LUMBOPELVIC POSTURAL CHANGES IN PREGNANT WOMEN AND POSTPARTUM

Biviá-Roig G.¹, Lisón J.F.², Lluch-Girbés E.³, Sánchez-Zuriaga D.⁴

¹University CEU-Cardenal Herrera, Department of Physiotherapy, Moncada, Spain, ²University CEU-Cardenal Herrera, Department of Medicine, Castellón de la Plana, Spain, ³Universitat de València, Department of Physiotherapy, Valencia, Spain, ⁴Universitat de València, Department of Anatomy and Human Embryology, Valencia, Spain

Background: Low back pain is one of the most common complications during pregnancy, with a 50-70% prevalence. Its incidence is higher in the third trimester of pregnancy, coinciding with the most important biomechanical and morphological changes. The increase in abdominal size has been linked to adaptive alterations in spinal curvatures, especially to increased lumbar lordosis, which in turn have been linked to low back pain. However, the results of previous studies about spinal changes during pregnancy are controversial. Findings vary from an increased to a flattened lordosis. On the other hand, there is no evidence on the activation of the extensor muscles in standing in this population.

Purpose: In order to shed more light on postural changes and the extensor muscle activation during pregnancy and postpartum, the aim of this study was to analyze the position of the lumbopelvic region and muscle activation of the erector spinae and biceps femoris muscles in a group of pregnant women in the third trimester, while keeping a static position. The hypothesis was that the biomechanical and morphological changes of pregnant women modify the position of the lumbopelvic region and the activation of the extensor muscles.

Methods: The study involved 34 nulliparous women (control group) and 34 pregnant women in the third trimester (week 36 ± 1). We recorded the position of the lumbar spine and pelvis in the sagittal plane, and the EMG activity of the erector spinae and biceps femoris, during standing, in both groups, and also two months after birth in the group of pregnant women. EMG activity was expressed as a percentage of a submaximal reference contraction.

Results: No significant differences in the position of the lumbar spine or pelvis between the group of pregnant women and control or postpartum were observed. A significant increase was observed in the EMG activity of erector spinae (4.6% vs 2.4% and 2.1% in the control group and postpartum respectively) and the biceps femoris (3.4% vs 1.2% and 1.4%) in pregnant women compared to the other two groups (p 0.01).

Conclusion(s): Contrary to popular belief, pregnant women in the third trimester show no alterations in lumbopelvic position compared to nulliparous and postpartum women. However, there is an increase of trunk extensors EMG activity. These results indicate that the extensor muscles of the trunk show, in static positions, adaptive responses to the increase of anterior loads.

Implications: The genesis of pregnancy-related low back pain could be related to this sustained increase in the activation of the trunk extensor muscles (which in turn may be causing muscle fatigue), and not to postural changes, as it was traditionally thought. The results of this research may help physiotherapists to choose the most appropriate treatment in pregnant women with low back pain.

Funding acknowledgements: No external funding was used for this work.

Topic: Musculoskeletal: spine

Ethics approval: Approved by the Clinical Research Corporate Ethics Committee and the Committee on Human Research of the University of Valencia (Spain)

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