Investigating high-risk biomechanics in agricultural work
Doud, Devon Michael
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Statement of Purpose: Osteoarthritis, a debilitating disease resulting in cartilage degradation and loss of mobility, is often instigated by injury or excessive loading of unconditioned articular cartilage. Although agricultural laborers are especially at risk of developing osteoarthritis, quantitative characterizations of occupation-specific activities have not previously been established. Deep flexion movements common to these groups (e.g., squatting or kneeling) may cause excessive contact forces on unconditioned cartilage, potentially initiating osteoarthritis development. Additionally, although cognitive loads can significantly alter gait mechanics, the effects of dual-task conditions (e.g., visual Stroop tests while walking) on contact forces have not previously been established. The purpose of this thesis is to better understand potential factors of osteoarthritis development in agricultural laborers by investigating occupational-specific movement patterns and joint loading during common occupational tasks. Methods: The first study evaluated seasonal differences in activity levels for farmers and ranchers by measuring movement intensity via wearable triaxial accelerometers. We hypothesized that ranchers would exhibit consistently high activity levels and that both groups would show an increase in movement intensity in their respective high seasons. The second study sought to establish the effects of cognitive challenges on tibiofemoral contact forces during normal gait and kneel-to-stand transitions in healthy adults. We hypothesized that dual-task conditions would correspond with increased peak tibiofemoral contact forces and that these forces would be positioned farther from the joint center along the mediolateral axis during dual-task conditions. Results: The first study findings largely supported the hypothesis: increased movement intensity during high seasons were recorded for both groups, with farmers exhibiting a larger seasonal fluctuation for moderate intensity activities. The second study did not support the hypothesis: cognitive loading did not significantly affect the magnitude of peak contact forces, and peak contact forces occurred closer to the joint center during dual-task conditions than during single-task conditions. However, post hoc analysis suggested that other portions of the contact force time series during stance phase were affected by cognitive challenges. Conclusions: This thesis provides foundational steps in understanding potential contributing factors of osteoarthritis development in agricultural laborers, directing future investigations towards transitional contact forces in movements simulating livestock handling.