Abstract
The differences in myoelectric activity of the right middle trapezius and the right middle deltoid were examined for twenty-one 18- to 35-year-old healthy females during two methods of warping yarn. All the women were right-handed and experienced at the task but did not have a preference for either a vertical or horizontal board placement. Baseline EMG data, consisting of unresisted isometric contraction of the shoulder joint at 90° of abduction with the elbow in extension, were collected from the selected muscles prior to the subjects' performance of the task. The baseline activity was used as a means of normalizing the EMG data. Two paired t tests of the normalized EMG activity demonstrated that both muscles were significantly more active when warping was performed in the horizontal position (p <. 001) than in the vertical position, making the horizontal positioning of a warping board better to use when these muscles need to be exercised.
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