Human Physiology Theses and Dissertations

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Browsing Human Physiology Theses and Dissertations by Subject "Aging"

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    Balance Control and Stability during Gait - An Evaluation of Fall Risk among Elderly Adults
    (University of Oregon, 2011-09) Lugade, Vipul Anand, 1980-
    Falls are a significant source of physical, social, and psychological suffering among elderly adults. Falls lead to morbidity and even mortality. Over one-third of adults over the age of 65 years will fall within a calendar year, with almost 10,000 deaths per year attributed to falls. The direct cost of falls exceeds $10 billion a year in the United States. Fall incidents have been linked to multiple risk factors, including cognitive function, muscle strength, and balance control. The ability to properly identify balance impairment is a tremendous challenge to the medical community, with accurate assessment of fall risk lacking. Therefore, the purpose of this study was to assess balance control during gait among young adults, elderly adults, and elderly fallers; determine which biomechanical measures can best identify fallers retrospectively; demonstrate longitudinal changes in elderly adults and prospectively assess fall risk; and provide a method for mapping clinical variables to sensitive balance control measures using artificial neural networks. The interaction of the whole body center of mass (CoM) in relation to the base of support (BoS) assessed static and dynamic balance control throughout gait. Elderly fallers demonstrated reduced balance control ability, specifically a decreased time to contact with the boundary of the BoS, when compared to young adults at heel strike. This decreased time might predispose older adults to additional falls due to an inability to properly respond to perturbations or slips. Inclusion of these balance control measures along with the Berg Balance Scale and spatiotemporal measures demonstrated sensitivity and specificity values of up to 90% when identifying 98 elderly fallers and non-fallers, respectively. Additionally, 27 older adults were followed longitudinally over a period of one year, with only the interaction of the CoM with the BoS demonstrating an ability to differentiate fallers and non-fallers prospectively. As the collection and analysis of these biomechanics measures can be time consuming and expensive, an artificial neural network demonstrated that clinical measures can accurately predict balance control during ambulation. This model approached a solution quickly and provides a means for assessing longitudinal changes, intervention effects, and future fall risk. This dissertation includes both previously published and unpublished co-authored material.
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    Clinical and Laboratory Balance Assessment in the Elderly
    (University of Oregon, 2013-07-11) Chen, Tzurei; Chou, Li-Shan
    Falls can have severe consequences for elderly adults. In 2000, nearly 10,300 people aged 65 years or older died as a result of falls, and 2.6 million individuals were treated for non-fatal fall-related injuries. In order to reduce fall incidences, it is important to identify possible causes of falls, such as muscle weakness and imbalance. In this study, we examined balance control in the elderly during task transitions while performing the Timed Up and Go test (TUG). The TUG is a commonly used clinical balance test that includes transition phases between three daily activity tasks: sit-to-stand, walking and turning. Our findings suggested that elderly adults, especially fallers, have reduced balance control ability while making transitions during TUG. During sit-to-walk (STW), when compared to young adults, elderly adults demonstrated a smaller forward center of mass (COM) velocity, a smaller anterior-posterior (A-P) COM-Ankle angle, and a larger upward kinetic energy ratio at seat-off. Additionally, the medial-lateral COM control in elderly fallers was also perturbed due to their significant reduction in forward COM velocity. The reduced initial hip extensor moment and increased ankle plantarflexor moment in elderly fallers was associated with their reduced generation of horizontal momentum during STW. Smaller A-P COM-Ankle angles and taking more steps when making a turn demonstrated a reduction in balance control ability in elderly adults. Our analyses suggest that balance control is an important factor contributing to longer STW and turning durations of TUG. Furthermore, lower extremity muscle strength at hip and knee joints demonstrated a stronger association with STW than turning duration. To enhance the early detection of fall risk, we also assessed the ability of balance tests to predict future risk of falling in elderly adults. Our results indicated that biomechanical balance parameters measured during TUG were associated with future fall status. Among all biomechanical parameters investigated, frontal plane balance control parameters appear to be the most significant predictors for future falls. This dissertation includes unpublished co-authored material.
