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BACKGROUND: It is hypothesized that inherent differences in movement strategies exist between control subjects and those with a history of lower back pain (LBP). Previous motion analysis studies focus primarily on tracking spinal movements, neglecting the connection between the lower limbs and spinal function. Lack of knowledge surrounding the functional implications of LBP may explain the diversity in success from general treatments currently offered to LBP patients. OBJECTIVE: This pilot study evaluated the response of healthy controls and individuals with a history of LBP (hLBP) to a postural disturbance. METHODS: Volunteers (n= 26) were asked to maintain standing balance in response to repeated balance disturbances delivered via a perturbation platform while both kinematic and electromyographic data were recorded from the trunk, pelvis, and lower limb. RESULTS: The healthy cohort utilized an upper body-focused strategy for balance control, with substantial activation of the external oblique muscles. The hLBP cohort implemented a lower limb-focused strategy, relying on activation of the semitendinosus and soleus muscles. No significant differences in joint range of motion were identified. CONCLUSIONS: These findings suggest that particular reactive movement patterns may indicate muscular deficits in subjects with hLBP. Identification of these deficits may aid in developing specific rehabilitation programs to prevent future LBP recurrence.

The spinal muscles have received great attention in low back pain (LBP) with suggestions of a de-conditioning syndrome. It is not known whether it is a long or short term consequence of LBP. This study explored the cross section area (CSA) and muscle quality of the spinal extensor group in LBP patients referred to a spinal clinic. MRI scans of 100 annoymised patients were retrospectively reviewed; sagittal and transverse (from levels L3-5) images were archived and analysed to determine CSA and levels of fat infiltration of the extensor muscle groups. Forty six patients had spinal stenosis (28 males, 18 females, mean age 66 ± 14.2 years) and 54 had a disc prolapse (28 males, 26 females, mean age 50 ± 12.9 years). CSA was significantly smaller in the stenotics at both L3/4 and L4/5. Patients presenting with leg pain and a disc herniation had a significantly smaller CSA (p < 0.01) at L3/4 and L4/5 levels. Fat infiltration was present in both groups but was significantly greater in the stenotic group (p < 0.01) and was present at a similar degree at all spinal levels. Multiple regression analysis confirmed that reduced CSA was linked to leg pain (p < 0.01) and age was linked with fat infiltration (p < 0.01). Future work should explore the extent of such changes in an age and sex matched control population with no current back pain or sciatica.