Associations of Thoracic Flexion and Hamstring Flexibility with Pregnancy-Related Low Back Pain after Childbirth

Abstract Objective: Pregnancy-related low back pain (PLBP) after childbirth is a major problem, but risk factor for this is not fully understood. The purpose of this cross-sectional study was to verify the associations of thoracic flexion and hamstring flexibility with PLBP 4 months after childbirth. Methods: This cross-sectional study was conducted in which seventy-four postpartum women who had PLBP during pregnancy (mean age: 31.1 ± 5.0 years) at A health and welfare center in Hyogo, Japan. PLBP 4 months after childbirth was assessed using a self-reported questionnaire. The range of motion (ROM) of thoracic flexion was measured using the double inclinometer method and classified based on tertile divisions. Limitations of 20° or more from full knee extension determined using the seated knee extension test were considered to indicate a tight hamstring. Results: PLBP after childbirth was more likely in women in the lowest tertile of thoracic flexion ROM than in those in the highest tertile (OR, 4.25; 95% CI, 1.29–14.03). A tight hamstring was associated with PLBP after childbirth (OR, 3.27; 95% CI, 1.14–9.32). After adjusting for relevant confounding variables, the thoracic flexion ROM and a tight hamstring remained significantly independently associated with PLBP after childbirth (thoracic flexion ROM: adjusted OR, 4.70; 95% CI, 1.16–19.01; tight hamstring: adjusted OR, 3.93; 95% CI, 1.03–15.02). Conclusion: Reduced thoracic flexion and hamstring flexibility are associated with PLBP after childbirth. Interventions for thoracic flexion and hamstring flexibility in postpartum women could help prevent and improve PLBP after childbirth.