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    Effects of single- vs. dual-task training on balance performance under dual-task conditions in older adults with balance impairment: A randomized, controlled trial
    (University of Oregon, 2008-09) Silsupadol, Patima, 1975-
    Among older adults, an impaired ability to maintain balance while simultaneously performing cognitive tasks is a common occurrence. Because poor dual-task balance performance is associated with increased fall risk and a decline in cognitive function, interventions to improve dual-task balance performance are needed. Although traditional rehabilitation programs emphasizing training balance under single-task conditions are effective in improving single-task balance performance, it is not known whether single-task training generalizes to balance control under dual-task contexts. Moreover, the effectiveness of approaches to training balance under dual-task conditions is not known. Thus, the purposes of this study were to determine whether elderly individuals with balance impairment can improve their balance performance under dual-task conditions; to investigate whether training balance under single-task conditions generalizes to balance control during dual-task contexts; and to evaluate the effect of instructional set on dual-task balance performance. Specifically, the efficiency of three different training strategies was examined in an effort to understand the mechanisms underlying training-related changes in dual-task balance performance. Twenty-three elderly adults with balance impairment were randomly assigned to 1 of 3 interventions: single-task balance training (ST); dual-task training with fixed-priority instruction (FP); and dual-task training with variable-priority instruction (VP). Clinical and laboratory measures were obtained at baseline and after training. In addition, selected clinical outcomes were repeated after the second week of training to examine interim balance change and at twelve weeks post training to test retention. Results indicate that dual-task training was effective in improving balance under dual-task conditions in the elderly with balance impairment. Training balance under single-task conditions may not generalize to balance control during dual-task contexts. Explicit instruction regarding attentional focus was an important factor for improvement in dual-task performance. The VP instructional set offered advantages over the FP instructional set in terms of the degree of improvement, the rate of learning, and the retention of the dual-task training effect. The dual-task processing skills learned during training were not transferred to novel dual-task conditions. Lastly, the training benefits acquired during VP training could be the result of both automatization of the individual task and the development of task-coordination skills.
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    The Role of Attention in Fall Avoidance: Evaluation of Dual Task Interference with Postural and Visual Working Memory Tasks in Young Versus Older Adults, Does Capacity Limitation Influence Postural Responses?
    (University of Oregon, 2013-07-11) Little, Carrie; Woollacott, Marjorie
    The primary goal of this research was to explore attentional factors contributing to normal balance control and to determine how age-related changes in these factors constrain balance in the aging adult. Though previous research has demonstrated attentional interference between postural control and performance of cognitive tasks in young (YA) and older adults (OA), the mechanisms contributing to interference have not been identified. This study utilized as a cognitive task, a visual working memory task (the change detection task), which identified the short term working memory (or attentional) capacity limits of participants. Participants were asked to perform the cognitive task (determining a change in the color of squares in a first vs. second memory array) either in isolation or with postural tasks of increasing complexity, including quiet sitting (control), quiet stance in isolation, quiet stance (but intermixed with support surface perturbations), and support surface perturbations. YA showed a significant decline in working memory capacity between the control and perturbation condition (p<0.01) but no change in postural performance between single and dual task conditions, as determined by increased steps in response to perturbations (p<0.33). In a second set of experiments, the performance of OA was compared to YA. Results showed that OA had reduced working memory capacity on the change detection task compared to YA even in the control condition (YA: 2.8±0.6 items; OA: 1.8±0.7; p<0.001). OA showed an even greater decline than YA in memory capacity in the dual task condition (p<0.001), along with difficulty regaining balance following perturbations, evidenced by significant increases in up on toes (p<0.05) and stepping strategies (p<0.05). These results suggest that visual working memory (for simple features) and postural control share a common attentional resource that is limited and that postural control is favored over the cognitive task in YA. In OA, attentional capacity was significantly reduced and both postural and cognitive tasks were impaired in the dual task condition, suggesting that with aging even simple cognitive tasks can negatively affect balance under challenging postural conditions.
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    The Interaction of Mental and Neuromuscular Fatigue and the Impact of Mental Fatigue on Function Across Different Age Groups
    (University of Oregon, 2019-09-18) Morris, Amanda; Christie, Anita
    Fatigue is a multidimensional concept with physical and psychological components. While neuromuscular fatigue has been studied extensively, its effects on cognitive function have been studied, few studies have focused on its impact on cognitive function. Further, the effect of mental fatigue on neuromuscular measures or physiological outcomes is not fully understood. Three studies were conducted to determine the interactions between mental and neuromuscular fatigue and the impact of mental fatigue on function and, to determine age related differences in these interactions. Study one investigated neuromuscular function in the tibialis anterior of young and older adults (transcranial magnetic stimulation, electrical stimulation, and force measurements) before and after a 20-minute mental fatigue task. Results suggested that mental fatigue may cause increased cortical inhibition in both age groups and that 20 minutes of a mentally fatiguing task may cause a decrease in the ability to produce maximal force in young adults, providing evidence of an interaction between mental fatigue and physical function. Study two examined the effect of neuromuscular fatigue on cognitive function in young and older adults. Measures of cognitive function (reaction time and errors during a 3-minute cognitive task) were taken before and after 16-minutes of intermittent isometric contraction of the ankle dorsiflexor muscles. Neuromuscular fatigue negatively affected cognitive function (slowed reaction time) in young adults only. Results suggested that a neuromuscular fatigue task may negatively affect cognitive function in young but not older adults. Study three examined the postural response to force platform perturbations in young and older women in response to mental fatigue. Only young women experienced mental fatigue (slower reaction times) and this was accompanied by significantly faster center of pressure velocity during the mental fatigue condition compared with the control condition. Performance of the mental fatigue task, not necessarily development of mental fatigue, affects neuromuscular activation in young women only, but does not affect the magnitude of postural response to perturbation. Taken together, these studies demonstrate that there is a complex and age-specific relationship between mental fatigue and physical function and physical fatigue and cognitive function. This dissertation includes unpublished co-authored material.