Association between muscle function and low back pain in relation to pregnancy.

OBJECTIVE To investigate the association of muscle function and subgroups of low back pain (no low back pain, pelvic girdle pain, lumbar pain and combined pelvic girdle pain and lumbar pain) in relation to pregnancy. DESIGN Prospective cohort study. SUBJECTS Consecutively enrolled pregnant women seen in gestational weeks 12-18 (n = 301) and 3 months postpartum (n = 262). METHODS Classification into subgroups by means of mechanical assessment of the lumbar spine, pelvic pain provocation tests, standard history and a pain drawing. Trunk muscle endurance, hip muscle strength (dynamometer) and gait speed were investigated. RESULTS In pregnancy 116 women had no low back pain, 33% (n = 99) had pelvic girdle pain, 11% (n = 32) had lumbar pain and 18% (n = 54) had combined pelvic girdle pain and lumbar pain. The prevalence of pelvic girdle pain/combined pelvic girdle pain and lumbar pain decreased postpartum, whereas the prevalence of lumbar pain remained stable. Women with pelvic girdle pain and/or combined pelvic girdle pain and lumbar pain had lower values for trunk muscle endurance, hip extension and gait speed as compared to women without low back pain in pregnancy and postpartum (p < 0.001-0.04). Women with pelvic girdle pain throughout the study had lower values of back flexor endurance compared with women without low back pain. CONCLUSION Muscle dysfunction was associated with pelvic girdle pain, which should be taken into consideration when developing treatment strategies and preventive measures.