VIRTUAL-REALITY EXERCISE SHAPING UP.

Byline: Judith Zimmer The New York Times

It used to take discipline for Cheryl Bailey to get up at 6 o'clock for her morning workout. Now, the 34-year-old advertising agency executive vice president can't wait.

For years, Bill Schreitmueller, 36, the executive producer of a television production company, went to the gym three days a week. Now he goes every weekday.

Their motivation? The Tectrix VR Bike, one of the first virtual-reality bicycles, which takes them through simulated adventures projected by a CD-ROM on a computer screen.

Bailey and Schreitmueller, both of whom are members of the Ritz Plaza Health Club, a gym in a midtown apartment building that has one VR Bike, prefer to exercise with the ski-slope CD-ROM. But they also can choose mountainside or tropical landscape excursions. They steer the bike by leaning left or right, and they can veer off the road to cycle on grass or snow or underwater.

``I hog it,'' Bailey said. ``You imagine you're in the scene. The truck ran me over one day. A bunch of chickens flew out of the back of the truck. There are always little surprises like that.''

The VR Bike, by Tectrix Fitness Equipment of Irvine, is the latest use of technology to keep the repetition-weary excited about moving in one place for minutes at a time. Other equipment includes cardiovascular machines that are like a cross between treadmills and step machines, and resistance machines that are like exercise buddies that encourage and monitor progress.

The most pronounced changes involve cardiovascular machines. The International Health, Racquet and Sports Club Association says that exercisers at health clubs favor cardiovascular machines almost twice as much as resistance machines.

Cardiovascular exercise, like running or bicycling (or any activity that uses large muscle groups), is the basis of most exercise regimens, said Dr. James Rippe, a cardiologist and the director of the Center for Clinical and Lifestyle Research in Shrewsbury, Mass.

``Everyone knows that cardiovascular exercise reduces the risk of heart disease, burns calories and controls stress,'' he said. ``But there is tremendous boredom, especially at health clubs.''

Rippe cited a report released by the surgeon general in June recommending that a moderate level of exercise almost every day - like walking two miles in 30 minutes or even pushing a stroller 1-1/2 miles in 30 minutes - can improve a person's health. The report recommends supplementing such cardiovascular exercise with strength-training at least twice a week.

``People spend more time doing cardio,'' said Richard Miller, the president of the Gym Source, a New York supplier of fitness equipment, including the Tectrix VR Bike.

The company has sold other cardiovascular equipment to celebrities, including treadmills to Woody Allen, George Bush and Vice President Al Gore. ``Manufacturers are inventing it because there is more demand for it.''

These days, entertaining people while they exercise has become an industry standard. Television monitors are common sights in gyms. Interactive technology is just the latest step.

With its price tag of $7,995, the Tectrix VR Bike - and the VR Climber, a step machine that involves a simulated airplane and sells for $6,995 - is out of the price range of most consumers for home use. But Miller said that in three years such equipment should be less expensive.

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Photo: (1--2) Entertaining people while they work out ha s become an industry standard. Jill Ellen Lawton, left, uses the Tectrix VR Bike, one of the first virtual-reality bicycles, while Tom Heavy uses a Sit-Up Master.

The New York Times