| Summary: | This study examines the effect of an overhead drilling support and position of the arm on muscular activity of the shoulder. Five male participants simulated an overhead drilling task by using a drill in near, middle and far reach positions. Electromyographic measurements were taken from the dominant side anterior deltoid, bicep and trapezius muscles. Root mean square amplitude (RMS) of the EMG activity from these muscles was used to determine the load on the muscular system. The participants used a subjective rating scale to evaluate the overhead support stand and holding position. The results demonstrate that the overhead support stand was effective in reducing the muscular load. The mean RMS value reduction with overhead support stand, when compared to the without support in bicep muscles during near, middle and far reach positions were 18%, 24 % and 47%, respectively. For anterior deltoid muscles the percentage decrease in mean RMS values for near, middle and far reach positions were 24%, 33% and 49%, respectively; and for trapezius muscles the percentage decrease in mean RMS values during near, middle and far reach positions were 32%, 33% and 42%, respectively. The middle reach position, in contrast to near and far reach positions resulted in the lowest RMS values. The mean RMS values without support stand for biceps muscles was the lowest in middle position (0.139mv). Similarly the mean RMS values of anterior deltoid (0.231mv) and trapezius (0.066mv) muscles without overhead support stand were least for the middle position. The mean RMS values for the bicep (0.105 mv), anterior deltoid (0.155mv) and trapezius (0.041mv) muscles with overhead support stand were the lowest during the middle position. The subjective rating results also supported the above conclusions. These findings indicate that workers performing overhead drilling tasks in coronal plane should work in middle position in order to reduce the muscular load.
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