The Hot Cold Question: Understanding When to Use Heat or Ice to Manage Pain

Whether you are looking to soothe an acute injury or manage chronic pain, you may find yourself reaching for your Magic Bag but are unsure of whether to throw it into the microwave or the freezer.  Cryotherapy (ice) and thermotherapy (heat) are both easy and cheap ways to manage pain at home.  However, it is sometimes difficult to determine which one is more appropriate.  At MMTR Physiotherapy, we encourage our patients to be informed, because we strongly believe that you are much more likely to remember something and do it correctly when you understand it.  This guide will explain the physiology behind both heat and ice therapy so that you can manage your own pain at home without confusion.

How does heat and ice affect the body?

Heat and ice both work using the same mechanism by changing the amount of blood flow to the affected area, but with opposite results.  When ice is applied to tissue, the blood vessels in that area will get smaller.  This is called vasoconstriction and decreases the amount of blood that can reach the tissue.  When heat is applied, the blood vessels in that area will get wider.  This is called vasodilation and will increase the amount of blood that can reach the tissue.  Therefore, when you are trying to choose between heat or ice, all you need to do is figure out whether you want more or less blood flow to your affected area.

How do you know whether your affected area needs more or less blood flow?

Generally, new injuries such as sprains, strains, and tears come with some degree of inflammation.  Inflammation is the body’s immune response to injury and is characterized by local swelling, redness, heat, and pain.  Decreasing blood flow to the affected area can decrease fluid build-up and bring down inflammation.  So if you think you have any degree of inflammation you should be heading to the freezer for your ice pack because not only will it combat pain by numbing the surrounding nerves, but it will also help reduce your inflammation!

Why would you ever need heat?

Tight muscles, stiff joints and old injuries all require an increase in blood flow to help manage pain.  Blood is rich with oxygen and nutrients that help promote healing and increase tissue extensibility.  This means that when heat is applied and blood flow is increased to the affected area, tight muscles are able to begin to relax, stiff joints regain some range of motion and scar tissue from old injuries can begin to break up.  So if you are suffering from muscle or joint pain, heat is definitely the way to go!

Helpful Hints: Heat can be applied to the body in a variety of different ways.  Heat packs and seat/lumbar warmers are great for localized pain but if you experience whole body pain from fibromyalgia, rheumatoid arthritis or generalized muscle tightness, you can experience the benefits of heat therapy from a warm bath, sauna, hot tub, shower or electric blanket.

How often, and for how long?

The best period to ice a new injury is within the first 72 hours after the injury occurred.  Ice can be applied anywhere from 10 to 30 minutes should be applied at least 3 times per day (and as much as once per hour) for those crucial 48 hours. If ice is applied any less than 10 minutes, the cold is not able to penetrate deep enough, to the muscular level and if ice is applied for more than 30 minutes, there is a risk of frostbite (and don’t forget to have a layer of clothing or a towel between the ice and your skin – you don’t want frostbite to deal with as well as a sprained ankle).

Heat should be applied for at least fifteen minutes but can even be used for 30 minutes!  When using heating pads ensure that the pads do not cover an area of skin where there is an open wound or dermatitis. If you have diabetes or any kind of vascular disease, talk to your doctor to ensure that using heat is safe for you.

What happens if you get it wrong?

First of all, if you apply heat to a sprained ankle or apply ice to tight shoulder muscles, it isn’t the end of the world.  When heat is applied to an area of inflammation, there could be an increase in swelling and pain, which can prolong the healing process.  If you apply ice to tight muscles, they may respond by tightening even more after ice is removed which, again, will only delay pain relief.  Sometimes it can be difficult to tell if pain is coming from a torn muscle or just tight muscle, so if ever you are unsure of where your pain is coming from, make sure you speak to your family doctor so there is no doubt that you are doing the right thing to manage your pain.

Now you, informed reader, have all the tools you need to make the good decisions about how to manage your pain at home using heat or ice!  However, it is important to note that although ice and heat can help manage pain, they do not treat the root problem that is causing your pain.  A sprained ankle needs rest and tight muscles need to be stretched; so although heat or ice can provide temporary pain relief, make sure you don’t ignore the source of your pain!  The staff at MMTR Physiotherapy are qualified to perform a complete assessment as well as to create and guide you through an individualized treatment plan that targets and eliminates pain at the source.  If you have any questions, please do not hesitate to comment below.

Quick Reference Table: Should you ice it or should you heat it?