CAREER: Understanding the Stabilizing Role of Muscle-Tendon Units in vivo

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This CAREER project combines research, training, and educational activities that focus on advancing knowledge of how muscles and tendons function during standing and walking. It is well understood that muscles in the lower body produce forces and that tendons, which attach to muscles, transmit those forces to the skeleton, allowing animals to stand and walk. However, most current knowledge about muscle and tendon comes from experiments that study these tissues when functioning outside of the body. What is not well understood is how muscle and tendon function as an integrated system within the body and, in particular, how they function to meet the demands of maintaining balance while moving. This project will measure the mechanical behavior of muscle and tendon when the body responds to a push intended to challenge the ability to maintain balance. Integrated within the research component is training for two students from underrepresented groups pursuing a PhD in STEM. These students will gain knowledge in the field, develop first-hand experience in carrying out scientific experiments, and develop as leaders in the next generation of interdisciplinary scientists. This CAREER project will impact society by translating new knowledge about how muscle and tendon function during movement by (1) contributing design principles for biologically inspired prosthetics and (2) developing teaching units and workshops offered to students at the Multicultural Education and Counseling through the Arts (MECA) non-profit organization, which serves K-12 grade students (~4,000 underserved youth) in Houston’s historic 6th Ward.This CAREER project focuses on understanding the role of muscle-tendon units to control movement and stability using a live, freely moving animal, and integrates research, education, training, and outreach. Movement stabilization can be accomplished by several interacting mechanisms: a muscle’s force-modulating properties, the energy-modulating capacity of variable-stiffness tendon springs, and the co-behavior of agonist-antagonist muscle-tendon units. The project’s primary research objectives and outcomes are to use a work-energy based framework to: (1) Determine the muscle-tendon unit properties that modulate the rapid flow of energy absorption during active lengthening in situ. (2) Determine the properties that allow ankle joint agonist-antagonist muscle-tendon units to govern the response of destabilizing perturbations elicited during standing in vivo. (3) Determine the properties that allow ankle joint agonist-antagonist muscle-tendon units to govern the response of destabilizing perturbations elicited during walking in vivo. The experimental approach involves the use of a custom-built, high performance linear actuator to elicit unexpected perturbations to the body during standing and walking. Custom sensors implanted into muscle-tendon tissue and force platform measurements are used to understand the response to perturbations at multiple scales, from muscle-tendon units that control ankle joint function to whole body mechanics. In addition, the project will implement an educational outreach plan that will advance a summer STEM camp curriculum that serves K-12th graders from underrepresented groups. The hands-on activities to be developed will focus on key biomechanical concepts that integrate math, physics, and physical models.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.