Advanced Imaging and Assistive Devices to Uncover and Address Novel Mechanisms of Age-Related Mobility Deficits - PROJECT SUMMARY Widespread deficits in ambulatory capacity (e.g., reduced walking speed and increased metabolic cost) with age have far-reaching health impacts and are strongly associated with older adult life expectancy. Recently, the foot’s muscles and joints have been implicated in regulating gait propulsion, an important variable for maintaining walking capacity. Older adults have substantially weaker foot muscles, deficits that are associated with diminished walking speed, highlighting the foot as a key new target for mitigating age-related mobility deficits. However, traditional analysis techniques which have formed the basis of our modern understanding of gait propulsion misattribute the foot’s mechanical contribution to the ankle joint and its associated musculature. This fundamental misunderstanding of gait propulsion thereby sets the stage for elucidating the foot’s role in age- related gait impairment and highlights new targets for restoring older adult ambulatory capacity. I posit that age- related toe flexor weakness results in impaired foot joint and muscle function, contributing to mobility deficits which can be mitigated using low-cost assistive devices. Across both of the proposal’s aims, I will for the first time leverage state-of-the-art biomedical imaging, gold standard indwelling electromyography, and high-fidelity musculoskeletal computational simulation to assess age-related differences at the foot that contribute to gait deficits. Aim 1: I will capture differences in foot bone motion, foot strength, and foot muscle behavior between healthy younger and older adults to define mechanistic linkages between foot muscle weakness, foot joint and muscle behavior, and hallmark age-related propulsion deficits. Aim 2: I will then examine how low-cost assistive devices (i.e., carbon fiber shoe insoles) directly influence foot bone motion, foot muscle dynamics, and clinical measures of walking ability. Using advanced bone motion and muscle measurement in conjunction with high- fidelity musculoskeletal simulation, this proposal will substantially improve our understanding of age-related mobility impairments by uncovering the role of foot-based deficits arising from pervasive toe flexor weakness that plagues the older adult population. As such, my findings will have an immediate clinical impact on targets for future therapeutic intervention as well as ideal device design to restore older adult ambulatory capacity. Through the research training plan I have developed, I will acquire novel training in biomedical measurement modalities (i.e., computed tomography, biplane fluoroscopy, cine B-mode ultrasonography, and indwelling electromyography), clinical gait analysis, and assistive device implementation. These new skills, along with my previous expertise in whole-body motion capture and high-fidelity computational simulations, will prepare me well to embark on an independent career as a principal investigator at a research-intensive university. Specifically, I will leverage this postdoctoral training to deploy in vivo and in silico approaches to examine mechanisms underlying efficient and inefficient human movement in health and disease.
