Effect of Upper Limb Muscle Activity on Different Horizontal Reach Envelope

摘要

Improved layout of workplace enables the operators from potential back injury problem. Therefore it is important in ergonomics design to include good posture and limitation of reach envelopes. Effect of upper limb muscles activity on different reach envelopes were investigated in this study. Ten samples of five females and five males aged between 22-25 years involved in the study. Subjects were required to accomplish the task consisted of repetitive lifting and lowering a 3kg metal disk of dumbbell between two fixed locations. In each experimental session (for normal, maximum and extreme workspaces) the distance of the subject from the table edge was varied accordingly. Muscle activity was measured using EMG electrodes attached to the skin of each subject. The results showed that Electromyography (EMG) reading percentage for anterior deltoid and upper trapezious muscles increased twice as moving from normal to maximum and extreme reach envelope. In the contrary the EMG readings percentage of biceps brachii muscles increases with minimal amount from normal position. As for Bicep Brachii muscle, the percentage of increased was only 1.4% for maximum workspace and only increase 1.2% for extreme when compared to normal workspace. The anterior deltoid and upper trapeziuos muscle also indicated significant increases from normal to maximum to extreme workspace. The findings indicated that standing repetitive with bench lifting task under normal, maximum and extreme reach envelope effect significantly anterior deltoid and upper trapezious muscles. The results of oxygen uptake showed an increased of 11% and 39% from normal reach to maximum and extreme reach respectively