Simply put, cryotherapy is the application of something cold to remove heat from the body. Properly used, cryotherapy can prevent/reduce edema (swelling), pain, inflammation, and muscle spasms. Cold (gel) packs, ice cups, and crushed ice are the most commonly used forms of cryotherapy.
Most people are familiar with applying ice or a cold pack to an acute injury such as a sprained ankle or muscle strain. We recommend against applying a gel pack directly to the skin—the gel packs can be so cold (much colder than ice) that they damage the skin. Instead, we recommend wrapping a wet towel around the gel pack before placing it on the skin. The wet towel should provide enough insulation to protect the skin from damage (frostbite). Crushed ice (in a bag) or ice cups can be safely applied directly to the skin. Whether using a gel pack or ice, cryotherapy is more effective if applied with compression (wrap with elastic bandage).
Cryotherapy needs to be applied for 30-60 minutes at a time for maximum benefit. It takes about 30 minutes to achieve significant cooling of tissues ½ inch deep and up to 60 minutes for the cold to penetrate an inch and ½. One of the reasons that it takes so long for cold to penetrate deeply is that the body is well insulated by a layer of adipose tissue (fat) just below the skin. The thicker the insulation, the longer it takes for cold to penetrate. Cryotherapy can be applied as often as every 1-2 hours (allow the tissues to warm up for at least as long as the cryotherapy was applied). Although applying heat may feel better, and is often recommended (incorrectly) in the days following initial cold application, it is usually much less effective than cryotherapy in reducing muscle spasms, edema and inflammation. In some instances, heat application will increase edema.
If used properly, cryotherapy is an inexpensive, simple, safe and effective form of treatment for most injuries.