Healing Injuries: Hot vs. Cold

(Originally posted on bcotoronto.com on Aug 16th, 2012)

Hot vs ColdThe Olympics have come to a close and our athletes have returned home again. The games have encouraged many of us to get out and test our skills on the field or court and so I would like to take some time this week and next to talk about how to properly heal your injuries. There is a lot of information out there on how to take care of an injury but and a lot of people seem to get confused. So the next few weeks I’m going to break down all the advice so that we can all understand why and what we are doing. This will help us all make the right decisions in the future. I’ll try to keep it simple without getting mired in too much of the nitty-gritty.

Hot vs. Cold
The biggest confusion seems to be around the use of heat or cold on an injury so I’m going to focus on it this week. Let’s talk about the effect of different temperatures on our physiology. We are, of course, only discussing the application heat and cold to the skin’s surface at this point.

The body’s first response to being “too hot” is blood vessels (both arteries and veins) expanding to have more blood flow through the area at a relatively slower pace so that more heat is released from the blood back into the environment. Therefore applying heat to the skin increases the blood flow in the area which brings with it all of the nutrients and healing factors (proteins and chemicals involved in healing tissue). Consequently, heat helps muscles and ligaments to relax through an increased oxygen supply, which in turn decreases pain generated from muscle spasm and tight ligaments.

When an injury initially occurs, some cells will be damaged beyond repair and so trigger an immune response to clean them up. This immune response involves some cellular activity but mostly the chemical side of immunity called inflammation. Heat increases the rate of chemical reactions. So when an injury is fresh and new and our immune response is actively cleaning up damaged and destroyed tissue heat should be avoided because this will over stimulate the processes involved which will eagerly damage still healthy tissue in an over zealous effort to “clean up”.

Heat also increases nerve conduction. Meaning signals travel faster and sometimes with more intensity. This is a good thing when our bodies are in recovery. Increasing the signals to muscles and blood vessels primes them for better stretching and exercise and gives better feedback to the brain. On the other hand, during the initial stages of the injury heat will increase the pain signal reaching the brain as well as increase inflammation which has a by product that induces pain as well.

Therefore heat is best for older injuries that no longer have an active inflammatory component and recovery is recommended. Heat is wonderful during rehabilitation and training to improve response.

Applying cold to an injury has pretty much the exact opposite physiological effects as heat. It reduces nerve conduction, decreases chemical reaction rates, and decreases blood flow. In this way, cold “numbs” the pain of the initial injury and the chemically induced pain from the inflammation for the few days after the injury.

The decrease in inflammation also helps to rein in the over eager chemicals during the clean up and avoid/limit collateral damage. This is aided by the decreased blood flow as fewer immune components will be able to reach the injured area and the smaller amount of fluid rushing in will decrease the amount of swelling that occurs.

Therefore cold is best used on new injuries to maintain control over the pain and immune processes. It can still be used later in the healing process is residual pain exists.

I hope this clears up some of the questions and confusion around this issue. Just remember the simple rule: Ice Early, Heat Later. If anyone has any questions about this or anything else please leave a comment below or e-mail me at drroffey@gmail.com. Come back next week when we’ll discuss immobilizing and injury vs keeping it moving.

Thanks for reading,
Dr. Ben


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