Vibrotactile sense and mechanical functional state of the arm and hand among computer users compared with a control group

Objectives: To measure sensory perception and mechanical muscle function of the arm among experienced female computer users with (+-sPC) and without (-sPC) symptoms compared with a control group (ctrl). Methods: Group + sPC had severe symptoms in the hand wrist and or the forearm elbow region. They worked with the computer 75% and used a computer mouse 50% of the working day. Group -sPC had no or minimal symptoms. They used the computer 80% and a computer mouse 58% of the working day. The control group had no symptoms and worked with the computer for 2 h or fewer per day. Sensory perception threshold was measured using vibrotactilometry at five sites on the right hand representing nn. medianus, ulnaris and radialis. Mechanical muscle function was assessed by measuring muscle strength, wrist extension endurance. hand-eye co-ordination, and range of motion. Furthermore, performance was measured during standardized computer work. Results: The perception thresholds for + sPC were greater in the areas innervated by n. medianus and n. ulnaris than for non-symptomatic groups, indicating that nerve compression is involved. For n. radialis. no differences were found between groups. No difference in isometric muscle strength was found for hand-grip, wrist extension, vertical pinch-grip and knee extension. However, for horizontal pinch-grip (pronated forearm.) lower values were obtained for the + sPC group than for non-symptomatic groups. At the end of the endurance task, the perceived exertion was highest for +sPC. Furthermore, slower recovery was found for + sPC. No differences in range of motion, hand-eye coordination, and error rate during computer work were found between groups, Conclusions: Increased perception threshold values indicating entrapment of n. medianus and n. ulnaris were found for + sPC. Only few differences in mechanical muscle performance were found among the groups. The + sPC group had lower pinch-grip strength when measured in the pronated hand position, and the results indicated shorter muscle endurance for + sPC than for -sPC and ctrl.