Theoretical Basis
The depth of penetration to which electromagnetic energy is absorbed depends on the wavelength. For all of the systems, the heating effect is the same for all thermotherapy techniques. The following information describes the additional benefit to the systems.
Integumentary System
The range for infrared rays for heating superficial tissue is divided into near infrared (770-1500 nm) and far infrared (1500-150,000 nm). When rays strike the skin or travel from one tissue to another, they can be either absorbed or reflected back toward the surface, depending on the angle. Optimal absorption occurs when the rays strike perpendicularly. Energy must be absorbed to have any effect. A disadvantage to infrared is that it dries the skin more than other modalities. It also does not treat uneven body parts well because of the uneven heating effects. It can increase the temperature of subcutaneous tissue and increase NCV. It has been demonstrated that at least 50 percent of infrared radiation of 1200-nm wavelength penetrates beyond 0.8 mm and is therefore able to pass through the skin to interact with subcutaneous capillaries and cutaneous nerve endings. The amount of melanin in the skin, texture of the skin, oiliness, dryness, smoothness, and roughness of the skin primarily affect the amount of reflection of infrared radiation. Darker skin absorbs more radiation than lighter skin, therefore increasing absorbed energy. Increasing tissue temperature can increase O2-hemoglobin dissociation, increasing the availability of O2 for tissue healing. The law of Grotthuss-Draper states that waves of different wavelengths produce different effects. The increase in infrared energy creates molecular motion in the object of lesser temperature. This continues until the temperature of the two objects is equal.
Source: Therapeutic Modalities in Rehabilitation 3rd Edition (McGraw-Hill) 2005
The depth of penetration to which electromagnetic energy is absorbed depends on the wavelength. For all of the systems, the heating effect is the same for all thermotherapy techniques. The following information describes the additional benefit to the systems.
Integumentary System
The range for infrared rays for heating superficial tissue is divided into near infrared (770-1500 nm) and far infrared (1500-150,000 nm). When rays strike the skin or travel from one tissue to another, they can be either absorbed or reflected back toward the surface, depending on the angle. Optimal absorption occurs when the rays strike perpendicularly. Energy must be absorbed to have any effect. A disadvantage to infrared is that it dries the skin more than other modalities. It also does not treat uneven body parts well because of the uneven heating effects. It can increase the temperature of subcutaneous tissue and increase NCV. It has been demonstrated that at least 50 percent of infrared radiation of 1200-nm wavelength penetrates beyond 0.8 mm and is therefore able to pass through the skin to interact with subcutaneous capillaries and cutaneous nerve endings. The amount of melanin in the skin, texture of the skin, oiliness, dryness, smoothness, and roughness of the skin primarily affect the amount of reflection of infrared radiation. Darker skin absorbs more radiation than lighter skin, therefore increasing absorbed energy. Increasing tissue temperature can increase O2-hemoglobin dissociation, increasing the availability of O2 for tissue healing. The law of Grotthuss-Draper states that waves of different wavelengths produce different effects. The increase in infrared energy creates molecular motion in the object of lesser temperature. This continues until the temperature of the two objects is equal.
Source: Therapeutic Modalities in Rehabilitation 3rd Edition (McGraw-Hill) 2005