Heat therapyHeat therapy is a form of physiotherapy used in many painful conditions eg. arthritis, sprains, muscle spasms etc. It is of 2 types depending on the penetration of heatSuperficial heat therapy Deep heat therapyA) Superficial heat therapyOnly the skin and subcutaneous tissues are heated Superficial heating modalities do not heat deep tissue because the subcutaneous layer of fat beneath the skin surface acts as a thermal insulator and inhibits heat transfer. Superficial heating modalities include :Hot warm bottle                                                                                                       Warm bath                                                                                                               Hot packs (eg. Kenny pack) Hot soaks or compresses Paraffin wax bath                             Moist air cabinet Chemical packs Infrared lampB) Deep heat therapyDeeper structures (including muscles) are heated In general, the transfer of heat is of three types- conduction, convection & conversion (or radiation) Whereas superficial heating modalities use all three modes of transfer of heat; deep heating modalities use only conversion or radiation method to heat the deep tissues. Deep heating modalities area) Shortwave diathermyHeat generated by high-frequency alternating current using a shortwave diathermy emitter.b) Microwave diathermyThis uses electromagnetic radiation energy to heat the deep tissuesc)   Ultrasound therapyUses high-frequency sound energy