
Infrared (IR) light is a type of electromagnetic radiation that lies just beyond the visible spectrum, between microwaves and visible light. It has longer wavelengths than visible light but shorter wavelengths than microwaves. Infrared radiation is often associated with heat because many objects emit infrared energy as a result of their temperature.
Infrared radiation falls within the electromagnetic spectrum, with wavelengths ranging from 700 nanometers (nm) to 1 millimeter (mm). The spectrum can be divided into three main regions:
Near-infrared (NIR): 700 nm – 1.4 µm (used in remote controls and fiber optics)
Mid-infrared (MIR): 1.4 µm – 3 µm (used in thermal imaging)
Far-infrared (FIR): 3 µm – 1 mm (associated with heat radiation and suited well for saunas)
As you can see, the far-infrared has the longest wavelengths of the three categories making FIR ideal for sauna use due to the deeper absorption which stimulates the beneficial cellular responses.
Infra is a Latin term meaning below. Thus Infrared light is “below” the visible light spectrum making it invisible to the human eye. It can be detected, however, using special sensors, cameras, or night vision devices.
What about blackbody radiation and thermal emission? Blackbody radiation is the thermal electromagnetic radiation within, or surrounding, a body, or object in thermodynamic equilibrium with its environment. Did you know that all objects with a temperature above absolute zero (0 K or -273.15°C) emit infrared radiation? This is due to the movement of their atoms and molecules. This process is described by the blackbody radiation, which states that an object's temperature determines the intensity and wavelength of the emitted infrared light.
Heat is transferred via three methods, one of which is infrared radiation. These three methods include: conduction, convection, and radiation. Infrared radiation is the primary mechanism for radiative heat transfer. Unlike conduction and convection, which require a medium (solid, liquid, or gas), infrared radiation can travel through a vacuum (example: the Sun's heat reaching Earth through space).
Infrared radiation is a fundamental part of the electromagnetic spectrum that is deeply intertwined with heat transfer, technological applications, and everyday life. While invisible to the naked eye, its presence can be felt as warmth, and it plays a crucial role in science, engineering, medicine, and of course, fitness, thanks to HOTWORX.
What about sweat from far-infrared? Why does far-infrared induce sweat?
Far-infrared (FIR) radiation has a unique ability to penetrate deeply into the skin, generating heat from the inside out. Unlike traditional saunas, which heat the air around you, FIR saunas use infrared light to directly warm your body’s tissues, leading to increased sweating and detoxification. Here’s a breakdown of how and why this happens:
Far-infrared radiation has the longer wavelengths (3 µm – 1 mm), allowing it to penetrate up to 1.5 inches (4 cm) beneath the skin. This deep heat warms the muscles, blood vessels, and internal tissues, triggering a physiological response, and you can just imagine the effect when combined with exercise.
FIR energy stimulates thermoregulation, the body’s natural way of maintaining temperature. As FIR penetrates tissues, the core temperature rises, activating sweat glands to release excess heat and cool the body down.
FIR activates sweat glands at a much lower temperature than that of traditional saunas. Heat generated by FIR signals the hypothalamus (the body's temperature control center) to activate sweat glands. This leads to profuse sweating, even at the more comfortable lower air temperatures.
The lower temperature of the FIR sauna allows for a longer sweat response. Traditional saunas require very high temperatures (160-200°F or 70-90°C) to induce sweating. As stated, FIR saunas work at much lower temperatures (110-140°F or 45-60°C) but still cause a deep sweat. This means users can sweat more efficiently for a longer duration, enhancing detox benefits without feeling overwhelmed by extreme heat. The HOTWORX recommended sauna temperature is 120-125ºF for infrared training.
The bottom line is this. Far-Infrared saunas induce more efficient sweating. Far-infrared heat works from the inside out, raising core temperature, stimulating sweat glands, and enhancing circulation—all while operating at lower, more comfortable temperatures than traditional saunas. This makes FIR saunas highly effective for detoxification, weight loss, and muscle tension release.
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