Falls precipitated by slipping are a major cause of injury, death and disability in the elderly. This research focused on muscle activation patterns generated in response to slipping and anticipation of slippery surfaces. The goal was to identify the muscle activation patterns of the stance leg in response to an unexpected slip (reactive strategies) and investigate muscle activity when anticipating slippery floors during gait on dry surfaces (proactive strategies). Additionally, age-related differences were examined. Electromyographic recordings were made from the Vastus Lateralis, Medial Hamstring, Tibialis Anterior and Medial Gastrocnemius of eleven young and nine older adults. Participants walked during the following conditions: (1) baseline dry (subjects knew the floor was dry); (2) unexpected slip (contaminant was applied to floor without subjects knowledge); (3) alert dry (subjects were uncertain of the floors condition). Reactive strategies, which were similar among young and older adults, consisted of activation of the Medial Hamstring at around 21% stance (~ 175 ms) followed by the Vastus Lateralis at around 29% stance (~ 240 ms). Corrective responses were scaled to slip severity with more severe slip reactions consisting of longer, higher magnitude responses. Delayed Vastus Lateralis latency and Medial Hamstring cessation were associated with an increased slip severity as quantified by peak slip velocity. Additionally, when experiencing a severe slip, young adults demonstrated a longer, more powerful response compared to older adults. Anticipation of a slippery surface resulted in increased magnitude of activation (48% increase) and ankle/knee co-contraction (30% increase), as well as earlier onsets and longer durations of posterior muscles. Young adults demonstrated earlier onsets (3% stance, 24 ms) and longer durations (10% stance, 83 ms) than older adults reducing their slip potential. Finally, adults with baseline gait on dry floors characterized by greater ankle co-contraction at heel contact and delayed Tibialis Anterior onset were predisposed to experience less severe slips when encountering an unexpected slippery floor. Older adults natural gait predisposes them to experience a less hazardous slip. However, once a slip occurs, older adults cannot react with the long, powerful response needed to prevent balance loss whereas young adults are capable of this response.
| Identifer | oai:union.ndltd.org:PITT/oai:PITTETD:etd-07252005-133816 |
| Date | 13 October 2005 |
| Creators | Chambers, April Jeannette |
| Contributors | Rakie Cham, Mark Redfern, Patrick Sparto, Michael Boninger |
| Publisher | University of Pittsburgh |
| Source Sets | University of Pittsburgh |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.pitt.edu/ETD/available/etd-07252005-133816/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto 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 University of Pittsburgh or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, 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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