Since ancient times people have known the beneficial power of heat or, in scientific terms, infrared radiation. Infrared radiation is part of the spectrum of solar radiation, which directly adjoins the red part of the visible spectrum and has the ability to heat most objects. The human eye is not able to see in this part of the spectrum, but we can feel the heat.
As you know, any object whose temperature exceeds (-273) degrees Celsius radiates, and the spectrum of its radiation is determined only by its temperature and emissivity. Infrared radiation has two important characteristics: wavelength (frequency) of radiation and intensity. Infrared rays were discovered in 1800 by the English physicist William Herschel.
Three regions of infrared radiation are subdivided according to the wavelength: near (0.75-1.5 micrometers), medium (1.5-5.6 microns) and far (5.6-100 microns) (1 micron = 1 / 1000000 m). Infrared rays are absolutely safe for the human body, in contrast to X-rays, ultraviolet or microwave.
In the infrared spectrum there is an area with wavelengths of about 7 to 14 μm (the so-called long-wave part of the infrared range), which exerts a truly unique beneficial effect on the human body. This part of the infrared radiation corresponds to the radiation of the human body itself with a maximum at a wavelength of about 10 μm. Therefore, any external radiation with such wavelengths our body perceives as "its". The most famous natural source of infrared rays on our Earth is the Sun, and the most famous in artificial source of long-wave infrared rays is the stove, and each person has necessarily experienced their beneficial influence.
Influencing the human body in the long-wave part of the infrared range, you can get a phenomenon called "resonance absorption", in which the external energy will be actively absorbed by the body. As a result of this action, the potential energy of the body cells increases, and unbound water leaves it, the activity of specific cellular structures rises, the level of immunoglobulins increases, the activity of enzymes and estrogens increases, and other biochemical reactions occur. This applies to all types of cells in the body and blood.