Sculptor, Shape Thyself : Health club members look a bit like artists as they take a new approach to muscle conditioning.

At a sculpting class in Encino, students are pulling green rubber tubes, lifting weighted red balls and squeezing hollow black cir cles between their thighs. In Van Nuys, they’re slipping long orange tubes underneath plastic benches.

No, they’re not abstract artists creating their masterpieces.

They’re health club members sculpting their biceps and deltoids.

Bored with weight machines, intimidated by barbells or turned off by the grunting at the gym, many exercisers are trying body sculpting, a method of muscle conditioning that is gaining popularity.

Instead of taxing muscles with heavy weights, they tax them with two-pound dumbbells, giant rubber bands, rubber tubes with handles or other gadgets that look as innocent as kindergarten toys. But the catch is, they don’t stop counting at 10. With some body parts, they perform two dozen repetitions without resting.

At least they try. In classes called “Bikini Buster Sculpt,” “Power Bands” and “Muscle Bench,” even well-conditioned body builders feel the burn.

“I’m talking about guys who look like Conan the Barbarian, and I had them crying,” says Kendra Alcock, who teaches sculpting at two Valley health clubs, the Westlake Sporthouse and Supreme Court Sports Center in Van Nuys. “They think, the little rubber band, no big deal. But they were screaming to stop.”

That’s not because body sculpting is more difficult than traditional weight training. It merely works the muscles in a different way. Using heavy weights generally results in more strength and bulk, whereas body sculpting tends to provide muscle endurance and tone.

“You’re able to build nice, lean muscle mass,” Alcock says. “And you’ll be able to keep your arms up longer in aerobics.”

If you want bulging biceps, however, you’ll have to hit the weight room. Body sculpting “will take you so far, but it has limited potential,” says Jean Holloway, an advisory board member for the UCLA Extension Certificated Program in Fitness Instruction. “You won’t get stronger unless you have more demand placed on the body. . . . With something like a rubber band, there’s only so much overload you can get.”

You can increase the overload--the amount of stress on the muscle--by using a shorter band or wrapping the tube around the wrists to decrease the slack. Unlike with weights, however, “you have no way of measuring how much work you’re doing,” says Cal State Northridge kinesiology professor George Holland.

Most body sculpting enthusiasts aren’t interested in knowing exactly how much weight they are lifting. They come to class for motivation (“OK, eight more! Everyone having fun?”) and a structured, total-body workout.

“You don’t have to think--she does it for you,” says Darryl Ingram, 50, of Sherman Oaks, a telephone technician who is a regular at Alcock’s Supreme Court classes.

This is fortunate, because it would take some serious thinking to devise these exercises. In Alcock’s class, to work the chest muscles you kneel on the floor to do pushups--with your hands atop a step aerobics bench, holding a tube wrapped behind your lower back. The tight tube provides extra resistance when you push up against it.

Exercises at Tight Moves fitness studio in Encino are equally inventive. Ann Lalo, 39, says they’re a lot more fun than Nautilus machines. “Here you have the music, and everyone’s doing it together. It’s warmer and friendlier than the weight room.”

It can also be safer. In a gym, some people lift more weight than they can handle, which can lead to tendinitis, muscle strain and other injuries. “When you have a weight in your hand, there’s a tendency not to control it on the way back,” says Tight Moves owner Ellen Kolarik. “But with a rubber band, if you let go, your arm will come flying down. It makes you pay attention.”

To fitness experts, the gadgets are helpful because they broaden the appeal of strength training. Muscle conditioning isn’t just about looking good, they say; it’s as important to good health as jogging, aerobics or the Stairmaster.

“Activity of purely aerobic nature isn’t going to prevent loss of muscle mass and strength that is part of the aging process,” Holland says. In addition, strength training, when combined with adequate calcium intake, has been shown to help prevent osteoporosis, the bone disease that commonly afflicts women after menopause.

In fact, research has shown strength training to be so vital that in 1990 the American College of Sports Medicine amended its guidelines, recommending two or three weekly sessions of strength training in addition to three to five weekly sessions of aerobic exercise. In response, a number of hourlong step aerobics classes have added half an hour of sculpting.

“Exercise doesn’t have to be fast and frantic,” Kolarik says. “The whole industry switched from high-impact to low-impact . . . and now we’ve added muscle conditioning. People are just realizing it’s a lot healthier for you.”

Where and When

Location: Tight Moves, 17223 Ventura Blvd., Encino.

Price: Classes cost $8.50.

Call: (818) 783-2331

Location: Supreme Court Sports Center, 7030 Havenhurst Ave., Van Nuys.

Price: Classes are free to members. Contact club for membership rates.

Call: (818) 988-5500.