| dc.description.abstract | In the United States, 28.7% of adults aged 65 or older experience a fall every year, amounting to an estimated 29 million falls. Of these falls, 7 million result in injuries that require medical treatment and contribute to an estimated $50 billion in medical costs. Even when provided proper medical care, fallers experience lasting mobility problems and face an increased risk of future falls, creating a vicious feedback loop of falls and injury. Though seemingly mundane, maintaining balance is a precarious act, requiring the body to overcome one of the most ubiqiutous forces in the universe – gravity. To do so, the body must constantly monitor conditions, both internal and external, and initiate fine muscular contractions to remain upright. One of the primary contributors to falls in older adults is visual, vestibular, and somatosensory degeneration, which dampens sensory input and limits an individual’s ability to produce well-informed, coordinated movements and overcome physical obstacles. Because these changes can initially be very subtle, predicting the first fall, and therefore preventing the vicious fall-injury cycle, can be incredibly challenging. Thus, the need for more sensitive measures of balance is apparent. The present work aims to tackle this gap in measurement through the evaluation of physiologically-inspired measures of sway and their relation to changes in sensation ability. More specifically, this work will capture the individual contributions and integration of vision, vestibular sense, and somatosensation as well as evaluate potential opportunities to augment sensation through the use of vibratory stochastic facilitation. This dissertation contains three specific aims, (1) characterizing sway behavior during a simulated, progressive decline in somatosensory function, (2) quantifying the influence of vision, vestibular sense, and somatosensation on underlying postural control mechanisms, and (3) investigating the effect of subthreshold vibratory noise on postural sway. In all of these aims, analysis will employ rambling-trembling decomposition of the center-of-pressure, a method that seeks to understand motion from mechanistic perspective by separating sway into rambling (central, supraspinal) and trembling (peripheral, spinal) components. Across these three studies, it is apparent that spinal control mechanisms, as opposed to supraspinal, are influenced most significantly by sensorineural input (or lack thereof). In healthy individuals facing sensory challenges, such as those included in this work, this is indicative of an intact ability to set and reset an equilibrium point, but an impaired ability to enact this “plan,” creating a large discrepancy between planned and actual motion. Though more work is required to fully understand this effect, the present work serves as a foundation for future investigations that will include a wider variety of sensory challenges and clinical populations. With this knowledge, we may one day be able to enhance fall risk assessment techniques and rehabilitation practices using a more efficient, targeted approach. Ultimately, these advancements may reduce the prevalence of geriatric falls and improve overall quality of life with age. | |
