Pilates, an old exercise regimen made fashionable in recent years by athletes and movie stars, builds strength and flexibility without adding bulk.

Unlike conventional weight training, which emphasizes repetition on one muscle group at a time, Pilates focuses on a series of precise, controlled movements that work muscles in several positions. The result: a longer, leaner look such as that seen on such Pilates converts as Madonna and Julia Roberts.

The low-impact exercises concentrate on strengthening the abdomen, lower back and buttocks. They are done on floor mats or by using several pieces of equipment that look like medieval torture devices but are actually gentle on the body.

A Brief History of Pilates

The basic tools of the system brought to the U.S. in the 1920s by its German immigrant creator, Joseph H. Pilates, use springs and pulleys to vary resistance. The most common, called a Reformer, consists of stirrups for either hands or feet and a bed-like platform that slides along a track. The Cadillac, or trapeze table, is surrounded by a metal frame and includes a push-through bar, a trapeze bar and leg straps.

Pilates had a lifelong interest in body conditioning. As a frail child determined to get stronger, he worked to become an accomplished skier, diver, gymnast and boxer. He developed the exercise method while he was detained in an English internment camp for German citizens at the onset of World War I.

Pilates opened a studio in New York City in 1926. Because many of the exercises focused on posture and body alignment, Pilates' approach quickly drew the notice of dancers, who also enjoyed being able to develop strength and flexibility without adding bulk.

In recent years Pilates has become the rage at health clubs. In addition to professional performers, housewives, grandparents — even pregnant women — are benefiting from the technique.

Cancer Survivor Becomes "Pilates Powerhouse"

Michele Aryant, a 46-year-old designer and educator in New York, took up Pilates while she was undergoing chemotherapy for breast cancer a number of years ago.

"I had read that you increase your chances of surviving (cancer) by exercising three to four times a week," she says. "I had also hurt myself doing a lot of other kinds of exercise. I was radically underweight and I wanted to build myself back up while I was in the process of doing the therapeutic tearing down of chemotherapy."

Now cancer-free, she says she looks and feels years younger than her 20-something design students at New York's Parsons College. "I have physical endurance in my day-to-day life that I would attribute to Pilates. My core muscles are astonishing. It's what they call the 'Pilates powerhouse.'" (The Pilates powerhouse is the area between the pubic bone and the ribcage, front to back. It includes the lower back muscles, stomach and the upper buttocks.)

Sean P. Gallagher, who bought the official Pilates Studio, based in New York, in 1992, says the poor posture of most Americans contributes to the epidemic of baby-boomer back problems.

"You can't have your head two inches off your center and not have some of the soft tissues overworking to hold you in place," he says. "You have to be able to sit with that idea of a good posture and a good alignment, but also have the endurance to hold it for a period of time, otherwise you'll just slouch as soon as you get tired.