Muscular performance during seated work elevated by two different EMG methods.

As part of a larger ergonomic survey of seated work, the myoelectric activity of soleus and erector spinae was studied during typing and desk work while sitting on three different office chairs. Muscular performance was evaluated by two EMG methods: (1) the frequently used analysis of the amplitude probability distribution function (APDF) of the EMG signals, and (2) a recently presented method which considers muscular contraction frequencies according to the load levels. The latter indicated significant differences in contraction frequencies which did not appear from the APDF. Moreover, the APDF illustrated differences in load levels which were not evident from the frequency analyses. It is suggested that both EMG methods should be used in evaluations of muscular activity.