Should I use Ice or Heat to treat an injury?

This question is very common when people have pain and injury. Both Ice and Heat are important and are beneficial at different points of injury. For acute injury (24-72 hours), the modality of choice would be to use Ice.

Ice helps decrease the pain response and provides vasoconstriction to an area (the closing of small blood vessels). Ice helps to limit the amount of swelling that happens immediately after injury. For example, if you place ice directly on a sprained ankle, you can prevent the joint from swelling up. Ice should not be placed directly on the skin due to a risk of frostbite. You should always place a thin layer between the skin and the ice pack. Ice should not be left on any area longer than 20 minutes at a time.

Heat is beneficial when an injury is more chronic, or past the acute phase (initial 24-72 hours after an injury). Heat promotes muscle relaxation, and is best used on postural muscles such as the lower back, mid-back and neck. Muscle soreness and spasms are the most common symptoms treated with heat. Heat causes vasodilatation (opening of the small blood vessels), the opposite of ice.

When heat is applied over an area of acute injury, active inflammation or swelling can get worse. Another danger of using a heating pad is burning the skin. Just like with ice, it is important to have layers such as towels, between the modality and the skin. It is dangerous for a person to fall asleep on the heating pad or to leave it on too long (>30 minutes). Moist heat is the most effective form to evenly heat a muscle. Physical therapists often use a machine called a hydrocollator that keeps the hot pack in 160 degree water.