A contrast bath, also called hot/cold immersion therapy, is a method of treating soreness, swelling, and inflammation in a person's joints or muscles. It is useful for treating joint injuries, such as mild sprains, and can also ease the symptoms of chronic conditions such as carpal tunnel syndrome. Some athletes also use contrast bathing to speed up recovery from exercise. A contrast bath involves immersing the joint in alternating hot and cold water, which helps to increase blood flow to the area and accelerate metabolic healing. Contrast bath therapy also causes numbness in the joint or muscle and increases the elasticity of the ligaments, giving the bather greater range of motion.
The process works through a repetition of two processes known as vasodilation and vasoconstriction. The hot water causes vasodilation, or the widening of the blood vessels, while the cold water causes vasoconstriction, which is when the blood vessels tighten. A contrast bath alternates between these two processes in order to create a pumping action in the area receiving the treatment. It is this pumping action that increases blood flow and helps to drain excess fluids out of a swollen joint or muscle.
In order to benefit from a contrast bath, the bather must first fill two separate basins; one with hot water and the other with cold. The cold water should be between 50° and 65° F (10° and 18° C) while the hot water should be between 100° and 110° F (38° and 44° C). Temperature will vary slightly depending on the comfort of the bather. The bather then alternates placing the joint in each basin. The amount of time the joint should remain in each basin varies depending on the injury, but generally it must remain in each basin for at least one minute for vasodilation and vasoconstriction to take place.
There is some disagreement among health professionals regarding the benefits of a contrast bath. While the pumping action that the process creates is undeniable, there is some debate over just how this process accelerates healing. In the case of more chronic ailments, contrast baths only offer a temporary relief from symptoms and often do very little to improve the overall condition of the joint. This temporary relief can cause some bathers to either further injure the area or to avoid more viable long-term solutions. For instance, someone with carpal tunnel syndrome might use contrast baths to ease the pain and increase range of motion in order to be able to continue the activity that is causing the problem in the first place, or as a substitute for surgery.