This therapy works by rapidly alternating between hot-water and cold-water immersions. Your blood vessels open and close in a pulsing, pump-like motion. When you expose part or all of your body in cold water, small blood vessels called capillaries respond to the cold by getting smaller. This is known as vasoconstriction. When you expose yourself in warm water, the opposite happens. Your blood vessels open up. This is known as vasodilation. Switching back and forth between warmth and cold creates a pumping action that may help decrease inflammation. This helps reduce muscle fatigue, spasms, pain, swelling and lactic acid buildup.
Recent studies suggest that contrast therapy is more effective in easing arthritis pain and stiffness than a hot bath alone.