Abstract

INTRODUCTION: Pregnant women have an elevated risk of developing lower limb musculoskeletal disorders, likely due to the rapid increase in body mass and joint laxity. While a few studies have evaluated changes in static foot posture due to pregnancy, it is unclear if body mass or joint laxity is the primary driver. Additionally, how pregnancy affects the mechanics of the foot during dynamic movements is still not understood. PURPOSE: The purpose of this study is to investigate the foot's response to pregnancy. First, we examined foot tissue characteristics across pregnancy, specifically plantar fascia (PF) stiffness, length, and thickness. Additionally, we examined how the foot's ability to modulate energy absorption and generation during walking changes while pregnant. Lastly, we investigated therelationship between PF stiffness (static) and anterior/posterior (AP) spreading forces during walking (dynamic). METHODS: 19 participants visited the Human Performance Lab four times during and after their pregnancy: a) <13 weeks (TR1), b) >25 and <27 weeks (TR2), c) >35 and <37 weeks (TR3), and d) 8 to 10 weeks postpartum (PP). Ultrasound was used to measure the stiffness, length and thickness of the PF. A multi-segment foot model in conjunction with a pressure/shear stress-sensitive film device was used during walking. AP spreading forces from the pressure/shear device were calculated as the amount of directional force that opposes the net AP force. Joint kinematics and kinetics were calculated across stance phase. RESULTS: Body mass increased by 14.3% and PF stiffness decreased by 28% between TR1 and TR3. PF thickness and length did not change. Spreading forces under the foot increased by 17%. Walking joint kinematics remained mostly unchanged while unnormalized joint kinetics increased. When normalized to body mass, differences in joint kinetics were attenuated. This suggests that passive and active structures that cross the medial longitudinal arch (MLA) compensate for the increased body mass to maintain normal gait kinematics during pregnancy. CONCLUSION: Pregnancy does not cause prominent changes to foot kinematics during walking, likely resulting from active and passive structures that cross the MLA compensating for the increased body mass and decreased PF stiffness that occur as pregnancy progresses. The increased demand of active and passive structures to maintain normal gait kinematics in the foot may partially explain the muscle cramps, pain, and fatigue women experience during pregnancy.

Degree

PhD

College and Department

Life Sciences; Exercise Sciences

Rights

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