Human body modeling has been undertaken in both the fields of biomechanics and computer graphics. Historically, each approach has lacked some of the advantages of the the other. This project further develops one model used for human task studies and computer animation by improving motion realism and facilitating user interaction with the model. Realism is provided by an interface that links a general purpose mechanism simulator with the JACK graphics environment and a prototype human figure with realistic mass and joint properties based on studies in the biomechanics literature. Improved interaction is achieved through software tools which can position several of the figures joints simultaneously. Also, a tool is developed for calculating the mass and inertia properties of an arbitrary polyhedron based on its geometry and an assumption of constant density. Finally, suggestions are offered for future study.