Heat therapy, or thermotherapy as doctors and physical therapists refer to it, is the application of either wet or dry heat to injured areas. While it can also be used to treat painful conditions like arthritis, athletes typically utilize it as a way to relieve injury pain as well as to help injuries heal quicker. As the body uses its own heat to help injuries heal, the added heat of heat therapy helps to remove joint stiffness, muscle pain and spasms, and chronic pain. The question is, when is it best to use heat therapy and not ice?