MUSCULOSKELETAL FUNCTION IN THE CONTEXT OF AGING AND THE ECOLOGICAL ENVIRONMENT

Vladimir Vladimirovich Borisov

The elderly population of the United States will double over the next quarter century, reaching 72 million. Roughly one-fifth of the general population will be over 65 years of age. According to the Centers for Disease Control (CDC), annually a third of those individuals will experience a falling incident, with moderate to severe health consequences. Related to this observation, aging brings forth a steady decline in mobility and functional motor capacity. Thus, understanding how aging changes the musculoskeletal components that determine the limits of human motor performance is important for improving the general health of elderly populations. This dissertation describes the development of lower limb musculoskeletal models representative of young and older adults. Aging was simulated by adjusting functional muscle group properties: maximal isometric force, force-velocity properties, and deactivation time constants. The young adult model was modified to produce a model representing a 60-70 year old individual. The young and elderly models were refined and validated by comparison to published experimental data. The simulations agreed with the experimental data for isometric and isokinetic conditions. Forward dynamic simulations were then used to optimize power output in a bicycling task. The reduction in power output from the young and elderly models compared to experimental findings, further validating the modeling approach. The computational aspect of this research was complemented with a study determining whether elderly individuals experience changes in muscle temperatures that could compromise motor performance during activities of daily living. Measurements from body-worn sensors showed that muscle temperatures did not decrease in elderly individuals during ecologically-relevant cold challenges compared to their younger counterparts. This result indicated that compromised thermoregulation, which commonly occurs in the elderly population, does not have biomechanical implications for short term cold exposures. In conclusion, this research shows the biomechanical consequences of natural aging in humans. It is envisioned that it will be possible to build upon this research to test hypotheses and develop solutions for health trends in elderly populations. This work provides a framework for enhancing therapeutic interventions through the development of parameter monitoring schemes and mobility assessments, in the context of ecological environments.

MUSCULOSKELETAL FUNCTION IN THE CONTEXT OF AGING AND THE ECOLOGICAL ENVIRONMENT

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