The objective of this study was to investigate the effects of lifting posture on muscle fatigue. Three healthy male students participated in the study to perform sustained isometric contraction at 50% MVC. The exertion was continued with the squat posture and the stoop posture until they can not maintain the required strength. During these periods electromyographic signals from the biceps brachii, the erector spinae, the rectus abdominis, the rectus femoris were recorded. The signals were nomalized to analyse relative muscle activity. The results showed that a significant difference was found between the squat posture and the stoop posture and among the muscles. The squat posture increased the rectus femoris activity but the stoop posture increased the others. It means that the squat posture is more stressful on the legs compare but decrease the stress to the other parts of the musculoskeletal system.