By Adam Pharr, PTA, CFMS, NSCA C-Pt, Advanced Physical Therapy Center
An injury to the body can take many forms, e.g., lacerations, burn, breaks, sprains,
infections, etc. When injuries occur, two things happen. First, there is pain. Pain in an
injury is caused by damage to the tissues, blood vessels, and bones. Second, the body makes attempts to heal and repair the damage. One of the ways it does this is by dilating the blood vessels and increasing blood flow in and around the damaged area. This helps the healing process by bringing oxygen and nutrients to the injured tissues and removing toxic waste products. However, the dilation of the blood vessels and all the increased blood flow actually are the root of pain. The dilation of the blood vessels and the increased amount of blood in the area causes swelling and pressure causing pain. Similar to when you have a sprained ankle, you won’t walk on it, because weight bearing causes pressure and the pressure causes pain.
How does this apply to the therapeutic use of heat and cold?
In physical therapy, we use heat when …
We use heat when we want to increase the blood flow to an area, because heat dilates the blood vessels. Heat is safe after all initial swelling has decreased, approximately two weeks after initial injury.
In physical therapy, we use cold when …
We use cold when we want to decrease the blood flow to an area, because cold constricts the blood vessels. Cold is used during the first two weeks of an injury, when swelling is at its greatest.
We use either heat or cold in other situations depending on the type of condition. Heat would be applied to tissues that are infected (without swelling) to bring oxygen, nutrients, and white blood cells that fight infection to the area. Cold would help an area that is painful because of swelling (e.g., a sprained ankle) by decreasing blood flow and pressure.
Heat and cold can also be used sequentially. Standard care for a sprained ankle is to first apply ice for a few days to decrease the pain caused by swelling and then apply heat to increase blood supply and promote healing.