Icing is most effective in the immediate period following a sport injury, typically within 48 hours after the injury. Ice brings down inflammation and helps numb the area from pain. Ice for 15-20 minutes, but never longer. Allow area to warm for at least 45 minutes or an hour before beginning the icing routine again. Repeat approximately 3 to 4 times a day. Heat is generally used for chronic injuries or injuries that have no inflammation or swelling. Sore, stiff, nagging muscle or joint pain is ideal for the use of heat therapy.