Stimulates local circulation

• A. Ultraviolet radiation
• B. Minimal erythema
• C. Second-degree erythema
• D. Infrared radiation

Answer: (D)

Heat from infrared radiation increases local circulation by warming the tissues and triggering vasodilation. As the tissue temperature rises, smooth muscle in the vessel walls relaxes, expanding arterioles and boosting capillary blood flow. This enhances delivery of oxygen and nutrients and helps remove metabolic wastes, supporting healing and comfort in the treated area. Infrared radiation can penetrate a bit below the surface, making it effective for the underlying tissues without relying on surface-only effects.

Ultraviolet radiation does not primarily stimulate local circulation; it mainly produces skin effects such as erythema and other photochemical reactions, and its use is not to boost regional blood flow. The terms minimal erythema and second-degree erythema describe skin reddening from UV exposure, which are signs of skin damage rather than a therapeutic method to increase circulation.