Let’s take a look at the therapeutic use of ice and heat.
As a rule of thumb, you should apply an ice pack as soon as possible after an injury; applying it for 10-15 minutes, and repeating after 60-90 minutes. Make sure that the ice pack is dry, and covered in a layer of material. The closer you can stick to this regime the better.
After the 3rd or 4th day, then it becomes a little less clear as to which you should use. Generally after this time, muscles will respond better to heat, whilst joints will respond better to ice. If you’re unsure, try alternating between the two. Apply ice for 10 minutes, then 45 minutes later, heat for 10 minutes; repeating this cycle.
Heat: Directly stimulates sensory nerve fibres, altering your perception of pain, by overloading the sensory pathways. Heat also increases the metabolic rate of the tissue, increasing the efficiency of what they’re doing at the time – namely, trying to heal the injury. Heat can also directly increase flexibility of tissue, resulting in relief from muscle spasm, and increased range of motion.
Heat may exacerbate bleeding &/ oedema locally. Possible side-effects include burning if too hot.
Cold: Applied for up to 5 minutes, narrows the blood vessels, which will help to reduce bleeding and oedema in the early stages of healing. If applied for more than 5 minutes (but less than 20 minutes), cold has the opposite effect, improving the local blood flow; but then, by removing the ice, the body’s own regulation systems will rapidly warm the area, exciting the cells, who can then use the extra blood supply provided.
Ice can also have an analgaesic effect through stimulation of some of the sensory nerves (similar to heat), combined with reducing the conductivity of the pain sensory fibres allowing some pain relief.
If overused then the use of cold therapy will slow down the healing process, and is currently something of a professional controversy. Possible side-effects include an ice-burn if used inappropriately (ice-pack not wrapped in dry tea-towel).
Ultimately, both can have a beneficial effect, and “using the wrong one” won’t do any damage. Equally, something hot and something cold work better than chemical mimics (such as deep heat or ice spray) though the chemical mimics can often be more convenient.