[Purpose] It is very important to consider effects that postural deviations has on muscle activity when treating low back pain. Therefore, activities of trunk and hip joint muscles in healthy adults while they attempted three postural conditions of neutral, sway-back, and lordosis was compared and evaluated in this study. [Subjects and Methods] The subjects comprised 17 healthy adult male volunteers. The muscle activity and spinal curve were measured while the subjects attempted different postural conditions (neutral, sway-back, and lordosis) as defined in the text. [Results] Activity of trunk and hip inner muscles was decreased in sway-back posture, and only activity of the trunk back muscles was increased in lordosis. [Conclusion] This results were suggested that postural deviations affected muscle control in the lumbo-pelvic area.