This document discusses different types of diathermy. Diathermy uses high-frequency electromagnetic waves or ultrasound to generate heat deep in tissues to provide therapeutic benefits. There are three main types: short-wave diathermy using radio frequencies from 1-100 MHz, microwave diathermy using 915 MHz or 2.45 GHz waves, and ultrasound diathermy using sound waves. All three types aim to increase blood flow, relieve pain, and improve mobility by heating tissues from within. Common applications include treating muscle sprains, strains, and contractures.