There are three .zip files available: (1) source_plugin This includes the source files required to build the Fatigable Muscle model as a plugin that can be loaded in to the OpenSim GUI. A pre-built library file (*.dll) is also provided. (2) source_forward This includes the source files required to build a tug-of-war model with a fatigable and non-fatigable muscle and run a 60-second forward simulation (3) source_optimization This includes the sources files required to load a tug-of-war model and run an optimization to fit the fatigable muscle model parameters to experimental data. The experimental data is not provided, but please read through the objective function definition to insert the file name of your own .sto data file. A pre-made tug-of-war .osim model is also provided.