Type of Document	Master's Thesis
Author	Matrangola, Sara Louise
Author's Email Address	smatrang@vt.edu
URN	etd-07162008-101646
Title	A Modeling Investigation of Obesity and Balance Recovery
Degree	Master of Science
Department	Biomedical Engineering
Advisory Committee	Advisor Name Title Madigan, Michael L. Committee Chair Davy, Kevin P. Committee Member Nussbaum, Maury A. Committee Member
Keywords	modeling obesity balance recovery
Date of Defense	2008-07-15
Availability	unrestricted
Abstract Obesity is associated with an increased risk of falls and subsequent injury. Previous studies have shown weight loss and strength training to be beneficial to balance, but knowing which is more beneficial will allow researchers to design interventions to maximize the benefits in terms of balance and reducing risk of falls. Therefore, the purpose of the first study was to evaluate the effects of weight loss and strength training on balance recovery using a combination of laboratory experiments and mathematical modeling. Nine male subjects with BMI 30.1 to 36.9 kg/m2 were released from a forward lean and attempted to recover balance using an ankle strategy. Lean angle was increased until subjects required a step or hip flexion to recover balance. The maximum lean angle, θmax, was used as the measure of balance recovery capability. Experimental data were used as inputs to an inverted pendulum model of balance recovery. Multiple simulations were used to determine the effects of strength (maximum ankle torque and ankle torque generation rate) and weight loss on θmax. Changes in weight and strength were linearly related to changes in θmax. A 6.6 ± 0.4% decrease in weight or 6.9 ± 0.9% increase in strength were estimated as required to improve (increase) θmax by 1 degree. Based on these results, balance recovery using an ankle strategy can improve with either reductions in weight or increases in strength. In addition, weight loss may be a more effective intervention than strength gain at improving balance recovery capability. The purpose of the second study was to quantify changes in body segment inertial parameters (BSIPs) with weight loss. These data were needed to alter BSIPs in the first study to mimic changes with weight loss. Both before and after weight loss, magnetic resonance imaging scans were acquired along the length of the body and were used to calculate segment masses, COM positions, and radii of gyration. A number of significant changes in BSIPs occurred with weight loss.
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