By JOHN O'NEIL

study released yesterday has some advice for people prone to fainting: cross your legs and squeeze.

Fainting occurs most commonly when the brain sends a signal that opens blood vessels wider, lowering blood pressure and causing blood to flow away from the brain and into the legs. The signal also slows the heart, in turn reducing the flow of oxygen to the brain. In some people, the signal, called the vasovagal reflex, is set off by emotional stress; in others, by prolonged standing.

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Researchers from the Academic Medical Center in Amsterdam decided to see whether fainters would benefit from a technique developed for people with a condition that causes their blood pressure to drop when they stand up.

The technique is simple: when the patients felt lightheadedness approaching, they crossed their legs, putting one ankle over another in what the researchers called the "cocktail party stance." They then tensed the muscles in their legs, buttocks and abdomen, forcing blood out of the legs and toward the brain.

In the new study, 20 patients who had suffered fainting spells were trained in the technique and strapped onto a tilting table. They were left upright for 20 minutes, and those who had not become lightheaded by then were given nitroglycerine, which opens up blood vessels, to speed the process.

Using the cross-and-squeeze maneuver stabilized the blood pressure and the heart rate in all the patients. The five patients who began the technique the most quickly when their blood pressures began to fall did not faint; in the others, the technique delayed the loss of consciousness by more than two minutes. Those minutes, the researchers noted, give the victims time to find a place to sit or lie down.

Nineteen of the patients were interviewed seven to 14 months later. Thirteen reported using the maneuver regularly to prevent fainting, and only two reported fainting spells in that time.