Behavior of the Lumbar Multifidus During Lower Extremity Movements in People With Recurrent Low Back Pain During Symptom Remission

STUDY DESIGN: Cross-sectional design. OBJECTIVES: To investigate lumbar multifidus (LM) thickness differences, using ultrasound imaging in people during remission from recurrent low back pain (LBP) and healthy participants, during the following lower extremity movements: (1) active straight leg raise (ASLR), (2) crook-lying active leg raise (CLR), and (3) prone straight leg raise (PSLR). BACKGROUND: ASLR, CLR, and PSLR are used clinically to challenge the ability of the trunk muscles to control spinal motion in people with LBP, and it is believed that decreased LM activity is related to altered spinal control in this population. However, it is unclear whether LM behavior differs between healthy individuals and people with recurrent LBP during symptom remission in such tasks. METHODS: The present study used ultrasound imaging to measure LM percentage thickness change parasagitally at the L4-5 and L5-S1 levels in people with recurrent LBP during symptom remission and in healthy participants, during the ASLR, CLR, and PSLR tasks. RESULTS: LM percentage thickness change was greater in the recurrent LBP group than in healthy participants during the PSLR task (P <.01) and greater in both groups during the PSLR than the ASLR and CLR tasks (P <.01). LM percentage thickness change was greatest at L4-5 in both groups (P <.01) and during all tasks (P <=.02). No difference was found in LM percentage thickness change between groups in either the ASLR (P = .70) or CLR (P = .69) task. CONCLUSIONS: These data suggest that, during symptom remission, individuals with recurrent LBP, compared to healthy individuals, may have greater activity in at least some parts of the LM. Further investigation is required to determine whether the LM percentage thickness change observed in this study may be explained by differential changes in deep and/or superficial fibers of LM activity. This observation may have implications for clinical practice, but requires further investigation. J Orthop Sports Phys Ther 2011;41(3):155-164, Epub 4 January 2011. doi:10.2519/jospt.2011.3410