Provided is at least one chemical entity chosen from compounds of Formula
I and compounds of Formula II: ##STR00001## and pharmaceutically
acceptable salts thereof, compositions thereof, and methods for their use
in modulating of one or more of skeletal myosin, skeletal actin, skeletal
tropomyosin, skeletal troponin C, skeletal troponin I, skeletal troponin
T, skeletal muscle, and skeletal sarcomere.