When to Ice or Heat an Injury

"When should I use hot or cold for an injury?" is one of the most common questions I get from patients. Before we answer it, let’s first review the effects of hot and cold.

Effect of Heat
When heat is applied to a superficial area, it increases the blood flow to that region. An increase in blood flow means more nutrient is brought to the area, and thus, healing is promoted. Heat, in general, reduces the viscosity of body fluid and so improves the overall flexibility of the soft tissue.

Effect of Cold
Use of cold, on the contrary, reduces the tissue metabolic activity. Hence, it greatly reduces the swelling produced by injury. In addition, it numbs the nerve endings, and so decreases pain.

Injury triggers inflammation. Inflammation produces swelling and increase in temperature. That is what happens in the tissue the first two to four days after an injury. It is called the acute stage. After that, the swelling and the temperature starts to calm down. It is important to control the swelling and pain in the acute stage to minimize the future stiffness. Therefore, cold therapy should be used. After 2-4 days of acute stage (after the swelling has gone down), heat should be used to promote healing and to restore the flexibility of the soft tissue.

Any form of heat is beneficial although moist heat is claimed to be more effective. The temperature used is a kind of subjective. I usually advise my patients to use the temperature they would use for a bath. A 30-minute application should be sufficient.  

For cold therapy, the temperature should be around the freezing point of water. Therefore, a bag of ice chips, frozen vegetable, or gel pack will do the job. The duration of cold therapy is debatable. Since the permeability of lymphatic vessels decreases after 10 minutes of cold, cold therapy should not be used for more than 10 minutes at a time.

Peggy Hau, PT, MscPT is a licensed physical therapist at Mettler Center. Do you have questions regarding management of an injury? Ask an Expert. Your injury can be evaluated by a physical therapist who can detect functional problems and make the best possible recommendation for treatment. Call 217-398-9800 to schedule a free 30-minute consultation with a physical therapist or request an appointment online.