Many occupational groups work under adverse conditions in which their spinal columns are fully flexed under load for substantial periods of time. This study was designed to determine the response of the lumbar spine to a static load of a substantial duration under a range of load magnitudes. The impact of static loads of 20, 40 and 60N were applied over 30 min flexion, 10 min rest, and 30 min flexion (for a total of one hour exposure) followed by a 7 h rest. Lumbar viscoelastic creep (laxity) and reflex electromyographic (EMG) activity were monitored over both flexion periods and the 7 h rest period. It was found that 10 min of rest was not sufficient for complete recovery of the creep developed in the first 30 min of flexion resulting in a large cumulative creep at the end of the work-rest session. Muscle activity indicated spasms during the static flexion periods and demonstrated the development of initial and delayed hyperexcitability in each of the 3 loads. Larger magnitudes of initial and delayed hyperexcitability were observed for larger loads although the differences were not statistically significant. Thus, intense periods of static flexion will result in neuromuscular disorders regardless of load magnitude. The results of the 3:1 work-rest ratio were compared with previously obtained data of a series of short static flexion periods (1:1 ratio) of the same cumulative time to determine which can best expedite the recovery of creep. Although the valuable effects of a 1:1 work-rest ratio have been documented (Sbriccoli, 2004), a 3:1 work-to-rest duration ratio was not sufficient to attenuate or prevent the development of any of the components of a neuromuscular disorder and the associated microdamage and inflammation. In conclusion, a cumulative low back disorder was elicited from exposure to two 30 min static loads spaced by a 10 min interval.
| Identifer | oai:union.ndltd.org:LSU/oai:etd.lsu.edu:etd-07062004-145926 |
| Date | 08 July 2004 |
| Creators | LaBry, Rebecca Victoria |
| Contributors | Li Li, Moshe Solomonow, Todd Monroe |
| 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-07062004-145926/ |
| 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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