Heat therapy can be beneficial in a range of injuries which result in muscle spasm and reduced flexibility. This treatment is usually more effective in chronic (long-standing) rather than acute conditions.
The rationale of heat therapy is that it dilates the blood vessels in the muscle/s which in turn increases it's supply of oxygen and nutrients, therefore enhancing the healing process. It is also thought that correctly applied heat treatment decreases the transmission of pain signals to the brain as well as increasing soft tissue flexibility.
For the majority of people heat therapy works most effectively when combined with other modalities such as mobilisations, massage, exercise rehabilitation and self-management advice for example.