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Webinar: OpenSim Framework to Estimate Muscle Dynamics with Elastic Exoskeletons

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  • Webinar: OpenSim Framework to Estimate Muscle Dynamics with Elastic Exoskeletons

    The OpenSim Project and the National Center for Simulation in Rehabilitation Research (NCSRR) at Stanford invite you to join our next webinar, featuring Dominic Farris from the University of Queensland and Gregory Sawicki from North Carolina State University and UNC-Chapel Hill.

    Title: An OpenSim Framework to Estimate Muscle Dynamics during Locomotion with Elastic Exoskeletons
    Speakers: Dominic Farris, The University of Queensland
    Gregory Sawicki, North Carolina State University and UNC-Chapel Hill
    Time: Thursday, February 6, 2014 at 2:00 p.m. Pacific Standard Time

    Engineering advances have ushered in a new class of biomechatronic machines, robotic exoskeletons that can be worn by humans to either enhance or restore locomotion performance. A key goal of our recent work is to incorporate these exoskeletal devices into a modeling and simulation framework to begin to address muscle-level responses to mechanical assistance. Ultimately we hope this approach will evolve into a design tool that engineers can use to fit and prescribe optimal device parameters (e.g., stiffness) that meet specific performance objectives.

    Inspired by biological elastic mechanisms, we have developed a class of ankle exoskeletons that uses elastic storage and return of energy in springs acting in parallel with the plantarflexor (PF) muscles in order to reduce the metabolic cost of locomotion. While it is clear that such devices help unload biological tissues, they may also cause side-effects and perturb the 'tuned' muscle-tendon interaction of PFs. To test the effects of our new device, we collected data from seven participants with and without elastic ankle exoskeletons. We also used OpenSim to simulate muscle-tendon dynamics and metabolic energy expenditure to establish a more direct link between the two. We found that providing exoskeleton assistance to reduce forces on compliant muscle-tendons may lead to non-intuitive and potentially unfavorable shifts in muscle operating length and velocity, making force production less economical. Furthermore, reductions in whole-body metabolic cost need not come from reduced forces at the joint local to exoskeleton assistance -- but could result from altered posture at other joints along the kinetic chain.

    In this presentation, we will discuss:
    • The utility and drawbacks of simple 'lumped' muscle-tendon models of ankle-driven hopping with exoskeletons
    • Development and implementation of an OpenSim-based approach to simulating muscle dynamics with and without ankle exoskeletons
    • Results from simulations of ankle muscle dynamics during hopping in elastic ankle exoskeletons

    For the complete abstract of the webinar, visit:

    Participation is free, but you must register in advance. We also ask that you join the webinar 5 minutes early to orient yourself to the webinar interface.

    Visit our website for more information and registration. The website also includes links to recordings of past webinars:

    The OpenSim Webinar Series is funded by the NIH National Center for Simulation in Rehabilitation Research (NCSRR). Find out more about the NCSRR and the webinar series by visiting our website,