This project is about developing a muscle model in OpenSim that demonstrates properties of muscle fatigue. This muscle model will also take into account fiber composition and some considerations for orderly recruitment of muscle fibers. This model is still a work in progress and was developed as part of 4-week project for a class on the modeling and simulation of human movement. A more detailed description and documentation of the model can be found on the OpenSim support page at http://simtk-confluence.stanford.edu:8080/display/OpenSim/Design+of+a+Fatigable+Muscle