Date of Award

Winter 2001

Document Type


Degree Name

Doctor of Philosophy (PhD)


Biomedical Engineering

First Advisor

C. J. Robinson


Slips and falls, and even the fear of failing, can represent a major medical and functional deterrent to living independently, especially among the elderly population. Various groups of elders are at known risk for falling including, but not limited to, those with vestibular dysfunction, those with low visual acuity including visual neuropathies, and those with peripheral neuropathies. The first two groups are fairly well studied, but the relationship between the level of peripheral neuropathy and extent of falling has received relatively less attention.

In this study, using sliding linear investigative platform for analyzing lower limb stability (SLIP-FALLS), the psychophysical thresholds and strategies used for, detecting uItra-low-vibration horizontal translations in the elderly population (age range of 50 and 75 years) with adult-onset diabetes or peripheral neuropathy were determined. Acceleration thresholds for anterior horizontal movements of 1, 4, and 16 mm were determined. These detection thresholds were compared with healthy young adults (age < 35 years) and age-matched elders without neuropathy. The extent of peripheral neuropathy was quantified by standard clinical nerve conduction tests of the sensory and motor nerves of the lower extremity by the Neurological Service of the Overton Brooks VAMC.

Psychophysically, the acceleration thresholds have a negative power law relationship with the perturbation distance and are significantly higher for the elderly population when compared to young adults. A predictive Balasubramanian-Robinson model for determining acceleration thresholds for perturbation has been presented. Among the elderly, neurologically intact individuals were found to have a lower threshold for detection than those with neurological impairments. Conversely, the conduction velocities of the sensory and motor nerves were lower in case of the elderly with adult-onset diabetes or peripheral neuropathy. It was also found that cognitive and tactile sensory responses alone cannot be used to differentiate between the two groups of elderly. The diabetic elderly had a significantly higher lateral sway and increased reaction time for foot touch, platform perturbation, and auditory stimuli. These factors probably contribute to the increased risk of failing in the diabetic elderly.