The Impact of Slip Exposure on Gait

Chambers, April Jeannette (2011) The Impact of Slip Exposure on Gait. Doctoral Dissertation, University of Pittsburgh.

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Abstract

Slips and falls are a major cause of injury in young and older adults. This research focused on investigating proactive strategies generated after experiencing a slippery surface without any additional awareness (Aim 1) and with awareness (Aim 2). The influence of aging was examined. Slip risk was assessed using required coefficient of friction (RCOF), center of mass (COM) state and general gait parameters. Slip severity was quantified using peak slip velocity. In Aim 3, a sensitivity analysis was performed on the lower extremity muscles included in a three-dimensional simulation of gait. Additionally, a preliminary comparison of the simulated muscle excitations between baseline and anticipation conditions provided insight into proactive strategies.(Aim 1) Fifty-two adults from two age groups (young/older) experienced an unexpected slip. Multiple dry trials were conducted to assess recovery gait and a second unexpected slip was collected. (Aim 2) Thirty-one young/older adults walked across a dry surface before and after experiencing a slip and with warning of another slippery surface. Slip risk and slip severity were analyzed for dry and slip trials, respectively. Overall, older adults maintained a more conservative proactive strategy than young regardless of the amount of awareness provided. This resulted in older adults experiencing less severe slips upon second exposure with and without awareness. Young adults appear to be affected by the specificity of knowledge provided. With no threat of a slippery surface, young adults eventually return to baseline levels of slip risk and a second unexpected slip can be generated. The addition of awareness resulted in young adults adopting a more conservative proactive strategy with decreased peak RCOF, amplified gait adaptations and increased COM stability compared to young adults without awareness. Consequently, young adults with awareness experienced a reduction in slip severity upon second exposure. A sensitivity analysis of a three-dimensional gait simulation revealed that the removal of one muscle was compensated by muscles in the same functional group or antagonistic muscle group. Additionally, the model was most sensitive to perturbations in tendon slack length. These findings highlight the importance of model selection and obtaining accurate estimates of muscle model parameters when modeling gait.

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