Updated: Aug 18, 2020
"Should I ice or should I use heat?" I get this question often. There are also various schools of thought out there that could be hard to sift though to help you choose and know why. The answer depends on the injury, and both can help with pain. Here is my general recommendation. I say "general" because again, every situation is unique and require something different. Be sure to ask your physical therapist what is best for you.
What Ice (Cryotherapy) Does
The cold property of ice causes blood vessels to constrict, reducing blood and thus reduces swelling. The cold also decreases nerve conduction velocity which can reduce the pain signal and also numbs the area. Less pain signal + numb body part = less pain.
Icing for 15-20 minutes at a time (max) and once per hour is sufficient to experience the benefits of the cold. Any longer can you run the risk of burns (yes, ice burns are real!). Additionally prolonged icing can cause some spasming and dilation of the vessels and thus increase your pain.
However, icing through something thick cover like a pillow case may require extra time. I usually tell my patients "Numb & Done" and the stages to get there (<20 min):
With that said, icing more ACUTE injuries (i.e. fresh ankle sprain, swollen joint) would benefit from icing within the first 2 weeks of the injury due to its inflammatory nature. Have significant swelling? Elevate the affected body part above your hear to encourage circulation with the ice.
What HEAT (Thermotherapy) Does
Heat can also decrease pain, but might be best used with chronic issues or non-inflammatory body pain. Heat can help relax the body and take the "edge" off of pain related to cramping or sensitivity. This is commonly related to acute soreness (not from injury), stiffness related to osteoarthritis, muscle "knots," or conditions with heightened sensitivity like fibromyalgia or drug side effects. Sometimes stiffer joints like those affected with arthritis do better in warmer temperatures, thus heating it can help reduce pain and improve mobility. Heating 10-15 minutes of comfortable warmth should be sufficient to achieve pain relief goals.
Heat can penetrate a few centimeters into the tissue and speed up the inflammatory effect inside. Topicals like IcyHot or Tiger Balm do not penetrate, but instead play on nerve sensation and distract the brain from feeling the pain signal. (I know, the nervous system is incredible).
With warmth being comfortable to us, it can be reassuring. According to pain scientist Lorimer Moseley, "to reduce pain, we need to reduce credible evidence of danger and increase credible evidence of safety."
As with ice, there are things to be cautious with heat.
Don't leave it on for too long or you can burn. Start with <10 minutes and do not exceed 20.
Be sure to place enough layers between the heating device and the body and always check the skin after -- especially with someone who has impaired temperature sensation or elderly individuals with thinner skin.
Do not heat over an open wound or rash! The heat will dilate blood vessels and surge the area with more blood flow.
Do not use on acute injuries because of the dilation/swelling concept.
In summary, ICE the acute injuries, and heat if you have something chronic that you know responds well to heat. If you're unsure, try a short bout of each or ask a professional. Every case is different and it's important to learn the cause of your pain in case things get tricky-- such as in an "acute on chronic injury." If this sounds like you, book an appointment today so we can figure out what is best for your unique case.
Dr. Malek, PT, DPT