This workshop covers advanced topics in OpenSim, an easy-to-use, extensible software for modeling, simulating, controlling, and analyzing the neuromusculoskeletal system. The workshop is an opportunity to learn more about how OpenSim works "under the hood" and get supervised, hands-on assistance with problems participants bring to the workshop. On the first day, a conceptual overview of OpenSim will be provided. The second and third days will be devoted to working on problems participants bring to the workshop. Participants have the opportunity to work in small breakout groups with OpenSim experts on their research problems.