Using risk factors, myoelectric signal, and finger tremor to distinguish computer users with and without musculoskeletal symptoms.

Most of previous studies use questionnaire to assess risk factors for cumulative trauma disorders of the upper extremity (CTDUE) for computer workers. Few studies combine both physical examination and questionnaire to assess musculoskeletal symptoms. Fifteen symptomatic and 15 non-symptomatic computer users were recruited. Both of them were asked to perform a repetitive tapping task (200 taps/min) as the fatigue task. Tremor of the index finger and surface electromyography (EMG) of the flexor digitorum superficial (FDS) were collected prior and after the tapping task. Muscle strength and range of motion for right wrist were collected before the tapping task. All subjects were asked to fill out the questionnaire about risk factors of CTDUE. Female users in the symptomatic group had weaker wrist extensor strength than those in the non-symptomatic group (P < 0.05). After performing the tapping task, FDS strength and median frequency of the FDS EMG at 25%, and 100% maximal voluntary contraction (MVC) for the symptomatic group decreased (P < 0.05). However, no significant differences were found in strength and median frequency of the FDS EMG between prior and after tapping task in the non-symptomatic group. There was no significant difference for root mean square of the finger tremor between and within groups. Regression analysis revealed that median frequency of the FDS EMG at 25% MVC, age, total time spent on computer, and mouse position were better factors to classify computer users into the symptomatic group compared to other factors obtained from questionnaire and physical exam. Besides, symptomatic computer users seem to have longer experience of computer use than non-symptomatic users. After the fatigue task, the symptomatic users decreased their muscle strength to a larger extent than the non-symptomatic users.