CAREER: Establishing Links between Musculoskeletal Morphology and the Biomechanics of Bipedal Hopping in Desert Environments

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Movement through their environments is a fundamental characteristic of most animals, (e.g., running, swimming, flying) and the mechanics of how animals perform this task have direct implications for evolutionary success because locomotion is involved with defense, finding mates, and foraging for food in efficient ways. For centuries, biomechanics research has provided a foundation for developing and testing hypotheses ranging from general governing principles of terrestrial locomotion to specific relationships between form and function of limbs and muscles. However, the vast majority of these studies have been conducted in laboratories on treadmills and tracks that bear little resemblance to the environments in which animals actually live. To truly understand the relationship between an animal's muscular and skeletal anatomy and locomotor performance, it is necessary to understand the mechanical demands of the tasks performed in the animal's natural environment. Understanding these relationships in natural habitats remains an important challenge. Therefore, the goal of this study is to examine the relationships between anatomy and locomotor performance through a series of experiments aimed at understanding in detail how different muscles contribute to movement tasks. Experiments will reveal how specific features of muscles and skeletons impact the function of particular muscles during locomotion in mechanically challenging natural environments. The outcomes of this research will advance knowledge about the functional roles of individual muscles, a topic that is rare in comparative biomechanics studies, and lay the groundwork for a better understanding of how mechanical energy is transferred through complex musculoskeletal systems. Application of this knowledge can lead to improvements in the design of autonomous robots, lower limb prosthetics, and other human locomotor enhancement devices.The purpose of this research is to elucidate the relationships between musculoskeletal morphology and bipedal hopping dynamics in desert environments using desert kangaroo rats (D. deserti) as an animal model. It is generally believed that bipedal hopping has evolved because it provides a locomotor performance advantage (e.g., faster top speed, higher endurance, acceleration capacity) related to exaggerated hind limb morphology; however a specific advantage has not been identified for all hopping species. To achieve the proposed objectives, this study will incorporate analyses of habitat use in the field, gait dynamics in the lab, in-vivo muscle dynamics and detailed computer modeling and simulations. This will be the first study to combine all of these methods to provide a comprehensive understanding of the relationships between musculoskeletal morphology and performance. This powerful, integrated approach will be used to pursue two specific research objectives: 1) Quantify the mechanical demands of bipedal hopping on substrates and terrain utilized by D. deserti in their natural environment and, 2) Elucidate the relationship between musculoskeletal morphology and habitat use. The outcomes of the proposed research will establish direct links between locomotor performance under natural conditions and musculoskeletal morphology and muscle function in a way that has not been previously possible. An enhanced understanding of how and why animals hop will advance the fields of evolutionary biology, comparative anatomy, and biomechanics, and lead to improvements in the design of autonomous robots, lower limb prosthetics, and other locomotor enhancement devices. This proposal supports an Educational Plan to develop a field course to provide an opportunity for students to integrate what they have learned about ecology and evolution through research-driven, field-based analyses of habitat use, functional morphology, and behavior. Data for behavior and habitat use from multiple years of this course will provide a broader context for interpreting morphological and biomechanical results.