2017 Volume 32 Issue 5 Pages 645-649
[Purpose] This study aimed to define the region where load is concentrated and to observe the temporal changes in the intervertebral angles of the lumbar spine of three types of sitting: lumbopelvic upright sitting, slump sitting, and thoracic upright sitting. [Subjects and Methods] The subjects were 16 healthy adult men who maintained each of the three sitting postures for 20 min with a 20% body weight load regulated by belts suspending the shoulders bilaterally. Intervertebral angle changes from L2 to S1 were measured using a three-dimensional ultrasonic motion analysis system. [Results] Significant kyphotic changes during lumbopelvic upright sitting were sequentially observed after 4, 5, 7 and 11 min from the upper segment downwards. In thoracic upright and slump sitting, no significant changes in intervertebral angles were observed. [Conclusion] The results of this study suggest that intervertebral angles of the lumbar spine during lumbopelvic and thoracic upright sitting converge with those of slump sitting. It is speculated that the mechanical demands of supporting the spinal structure are transferred from the spinal musculature to the passive tissues, which undergo elongation stress during slump sitting. Hence, sedentary workers should change their posture frequently.
