Sweatin’ to an Oldie : An exercise method developed in the 1920s is becoming popular among therapists and enthusiasts bored with lifting weights.

In this age of high-tech fitness equipment--stair climbers that count calories burned, stationary cycles that monitor heart rate--a growing number of fitness enthusiasts are turning to a machine invented in the 1920s.

The Pilates reformer, a horizontal apparatus that resembles a small bed frame, is the main component of a muscle-conditioning method developed by Joseph Pilates (pronounced Pi-LAH-tees), a German-born gymnast and circus performer who died in 1967. Pilates brought his technique to the United States in the late 1920s, after refusing the German government’s request to train its police force.

Known for producing lean, graceful bodies, the Pilates method has been revered by dancers for decades. Recently, however, it has become popular among physical therapists, who say it has rehabilitative benefits, and among ordinary exercisers who are bored with lifting weights.

“You feel like your muscles are being reawakened,” says Cathy Davis, 47, of Tarzana, an avid horseback rider who does Pilates exercises to increase her strength and flexibility. “It’s a very peaceful kind of feeling. You’re not thundering around some gym.”

For the most part, you are lying, kneeling or sitting on the reformer, pushing or pulling against tension provided by springs. Davis, for instance, lies face up on the machine, bends her knees, places her bare feet on a platform, then gently pushes herself backward until her legs straighten. She slowly returns to the starting position and repeats the move about 10 times, while her instructor, Quentin Josephy, corrects her posture and reminds her to relax her shoulders and breathe properly.

The exercise, which requires considerable concentration, is intended to do more than strengthen Davis’ thigh muscles. Unlike traditional weight machines, which tend to isolate a particular muscle group, Pilates exercises--even those focusing on the arms--require control of the entire body, particularly the abdominal muscles.

“At the gym, people tend to think of themselves in terms of body parts, and their workouts reflect it,” says Josephy, owner of Kinetic Fitness Studio in Tarzana. “With Pilates, the focus isn’t on trimming your thighs to fit into a bathing suit.” He says he tries to get his clients to work with their body as a whole. “In many cases, I’m unlearning a lot of people.”

Because Pilates workouts require an instructor, a single session can cost between $20 and $45--the equivalent of a monthly health club membership. Nevertheless, the method is surging in popularity. A decade ago there were a half-dozen Pilates studios in the United States; today there are more than 100, according to Ken Endelman, owner of Current Concepts, a Sacramento company that manufactures most of the Pilates reformers in the country.

“My business has grown 35% a year for the last five years,” Endelman says. Reformers sell for about $2,500, but Endelman is working on designs that will cost less. And to accommodate the growing interest of physical therapists in Pilates, he also has developed a model for people in wheelchairs.

Why is Pilates booming now--70 years after it was invented?

“Demographics, pure and simple,” says Joan Breibart, president of the Pilates Institute, an organization in Santa Fe, N.M., that trains instructors. “It’s an aging population. After 20 years of going for the burn, people are either injured or bored or they don’t have the body they feel they should have.”

Carol Monaco, who teaches Pilates out of her West Hills home, says her students--men and women--range in age from 13 to 65.

“The main reason Pilates is so sound is that it has an even amount of strength and stretch,” Monaco says. “So many of the other programs emphasize strength over flexibility. But in the natural process of aging, you lose your flexibility. A person who’s been playing tennis all their life and never pulled their hamstring will all of a sudden pull their hamstring.”

Pilates won’t build as much strength as lifting heavy weights, but it does have some advantages over traditional weight training, experts say.

“With weight training, flexibility tends to be an afterthought,” says George Salem, a lecturer in the UCLA department of physiological sciences.

In addition, Salem says, Pilates exercises are more like real-life movements because they involve several muscle groups.

“Rarely are we in a position when we’d just extend our legs up and down. Normally, we’d be extending the knee, flexing the hip, using the back and shoulder muscles at the same time, like when we’re riding a bike.”

However, Salem cautions, multi-muscle exercises require a lot more concentration than exercises that isolate a muscle group.

“You wouldn’t want to just go in and jump on this machine and do these techniques,” Salem says. “They should only be done with a highly qualified instructor.”

There is some controversy in the Pilates community about who exactly is qualified.

Joseph Pilates never fully described his exercise on paper and trained only a half-dozen instructors. These instructors, now in their 80s and spread out across the country, trained a second generation of instructors, who, in turn, trained a third generation.

The Pilates Institute--which is affiliated with some of Pilates’ octogenarian proteges--was founded to preserve the method in its original form, according to Breibart, and to certify instructors who have mastered the technique as Joseph Pilates developed it. However, many instructors believe the Pilates technique can be successfully combined with more modern methods of exercise and rehabilitation.

Arlene Alstadt, who runs West Valley Physical Therapy in West Hills with her husband, plans to get a reformer for their practice.

“It’s very, very beneficial for particular back problems,” says Alstadt, who is learning the technique from Carol Monaco. “The abdominal strength you gain from this is unbelievable. If you don’t have a strong abdominal wall, you’ll have a weak back.”

Where and When What: Private sessions in the Pilates method. Location: Carol Monaco’s home studio in West Hills, call (818) 703-8743; Quentin Josephy, Kinetic Fitness Studio, 19458 Ventura Blvd., Tarzana, (818) 342-3676; Michael Levy, Private Moves fitness studio, 17223 Ventura Blvd., Encino, (818) 783-0097.