Title page for ETD etd-02162005-131821


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
  • Reflex
  • Flexion
  • Spine
  • Stability
  • Low back pain
Date of Defense 2005-02-16
Availability unrestricted
Abstract
The 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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