Type of Document Master's Thesis Author Rogers, Ellen Louise URN etd-02162005-131821 Title Prolonged Lumbar Flexion Disturbs Paraspinal Reflex Behavior Degree Master of Science Department Mechanical Engineering Advisory Committee
Advisor Name Title Granata, Kevin P. Committee Chair Madigan, Michael L. Committee Member Nussbaum, Maury A. Committee Member Keywords
- Low back pain
Date of Defense 2005-02-16 Availability unrestricted AbstractThe neuromuscular response to prolonged lumbar flexion has recently been extensively studied in felines but has not been examined in humans. Animal studies suggest that prolonged lumbar flexion disturbs neuromuscular control of paraspinal muscles. This disturbance was linked to creep deformation of passive spinal tissues. Past research indicates that disturbance of paraspinal reflexes may limit spinal stability. The current study aimed to examine this behavior in humans. We hypothesized that prolonged lumbar flexion will disturb paraspinal reflex behavior in human subjects.
Reflex behavior was quantified following a fifteen minute period of static flexion. There was a trend suggesting an increase in reflex magnitude after flexion (p = 0.055). This trend was only significant in female subjects (p < 0.003). Increased reflex following flexion was associated with a transient period of EMG hyperexcitability similar to felines.
A second study was performed to quantify reflex behavior and creep deformation during flexion and recovery. Results indicated that creep occurred during prolonged flexion (p < 0.001). Reflexes were inhibited following flexion (p < 0.03). Both creep deformation and paraspinal reflex (p > 0.05) failed to exhibit significant recovery during the length of the test.
Inhibited paraspinal reflexes may contribute to spinal instability and risk of low back pain for workers using flexed postures, due to the inability of the neuromuscular system to coordinate an appropriate muscle response following an unexpected loading event. Future studies must examine appropriate work/rest intervals for workers using flexed postures to limit reflex disturbance from prolonged ligament strain.
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