Should I apply hot or cold?

January 20th 9:50am

The decision on whether to apply heat or cold to an injury is sometimes a confusing one, which can have quite a significant impact on the healing of the injury. Here is a quick guide to help you know if cold therapy or heat is the way to go for your injury.

Cold therapy

The aim of applying cold, in whatever form, to an injury is multi-faceted. The benefits of cold application include:

  • Blood vessel constriction which results in reduced bleeding and swelling
  • Localised analgesia & reduced pain
  • Reduced inflammation
  • Reduced metabolism at the injury site which reduces cell death from diminished oxygen availability.

Cold therapy should therefore be applied to any injury which causes bleeding, swelling, inflammation and pain. This tends to include all forms of acute injuries such as ligament sprains, muscle strains, contusions, impacts and acute swelling. It also includes many overuse injuries where there is inflamed tissue, such as tendonitis, plantar fasciitis and IT band syndrome for example.

The next part of the dilemma is how long should you continue to ice for? The answer to that is until all bleeding, swelling and inflammation has ceased. How long this takes depends on the extent of the injury. A more severe injury will result in more bleeding, pain and swelling than a minor injury. Whilst as a guide, 2-5 days is usually sufficient, symptoms should be used as a more accurate guide.

Continue to ice whilst:

  • New bruising continues to appear
  • Swelling is increasing or not going down
  • There is warmth over the injury site
  • Pain or stiffness is worse after periods of inactivity (both of the last points suggest inflammation is still present)


The aims of applying heat differ considerably to the aims listed above for cold therapy. The purpose of warming an area is to:

  • Increase local blood flow for healing
  • Reduce pain
  • Reduce muscle tension / spasm

Heat therapy is applied to old or chronic injuries, or pain conditions where no acute injury has occurred and no inflammation is suspected. Such conditions may include areas where increased muscular tension is causing discomfort, such as the lower back or neck and acute injuries like muscles strains which are past the early, inflammatory stages and now require an increase in blood flow to heal and increase flexibility.

DO NOT apply heat to new, acute injuries where there may be bleeding or inflammation as this can make the injury worse! A classic example of this is the early use of heat on a muscle strain or contusion, which can result in a condition known as myositis ossificans. This is the development of a bony growth within the muscle tissue.

At what point is it safe to apply heat to an old acute injury? Once you are sure that all bleeding and swelling has stopped and there are no signs of inflammation (warmth over the area and stiffness/pain after periods of rest). This will take at least 3 days, but to be safe, wait 5 days (7 for severe injuries)!

Contrast Therapy

Contrast therapy is the alternating of hot and cold therapy within one treatment. Protocols may include the application of cold for 2 minutes, followed by warmth for 4 minutes, repeated two or three times.

The purpose of contrast therapy is to cause a pumping effect of the blood through the area as the vessels contract in response to the cold and then dilate when warmth is applied. This helps to reduce swelling and flush out metabolites and to increase blood flow and provide the injury with the necessary nutrients for healing.

Contrast therapy is often used as a transition treatment between the use of cold therapy and warmth alone, for sub-acute injuries, as well as stiff joints and nervous system mediated pain.

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