EFFECT ON SHOULDER IN OVERHEAD DRILLING WITH SHOULDER SUPPORT

Abstract

This study examines the effect of an overhead drilling on muscular activity of the shoulder. Five men of average health simulated the overhead drilling process by using a portable hand drill in three reach positions in two planes namely coronal and saggital. Electromyographic observations are taken from the Biceps, triceps, and anterior deltoid, mid deltoid and trapezius muscles. Root mean square amplitude (RMS) of the EMG activity is used to determine the load on the muscular system of the shoulder. The various aspects of the surface electromyography like skin preparation, electrode placement have been carefully studied. Observations at low, mid and high reach positions are analysed and recommended that low reach position is preferable in either coronal or saggital planes. Therefore,. the work place should be designed such that the height of the work is minimum. An support stand has been fabricated and the same number experiments have been repeated. It shows that the use of support minimize the stress on muscles. The mean RMS value reduction with overhead support stand, when compared to the without support in bicep muscles during low, middle and high reach positions are 30.86%, 37.5 % and 48%, respectively in coronal plane. Similarly; mean RMS value reduction with overhead support stand, in saggital plane were 26.94%, 32 % and 46.79%, respectively compared to the without support low, middle and high reach positions. For anterior deltoid muscles the percentage decrease in mean RMS values for low, middle and high reach positions are 28.79%, 39.39% and 51.47% respectively in coronal plane. For saggital plane the percentage decrease in mean RMS values for these three reach positions are 28.32%, 39.1 % and 44.68% respectively For mid deltoid muscles the percentage decrease in mean RMS values has been observed as 27.13%, 34.3% and 47.75% respectively.in coronal plane. While for saggital plane this. reduction in values are 25.5%, 32.66% and 45.76% respectively. For trapezius muscles the %age decrease is 26.1 %, 32.8% and 47.3% respectively in coronal plane. While for saggital plane it is 25.3%, 34.41% and 43.85% respectively. Itl For triceps muscles the percentage decrease in mean RMS values are 25%, 34.1% and 43% respectively in coronal plane. While for saggital plane it is 27.3%, 35.1% and 45.4% respectively. Thus, it is observed that as compared to mid and high reach position the low reach position resulted the lowest RMS values. The mean RMS values without support stand for biceps muscles was the lowest in low position (43.8mV) which is 27% lesser than the value for mid position and 41% lesser than the value for high position . Similarly the mean RMS values of anterior deltoid (64.6mV) which is 11% lesser than the value for mid position and 40.4% lesser than the value for high position. The mean RMS values of mid deltoid (47.8mV) which is 40.39% lesser than the value for mid position and 66.24% lesser than the value for high position. The mean RMS values of trapezius (54mV) which is 20% lesser than the value for mid position and 39% lesser than the value for high position . RMS values of the muscles with and without overhead support stand were least for the lowest position. The subjective rating results also supported the above conclusions. The findings of the thesis indicate that to reduce fatigue and worker efficiency during overhead work place the workers should adopt low position in coronal and saggital plane and use the support to reduce the muscular load.