Association between lumbar paraspinal muscle activities and quality in chronic low back pain: a cross-sectional...

This study aimed to investigate the associations between electromyography (EMG) activity and key muscle quality parameters, including cross-sectional area (CSA), functional cross-sectional area (FCSA), fat area (FA), and fat infiltration (FI), in individuals with chronic low back pain (cLBP) and those without back pain (no-BP). The objective was to explore how variations in muscle quality affect muscle activation patterns in the erector spinae (ES) and multifidus (MF) muscles during a standardized lifting task in both groups.

A total of 102 participants were enrolled, comprising 60 individuals with cLBP and 42 without back pain. Muscle activation was measured using a bipolar wireless EMG system during the performance of a 10 kg lifting task. Magnetic resonance imaging (MRI) was utilized to assess muscle quality indicators (CSA, FCSA, FA, and FI) at the L3 level for the ES muscle and the L5 level for the MF muscle. Linear regression models were applied to examine the associations between EMG activity and muscle quality metrics, with adjustments for age, sex, and body mass index (BMI).

In the no-BP group, significant negative associations were found between CSA, FCSA, and EMG activity in the ES muscles (p < 0.05). However, in the cLBP group, no significant associations were observed between CSA or FCSA and EMG activity. Instead, there was a significant negative association between EMG activity and FA/FI in the ES muscles of the cLBP group (p < 0.05).

Muscle quality, particularly fat infiltration, appears to have a greater impact on the amplitude of muscle activities in cLBP patients compared to CSA and FCSA. In contrast to the no-BP group, CSA and FCSA were not significantly associated with muscle activation in the cLBP group, highlighting the need for rehabilitation strategies focused on reducing fat infiltration to improve muscle performance in these patients.