Hot or cold?

All active sportsmen and women suffer injury at some point. Broadly speaking, these can be divided into those which are acute – derived from sudden trauma such as a sprain or impact of some kind – and those which are chronic, characterised by stiffness and/or less severe pain and which often result from overuse or over-exertion.

Clearly in the case of any severe injury, you should see a doctor, but more often the injury is less serious and – whether acute or chronic – the most effective treatment can be the simple application of heat and/or cold to the affected area. In many cases however, people don’t use either, because they don’t think it necessary, or for fear of doing more harm than good. It is smart to be cautious, but with some general guidelines in mind, using these simple tools that everyone has at their disposal can aid the healing process and avoid potential complications in the longer term.

How it works
The exact way in which applications of hot and cold work is still hotly debated, but one suggested mechanism is in the way they affect the capillaries in the affected area.
In an acute injury, the capillaries vasodilate, or get bigger, to allow the immune system to send huge amounts of white blood cells to the area to deal with any possible causes of infection, and to help repair the tissue. This causes the inflammation and redness we see on the outside. If there is any tissue tearing, we also see bruising from the blood flowing out of the tissue. Although this process is a necessary part of healing, we can control it, and the consequent pain, by applying cold to cause the capillaries to vasoconstrict or get smaller again.
When we use heat on the body, the converse happens: we cause the capillaries to swell. Because the tissue is getting warmer than usual, the body sends more blood to the area, to help cool it. This fresh blood provides nutrients for the tissues and relaxes the muscle’s fibres. At the same time, it carries away waste products that have built up. Clearly therefore, heat should never be used on tissue that is already inflamed, as it will only increase the inflammation.


Acute injuries

  • Time frame: starting from the moment of injury and lasting for up to three or four days
  • Symptoms: Redness, swelling (oedema), heat, pain. If bruising is present, it is black, blue, red or purple
  • Hot/Cold indication: Cold

Trauma-induced injuries can be accompanied by immediate and sometimes considerable pain and swelling. Using cold applications, starting as soon as possible after the injury is suffered, can decrease healing time and pain, as well as enable the recovery of full function sooner. Continue as long as heat, swelling and/or bruising are present. This is one component of the First Aid acronym, RICE: Rest, Ice, Compress and Elevate (see above).

Sub-acute injuries (optional)

  • Time frame: Two or more weeks after an acute injury
  • Symptoms: Some residual swelling. If bruising is present it has faded to yellow, brown or green
  • Hot/Cold indication: contrasting applications of hot and cold

Depending on the severity of the initial injury, there may be a sub-acute stage during recovery during which you still wish to continue with treatment. There may still be some inflammation present so if alternating hot and cold, it is important to finish each time with cold to control this.

Chronic injuries

  • Time frame: Onset may be delayed, but may last for several weeks or even up to years in severe cases. May also follow on from the initial phase of an acute injury
  • Symptoms: Muscle stiffness, dull pain associated with movement of affected area, residual soreness after an acute injury
  • Hot/Cold indication: heat

Heat is used particularly with muscle tension which occurs when a muscle is overused and/or placed in a shortened position for a long period of time. The actual muscle fibres tighten and shorten, and an aching soreness ensues. Examples of such injuries include sore shoulders from backpack straps after a long hike or tight hamstrings after a hard run.
In the case of continuing treatment for an acute injury, wait until all inflammation associated with the injury is gone before applying heat. Inflammation denotes heat and therefore should never be treated by applying additional heat to the site of an injury.

How to apply

Ice packs are the normal approach, though even a cloth soaked in cold water, bag of frozen vegetables or cold can of drink can help in emergencies. You can buy special ice packs or make your own but the key is to avoid actually freezing the skin by having a cloth barrier between the two wherever possible.

The treatment will be more effective too if the pack conforms to the body. This is where commercial products are useful as they use special gels that remain pliant even when very cold. A good brand is Softouch, which has a covering that is softer than the usual plastic.
Leave the pack on until the area becomes numb: at least 10 minutes but no more than 20, less on parts of the body with less fat like feet and hands. First apply as soon after injury as possible and re-apply several times a day.

Apply heat first, for roughly one or two minutes, followed by 30 seconds of cold. Alternate this a few times, and remember to finish with cold.

The best types of heat applications employ deep moist heat which penetrates muscles much more effectively than dry heat. A cloth soaked in hot water (fold it first to help retain more heat) or hot water bottle is helpful, but for the very best results you should use a commercial heat pack. Several types are on the market including some you microwave and others that are activated using a metal disc.

You may also consider visiting a clinical massage therapist – a specialist in soft tissue treatments as opposed to the more general approach of a physio – as part of your recovery process. They will commonly use either hydrocollator packs made of silica-filled canvas, which are really only practical in the clinic, or thermophores, which are effectively mini electric heating blankets. They come with a special flannel-type cover, which traps moisture from the air to provide the best sort of heat. These are often available for sale at clinical massage centres.

Two warnings with the application of heat: don’t overdo it and burn yourself – apply for only up to 10 minutes at a time – and make sure you use it before rather than after exercise.        

Rest – if it hurts to keep moving then the body is telling you something. Stop moving if possible until you get medical advice. At a minimum, try to take as much strain as possible off the affected area.
Ice – reducing the swelling will help reduce the pain too and speed recovery. See the main text for more on application.
Compression – use a pressure bandage if possible but make sure it does not impede blood flow. Tingly or throbbing sensations in extremities are a signal to relax the pressure. Reapply bandage every few hours.
Elevation – raise the affected area 30cm or more above the heart to help control swelling.

Jenny K. Woolsey is a Registered Massage Therapist (RMT) and Managing Director of Sutherland-Chan Centre, in Hong Kong