FUNCTIONAL-CHANGES IN BACK MUSCLE-ACTIVITY CORRELATE WITH PAIN INTENSITY AND PREDICTION OF LOW-BACK-PAIN DURING PREGNANCY

Objective: To assess low back pain (LBP intensity and subjective disab ility during pregnancy and compare the pain scores with lumbar motion patterns. Design: A prospective study of pregnant back pain sufferers and healthy controls. Setting: Kuopio University Hospital, Kuopio, Fin land. Participants: Study group consisted of 32 pregnant women with LB P; control group consisted of 21 healthy pregnant women. Main Outcome Measures: Back pain intensity was assessed by visual analog scale (VAS ), and subjective disability index was measured by Oswestry Lots Back Disability Questionnaire, at 20 and 36 weeks of pregnancy. Back muscle activities were recorded by surface electromyography, and movement se nsors were used to detect lumbar motion. Results: In the study group c urrent pain scores (VAS) at first and last trimester correlated strong ly (r =.82, p <.00). Pain scores correlated with body weight at the fi rst trimester (r =.54, p =.003) and at the last trimester (r =.67, p < .00). Significant correlation was noted between current pain intensity and back muscle activity level during forward body flexion at first t rimester (r =.704, p <.00). Back muscle activity during bending measur ed at first trimester significantly correlated with pain intensity at last trimester (r =.703,p <.00). Back muscle activity during the first trimester of pregnancy had a negative correlation with current (r = - .57, p =.002) and later subjective disability index (r = -.42, p =.02) . It correlated inversely (r = -.54, p =.003) with pain score at last trimester of pregnancy ie, the lower the back muscle activity at the b eginning of pregnancy, the more pain and disability throughout pregnan cy. Ln the control group, three women developed LBP and disability fee lings during pregnancy. They had increased muscle activity during flex ion at delivery, ie, disturbed flexion relaxation. Conclusions: Prepre gnancy LBP predicts renewed pain during pregnancy, and dysfunction of back muscles has been established in LBP. In this study, disturbance i n the relaxation of the back muscles was linearly related to current, and also to later, pain scores. In addition, back muscle activity leve l was inversely related to the disability index. For the first time, i t has been shown prospectively that the function pattern of back exten sors seems to predict. and is related to, future back pain. Simple fun ction testing is promising and might be valuable in identifying mother s with a high risk of pregnancy-related back pain and in directing pre ventive intervention to high risk women by making them aware of self-t reatment methods. (C) 1998 by the American Congress of Rehabilitation Medicine and The American Academy of Physical Medicine and Rehabilitat ion.