The spatial distribution of lumbar muscle activity in people with chronic non-specific low back pain

Chronic non-specific low back pain (CNSLBP) is the leading global cause of disability, with economic/societal implications. Lumbar muscle activity is investigated as a mechanism to understand the presence and/or persistence of symptoms. High-density electromyography (HDEMG) allows detailed recording of muscle activity across a large region; permitting identification of subtle differences in activation. This thesis consists of five studies. A systematic review identified weak level of evidence for no differences in the magnitude of muscle activity between CNSLBP and healthy populations. However, identified trends supported further investigation of the erector spinae (ES) muscle, and trunk flexion and extension tasks. Three observational studies subsequently used HDEMG to assess ES activity during static, simple monoplanar, and complex multiplanar dynamic tasks. Results identified a less diffuse and more cranially focussed distribution of muscle activity in people experiencing CNSLBP. Finally, an exploratory quasi-experimental study investigated if HDEMG biofeedback could enable people with CNSLBP to activate caudal regions of the ES. Results identified an altered distribution of activity with biofeedback during a dynamic task, but with no changes in pain or exertion. In this thesis, HDEMG recordings identified altered distributions of ES activity in people with CNSLBP, and HDEMG biofeedback may alter this distribution