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Chambers, April Jeannette (2005) SLIP-RELATED MUSCLE ACTIVATION PATTERNS OF THE STANCE LEG DURING GAIT. Master's Thesis, University of Pittsburgh. (Unpublished)

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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 floor's 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.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Chambers, April Jeannetteajcst49@pitt.eduAJCST49
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairCham,
Committee MemberRedfern,
Committee MemberBoninger, Michaelboninger@pitt.eduBONINGER
Committee MemberSparto, Patrickspartopj@upmc.eduPSPARTO
Date: 13 October 2005
Date Type: Completion
Defense Date: 15 July 2005
Approval Date: 13 October 2005
Submission Date: 25 July 2005
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Institution: University of Pittsburgh
Schools and Programs: Swanson School of Engineering > Bioengineering
Degree: MSBeng - Master of Science in Bioengineering
Thesis Type: Master's Thesis
Refereed: Yes
Uncontrolled Keywords: biomechanics; EMG
Other ID:, etd-07252005-133816
Date Deposited: 10 Nov 2011 19:53
Last Modified: 19 Dec 2016 14:36


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