Provided are certain chemical entities, and methods of use to modulate skeletal myosin, skeletal actin, skeletal tropomyosin, skeletal troponin C, skeletal troponin I, skeletal troponin T, and skeletal muscle, including fragments and isoforms thereof, as well as the skeletal sarcomere, and methods of use in the treatment of muscle weakness and/or cachexia, as part of a rehabilitation or conditioning exercise regimen, or in the treatment of fraility, post-polio syndrome, obesity, sarcopenia, wasting syndrome, muscle spasm, and other indications.