Heat is often used in the chronic phase of an injury. It may also be used prior to therapy or exercise to decrease muscle tension and increase flexibility and range of motion. It also plays a role in pain management and reduction of muscle spasms, muscle tension, and joint stiffness.
Moist heat such as the hot packs is preferred over dry heat such as cloth beanbags, because damp heat penetrates deeper. To create moist heat at home when using a non-electrical heat source, first wrap a damp towel around the hot pack, cover with dry towelling and apply it to the treatment area.
No matter what type of heating agent you use, several layers of towelling should be used as a barrier between the skin and the hot pack to help prevent skin irritation or burns. Hot packs should be applied for 15 to 20 minutes. Visually check the skin every five minutes and discontinue treatment if there are persistent abnormal changes in skin colour or you experience increased discomfort.
Do not lie on a hot pack or apply heat at bedtime since it increases the likelihood of burns resulting from close or prolonged contact with the heat source. Heat therapy should be avoided in the acute phase of an injury when swelling is present and the skin is hot to touch. In addition, people with certain medical conditions should not use heat therapy.