The relationship between functionality and erector spinae activity in patients with specific low back pain during dynamic and static movements

Background: Alterations in the activity of the lumbar erector spinae (LES) muscles on both sides of the spine have been inconsistently reported in patients with specific low back pain (sLBP) after measuring the muscular activity with surface electromyography (sEMG). It also remains unclear whether these alterations in LES activity can be related to the functional level of patients with sLBP.

Research question: This study investigated the LES activity in patients with sLBP during activities of daily living (ADL) which included dynamic and static movement tasks. Moreover, the alterations in LES activity were correlated with the first seven questions of the Zurich Claudication Questionnaire (ZCQ-SS).

Methods: Thirty patients with specific LBP and twenty healthy subjects were recruited to perform five ADLs including 'static waist flexion', 'sit to stand',' 30-seconds standing', '6-minutes walking' and 'climbing stairs'. sEMG sensors were mounted on the left and right LES muscles. The integrated EMG (IEMG) was calculated from the preprocessed sEMG data as statistical comparison criteria.

Results: LES activity was significantly higher in patients during 'sit to stand',' 30-seconds standing' and 'climbing stairs' and significantly lower during 'static waist flexion' compared to healthy controls. All tasks showed a significant correlation with the ZCQ-SS score except for '6-minutes walking', whereby LES activity and ZCQ-SS score correspondingly increased during 'sit to stand' and 'climbing stairs' and the LES activity decreased with an increasing ZCQ-SS score during 'static waist flexion' and' 30-seconds standing'.

Significance: There was a high correlation between alterations in LES activity and the level of functionality in LBP patients. However, the LES activity showed an opposite behavior during static and dynamic movement tasks. The methodology presented can be a useful tool for quantifying improvements in functionality after rehabilitation processes.