The benefits of cryotherapy or cold therapy include pain relief, reduced inflammation, swelling and muscle spasm. It is important for treating sports injuries.
Why does ice or cryotherapy reduce pain? The reason cryotherapy relieves pain is not completely clear. There are many theories and it is possible a number of mechanisms in combination have an anaesthetic effect. Possible mechanisms are:
- Decreased nerve transmission in pain fibres
- Reduced activity of free nerve endings
- Cold raises your pain threshold
- Cryotherapy releases endorphins, the body’s feel good chemicals
- Cold sensations over-ride the pain sensations (pain gate theory)
Reduced bleeding and swelling
Another cryotherapy benefit is it reduces swelling and internal bleeding. By cooling the surface of the skin and the underlying tissues, ice causes blood vessels to narrow (vasoconstriction). This therefore leads to a decrease in the amount of blood delivered to the area. As a result, swelling reduces.
Hunting response & vasodilation
The Hunting response occurs when blood vessels dilate folloing a period of vasoconstriction. If you apply cryotherapy to an area, then blood vessels constrict. Then remove the cold pack. After a few minutes the blood vessels re-open (dilate). As a result, allowing more blood to return to the area.
Although blood still flows into the area, swelling is significantly less. This decreased swelling (edema), allows more movement in the muscle and so lessens the functional loss associated with the injury.
Inflammatory response & cold therapy benefits
The swelling associated with the inflammatory response also causes a pressure increase in the tissues. This leads to the area becoming more painful. Pain intensifies when certain chemicals release into the blood as a result of tissue damage. Hence, vasoconstriction from applying ice also decreases pain.
Reduce muscle spasm
Another cryotherapy benefit is reduced muscle spasm. This is often a response to pain as muscles surrounding the injury contract to protect it. This is muscle guarding and prevents further damage. Because ice has a pain killing effect, the muscle relaxes as a result of decreased pain.
Overuse related muscles spasm may also reduce as a benefit of cryotherapy.
We do not fully understood this but is may be to be due to cryotherapy slowing the conduction velocity of sensory and motor nerves. Also, the activity of muscle spindle cells is decreased. Muscle spindles are sensor in the muscle which sense muscle tone.
Decrease metabolic rate
By reducing the cells metabolic rate, ice reduces the cells oxygen requirements. Therefore, when blood flow is limited by vasoconstriction, the risk of cell death (called secondary cell necrosis) is reduced.
References & further information
- Updates on PRICE – Br J Sports Med 2012;46:220-221 doi:10.1136/bjsports-2011-090297
- What is the evidence for PRICE? – J Athl Train. 2012 Aug; 47(4): 435–443.