Timeless question finally answered: when to use cold and when to use heat?

Cold (medically known as cryotherapy):

Used to control inflammation, pain, and edema (swelling) and to reduce spasticity (muscle spasm). Cold causes immediate constriction of blood vessels that supply the skin; this effect lasts as long as the cold is applied, as long as it is limited to less than 15 minutes. If the cold application is longer than 15 minutes, then vasodilation (increase in circulation) may occur, which will increase swelling. Cold should be applied every 2-3 hours post injury for 2-3 days.

Cold has powerful neuromuscular effects: it decreases the speed of nerve conduction, elevates pain threshold and decrease muscle spasm – all of which are helpful to combat pain immediately post injury. Cold therapy also decreases the amount of tone in the muscle, which can help with stretching the muscle.

Cold therapy can be used to control acute inflammation (24-72 hours post-injury) and thereby accelerate recovery from injury or trauma. Decreasing tissue temperature slows the rate of the chemical reactions that occur after injury. This lowers the amount of oxygen the area needs, and reduces the risk of further injury to the area from lack of oxygen to the tissues.

After an acute injury, there is an imbalance between oxygen demand and supply in the injured area from the damaged blood vessels. When there is not enough oxygen for the tissue, secondary tissue injury can occur from inadequate oxygenation of the tissues.

Cold can reduce muscle strength, can limit how much your joint can move and delays tissue repair.

Heat

Used to control pain and decrease muscle tone. Heat will increase swelling, cell metabolism (how hard your cells work), joint mobility and how much your muscles can stretch. Heat causes dilation of the blood vessels to the skin making the skin appear red. Heat will make it easier to stretch your muscles because it decreases muscle tone, the thickness of the body fluids and the resistance of the collagen tissue to stretch.

Heat will decrease the healing time by increasing the amount of oxygen available to the tissues and increase the rate of work of the healing cells. After acute injuries, the application of heat is not advised because it increases swelling, metabolic rate and oxygen demand to the tissues, increasing the risk of getting a second injury from not enough oxygen reaching the tissues. Heat can be used for chronic inflammation (after 4-6 weeks) to help increase blood flow to the area and promote healing.

Heat decreases muscle spasm and works by the same physiological mechanism as cold.

Heat should be applied for 15 minutes. Heat should be used for: pain control, muscle spasms, scar management, on injuries that are no longer acute, and for joint stiffness. Cold should be used on acute injuries, to control pain and for muscle spasms. Do not use heat or cold before balance or strengthening training.