Date of Award

5-4-2018

Degree Type

Creative Project

Degree Name

Master of Science (MS)

Department

Education

First Advisor

Chris Dakin

Second Advisor

Eadric Bressel

Third Advisor

Lori Olsen

Abstract

Stair negotiation accounts for 16% of fall related traumatic spinal cord injuries and the vestibular system plays a crucial role in fall avoidance through its role in maintaining balance during human locomotion, but its role in stair negotiation is unclear. The aim of this study was to compare the vestibular contribution to a) stair negotiation versus locomotion and b) stair ascent to stair descent in healthy young participants. It was hypothesized that, with cadence held constant, vestibular influence would increase during stair negotiation when compared to locomotion. We also expected the vestibular influence to increase during stair descent vs. ascent. The timing of muscle responses were expected to change due to differences in gait patterns. Differences in vestibular influence were analyzed using time-dependent coherence and time-independent cross-correlation. To probe the vestibular system, we used a random bandwidth limited white noise stimulus and recorded EMG signals from muscles of the lower leg, upper leg, and hip. Participants completed 300 steps on the treadmill at a cadence of 76 steps/min and a velocity of 0.4 m/s (0.9 m/h). Participants also ascended and descended a 9-step staircase for a total of 300 steps at a cadence of 76 steps/min. When comparing stair negotiation to locomotion, we found increases in mean peak coherence values across most muscles, however, only the soleus was significantly different during locomotion vs. ascent (.146 ∓ .080 vs. .259 ∓ .105, p = 0.001). Surprisingly, we also observed decreases in coherence values during stair descent vs. ascent. Finally, differences were seen in the timing of muscle responses when comparing the three conditions. For example, the medial gastrocnemius showed greatest vestibular influence before peak EMG recording during locomotion and stair ascent, but after peak EMG recording on descent. Our findings suggest that the magnitude of difference in the influence of the vestibular system is muscle-dependent. Also, the findings of this study suggest that we rely more heavily on the vestibular system during ascent than descent.

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