Browsing by Author "Burks, William Garret"
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- The Impact of Lower Limb Dominance on Side-to-Side Symmetry in Daily Living and Sports-related TasksScott, Tyana (Virginia Tech, 2023-06-30)Evaluating side-to-side symmetry in the lower extremity has been significant in assessing injury risk and the success of rehabilitation programs. Considering limb dominance in the lower limbs is also important as limb dominance could influence symmetry measures. There is a need to assess symmetry, particularly in healthy populations, in tasks other than walking and running and establish how the dominant limb can impact symmetry. By evaluating symmetry in healthy adults, how the limbs function with respect to one another can be determined. Therefore, the first purpose of this study was to investigate the impact of lower limb dominance on walking and sitting-to-standing. Data was collected from 49 healthy older adults, aged 50-89 years old. Using loadsol® sensors (Novel, St. Paul, MN, USA), plantar loading data such as peak impact force and loading rate was calculated. Participants completed one sit-to-stand trial and three 10-meter walking trials, as these serve as prime examples of daily activities. The secondary purpose of this study was to assess the impact of lower limb dominance on athletic tasks like running and agility. The pedar-X® pressure insoles (Novel, St. Paul, MN, USA) were used to collect plantar loading data such as peak force, contact area, and contact time, from 10 athletes. Participants completed five t-drill trials and five agility ladder drill trials. The acceleration phase of the t-drill served as standard running. A mixed effects model was used to test if differences existed in various plantar loading outcome measures based on limb dominance. Non-parametric tests were used for non-normally distributed data. The statistical analysis determined that no significant differences existed between the dominant limb and non-dominant limb for the 10-meter walking trials peak impact force (p=0.245) or average loading rate (p=0.943). During the sit-to-stand trial, no significant differences existed in peak impact force (p=0.317) or average loading rate (p=0.943). For the agility ladder drill, the maximum force (p=0.427), contact area (p=0.517), or contact time (p=0.734) showed no significant differences. In the T-drill, the maximum force (p=0.385), contact area (p=0.571), or contact time (p=0.571) had no significant differences. These drive the conclusion that limb dominance does not need to be considered when assessing side-to-side symmetry.
- Modeling and Manufacturing of Dynamic Vocal Folds: First Steps Towards an Active Voice-Box ProsthesisBurks, William Garret (Virginia Tech, 2020-01-22)The movement and control of the vocal folds within the laryngeal cavity enables three crucial physiological functions: 1) allowing respiration by opening, 2) aiding in airway protection by closing, and 3) regulating sound production during phonation. Although treatment options have improved, many of the estimated 7.5 million individuals in the United States who are annually affected by voice-related disorders still face serious challenges related to dysphonia and dysphagia. The need for improved voice-disorder treatments has motivated the work presented in this dissertation which focuses on modeling and manufacturing the vocal folds and aims to answer three main questions: 1) what are the mechanical properties of the vocal folds and how do they change across the full vocal range? 2) how do those properties influence the dynamic behavior of the tissue? and 3) can we manufacture a synthetic vocal fold model that exhibits a desired and controllable dynamic behavior? First, the elastic properties of sixteen porcine vocal folds were evaluated through uniaxial tensile tests on a custom built experimental setup. Stress-strain data was analyzed using an optimization method to yield continuous model parameters which described the linear and nonlinear elastic regions as well as transition points between those regions. Next, the impact of the vocal fold elastic properties on the frequencies of vibration was evaluated through dynamic tests on excised porcine larynges. Sound data was analyzed via a spectrogram and through the use of fast Fourier transforms to study changes in the frequency of vibration while the vocal folds were stretched. Additionally, a mathematical aeroelastic model of phonation was implemented to further evaluate the changing elastic properties on vocal fold dynamics. Next, eight synthetic vocal fold models were created, each with varying mechanical properties and a geometry based on reported anatomical measurements of porcine vocal folds. The synthetic models were then dynamically tested to further study the impact of changes in mechanical properties on the dynamic behavior of the synthetic vocal folds.