Analysis of the mechanical and neural regulatory mechanisms of the flexion-relaxation phenomenon (FRP), observed in deep trunk flexion, was performed since it is believed these mechanisms provide insight into the causes of low back injury and pain. Three methods were used to analyze the behavior of the lumbar tissues during trunk flexion-extension exercises: 1) active continuous cyclic movement, 2) acute cyclic movement at different orientations, and 3) passive continuous cyclic movement. All activities were performed at a rate of 0.1 Hz (6 cyclesmin-1) while monitoring the surface electromyography (EMG) of the lumbar paraspinal muscles. Abdominal, hamstring, and quadriceps muscle activities were also monitored during acute cyclic movement. Trunk inclination and lumbar flexion angles were time synchronized with the recorded EMG signals. Increases in the myoelectric silent period with respect to inclination and flexion angles were apparent over time (p < 0.001) during the active continuous cyclic activity. Muscular fatigue and constant gravitational loading of the system were thought to influence the observations. Acute cyclic movements of trunk flexion-extension were performed in standing and supine positions. In standing, abdominal EMG activity increased when silent periods were present in lumbar paraspinal and hamstring muscles. Performance of flexion-extension from the supine position resulted in sustained silence of the paraspianl muscles once gravitational load was presented as the trunk flexed beyond vertical into deep flexion. EMG activity within the paraspinal muscles increased while extension was executed. During passive continuous cyclic movement the trunk motion was controlled by an external mechanical system to isolate the movement from fatigue. A significant decrease in the torque supplied by the posterior passive tissues was observed. EMG amplitudes remained relatively low during the passive session. A significant increase in the EMG amplitude and frequency was observed during active flexion movements performed after the passive session. Evidence suggests the primary control mechanism of the FRP to be mechanical in origin for acute loading. Decrease stability of the spine may occur with prolonged repetitive trunk flexion-extension. The increased duration of the FRP during continuous cyclic flexion-extension suggests neural mechanisms may supersede mechanical mechanisms during repetitive lifting activities.
| Identifer | oai:union.ndltd.org:LSU/oai:etd.lsu.edu:etd-03202006-080052 |
| Date | 21 March 2006 |
| Creators | Olson, Michael William |
| Contributors | Ram Devireddy, Jim Belanger, Richard Magill, Moshe Solomonow, Li Li |
| Publisher | LSU |
| Source Sets | Louisiana State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lsu.edu/docs/available/etd-03202006-080052/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached herein a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to LSU or its agents the non-exclusive license to archive and make accessible, under the conditions specified below and in appropriate University policies, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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