The purpose of this study was to quantitatively prove the asymmetric lifting acts on the risk factor of low back pain by a comparison of muscle activities of spinal loading and muscle strength(hand grip and back strength) between two types of lifting tasks(symmetric and asymmetric). Fourteen male subjects were participated in the experiment. We analysed and compared hand grip force, back strength, EMG(Electromyography), and IEMG(Integrated Electromyography) values for the stoop posture between symmetric and asymmetric lifting tasks using paired t-test. As the result, the back strength decreased in twisting posture. According to the result of EMG analysis, there were significant differences between right and left erector spinae muscle in asymmetric lifting task regardless of load. When subjects lifted boxes of right side, EMG values of left muscle were higher than those of right muscle. As twisting angle increased, EMG values of left muscle increased and EMG values of right muscle decreased. The results of IEMG analysis were similar to the results of EMG analysis. The results of EMG values during lifting indicated that the take-of stage was most stressful.