Contrast bath therapy, also known as "hot/cold immersion therapy",[1] is a form of treatment where a limb or the entire body is immersed in ice water followed by the immediate immersion of the limb or body in warm water.[2] This procedure is repeated several times, alternating hot and cold.
The theory behind contrast bath therapy is that the warm water causes vasodilation of the blood flow in the limb or body followed by the cold water which causes vasoconstriction. The effect is increase the blood circulation and thus assist the healing process. A study ([3]) showed that fluctuations in intramuscular temperature were lower than those caused by a hot bath alone.
Other studies indicates that thermal stress seems to positively influence the immune system.[4][5]
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 (Contrast bathing - a brief summary of evidences)