Reduced task-induced variations in the distribution of activity across back muscle regions in individuals with low back pain

Abstract

This study investigated change in the distribution of lumbar erector spinae muscle activity and pressure pain sensitivity across the low back in individuals with low back pain (LBP) and healthy controls. Surface electromyographic (EMG) signals were recorded from multiple locations over the lumbar erector spinae muscle with a 13×5 grid of electrodes from 19 people with chronic nonspecific LBP and 17 control subjects as they performed a repetitive lifting task. The EMG root mean square (RMS) was computed for each location of the grid to form a map of the EMG amplitude distribution. Pressure pain thresholds (PPT) were recorded before and after the lifting task over a similar area of the back. For the control subjects, the EMG RMS progressively increased more in the caudal region of the lumbar erector spinae during the repetitive task, resulting in a shift in the distribution of muscle activity. In contrast, the distribution of muscle activity remained unaltered in the LBP group despite an overall increase in EMG amplitude. PPT was lower in the LBP group after completion of the repetitive task compared to baseline (average across all locations: pre: 268.0±165.9 kPa; post: 242.0±166.7 kPa), whereas no change in PPT over time was observed for the control group (320.1±162.1 kPa; post: 322.0±179.5 kPa). The results demonstrate that LBP alters the normal adaptation of lumbar erector spinae muscle activity to exercise, which occurs in the presence of exercise-induced hyperalgesia. Reduced variability of muscle activity may have important implications for the provocation and recurrence of LBP due to repetitive tasks.

Can neck exercises enhance the activation of the semispinalis cervicis relative to the splenius capitis at specific spinal levels?

“…This is line with previous studies demonstrating a non-uniform distribution of muscle activity (e.g. trapezius, lumbar erector spinae) with the possibility of activating different muscle regions depending on the task performed (Falla and Farina, 2008;Falla et al, 2014).…”

Test-Retest Reliability of Trunk Motor Variability Measured By Large-Array Surface Electromyography

“…Other studies specifically reported a caudal shift of back muscle activity centroid during muscle fatigue in asymptomatic participants. 5,6,22 This observation confirms that the lumbar erector spinae muscles adapt over time in the presence of muscle fatigue. These adaptations in muscle activity during sustained contractions may reflect an efficient strategy to maintain task requirements by distributing the activity across different regions of the muscle.…”

“…The centroid position is one of the commonly used variables, as the literature and recent studies reported changes in the distribution of muscle activity characterized by a migration of the centroid during a fatigue task. 2,5,6 Indeed, a caudal and lateral shift of the centroid was observed in the current study. Other studies specifically reported a caudal shift of back muscle activity centroid during muscle fatigue in asymptomatic participants.…”

“…Using large-array surface electromyography (sEMG) to document the topographical representation of muscle activation, 4 several investigators have revisited the muscle recruitment changes associated to lower back muscle fatigue. [5][6][7] In short, the use of large-array sEMG has enabled the identification of distinctive neuromuscular patterns such as the redistribution of muscle activity in the presence of muscle fatigue and an increase in motor variability. 7 Moreover, even though muscle fatigue leads to increases in motor variability in both patients with chronic low back pain (LBP) and asymptomatic participants, motor variability remains lower in patients with chronic LBP.…”

Influence of Lumbar Muscle Fatigue on Trunk Adaptations during Sudden External Perturbations

“…Adopting non-uniform muscle activity recruitment may help participants develop motor strategies and facilitate adaptation to different physiological and/or mechanical perturbations of the spine. Low back muscle activity measured by high-density sEMG has also been shown to discriminate patients with chronic low back pain from healthy individuals through different motor tasks (Abboud et al, 2014; Falla et al, 2014). To our knowledge, no study has investigated muscle activity reflex variables with high-density sEMG.…”