One of the most common recommendations I make to clients is either to apply heat or ice to an area of their body. I find there’s a lot of confusion among clients as to which is appropriate for their needs. To understand which therapy is used for what we need a basic understanding of the effects of heat and cold.
First, let’s a take a very quick look at what effect heat or cold has on the body. When we apply ice we are forcing blood vessels to constrict, or get smaller. This leads to a decrease in swelling, by limiting the amount of blood that can enter a given area.
Another effect of ice is that it creates a numbing sensation in the area of application. Pain travels as an electrical signal to our brain and temperature can affect that signal. Just like you learned way back in High School Chemistry, heat speeds molecules up while cold slows them down. Applying ice is actually slowing down the speed of pain to the brain.
In contrast to the constricting effects of ice on blood vessels, heat does the opposite and opens the blood vessels, which is called vasodilation. Heat allows for greater blood flow into an area which allows nutrients to get in and wastes to move out. Yes, even cells excrete waste.
As we discussed above, ice has a numbing sensation which makes it beneficial for acute injuries (usually the first 3 days and up to several weeks). Generally we would recommend ice for any type of injury that would cause swelling, or inflammation such as a tear in a muscle or tendon. It should be noted that not all inflammation is bad. Areas of injury swell because they are flooded with your body’s helpers trying to repair the damage. The problem arises when the area becomes too overcrowded to the point where surrounding tissue may end up getting damaged or when the creation of scar tissue overtakes the natural replacement or regular muscle tissue. Ice is preferable to anti-inflammatory medicines because ice simply limits the amount of cells coming in instead of blocking the entire inflammatory process.
The next use for ice is for pain that arises from the nerve itself. A common example of this is sciatica, which is a compression of the sciatic nerve that causes intense pain down the leg. Ice is appropriate in this case because we are attempting to slow down that pain signal to give some relief.
The Takeaway: Ice for pain management but don’t be afraid to have a little swelling around an injury. Ice for nerve pain to slow pain signals to the brain.
We know now that heat opens up the blood vessels and allows for a greater passage of nutrients and wastes to the cells and we know that inflammation is usually accompanied by swelling and redness. This should throw up some red flags in regards to putting heat on inflamed areas.
Never put heat on inflammation because it will make it worse, and also feel pretty terrible (like applying more heat to a burn). This is why we ice for inflammation, because it restricts the blood flow instead of increasing it.
So when is heat appropriate? Any type of general muscle pain is the best application for heat. When your muscles are tight they are held in a state of contraction which restricts the natural flow of blood and nutrients. When muscles are abused or injured or even just stressed out, the body responds by contracting them to prevent further damage. When an area is cut off from blood supply it can form a “knot” or a “trigger point” and fail to function correctly- more about that coming up in another post.
Allowing more blood to enter a restricted area like this will allow the blood and lymph to clear away wastes and bring nutrients needed to supply healthy muscles. Many people experience chronic pain (pain that has lasted months to years) in their neck and shoulders because their muscles are so tightly contracted that they are deprived of blood flow. For these clients I recommend application of heat to the area at least a few times a week if not more in between massages.
The Takeaway: Use heat for areas of chronic pain, muscle tension and stress. Never put heat on a recent injury or inflamed area.
General Usage Guideline
No matter what, you should use caution with ice and heat therapies as prolonged exposure to either extreme can have the opposite of the intended effect. Generally about 20 minutes of either hot or cold therapy is the maximum that should be done in one sitting. Either can be reapplied after an hour or so.
Heat may be either moist or dry, however studies have shown that moist heat can penetrate deeper in a shorter amount of time than dry heat. For convenience I usually just use a dry hot pack made from rice in a cloth bag.
Cold therapy is fairly straightforward and can be applied with an icepack, ice in a bag. Never apply ice directly to the skin for a prolonged period. Wrap your ice pack in a towel to prevent skin damage.
If you really want to get into the details of moist heat vs. dry heat check out this research study: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3808259/