Should I Use Ice or Heat on an Injury?

By William Robert, MD | Runners World

Dear Doc,

When should I use ice on an injury and when should I use heat? I get conflicting answers when I ask the question.



Dear Mark,

In the face of an acute injury, like an ankle sprain, ice works to keep the swelling down, which allows the injured parts to stay physically close in the repair process. Once an injury occurs, the repair process follows in three phases. The first phase clears the damaged cells, the second brings in the cells to form the repair structure, and the third does the finish work to give the cells the final structure and strength. In the case of a sprain, the damaged ligament tissue has to be removed, new fibrous cells moved in, and the new cells transformed into ligament tissue. Swelling from tissue damage slows this process.

Heat promotes blood flow and increases swelling in the acute phase, so immediately following injury, heat will increase swelling and harm the healing process. Cold reduces blood flow, decreases swelling, relieves pain, and promotes better healing.

Heat does have a place in chronic injury and after the acute phase of injury. It is not always easy to say exactly when heat is acceptable in injury care, so I tend to stick with ice until all the swelling is gone and the pain is tolerable. Two to three days is probably a safe time period for ice, but holding off on heat and using ice longer does no harm. In chronic injuries, heat can relieve pain and loosen tissues.

Ice packing cools the surrounding tissues, and it is critical that the ice be removed before the tissue freezes. Fifteen to 20 minutes on and 15 to 20 minutes off is a reasonable cycle for icing an injury. Leave the ice on too long and you can damage nerves and other critical tissues. I had a patient who sprained his knee and decided to wrap an ice pack to the knee area while flying home from his game site. He fell asleep and when he awakened two hours later, he had permanently damaged his peroneal nerve, leaving him with a foot drop and unable to play his sport. His athletic career was cut short by too much icing for an injury that would have healed well with conservative measures. Like everything, icing can be overdone.

Read when you should use heat or ice.


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