MA 02115
Grant-Number-R01-OH-003997; Grant-Number-R01-OH-008373; B01182012
Harvard University, Boston, Massachusetts