Injured? Ice or heat, that is the question….

by Lori Zucker DPT |
November, 2012
heat vs ice for injuries

To ice or to heat, that is the question.  I’m often asked whether it’s better to use ice or heat to help an injury heal so let’s review some basic information about both thermal modalities.

Ice is used as an anti-inflammatory (decreases swelling) and an analgesic (pain reliever). When cold is applied to a local area, the blood vessels constrict and reduce the flow of blood to the area.  In an acute injury, the blood vessels can be injured and thus allow fluid to leak into the surrounding soft tissues causing swelling (edema). Applying ice as soon as possible after an acute injury will constrict (narrow) the blood vessels in the area, decrease the amount of blood flow and thus, the amount of fluid that is available to leak into the soft tissues. In this way, swelling is reduced.  (This is the idea behind the first aid protocol of RICE – Rest, Ice, Compression and Elevation) Of course compression and elevation are also ways to keep swelling in check by applying pressure to the immediate area and by elevating the injured part above the heart so fluid will be encouraged to drain from the injured area.  A surgical procedure is considered an acute injury, and ice is often applied for the same reasons, to reduce swelling in the immediate area.

Now, let’s consider the other effect of icing an area – analgesia or pain relief. The proper application of ice should feel as follows: cold, colder, a burning sensation and then numbness. When the area being iced feels numb, that is the time to remove the ice/cold. (Take note: leaving ice on longer than necessary triggers an opposite reaction and you will actually end up dilating the local blood vessels, flooding the area with blood, as your body attempts to buffer against the cold.) So how does ice function as a pain killer? If the injured area is numbed, you can’t feel the pain, throbbing or discomfort! It’s a temporary effect, and the area will return to full sensation slowly when the ice/cold is removed, but the numbing effect will take time to wear off and ice can be applied again intermittently to help maintain the pain relief. In combination, swelling can be the cause of pain and discomfort, so if you can reduce swelling with ice and benefit from a numbing effect, you can get to pain relief from two sides.

And then there is heat. Heating or warming an area of the body brings blood flow to that region. The blood vessels dilate (open) and allow more blood to rush to and from that body part. Blood leaving the injured/sore area will carry away toxins and other debris that irritate soft tissues. Muscles that are not hydrated well are often stiff and sore, and the muscle fibers do not glide smoothly over each other.  Heating an area, bringing fluid to that region, can help re-hydrate, bring nutrients to the tissues and thus, decrease spasms, helping to relieve “knots” in the muscle or relax muscle tissue. Warming the tissues often allows for greater mobility and thus, decreased pain or stiffness. It’s fairly typical that when a body part hurts, we tighten up around that area to protect it and hopefully prevent further injury. That tightening doesn’t necessarily help. In fact, it often causes adjacent body parts to feel sore and painful. For a healthy individual, heat often allows us to relax and “let go” of the things we are holding on to or trying to protect. Physiologically, increasing the temperature of tissue will change the conduction of nerve impulses, impact pain thresholds and increase the rate of metabolism in the local area that is heated.  All of these play a role in the benefit of using heat for tissue healing and pain control.

So what’s the answer to that most frequent question, should I use ice or heat? In my opinion, consider using ice when you are trying to control for swelling or relieve pain from an acute injury. Heat may be more appropriate for longer standing issues that require relaxation/mobility, blood flow to promote healing and relief of muscle tightness/spasms.