For injury recovery, contrasting is a good, cheap, safe, and simple idea, and trust me its so much better than it sounds, when it’s done right.
Ice bath recovery can decrease inflammation, desensitise pain receptors and enhance muscular and cardiovascular health. Likewise, heat can soothe muscles and improve mobility and blood flow. Together, the benefits are complementary.
The point is to force your tissues to adapt to the sudden changes and requires a lot of metabolic activity and circulatory gymnastics. Basically, you are giving your body a gentle tissue workout without (physical) stress or movement, this can be helpful for a body part that badly needs some rest while it heals. It’s difficult to explain to someone who’s never done it, just how good this feels!
The key to contrast bath therapy is in the rapid changes produced in your circulatory system when you go from very warm to very cold water.
Cold water causes vasoconstriction (blood vessels get smaller), hot water causes vasodilation (blood vessels get bigger).
When you rapidly alternated between hot and cold water your blood vessels change rapidly from big to small in a pump like fashion, this pumping action can help relieve various injury symptoms and helps to remove excess lactic acid post-exercise, and works well in conjunction with other more active therapies such as stretching.
You can find out more about hot/cold contrast therapy Here.