Fall 2025

Abstract 

The glenohumeral joint’s stability is primarily achieved through muscular activation rather than bony constraints. This talk will start with an analysis of in vivo subject specific variability in glenohumeral translations measured with biplanar fluoroscopy. This will be followed by an overview of our development of subject-specific, 6 DoF glenohumeral joint models, including our efforts to dynamically couple finite element and multibody dynamics methods to produce more biofidelic loading scenarios for shoulder treatment development.

Abstract 

Muscle models are essential for our understanding of muscle function. While traditional models may work well for single fibres during steady contractions, their performance is much worse for whole muscles during natural behaviours. This presentation will consider different aspect of physiology and mechanics that influence the forces that muscles develop, how these features can be incorporated into muscle models, and the insights that we gain about how muscle design and use is related to whole muscle energetics and mechanical performance.

Spring 2026

Abstract 

Since Anderson’s “More is different” and Schrödinger’s “What is life?”, physics has appreciated that the rules governing living systems may be irreducible to elemental components and hence emergent. Their composition matters. Locomotion arises from interacting physiological systems (neural, mechanical, muscular) all mediated through feedback from the environment. What sets living systems apart from simple active matter is that evolution has tinkered with this composition to produce behaviors that afford function. One of the most successful evolutionary examples of movement is the vast diversity of insect flight. Energetic costs to fly at small body sizes are high, dynamic stability is difficult to ensure, and yet thousands of insect species fly, often with quite different wingbeat frequencies, mass, and wing morphology. In this talk, I will use the agile flight of insects to show how an organismal physics approach can give insights into this emergent functionality. I will show how nearly all insects operate as resonant “spring-wing” systems to power flight. This reduces the inertial power costs to accelerate their wings on each stroke. But contrary to the prevailing idea that many insects must operate at their resonant frequency, we find that they are in fact supra-resonant, flapping at frequencies often well above what would seem ideal. This arises from constraints on how muscle functions, but can also be functionally useful because rapid modulation and control of resonating wings would be quite difficult. We will then explore how insects have evolved two different strategies for powering this resonant flight system using muscles that either provide periodic oscillatory forcing or use a stretch-responsive activation to set up self-excited limit cycles. While these two strategies seem dichotomous both in their evolution and their physics, we find that they can be unified in a single dynamic systems framework that shows how major evolutionary transitions reflect transitions in emergent dynamics. We embody this framework in robotic models and test the parameter space for flapping flight. We find that these two dynamic regimes are separated by a classic entrainment boundary but also bridged by a region of parameter space enabling smooth transitions between the two flight modes. Our biophysical models help explain the repeated transitions and diversification of insect flight strategies.

Abstract 

When people walk, they don’t merely take steps but, instead, they aim to accomplish certain tasks, such as maintaining a desired speed or heading. Laboratory observations of human walking support the general hypothesis that stepping regulation is optimal with respect to task-dependent goals. This hypothesis has been tested by analyzing stepping time series with linear update models based on multi-objective error minimization. Such models explain the statistical structure of stepping fluctuations in a way that, for example, global energy minimization cannot. We review how these experimental findings uncovered the goal-equivalent structure of stepping regulation in human walking. We then discuss how these empirical regulation strategies can be grounded in physics-based dynamic walking models. In the sagittal plane, such integrated template models reveal that goal-directed stepping greatly enhances a walker’s ability to reject large disturbances, and suggests a mechanism for fall recovery by a process of task switching. Models for lateral stepping capture and explain the statistical structure of observed stepping behavior in terms of competing costs, and demonstrate the existence of semistable goal-equivalent setsS of steady gaits: perturbations off of any one gait typically return to a different gait in the set satisfying the same stepping goals. Semistable dynamics provides a walking paradigm that is much less constraining than provided by asymptotically stable limit cycles and, therefore, is more suitable for biological walking, which is characterized by its flexibility and adaptability.

Abstract 

TBA

Abstract 

TBA

Abstract 

Locomotion has played a key role in the evolutionary adaptive strategies of primates. Although primates exhibit a wide diversity of locomotor behaviors, arboreal quadrupedalism is considered to be the ancestral form of locomotion for primates. Decades of laboratory research on primate quadrupedalism has revealed that primates are distinctive in their quadrupedal biomechanics compared to most mammals, and controlled experiments have attempted to discern which aspects of the arboreal environment might have been critical during the evolution of these biomechanical features. However, lab-studies are necessarily limited in recreating the complexities of the arboreal environment. A more ecologically relevant understanding of primate quadrupedalism requires analysis of primates moving in their natural habitats. In this talk, I will review what is unique about primate quadrupedalism and then discuss how I have used both lab and field-based techniques (videography and remote measurement of substrate characteristics) to obtain further insight about the adaptation and evolution of primate quadrupedal kinematics.