Effect of pregnancy on trunk range of motion when sitting and standing

Background. During pregnancy, apposition of body segments and changes in trunk mobility and motion control due to increased mass and dimensions may reduce the functional range of motion of the trunk segments. Although static postures have been investigated, dynamic trunk motion during pregnancy in sitting and standing has had very limited investigation. Methods. Included in the study was a volunteer sample of convenience of nine primiparous and multiparous women. Twelve nulliparous females formed a control group. The subjects were filmed while performing maximum seated and standing trunk forward flexion, side-to-side flexion and seated axial rotation. A repeated measures anova was used to investigate systematic changes in the motion of the pelvic and thoracic segments and the thoracolumbar spines during pregnancy. Results. As pregnancy progressed, there was no significant decrease in the range of side-to-side flexion. For forward flexion and axial rotation, motion of the thoracic segment and the thoracolumbar spine was significantly reduced. Movement of the pelvis was less affected. Base of support width was increased for forward flexion and side-to-side flexion. Conclusions. In late pregnancy, strategies such as increasing the width of the base of support and reducing obstruction from other body parts were used to minimize the effects of increased trunk mass and girths. Not all trunk segment motion was affected equally. The differing effect on individual trunk segment motion may lead to altered movement patterns during functional tasks.