Hydrotherapy is the use of heat and cold for therapeutic effects. Thermal effects occur with applications of water above or below that of the body. These applications include but are not restricted to the following:

Heat is used to make muscles and fascia softer and more flexible, increase circulation, reduce pain, and provide relaxation. It is often applied for relief of tight, achy muscles present in chronic conditions.

Cold is used to reduce pain and decrease blood flow. It is commonly used in first aid to minimize pain and swelling after an injury. Ice is often used following a deep or specific massage treatment to ensure the greatest benefit from the treatment.

Contrast is an application of heat followed by an application of cold. This increases blood flow to and from the area, which speeds healing.