As PTs, we are often asked when to use ice versus heat for injuries. The answer definitely depends on the injury. Ice and heat can both be used to reduce pain, but they are best applied in different situations. A recent literature review conducted by Malanga, Yan, and Stark examined the differences between heat and ice applications and their effectiveness. Ice is most beneficial in situations where there is acute injury to tissues.
With an acute injury, there is an active inflammatory process releasing chemicals from injured cells causing pain. Cold acts to reduce blood flow to the area and decrease the release of these chemicals, which overall reduces inflammation. Cold also affects local nerves, decreasing their sensitivity and conduction speeds. Together all of these mechanisms help to reduce inflammation and pain resulting from acute tissue injury.
Conversely, heat increases blood flow and activity in the targeted area. Heat causes local vasodilation (widening of blood vessels) which increases the supply of nutrients and oxygen, which can aid in tissue healing. Heat also results in an increase in elastic properties of collagen, which can increase tissue flexibility and joint range of motion, and decrease local muscle spasms. An increase in blood flow and in tissue activity might be irritating in cases of acute injury, so heat is best reserved for post-activity soreness and pain, or when muscles and joints are feeling tight. Both ice and cold can be used for pain relief, but are best applied in different situations.
According to current literature, ice should be applied to tissues within the initial 72 hours of acute injuries (sprains, strains) following the RICE protocol, or when an inflammatory process appears to be the causes of pain (heat, redness, and swelling). Heat should be applied for muscular pain and soreness, as well as for joint pain and stiffness. An instance of low back pain and tightness, or post-exercise delayed onset muscle soreness (DOMs) would be an indication for heat. There are not strict guidelines for the application of heat, but care should be taken to avoid burns; avoid heat of extreme temperatures and by remove heat after 30 minutes.
Both heat and ice appear to provide non-pharmacological treatments for pain and the promotion of healing, but evidence is insufficient to define correct and incorrect uses. Be sure to listen to your body when using modalities and keep a protective layer between your skin and ice or heat pack.
Malanga, Gerard & Yan, Ning & Stark, Jill. (2014). Mechanisms and efficacy of heat and cold therapies for musculoskeletal injury. Postgraduate medicine. 127. 1-9.
Andrew Ward, SPT