Abstract
Introduction
Chronic low back pain (LBP) is globally recognised as a leading cause of disability, with a global point-prevalence of 540 million people experiencing ‘activity-limiting’ LBP. A lack of muscle endurance is common in people with LBP, however the mechanisms underlying reduced endurance remain unclear. This study utilised high-density EMG (HDEMG) to evaluate differences in the spatial distribution and redistribution of lumbar erector spinae (ES) activity during an endurance task.
Methods
Thirteen control (Age:26.46±5.0, 7 Males) and 13 LBP participants (Age:27.39±9.7, 6 Males) were recruited and HDEMG signals were detected from ES unilaterally using a 13×5 electrode grid adhered 2cm lateral to the L5 spinous process. Participants were asked to complete an isometric endurance task until failure (>10° trunk deviation) with muscle activity simultaneously recorded. The activity was computed to form a map of the EMG amplitude distribution and the position of the centre of activity (centroid) was monitored throughout the task.
Results
The LBP group showed significantly lower endurance than controls (LBP:186.2±72.3s, control:283.0±33.0s). The EMG map showed a less diffuse contraction of ES in LBP participants, with greater activation in cranial portions. In the LBP group, throughout the task the centroid was 12mm more cranial, and less redistribution of activity was seen (LBP:1.40±0.29mm, control:2.10±0.45mm).
Conclusions
LBP participants utilised a different motor strategy to complete the task, characterised by more cranial activation of ES and less redistribution of activity. These findings provide new insight into the mechanisms underlying impaired endurance in people with LBP and may lead to the development of new exercise approaches.
Conflicts of interest: No conflicts of interest
Sources of funding: No funding obtained
