Our model is built upon the OpenSim 3.x “Full Body Model for use in Dynamic Simulations of Human Gait” (Rajagopal, et al.) https://simtk.org/projects/full_body. With the addition of joints separating the upper body into multiple segments, the modified multi-joint (MJ) model has been adapted for use with a variety of resistive and aerobic exercise motions (e.g., squats, rowing, cycling, etc.). Subsequent modifications to the model have since been made to facilitate Inverse Kinematics of more complex motions (e.g., chops, hang clean, overhead press, etc.) and updated for use in OpenSim 4.x.