Should I use hot or cold packs on a sprained foot?(ask the doctor)(Column)

--Jose Valdez, Los Angeles.

When you sprain a joint, a series of biochemical reactions--known as an inflammatory cascade--happens as a result of the tissue damage. This cascade is mediated by several substances such as prostaglandins; cytokines such as interleukin-1 (IL-I), IL-6, IL-8, and IL-12; the Cox-2 enzyme; glutamate and substance P. The injury, also releases nitric oxide, which causes pain and slows the healing process.

These chemicals cause changes in the sprained joint. The blood vessels widen in an attempt to bring more blood to the injured joint.

Applying heat causes blood vessels to open wide. This is useful for chronic conditions where circulation is permanently impeded to the joint. This is why heat is popular with older people--their pain is chronic and they need to stimulate circulation--but it is of little value in treating all acute injury.

Applying cold to a recent sprain causes the blood vessels to constrict. It also deadens pain receptors at the injury site. Athletes, for example, apply ice to their bodies immediately after sporting events to reduce inflammation and lessen pain.

But if you also want to heal the injury quickly, you can use what is called contrast therapy a combination of hot and cold packs. Contrast therapy maximizes the flow of blood and causes pain modulators to be flushed from the site of injury and to be broken down elsewhere in the body. The increased blood flow also speeds healing of the joint.

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