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

João Carlos Comel, João Pedro Batista Junior, Eliana Paula Chini, Hugo Maxwell Pereira, Rodrigo Luiz Carregaro, Jefferson Rosa Cardoso


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.

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