C. Kotson, E. Warnecke, K. Ackerman, L. McCallum, A. D. Gidley

Gonzaga University, Spokane, WA

Parkinson’s disease is a neurodegenerative disorder kinematically characterized by a hunched posture and freezing at gait initiation. Visual cues and obstacles are used therapeutically to assist patients during gait initiation. PURPOSE: To determine the effects of Parkinsonian posture and obstacle clearance on center of pressure (CoP) and ground reaction force (GRF) variables during quiet standing and gait initiation in young adults. METHODS: Five male and five female college students quietly stood on a force plate for five seconds, initiated gait with their right foot upon hearing an audible prompt, and then walked for three meters. Participants completed this procedure for three trials in the following four conditions: no obstacle (NU) and over a two-inch-high obstacle (OU) in their normal posture and no obstacle (NP) and walking over the two-inch-high obstacle (OP) in a Parkinsonian posture with 25 degrees of trunk flexion. Means of several computed CoP and GRF variables were evaluated between the two postures for quiet standing (t-test) and across the four conditions for gait initiation (ANOVA) (α = .05). RESULTS: During quiet standing, there were no significant differences between the normal and Parkinsonian postures in CoP distance, displacement, velocity, jerk, and maximum or minimum values; however, the minimum (backwards) anteroposterior position was different (NP=-0.015 ± 0.02, NU=-0.010 ± 0.007, p=.021). During gait initiation, there were significant differences in mediolateral impulse between NU and NP (NU=-83.2 ± 13.4, NP=-63.2 ± 12.4, p=.006), and between NP and OU (NP=-63.2 ± 12.4, OU=-79.8 ± 13.6, p=.033). There were also significant differences (p<.05) in maximum mediolateral force (NP>OU), minimum mediolateral force (NP>NU, NP>OP, and NP>OU), and maximum vertical force (NU>NP), though there were no significant differences (p>.05) of any variables between NU and OP. CONCLUSION: Stepping over an obstacle while assuming a Parkinsonian posture resulted in mediolateral mechanical variables during gait initiation that were more like those of normal walking compared to walking without an obstacle in that same posture. This finding may help explain why patients with Parkinson’s disease who experience freezing of gait are able to initiate gait more easily when stepping over an obstacle.

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