This has been a question that many healthcare providers have vacillated on. In past 10 years or more there has been a change from using varying hot and cold packs every 24 hours. Now the understanding is that heat should be used for chronic muscle stiffness and ice should be used for acute muscle pain. To understand how and when to use these modalities we need to understand the basic functions of hot and cold on the human body. Cold constricts while heat inflames. When considering an injury we first and foremost need to control the inflammatory response. Using ice for 10-15 minutes will decrease the inflammation and decrease the pain response. Using ice for more than 15 minutes increases the chance for frostbite and will also trigger the body’s natural protective response to sustained cold by increasing blood flow to the affected area. This increased blood flow will undue the positive affects by again increasing inflammation. Heat should only be used with a chronic problem area in order to temporarily increase blood flow. For example, before stretching or exercising. As a rule of thumb, never use heat after any activities since the body temperature and ensuing inflammatory response is already heightened.