Summary
Highlights
Thermotherapy, one of the earliest physical therapies, uses heat as its primary agent. It is classified into superficial and deep thermotherapy. Superficial thermotherapy involves heat transfer through conduction (direct contact), convection (through fluids like liquids and gases), and conversion (transforming other energy into heat, e.g., infrared). Deep thermotherapy also relies on conversion, such as shortwave therapy converting high-frequency current into heat within tissues.
The human body naturally transfers heat through various mechanisms: conduction (e.g., touching another body), convection (e.g., respiration), radiation (emitting infrared waves, accounting for 60% of heat loss), and evaporation (sweat evaporating, accounting for 25% of heat transfer).
Heat directly or indirectly causes vasodilation, leading to several physiological and therapeutic effects. These include an analgesic effect (pain relief due to increased blood flow and higher excitation threshold), reduction of inflammation (by increasing elimination of prostaglandins and histamines), improved nerve conduction, and a counter-irritant effect through the gate control theory, suppressing pain signals to the brain.
Vasodilation improves cell nutrition and oxygenation, enhances metabolic product reabsorption, has a bactericidal action, reduces inflammation, acts as an antispasmodic (relaxing smooth muscles and reducing pain), and promotes tissue restoration by increasing metabolism and repair processes.
Superficial thermotherapy primarily utilizes convection (e.g., heated water rising), conduction (heat transfer through direct contact from hot to cold, like a metal object), and radiation (infrared rays impacting and heating a surface). The sensation of heat is directly related to these processes.
Effective thermotherapy requires considering several factors: temperature difference (hotter body required), specific heat of the agent (metals heat up quickly and can burn, while other materials do not), thermal conductivity (metals are more conductive than paraffin), duration of the stimulus (short applications stimulate, prolonged applications relax), surface area of application, and crucially, the patient's sensitivity. Patients with impaired heat perception should not receive superficial thermotherapy due to burn risk.