Evaluation of Lumbar Stabilizing Muscles in Dynamic Sagittal Imbalance Based on Surface Electromyography

Study DesignCase-control Study.ObjectiveTo evaluate the alterations in lumbar stabilizing muscles, particularly the erector spinae (ES), lumbar multifidus (LM), and gluteus maximus (Gmax), and their association with dynamic sagittal imbalance (DSI) after ambulation.MethodsThis study included patients with low back pain and anterior trunk tilt (defined as the DSI group), alongside a control group without significant anterior trunk tilt (defined as the dynamic sagittal balance, DSB group). Propensity score matching was used to align participants for comparison. The participants underwent whole-spine radiography before and after a 10-min walk. Alterations in muscle activity and fatigue were evaluated through surface electromyography (sEMG).ResultsFollowing a 10-min walk, the DSI group exhibited marked deterioration in sagittal parameters, particularly in LL and PT, whereas the parameters in the DSB group remained unchanged. Significant intergroup differences were identified in the changes (Δ) of LL and PT. The sEMG results revealed that after the 10-min walk, the DSI group experienced increased muscle activity and notable fatigue in the ES, LM and Gmax. While the DSB group also showed changes in the activity of ES and LM after walking, the activation and fatigue metrics of the LM didn't demonstrate significant alterations. In contrast, the DSI group exhibited substantially greater changes in the activation of ES and LM, as well as the fatigue levels of LM.ConclusionThis study highlighted the pivotal role of lumbar stabilizing muscles, particularly the LM, whose aberrant activation and fatigue were identified as key contributors to the progression of DSI.