Comparison of the electrical activity in upper trapezius and wrist extensor muscles during two typewriting conditions

Abstract

Introduction: The proper use of the position of the arm and wrist while typing may reduce muscle overload and prevent musculoskeletal disorders. Objective: To evaluate the electromyographic activity of upper trapezius and wrist extensor muscles during two typewriting conditions. Materials and methods: Six healthy females ( age = 42 years, SD = 10), ( height = 1.65m, SD = 0.05) and ( weight = 71kg, SD = 16) participated in this study. The task was performed with a newly developed arm support and without the support. A perceived exertion scale was used with all subjects. An ANOVA with repeated measures was used to verify differences in perceived exertion and root mean square (RMS). Results: There were no statistically significant differences for the RMS between the typewriting tasks. The condition without arm support presented a significantly greater mean velocity and amount of words typed (P = 0.02; P = 0.03) and there was a significant difference in perceived exertion during the condition without arm support (P = 0.03). Electromyographic activity did not present differences. Conclusion: The muscle electrical activity was not altered regardless the arm support and occurred the improvement of the perceived exertion after 10 minutes of typing without support. Long-term studies are needed.