Michael Granatosky is an evolutionary biomechanist primarily interested in the origins of quadrupedal locomotion. He received his Ph.D. from Duke University and worked as a postdoctoral scholar at the University of Chicago. Granatosky has been collecting biomechanical data for 10+ years from over 75 tetrapod species, including tigers, red pandas, sloths, and crocodiles. He is considered one of the leading experts in the analysis of animal motion data.
Dr. Granatosky’s research explores locomotor biomechanics in a comparative evolutionary framework to address the overarching question: How to build a quadruped? Quadrupedal locomotion is a complex form of movement that requires animals to coordinate multiple oscillating anatomical and neurological components across space and time. The neural and musculoskeletal substrates for quadrupedal movement are ancient and represent the primitive condition on which all other tetrapod locomotor modes are based. As such, explorations of important evolutionary events such as the fin-to-limb transition, the advent of flight, or the origins of bipedalism must be based on a sound knowledge of quadrupedal gait mechanics.
With these considerations in mind, the question of “How to build a quadruped?” becomes a fascinating area of inquiry that requires a collaborative and interdisciplinary investigative approach. Current projects in his lab that address this broader research agenda include using “walking” fish and phylogenetic analyses of quadrupedal gaits to investigate neuromuscular evolution during the fin-to-limb transition, exploring the importance of proprioceptive sensory information in dictating performance during quadrupedal locomotion, and building bio-inspired robots to test evolutionary hypotheses about the origins of quadrupedal gaits.
- Assess the importance of sensory feedback for locomotor performance in tetrapods
When you or I walk, the way we move and load our limbs is remarkably consistent from step-to-step. This same pattern is observed in other mammals and birds. However, when one looks at locomotor characteristics of say a turtle, gecko, or alligator, a different story emerges. For these animals, spatiotemporal gait characteristics and limb-loading are highly variable. These differences among tetrapods are hypothesized to be a result of derived neuromuscular adaptions (e.g., Golgi tendon organ morphology, enlarged cerebellum, and γ-motoneuron innervation of muscle spindles) in birds and mammals compared to other tetrapods. By utilizing these “natural experiments” in sensorimotor evolution and animal models with targeted somatosensory loss, my lab explores the effects that proprioceptive sensory feedback has overall locomotor energetics, the ability to recover from unexpected perturbations, and bony safety factors.
- The evolution of the muscle spindle during the fin-to-limb transition
One of the greatest, but often underappreciated, innovations that occurred as tetrapods made their first forays onto land was the evolution of muscle-spindles, stretch receptors within the body of a muscle that primarily detect muscular length changes. While muscle-spindles have not been observed in non-tetrapod gnathostomes, certain benthic “walking” fishes do demonstrate an elaboration of free-nerve ending that have been hypothesized to report similar sensory feedback. However, there exists no experimental data to support this claim. This new project combines techniques in histology, neurophysiology, and locomotor biomechanics to assess the functional role of these elaborated free-nerve endings in “walking” fishes and explores hypotheses about the initial origins and importance of muscle-spindles during the fin-to-limb transition.
- Using bio-inspired robotics to explore the evolutionary origins of gait
Mechanically, there is an almost infinite combination of ways a quadrupedal animal can coordinate its limb movements and timing to achieve an effective gait. However, a survey of living quadrupedal animals reveals only a limited number of limb coordination patterns. My lab seeks to understand why animals are limited in the way they use their limbs by using a bio-inspired robot that accurately matches the movements of a blue-tongued skink (Tiliqua scincoides). Blue-tongued skinks are remarkable model systems to explore the evolutionary origins of quadrupedal gaits because they are often utilized as an anatomical representative of early tetrapods and use a combination of “belly-dragging” and “high-stepping” steps while walking. However, the use of a bio-inspired robot allows us to alter aspects of the anatomy and motor control and directly assess how these changes alter overall system energetics and stability. Such manipulation is not possible with living animals.
- Cullen, M. M., D. Schmitt, M. C. Granatosky, C. E. Wall, M. Platt, and R. Larsen. 2020. Gaze-behaviors of runners in a natural, urban running environment. PLOS ONE 15:e0233158. Public Library of Science.
- Granatosky, M. C. 2020. Testing the propulsive role of m. peroneus longus during quadrupedal walking in Varanus exanthematicus. Journal of Experimental Zoology Part A: Ecological and Integrative Physiology, doi: 10.1002/jez.2361.
- Granatosky, M. C., E. J. McElroy, P. Lemelin, S. M. Reilly, J. A. Nyakatura, E. Andrada, B. M. Kilbourne, V. R. Allen, M. T. Butcher, R. W. Blob, and C. F. Ross. 2020. Variation in limb loading magnitude and timing in tetrapods. J. Exp. Biol. 223.
- Granatosky, M. C., and C. F. Ross. 2020. Differences in muscle mechanics underlie divergent optimality criteria between feeding and locomotor systems. Journal of Anatomy 237:1072–1086.
- Usherwood, J. R., and M. C. Granatosky. 2020. Limb work and joint work minimization reveal an energetic benefit to the elbows-back, knees-forward limb design in parasagittal quadrupeds. Proceedings of the Royal Society B: Biological Sciences 287:20201517. Royal Society.
Courses Taught at New York Tech
- Form and Function: From genotype to phenotype