Therapy with microwaves is classified as high frequency therapy. The one thing the varying frequencies used in high frequency therapy have in common is the fact that warmth is created in the tissue under their influence.
Microwaves are applied using the radiation field method, which applies beams of electromagnetic waves to the tissue depending on the usage of emitters of varying shapes and sizes. The energy from these waves is directly absorbed in the tissue and makes it warm. The penetration of the microwaves is inferior compared to shortwaves. Microwave therapy is the preferred application if you want local heating of the muscles or connective tissue structures, such as ligaments, sinews, capsules, etc.