One of biggest challenges in biology is understanding how "molecular motors" convert chemical energy into mechanical energy. In our muscles, two different long molecules, actin and myosin, slide along each other in one direction and generate force while breaking down molecules of adenosine triphosphate (ATP), which is the general-purpose fuel used by cells. Other molecules, such as tropomyosin, help to control the motions. Many experiments have been done to figure out things such as the speed at which these molecules move, the forces they exert, and how much ATP they burn. Also, "still pictures" of the molecules themselves have been obtained by x-ray crystallography experiments. However, the details of the motions of actin and myosin still remain a mystery. We plan to use computer models to fill in these details and perhaps shed some light on the pathology of congenital muscle diseases caused by mutations in these molecules. We will also link our models with the models of the heart developed by Prof. McCulloch's group in our department.