Updated: Aug 21, 2021
It’s a question a lot of people have when training:
“I’m hurting after that workout yesterday, so do I ice it or use heat?”
It’s inevitable: you stretch and stay hydrated but you still sometimes get injured during a workout. So what do you do with the nagging pain, do you ice it or use heat?
Cryotherapy (cold therapy) and thermotherapy (heat therapy) have long been the choices for relieving pain, but they are appropriate for different situations.
Much of the choice depends on the person and the injury, but a little basic knowledge about each strategy can help you make the right choice every time.
What Happens When You Ice?
First, let’s take a look at what icing actually does to your body. Skin receptors pick up different sensations, like pressure and temperature. Our skin has more cold receptors than heat receptors.
When the skin senses a cold temperature, it activates the cold receptors and these block some of the sensation of pain.
Icing also causes vasoconstriction—the narrowing of blood vessels. This decreases the blood flow and helps to slow down the inflammatory response. When an injury is inflamed, the area may be swollen, red, and warm to the touch. Applying ice helps to reduce or even prevent the inflammatory response.
When to Ice…
There are a few different situations in which you should use ice:
If the injury is acute, or sudden, you use ice to help relieve and prevent swelling by reducing blood flow to the area. For example, if you sprain your ankle working out, reach for a bag of frozen peas to reduce the swelling. The sooner you ice, the better the effect will be.
Ice can also be helpful for many soft tissue injuries. For example, ice after a tough exercise to relieve muscle soreness and shorten recovery time.
Icing is also a useful way to recover from surgery by reducing swelling around the site; just don’t put ice directly on the incisions.
When icing an injury or after surgery, do it as soon as possible and for up to 72 hours for the greatest effectiveness. If swelling persists, see your doctor.
When Not to Ice…
Icing is not always the best solution. There are some situations in which you should avoid the cold pack:
Stiff joints. Do not use ice to relieve stiffness. Doing so will actually increase stiffness.
Pre-workout. Don’t ice before you exercise because it will mask pain, causing you to end up with more damage. An exception is if you need to stretch for therapy and recovery purposes, icing beforehand can help increase your range of motion and reduce pain.
High blood pressure. If you have high blood pressure, icing can raise both your systolic and diastolic blood pressure because of the decrease in blood flow in blood vessels.
Wounds. Don’t apply ice to open wounds. Cold doesn’t help wounds heal any faster and, in fact, could impede the healing process.
Poor circulation. If you have problems with circulation, such as Raynaud’s, take care when icing. The vasoconstriction can decrease circulation even more.
Anesthesia. Don’t ice areas that have been treated with local anesthesia. You won’t be able to feel pain, which means you could be damaging nerves or getting frostbite without realizing it.
Chronic Injuries. Ice is best if used for acute injuries. Icing chronic injuries, such as low back pain, is not beneficial. How Long and How Often Should You Ice? If icing is the right choice for your injury, there are a few things you should know before you get started. Don’t ice for more than 20 minutes at a time. It isn’t beneficial once past a certain point. Icing for 15-20 minutes is optimal. There is also some evidence that icing intermittently can be helpful for pain relief in acute soft tissue injury, so if needed, you can even do two 10 minute sessions. The length of time to ice the injury can also depend on the injury and the person icing. If the injury isn’t deep, you don’t need to ice for as long. The deeper the injury the longer you need to ice. For example, a finger injury needs less ice time than a hamstring injury. You should also make sure you leave enough time in between icing applications for your temperature to return to normal. If you have any sensitivity to cold you may not be able to ice as long. Icing for too long can cause frostbite and tissue damage. If your skin starts to turn red and splotchy you may have iced for too long and it’s time to stop. A Few Icing Strategies There are a few different methods you can use to ice injuries. Frozen ice packs are easy to use and will mold to the shape of the body part you are icing. Ice cups are another easy way to use cryotherapy. You can even make your own with paper cups. Just add water and freeze. Apply the ice at the top of the cup to your injury site and tear back the paper as the ice melts. You can use a wrap to hold ice or a cold pack to your body. This helps keep it in place, but as an added bonus the compression from the wrap makes the ice more effective. If you are sensitive to the cold, add a barrier, like a thin cloth, between the ice or cold pack and your skin. This will protect your skin, but may cut back on the effectiveness. When icing for muscle soreness after exercise, you can take an ice bath, but these are not for the faint of heart. Ice is great for a lot of injuries, but what about heat? There are some situations in which heat beats cold. What Happens When You Use Heat? Heating is often used as a therapy to help relieve pain and promote healing. When you heat an injury, the warmth causes vasodilation—the widening of blood vessels. This increases blood flow to the injured tissue, which in turn increases the amount of oxygen and speeds healing. As a bonus, heat therapy is soothing and relaxing. When to Heat… Heat therapy is best used for injuries that are past the acute stage. After 72 hours, or after the swelling has gone down from the initial injury, use heat to trigger the healing response. If you have a chronic or reoccurring injury, you can also use heat for pain relief. Heating also can help with stiffness; the increase of blood flow from the vasodilation can help to increase flexibility. When Not to Heat… As with icing, heat is not right for every situation. Heat shouldn’t be applied to a new or acute injury. This can cause an increase of blood flow to the injury and create more inflammation. Don’t add heat to any injury that is swollen or inflamed. How Long Should You Use Heat? You can apply heat for 15 to 30 minutes, but the time may vary depending on the method of heat you use. Always have a barrier in between your skin and the heat pack. This is important to prevent burning. If it feels too hot, add another layer. Check for comfort every so often to be sure that you aren’t getting burned. The applied heat should not be so hot that you feel uncomfortable. How to Apply Heat? Applying a heat pack to the injured area is a good way to transfer heat. Again, you will need a barrier between your skin and the heat pack. You can also use a Jacuzzi for some hot water, which is the best option for whole-body heat therapy. Both heat and ice have their place in training. Know how each one affects injuries and you will be able to make the right therapeutic choice for yourself and for your training clients. Some situations may be more complicated, and if you aren’t sure what to do, follow the advice of a doctor or physical therapist.