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For decades, health care practitioners have been telling patients to ice their injuries. But lately people are starting to hear a new message.

Based on mounting evidence that icing injuries can slow healing, some health care practitioners have done a 180-degree turn. In some cases, they're saying don't ice. In others, they're saying use heat instead. What's a person supposed to do with this conflicting advice?

The reason practitioners recommend icing at all is to control inflammation. This philosophy is at the heart of the debate.

The inflammatory response associated with tissue damage has been made out to be the enemy when it comes to rehabilitation. Actually, the inflammatory response is necessary to begin healing. From an evolutionary perspective this makes sense. Why would our bodies have developed a process that is unnecessary or damaging? You would expect that our inflammatory reaction would be fine-tuned to optimize healing.

While the inflammatory response might be perfect in some cases, it might be excessive in others. When there's a threat of infection, the inflammatory reaction should be robust as our white blood cells fight to ensure that bacteria don't get a foothold. However, the body seems to have trouble telling the difference between this situation and one where the threat of infection is low, such as when the skin is unbroken. The white blood cells that attack bacteria can also wage a small war on your own tissues in the area, which is why inflammation hurts. Given that before the discovery of antibiotics, infection was a more serious threat to life, perhaps this oversensitivity provided an evolutionary advantage by reducing the risk of infection, albeit at the expense of comfort and optimal healing times for minor injuries.

When to ice

When an injury is new, the skin is intact and the inflammatory reaction seems excessive and painful, I would recommend icing for just a few days. Three to five days is a good rule of thumb, but this acute period can vary depending on the severity of the injury. Icing won't eliminate the inflammatory reaction. It only mitigates it to some degree and provides pain relief by slowing the physiology of the nerve fibers and decreasing the activity of some white blood cells. Beyond limiting the potential for chronicity of symptoms, decreasing the pain serves to promote normal movement and function.

Another example where ice is warranted is a joint effusion — when the swelling is in the joint. A joint effusion makes the joint look large and swollen, usually with a feeling of fullness and loss of range of motion. In this situation, we know that prolonged inflammation causes damage. According to Toronto-based sport medicine specialist, Dr. Noor Amin, "some types of swelling can be toxic to the cartilage of the joint." In these cases, Amin suggests trying to diminish the swelling as quickly as possible by reducing painful activity, icing, elevating and compressing with a tensor bandage.

When to use heat instead

Inflammation is at its peak in the early stages of healing. Depending on your stage of healing, your injury might be inflammatory or it might be more mechanical, meaning the physical stress on a tissue causes the pain, rather than the chemical irritants of the inflammatory process.

New injuries, like ligament sprains and muscle tears, that are hot, swollen, red and ache at rest are more inflammatory. As time passes and the injury becomes more chronic, inflammation becomes less of an issue. Much of the time, when we see a case of tennis elbow or plantar fasciitis in the clinic, the injury has been around for months and the inflammatory stage has long since passed. In these cases, icing does little to promote healing. It may provide some pain relief, but the trade-off is a decrease in circulation and some metabolic processes that are good for healing. (However, if you overdo an activity during this phase, the injury can become inflamed temporarily. Icing once or twice might help just as it did in the acute phase, but overall, icing isn't the optimal strategy for chronic injuries.)

If your injury is more than a few days old and you've done a good job of protecting the injury with relative rest, the inflammatory stage has likely passed. The injury may continue to be painful with movement, but the pain at rest will have diminished. There will be less redness and swelling. In this stage, heat application is more appropriate. Heat improves circulation and tissue extensibility and helps prepare the tissue for your rehabilitation exercises.

The best way to ice

If you do apply a cold compress, be careful not to freeze the skin. Frostbite happens more often than you'd think and will only make matters worse. For safety, use a thin towel or a pillowcase as a barrier between the cold compress and the skin. To ensure maximum therapeutic effect, apply the compress for 10 to 20 minutes at a time, approximately once hourly, checking the skin regularly. This can be performed throughout the acute phase. Four or five times a day should be sufficient.

When in doubt about the best treatment, consult your physiotherapist or health provider for more information on how to treat your specific injury.

Health Advisor contributors share their knowledge in fields ranging from fitness to psychology, pediatrics to aging.

Justin Vanderleest is a Toronto-based physiotherapist at Athlete's Care and LiveActive Sport Medicine. He has a Master's of Clinical Science in Advanced Orthopaedics and Manipulation from the University of Western Ontario. He is a Fellow of the Canadian Academy of Manipulative Physical Therapists. An elite squash player and former national champion sprint canoeist, Vanderleest has developed special interests in training programs and injury prevention. You can follow him on Twitter @JDvanderLeest