Abstract
[Purpose] This study compared the differences between sitting with or without a backrest of shoulder, and trunk muscle activities during computer work. [Subjects] Fifteen healthy adults participated in this study. The participants had no history of injury to, or neurologic deficits of the neck muscles and upper extremities at the time of participation. [Methods] Surface electromyography (EMG) of the upper trapezius, serratus anterior, middle trapezius, external abdominal oblique, gluteus maximus muscles were recorded of 15 adults while they performed computer work. The recorded signals were averaged and normalized to the mean amplitude of the EMG signal obtained during submaximal reference voluntary contractions. [Results] The upper trapezius muscle activity significantly increased in sitting with a backrest. The muscle activities of the serratus anterior, middle trapezius muscle, external abdominal oblique, and gluteus maximus significantly decreased in sitting with a backrest. [Conclusion] The selection of a backrest is a very important factor for preventing work-related disorders.
