People With Low Back Pain Display a Different Distribution of Erector Spinae Activity During a Singular Mono-Planar Lifting Task

Abstract

This study aimed to investigate the variation in muscle activity and movement in the lumbar and lumbothoracic region during a singular mono-planar lifting task, and how this is altered in individuals experiencing low back pain (LBP). Muscle activity from the lumbar and lumbothoracic erector spinae of 14 control and 11 LBP participants was recorded using four 13 × 5 high-density surface electromyography (HDEMG) grids. Root mean squared HDEMG signals were used to create spatial maps of the distribution of muscle activity. Three-dimensional kinematic data were recorded focusing on the relationship between lumbar and thoracic movements. In the task, participants lifted a 5 kg box from knee height to sternal height, and then returned the box to the starting position. The center of muscle activity for LBP participants was found to be systematically more cranial throughout the task compared to the control participants (P < 0.05). Participants with LBP also had lower signal entropy (P < 0.05) and lower absolute root mean squared values (P < 0.05). However, there were no differences between groups in kinematic variables, with no difference in contributions between lumbar and thoracic motion segments (P > 0.05). These results indicate that participants with LBP utilize an altered motor control strategy to complete a singular lifting task which is not reflected in their movement strategy. While no differences were identified between groups in the motion between lumbar and thoracic motion segments, participants with LBP utilized a less homogenous, less diffuse and more cranially focussed contraction of their erector spinae to complete the lifting movement. These results may have relevance for the persistence of LBP symptoms and the development of new treatments focussing on muscle retraining in LBP.

People with chronic low back pain display spatial alterations in high-density surface EMG-torque oscillations

“…Regional variations in HDsEMG-torque coherence. Moreover, given that regional differences in myoelectric activity of lumbar ES is a common finding in people with CLBP [23][24][25][26][27]61 and that altered distribution of input to the motoneurons can change motor unit recruitment patterns during pain 62 , we investigated whether regional differences in sEMG-torque coherence also existed between people with CLBP and asymptomatic controls. Differences in topographical representation of coherence were observed at 50%MVC, since the lumbar ES coherence centroid in the CLBP group was displaced more cranially (suggesting higher coherence in the upper region of the muscle), while in the asymptomatic controls, the centroid of coherence was displaced towards more middle-caudal regions of the lumbar ES.…”

“…Then, the HDsEMG grid was placed unilaterally over the lumbar ES, 2 cm lateral to the L5 spinous process (AS controls: right side, CLBP group: most painful side) (Fig. 1 ) 23 , 24 , 26 , 36 . The electrode was placed on the most painful side for the CLBP group as it was expected that this side would show greater changes in myoelectric activity 25 .…”

“…This would allow to determine whether certain muscle regions contribute more to the exerted torque than others. In the case of CLBP, several studies have revealed variations in lumbar ES amplitude distribution [23][24][25][26][27] , and in particular, studies have shown that people with CLBP often display less activity in the more caudal regions of the lumbar ES during static-fatiguing and dynamic lumbar extension tasks 23,24,26,27 . It is possible that regional variations in sEMG-torque relationships are responsible for poorer control of force during visuomotor torque-matching tasks, yet this has never been examined.The aims of this study are to (1) quantify the relationship between HDsEMG oscillations and isometric trunk-extension torque oscillations in both time (i.e., cross-correlation) and frequency domains (i.e., coherence) and (2) examine and compare regional differences in sEMG-torque coherence of the ES muscle in individuals with CLBP and asymptomatic controls.…”

“…This would allow to determine whether certain muscle regions contribute more to the exerted torque than others. In the case of CLBP, several studies have revealed variations in lumbar ES amplitude distribution [23][24][25][26][27] , and in particular, studies have shown that people with CLBP often display less activity in the more caudal regions of the lumbar ES during static-fatiguing and dynamic lumbar extension tasks 23,24,26,27 . It is possible that regional variations in sEMG-torque relationships are responsible for poorer control of force during visuomotor torque-matching tasks, yet this has never been examined.…”

New insights into pain-related changes in muscle activation revealed by high-density surface electromyography

“…This redistribution of activity is thought to have the physiological significance of redistributing load, minimising muscle fatigue and prolonging endurance, possibly by preventing overload on the muscle fibres active at the beginning of the task. This variation in activation within regions of the same muscle appears to be of particular relevance for muscles commonly exposed to repetitive or sustained activation, such as the upper trapezius muscle (Falla et al, 2017Farina et al, 2008;Gallina et al, 2013) and the lumbar erector spinae (Abboud et al, 2015;Falla et al, 2014;Martinez-Valdes et al, 2019;Sanderson et al, 2019bSanderson et al, , 2019aTucker et al, 2009). For instance, Abboud and colleagues (Abboud et al, 2016) observed that the variability in the spatial location of the activation of the lumbar erector spinae is reduced in response to sudden trunk mechanical perturbations during the presence of fatigue.…”