Thesis Defense Announcement

The School of Health Studies announces the Final Thesis of

Ramzi Majaj

for the Degree of Master of Science

March 29, 2018 at 11:00 AM in Elma Neal Roane Field House

Advisor: Max Paquette

Ankle Kinetics and Plantarflexor Morphology in Older Runners with Different Lifetime Running Exposures

ABSTRACT: Aging is related to a decline in physical function, cardiovascular health and quality of life. Changes in locomotor function including slow gait speeds contribute to the negative health outcomes of aging. Running promotes better cardiovascular health and has positive effects on the musculoskeletal system in older adults. However, older adults have lower ankle moments and positive powers during running, and exhibit changes in plantarflexor morphology compared to young adults. These age-related changes contribute to slower running speeds and reduced movement intensity. Older runners who run as much as younger runners exhibit youthful ankle mechanical outputs. Therefore, running exposure may preserve the locomotor factors that mediate movement speed. PURPOSE: To compare ankle mechanical output during running and plantarflexor morphological characteristics between older runners who have low or high lifetime running exposure. It was expected that older runners with high lifetime running exposure would have larger ankle mechanical output during running and more youthful plantarflexor morphological characteristics compared to runners with low lifetime running exposure. METHODS: Twelve older runners with low and eight older runners with high lifetime running exposure participated in the study. Participants performed over-ground running trials at 2.7m/s (±5%) while kinematic and ground reaction force (GRF) data were collected. Joint moments and powers were computed using kinematic and GRF data. Right medial gastrocnemius morphological characteristics were assessed using ultrasonography under static and dynamic conditions. Ankle moment and power, and plantarflexor morphology were compared between groups using independent t-tests (p<0.05) and Cohen's d effect sizes. RESULTS: Contrary to our hypothesis older runners with different lifetime running exposures ran with similar ankle mechanical output. However, older runners with high lifetime exposure ran with greater hip concentric power , despite similar hip extension torques , compared to runners with low lifetime exposure. Plantarflexor morphological characteristics were not different between lifetime running exposure groups. CONCLUSION: The findings from this study demonstrate that lifetime running exposure does not influence ankle mechanical output or plantarflexor morphology in older runners but that high lifetime running exposure may result in a proximal shift in mechanical output to improve hip joint concentric power.