Near infrared spectroscopy confirms recruitment of specific lumbar extensors through neuromuscular electrical stimulation.

Background: Lumbar multifidus impairments are associated with low back pain (LBP), with sustained impairments thought to contribute to recurrence and chronicity of pain. Ability to regain muscle function can be challenging. While neuromuscular electrical stimulation (NMES) may aid in muscle function recovery, validity of its ability to selectively recruit the lumbar multifidus and provide adequate dosage for muscle overload has not been demonstrated. Near infrared spectroscopy (NIRS) can be used to determine muscle selectivity and overload during NMES and offers advantages over electromyography (EMG), which is affected by electrical interference. Objective: The aim of this study was to determine the ability of NMES to activate and overload the lumbar multifidus in isolation. Methods: EMG and NIRS were collected over the trunk extensors during standardized movements followed by delivery of NMES in 10 healthy participants. NIRS was used to determine the ability of NMES to selectively recruit the lumbar multifidus at the L5 region relative to other trunk extensors. EMG and NIRS data were then entered into a linear regression model to predict muscle activity during NMES relative to the standardized movements. Results: There was a significant correlation (r = 0.81, p < 0.001) between EMG and NIRS in the lumbar multifidus. There was significantly greater activation of lumbar multifidus compared to lumbar erector spinae using specific NMES electrode placement (p < 0.001). Conclusion: NMES can preferentially activate lumbar multifidus with potential to provide a therapeutic overload to these muscles in healthy participants. It may be a promising intervention for individuals with LBP.