By alternating hot and cold, it is believed that lymph vessels dilate and contract to "pump" and move stagnant fluid out of the injured area and that this positively affects the inflammation process, which is the body's primary mechanism for healing damaged tissue.
[medical citation needed] Contrast bathing can be used to reduce swelling around injuries or to aid recovery from exercise.
It can also significantly improve muscle recovery following exercise by reducing the levels of blood lactate concentration.
For any injury presenting with palpable swelling and heat, and visible redness - such as a strain/sprain - contrast baths are contraindicated during the acute inflammation stage.
The current evidence[1] base suggests that contrast water therapy (CWT) is superior to using passive recovery or rest after exercise; the magnitudes of these effects may be most relevant to an elite sporting population.