Abstract
Background: Abdominal and back muscles are integral components in low back mechanics and control. Disturbances in their activities could result in chronic low back pain (LBP). Objectives: To assess the relationship between the electromyographic (EMG) activities of abdominal and back muscles and to establish a ratio between the EMG of both groups of muscles. Methods: Thirty patients diagnosed with chronic LBP participated in this study. EMG activities, measured as mean root squared, were recorded using surface EMG device during maximum voluntary isometric contraction. Tested muscles were rectus abdominus, external oblique, erectrospinae, and lumbar multifidus. Results: A strong positive relationship, ipsilaterally, was reported between the EMG of the rectus abdominus and both back muscles (p< 0.05). External oblique muscles showed insignificant relationship to the erectrospinae and lumbar multifidus muscles on the ipsilateral side (p > 0.05). Conclusion: Rectus abdominus EMG activities, during maximum voluntary isometric contraction, are positively proportional to the EMG of ipsilateral erectrospinae and lumbar multifidus under similar conditions. Patient with LBP induced back muscle weakness could also demonstrate abdominal muscle weakness.