Repetitive Stress Injury Hand Pain
from Stop Muscle Pain

This study established normative values of the kinematics of the fingers and hands during computer keyboard use by studying the angles, angular velocities, and angular accelerations of the metacarpophalangeal joints and proximal interphalangeal joints for the right and left hands of 20 computer keyboard users during a word-processing task.

A new kinematic variable for computer keyboard use, hand/wrist displacement, was also defined and examined. Hand/wrist displacement refers to the translational movements of the hands in which the entire hand is repositioned to strike the keys. Kinematics of both hands of the keyboard users were captured using a three-dimensional motion capture system. 

Metacarpophalangeal joint kinematics in flexion/extension and abduction/adduction during typing and proximal interphalangeal joint kinematics in flexion/extension were reported. The means and standard deviations for finger postures, velocities and acceleration were generally not significantly different between the right and left hands, with the exception of the 1st digit (thumb). Hand/wrist displacement was significantly different between the right and left hands for side to side movements. These differences in kinematics among the fingers are potential risk factors for musculoskeletal disorders.  (Baker NA, Cham R, Cidboy EH, Cook J, Redfern MS: Kinematics of the fingers and hands during computer keyboard use. Clinical Biomechanics. 22(1):34-43, 2007 Jan). 

This following study assessed the wrist kinetics (range of motion, mean position, velocity and mean power frequency in radial/ulnar deviation, flexion/extension, and pronation/supination) associated with performing a mouse-operated computerized task involving painting rectangles on a computer screen. The effects of the painting task on subjective perception of fatigue and wrist position sense was also evaluated. 

The results showed that the painting task required constrained wrist movements, and repetitive movements of about the same magnitude as those performed in mouse-operated design tasks. In addition, the painting task induced a perception of muscle fatigue in the upper extremity (Borg CR-scale: 3.5, p<0.001) and caused a reduction in the position sense accuracy of the wrist (error before: 4.6 degrees , error after: 5.6 degrees , p<0.05).  

This standardized painting task appears suitable for studying relevant risk factors, and therefore it offers a potential for investigating the pathophysiological mechanisms behind musculoskeletal disorders related to computer mouse use.  (Flodgren G, Heiden M, Lyskov E, Crenshaw AG: Characterization of a laboratory model of computer mouse use - applications for studying risk factors for musculoskeletal disorders. Applied Ergonomics. 38(2):213-8, 2007) - www.stopmusclepain.com

 

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