Torso Kinematics during Stair Descent in Pregnancy

Abstract

Pregnant women demonstrate altered torso kinematics during gait: namely, increased anterior pelvic tilt, posterior thoracic lean, and side-to-side movement. Fall-risk is elevated in pregnancy. 40% of falls in pregnancy occur during staircase locomotion. The extent to which torso mechanics are altered during staircase gait in pregnancy has not been reported. PURPOSE: To examine the effect of pregnancy on thoracopelvic kinematics and mediolateral motion of the spine during stair descent. METHODS: Data were collected on 26 pregnant women in the mid-2nd and 3rd trimesters and on 28 control women. An 8 camera motion capture system (120 Hz) collected data of subjects walking down a four step staircase at their self-selected speed. Subjects wore a modified Helen Hayes marker set. Foot contact (FC) of two sequential right foot contacts was indicated by force plate data (1080 Hz). 3D thoracic and pelvic angles were determined at FC during descent. Frontal plane movement of the C7 and L3 markers and max and min thoracic and pelvic angles and ROMs were determined. An ANOVA examined differences between pregnant women in their 2nd trimester, 3rd trimester, and controls (α=0.05). RESULTS: Pregnant women in their 3rd trimester demonstrated increased anterior pelvic tilt and posterior thoracic lean during stair descent (Table 1). Thoracic rotation at FC was increased in late pregnancy (p=0.12; Control: 3.4±5.3°, 2nd tri.: 4.0±5.3°, 3rd tri.: 6.2±4.4°). CONCLUSIONS: Increased abdominal volume in the 3rd trimester likely resulted in altered sagittal plane kinematics. Increased anterior pelvic tilt and posterior thoracic lean make it more difficult for the pregnant women to see the stairs below them. This combination may be related to the high risk of falling during staircase descent. *Funding: NIOSH K01 008458.Table 1: Sagittal plane thoracopelvic kinematics