Individuals With Recurrent Low Back Pain Exhibit Significant Changes in Paraspinal Muscle Strength After Intramuscular Fine Wire Electrode Insertion.

OBJECTIVE: To examine how insertion and presence of intramuscular fine-wire electromyography electrodes (IFWEs) in lumbar multifidus affect paraspinal muscle strength, endurance, and activation in persons with and without recurrent lower back pain (RLBP) during activities that require high levels of muscle contraction. DESIGN: Case-control with randomization of conditions. SETTING: Clinical research laboratory. PARTICIPANTS: Forty participants age 18 to 40 years were recruited (18 female; mean age = 25.5 years); 20 with a history of RLBP were compared to a matching control group of 20 without RLBP. INTERVENTIONS: Each participant was tested under three conditions over three sessions. On Session 1, the baseline condition, we assessed muscle performance without IFWE insertion. On Sessions 2 and 3, participants were randomly alternated between two experimental conditions: (1) wire-in, in which the IFWE was inserted and remained within the muscle during testing; and (2) wire-out, in which the IFWE was inserted and immediately removed. MAIN OUTCOME MEASUREMENTS: Lumbar spinal extensor peak strength, endurance, and normalized electromyography (EMG) amplitude during the endurance test. RESULTS: Individuals with RLBP showed a significant decrease in peak strength during conditions that involved IFWE insertion and tend to experience more pain during muscle testing. Both groups exhibited similar levels of performance and muscle activation during the endurance test. CONCLUSION: Our findings indicate that individuals with RLBP exhibited reduced lumbar extensor strength in response to IFWE insertion to the deep paraspinal muscles. This behavior is different from those without RLBP. Researchers should carefully consider the use of IFWE in individuals with RLBP during high exertion activities.