Comparison of Symmetry in EMG Activity of Selected Muscles in Response to Increased External Load during Walking in Individuals with and without Chronic Low Back Pain

This study aimed to compare the symmetry of electromyography (EMG) activity of selected muscles in response to increased external load in individuals with and without chronic low back pain (CLBP) during walking. To this end, 30 men (15 healthy and 15 with CLBP) aged 23 to 28 years were purposefully selected. Participants walked on a 20 -meter track under different loading conditions (no load, 10% body weight in one hand, $10 \%$ body weight in both hands, $20 \%$ body weight in one hand, and $20 \%$ body weight in both hands). EMG activity was recorded from 14 lumbosacral and abdominal muscles on both the left and right sides of the body. The results showed that external loading significantly affected the symmetry of muscle activity, with more pronounced effects in individuals with CLBP. Significant statistical differences in the symmetry of the right and left abdominal muscles and the external and internal oblique muscles between the groups under various loading conditions were observed. Additionally, the back muscles (latissimus dorsi, thoracolumbar fascia, lumbar spinalis, and multifidus) also exhibited significant asymmetry under different loading conditions. These findings suggest that even relatively light loads can disrupt the balance of activation in core stabilizing muscles, especially in individuals with CLBP. The reduced symmetry in the studied muscles may be due to changes in motor control strategies and compensatory mechanisms to avoid pain. These asymmetries may lead to an increased risk of injury and exacerbation of CLBP symptoms. The study’s findings have important implications for rehabilitation programs and ergonomic recommendations. Future research should explore the relationship between specific muscle asymmetries and pain levels or functional outcomes in individuals with CLBP.