Shortly after she arrived home, Weinberg noticed a dull ache in her right calf. At first she thought she had slept on it wrong. "But the weird ache perisisted, and I thought maybe I should go to the emergency room," Weinberg recalled recently.

It's a good thing she did.

Weinberg had a case of DVT (deep vein thrombosis), which could have led to either a pulmonary embolism or a stroke - either of which could have killed her or left her severely handicapped.

DVT is the formation of a blood clot (thrombus) in a vein, typically in the thigh or calf. This dangerous condition - which can occur when a person sits for long periods - affects up to 600,000 people a year. Women are at increased risk for DVT, according to the National Aeronautics and Space Administration (NASA), which has information about DVT on its Web site.

Experts say that inactivity, dehydration and decreased circulation make for a deadly mix. Though typically thought of as an air traveler's condition, DVT can potentially affect anyone who takes a long trip of more than five hours by car, plane or train.

"Being immobile for a long period of time can create the right conditions for DVT," said Dr. Anita Chopra, a professor of medicine and the Director of Education and Clinical Programs at the New Jersey Institute For Successful Aging. "Our bodies are not designed for sitting for long periods."

She urged travelers to "exercise the legs and move every hour during long flights of seven to nine hours."

Among the serious conditions that may result from DVT are:

_ Pulmonary embolism: This happens when a blood clot breaks free and travels through the veins, reaching the lungs.

_ Stroke: The result of a clot that travels to the brain.

_ Post-thrombosis syndrome: Damage to the valves along the length of the vein. It is characteristically a painful condition accompanied by swelling and ulceration of the skin around the affected area.

Are you at risk?

Estrogen and their use of oral contraceptives places women at increased risk, according to the experts. (Randy said she was taking oral contraceptives.) Smoking, obesity, cancer and varicose veins also significantly increase your risk.

What are the symptoms?

Randy's DVT was detected by ultrasound, the most commonly used method. Doctors told her to stop taking oral contraceptives and treated her with blood thinners.

Preventive measures

Take breaks regularly if driving, or walk up and down the aisle of the train or plane.

"Exercise the legs while sitting by flexing and pointing the toes, rotating the ankles and wiggling the toes, which helps prevent the blood from pooling in the feet," recommended certified trainer Charles Morris, of True Health and Fitness.

Additionally, NASA recommends the following prevention strategies:

_ Lose weight.

_ Don't smoke.

_ Stay hydrated.

_ Avoid alcohol (causes dehydration).

_ Don't take sleeping pills.

_ Don't sit with your legs crossed.

_ Wear unrestricted clothing.

Weinberg has some advice, too: "When in doubt, get to the hospital." *

Kimberly Garrison is a certified personal trainer and owner of One on One Ultimate Fitness in Philadelphia (www.1on1ultimatefitness.com).

E-mail her at

kimberly@1on1ultimatefitness.com. Her column appears each Thursday in Yo!