Among massage therapists, physical therapists, trainers, and medical professionals of all stripes, one of the most contested topics is whether sites of soreness or injury should be treated with heat or cold. It turns out that at least some of the divergence can be resolved based on what the cause of pain is and how long the area has been painful—although as the Merck Online Medical Manual points out, “Whether to use heat or cold therapy is often a personal choice.” Consequently, the decision of which to use may always be open to question.
The first thing to consider, though, is what each type of treatment does to tissue. According to the University of Chicago Medical Center, for instance, the application of heat brings more blood to the area, reduces joint stiffness and muscle spasm, and helps resolve inflammation. Merck adds to this the fact that heat makes connective tissue more flexible and reduces the buildup of fluid in tissues. Cold, in contrast, relieves pain by numbing the affected area, reduces swelling and inflammation, and reduces bleeding. Already you can see that the issue gets a little muddy in that both cold and heat help reduce inflammation.
So when do you use which? The August issue of the Mayo Clinic Health Letter advises cold first, to soothe inflamed muscles, and heat later, per Medical News Today. So if you have injured a muscle or ligament, having sustained a sprain, strain, or pull, the application of a cold pack or cold compress will act like a local anesthetic, numbing the area, thus relieving the pain. Cold will also slow the flow of blood to the area, which helps reduce bruising. Because of this reduction of blood flow, though, cold should not be applied to areas where the supply of blood is already compromised, such as where arteries are narrowed by peripheral arterial disease. Cryotherapy (treatment using cold) should also be avoided for areas with trigger points (tight bands or knots in a muscle) since chilling activates them owing to decreased circulation.
In contrast, heat therapy is in order once the pain and swelling of an injury have decreased or for chronic pain, such as when muscles are simply tight or sore but haven’t sustained an injury, per se, or for arthritis. The increased blood flow brought about by the application of heat helps soften the connective tissue. If you imagine connective tissue to be like taffy, think about how rigid and inflexible it becomes when cold versus how pliable it is when warm. Furthermore, since blood helps eliminate the chemical by-products produced during exercise that make muscles tight and compressed, the increase in its flow will aid in this elimination.
If all else fails, use your head. Not as a compress! But, rather, to think about this: you already know that cold makes your muscles stiff, right? So why would you treat stiff muscles with cold? Certainly cold will numb the pain of, say, a tight back or shoulder. But unless an area was just injured, the use of cryotherapy won’t promote the relaxing of the tissue to which it’s applied. So for stiff, chronically achy muscles, I recommend heat. That’s a “personal choice,” certainly, but it’s one I’ve come to after careful examination of research and based on logical extrapolation of the findings of that research.