Other Therapeutic Effects of Infrared Heat

summarized from Chapter 9 of Therapeutic Heat and Cold, Fourth Edition, Editors Justus F. Lehmann, M.D., Williams, and Wilkin

 Infrared heat affects soft tissue injury.
Infrared healing is now becoming a leading edge care for soft tissue injuries to promote both relief in chronic or intractable "permanent" cases, and accelerated healing in newer injuries.

 Infrared heat assists in resolution of inflammatory infiltrates, edema, and exudates.
Increased peripheral circulation provides the transport needed to help evacuate edema, which can help inflammation, decrease pain, and help speed healing

 Infrared heat relieves muscle spasms.
Muscle spasms have long been observed to be reduced through the use of heat, be they secondary to underlying skeletal, joint, or neuropathological conditions. This result is possibly produced by the combined effect of heat on both primary and secondary afferent nerves from spindle cells and from its effects on Golgi tendon organs. The results produced demonstrated their peak effect within the therapeutic temperature range obtainable with radiant heat.

 Infrared heat treatment leads to pain relief.
Pain may be relieved via the reduction of attendant or secondary spasms. Pain is also at times related to ischemia (lack of blood supply) due to tension or spasm that can be improved by the hyperemia that heat-induced vasodilatation produces, thus breaking the feedback loop in which the ischemia leads to further spasm and then more pain.  Heat has been shown to reduce pain sensation by direct action on both free-nerve endings in tissues and on peripheral nerves.

 Infrared heat increases blood flow.
Heating one area of the body produces reflex-modulated vasodilators in distant-body areas, even in the absence of a change in core body temperature. Heating muscles produces an increased blood flow level similar to that seen during exercise. Temperature elevation also produces an increased blood flow and dilation directly in capillaries, arterioles, and venules, probably through direct action on their smooth muscles. The release of bradykinin, released as a consequence of sweat-gland activity, also produces increased blood flow and vasodilatation.

 Infrared heat increases the extensibility of collagen tissues.
Tissues heated to 45 degrees Celsius and then stretched exhibit a nonelastic residual elongation of about 0.5 to 0.9 percent that persists after the stretch is removed. Stretching of tissue in the presence of heat would be especially valuable in working with ligaments, joint capsules, tendons, fasciae, and synoviurn that have become scarred, thickened, or contracted. Such stretching at 45 degrees Celsius caused much less weakening in stretched tissues for a given elongation than a similar elongation produced at normal tissue temperatures.