Ergonomic Evaluation of Manual Assembly Operations Using Direct and Indirect Observation Workstations in Sitting and Standing Positions

Pain in the upper extremity, particufariy in the neck and shoulder region is a major source of work place injuries in i ndust ri esThe occurrence of such occupational injuries is also on the rise. Shoulder and neck pain has been associateâ with awkward and statïc postures, repetitive a m movements and lack of rest A W a r d working postures at the trunk, neck and shoulderç may be caused by a number of factors including workstatïon layout and work methods. This can lead to the development of fatigue, discornfort and disabiiiiAs a result, the elimination or reduction of awkward postures is a major objective of many woricplace ergonornic programa This research evaiuated the trad'ional or direct observation workstation and the newly developed indirect observation workstation in manual assembly operaüons. The direct observation workstation requires the bending of the head and trunk in order to perforrn the task The indirect observation workstation uses a video camera to project the work area onto a television monitor diin front of the worker. Musck a c ü v i i of the trapezius and anterior deltoid muscles were quantifieci using Electromyography (EMG). This research found that static Ioad on the trapezius muscle was lower when using the indirect observation workstation particularly in the standing position. The intenial between the activation of motor unit potential is measured in micropauses, Duration in micropauses or micro-breaks were longer when using the indirect observation worksbtion for both the trapezius and anterior deitoid muscles. This research also found that excessive bending of the head can be reduced by using the indirect observation workstation. Productivity, however, is slower when using the indirect observation workstation compared to the direct observation workstation due to the two dimensional image projected by the television monitor. Dynamic workstation which utilizes a combination of direct and indirect observations, in the sitting and standing positions, shows an improvement in productivity but is accompanied by an increase in static load and shorter duration in micropauses particularly in the trapezius muscle, Data from the laboratat'y expriment also supports the field study conducteci at the Northem Telecom Plant in Calgary in terms of reduction in static loading of the trapezius muscle when using the indirect observation workstation. The newly developed indirect observation workstation is capable of reducing muscle strain especially in the baperius muscle as each subject is able to keep the head in an upright position while performing specific tasks. It also provides an option to the workers to continue with their work when neck and shoulder pain become intolerable due to excessive bending of the head when using the traditional workstationI would like to thank Professor Valefy Venda br his guidance, support, and encouragement throughout the course of this research, The invaluable help and suggestions which he has provided made this research possibleI would also like to acknowledge the assistance of the following indiduals for this thesis: Mr. Ola Ro of Premed AB, Oslo, Norway Mt. Arne b r a s of lnstitute of Work Physiology, Oslo, Norway Finally, I am gratefu l r the support from my family, fnends and colleagues during this endless journey of leaming, Table of