Sauna, heat/infrared cabin
When speaking of whole-body heat applications in the context of wellness centres or the home, usually we mean a sauna, a steam bath or an infrared cabin.
Today, a range of whole-body heat applications are on offer, differing primarily in terms of room temperature, air humidity, recommended session time and the method for the application of heat via convection (air) and infrared radiation. The strains on the cardiovascular system are very different in each case.
Whole-body applications, put simply, can have one of two different principles or goals:
These include Kneipp-style stimulation (Finnish sauna, bio-sauna, standard infrared cabins), on the one hand, and whole-body heating (low-temperature infrared cabins and Waon therapy) on the other hand. The difference lies in the type of heat regulation reaction that is stimulated in the body.
Saunas (classic sauna, bio-sauna, standard infrared cabins or steam baths) are generally at room temperatures of approx. 50 and 90 °C, so always higher than the thermo-neutral zone. Between 50 and 70% of the heat is applied via heated air and up to 30-50% via infrared radiation, depending on the design.
The aim of saunas etc. is not to heat the whole body (the core & shell), but to stimulate a greater or lesser reaction in the nervous system and skin. A significant aspect in this process is alternation between cold and hot. Alternation stimulates skin reflex zones, which in turn has stimulating effects on internal organs (following the Kneipp principle).
In whole-body heat applications that follow this basic principle, scarcely any heat enters the body shell during a typical session and there is no heating throughout the body.
The fact that the body takes on more heat through the entire skin area than it can release is problematic. The body has to limit the return flow of the blood heated in the skin in order to maintain a constant core temperature. More and more blood is sent to cool the skin and less and less blood is available to the central circulation system. The stress on the cardiovascular system increases massively.
If the session is ended in good time, the blood cools the skin and is then gradually redirected back to the circulation system. The core body temperature remains constant.
However, if the session is not ended in good time, the body has to retrieve the heated blood from the skin to prevent cardiovascular collapse. The core body temperature can then rise into the fever range above 38 °C. Artificial fever, however, should be avoided in the absence of medical supervision.
If you want to achieve easily tolerated whole-body heating, you should not work against the body’s natural heat regulation system. The environment should therefore be thermo-neutral – the body is then in thermal equilibrium with the environment and the blood can flow freely into the interior of the body. This is still not a form of heat application.
However, if you apply heat to no more than approx. 10 to 12% of the surface area of the skin (ideally the back), thermo-neutral blood (from 90% of the skin’s surface) mixes with heated blood (from 10 to 12% of the skin’s surface).
The heat alarm system within the body is not activated at this quantity of heat and the flow of slightly heated blood to the interior of the body is not prevented. The core body temperature rises continuously and slowly from the start.
The applied heat is then gradually redistributed from the inside (the core) to the outside (the body shell: muscles, connective and fatty tissue, bones, joints etc.) via a change in circulation. This allows heat to diffuse gently from inside to outside (deep heat). The whole body is then heated throughout.
The increased circulation and temperature in the tissue stimulates metabolism and improves circulation. Following the onset of sweating, effects occur that are referred to as “detoxification” or “purification”.
This method, as used in low-temperature infrared cabins, has a different aim than traditional whole-body applications such as saunas, steam baths, standard infrared cabins etc. and can help to alleviate conditions associated with musculoskeletal conditions and metabolic disorders.