Physical therapists often use heat therapy—also known as thermotherapy—to relieve pain and promote healing for injuries and conditions such as muscle spasms, arthritis, fibromyalgia, and bursitis. It is especially common in the treatment of low back pain. This technique involves applying heat to the site of the issue using a warming device such as a hot cloth or towel, hot water, a heating pad, heat therapy wraps, or ultrasound technology. When exposed to heat, tissues increase in temperature, which leads to vasodilation—a process in which the tissue’s oxygen and nutrient supply increases as its carbon dioxide and metabolic waste levels decrease. Therapeutic heating also increases nerve conduction velocity, which may explain why people experience decreased pain in response to the application of heat. Heat also can be used to increase soft tissue extensibility—and, thus, range of motion—prior to stretching or exercise. Heat therapy involving warm liquids is, in many cases, thought to be more effective than that involving dry heat sources, because water transfers heat faster than air. One of the great things about heat therapy is that it is relatively inexpensive and convenient compared to many other types of therapy treatments. It’s also completely non-invasive and non-pharmaceutical. However, it often works best when provided in conjunction with other physical therapy modalities, such as therapeutic exercise.