New research shows that neuromuscular changes during pregnancy lead to bouts of lower-back pain and not an increase in the lumbar curvature, as has traditionally been thought
One of the most common complications during pregnancy is low-back pain, which affects between 50% and 70% of pregnant women. For the population on the whole, lower-back pain is associated to changes in the spine's biomechanics. However, these changes had not been comprehensively studied until now in the case of pregnant women. CEU UCH researchers Gemma Biviá and Juan Francisco Lisón, together with Daniel Sánchez Zuriaga, of Valencia University (UV), have analysed the changes to the spine and the muscle groups of the lower back during the last three months of pregnancy, comparing results to the same women after birth and to women who were not pregnant. The results, which help understand the neuromuscular mechanisms that could be behind lower-back pain, have recently been published in two scientific journals: Plos One and The Spine Journal, edited by the North American Spine Society.
In the study, the CEU UCH and UV researchers have compared the curvature of the spine and muscle activation in the lower back of 34 pregnant women, entering the third trimester of pregnancy, to another group of 34 women who had not given birth. In the case of the 34 pregnant women, the study was repeated two months after giving birth in order to compare the results. In the first phase of the study, the activation level of the erector spinae and femoral biceps muscles were studied with electromyography techniques, as well as the lower-back curvature while standing.
The curvature is an optical illusion
UCH CEU researcher Gemma Biviá highlights that "pregnancy does not seem to modify lumbar lordosis, as traditionally thought. The common belief that pregnancy increases the lower-back curvature could be related to a simple optical illusion. What we did observe was that pregnant women activate the lumbar muscles more intensely during the last three months of pregnancy when compared to those who are not pregnant."
The results of this research show that lumbar muscles develop an adaptative response to be able to face the increase in abdominal volume due to the size of the child in the last stage of pregnancy. "Until now, the origin of the lower-back pain had been associated to an increase in the lumbar curvature, to the point that exercises to decrease it were recommended. However, our results show that pregnancy alters the muscular response, which is key when designing exercises that decrease lower-back pain - which is so common among pregnant women," Biviá adds.
The origin of lower-back pain during pregnancy
Based on these results, and to examine the possible relation between lower-back pain during pregnancy and the alteration of muscular activation, the CEU UCH and UV researchers also studied the lumbar spine movement and the activation of the erector spinae muscle when bending over, comparing the results of the pregnant women to those of the group who had never given birth.
In this case "we saw that pregnant women in the last three months of their pregnancy modified the lumbar movement and the way in which their erector muscles activate when bending over. These biomechanical changes take place as a specific mechanism that pregnant women develop to protect their lower back from both the increased abdominal volume, and the increased ligament laxity caused by pregnancy hormones. Results of our research shine a light for the first time on the lumbo-pelvic movement alterations and the way in which the extensor muscles of the back activate. These findings can be of great help for health professionals, as a guide to prescribe specific exercises to decrease lower-back pain during pregnancy," Doctor Biviá explains.
The results of these studies on the biomechanics of the lumbar region of pregnant woman have been part of the doctoral thesis of CEU Cardenal Herrera University Physiotherapy professor Gemma Biviá Roig, whose work as a researcher is centred on women's lifestyle and health. Research for her thesis was guided by doctor Daniel Sánchez Zuriaga, professor of the Department of Anatomy and Human Embryology at the UV and Juan Francisco Lisón, head of the Medicine Department of the CEU UCH.