Compared with weights, hefting a big, vinyl ball seemed a "wimpy" way to work out, thought Cindy Bujosa. Just one "Get on the Ball" class at Medford's Superior Athletic Club was enough to bust Bujosa's bias.

Compared with weights, hefting a big, vinyl ball seemed a "wimpy" way to work out, thought Cindy Bujosa. Just one "Get on the Ball" class at Medford's Superior Athletic Club was enough to bust Bujosa's bias.

Like so many other fans of the PhysioBall, or fitness ball, Bujosa has found she can roll, bounce and balance her way through challenging workouts with surprising results.

"You can gain a lot of strength from it without being so hard on your body," the 42-year-old Medford resident says. "It's so much more difficult than it looks."

Bruising her pride — if not her backside — in Superior's Monday-morning class, Cathy Barr can vouch for the concentration required to literally stay on the ball. Barr and the entire class of 15 women burst out laughing when Barr's silver ball shot straight out from under her during a stretching exercise.

"Actually, it's never happened to me before," she says after class.

Barr, 47, says she had plenty of practice using the ball at home before Superior instructor Sue Oppelt started Get on the Ball several months ago. But Barr was "thrilled" about the new class, which combines Pilates movements and lifting weights with the balance and precision needed to keep the ball under control.

"You can sit on it; you can lay over it; you can lean against it," Oppelt says. "There's the whole bouncing thing about the ball."

Bouncing on their balls to the beat of music, Oppelt's students start the class smiling. Grins soon turn to groans as Oppelt tests participants' "core" strength and endurance. Near the 45-minute session's end, even Oppelt's ball quivers as she braces her feet — pelvis pointing toward the ceiling — on the precarious surface.

Supporting and stabilizing the body on a fitness ball taxes muscles that aren't used so much during more stationary exercises, says Jeni Beck, fitness coordinator for Rogue Valley Family YMCA in Medford. This "neuromuscular integration" ramps up a workout's intensity, she says.

"You're just getting a lot more bang for your buck."

YMCA members use fitness balls in most of their classes, including core-conditioning, yoga and Pilates, Beck says. While instructors promote the benefits of fitness balls, members are happier when exercise revolves around them, Beck adds.

"People just really like them because they're fun," she says. "You get the ball out, and people just smile.

"When I don't get the ball out, they're really disappointed."

Oppelt gets similar reactions.

"It's fun; it's a toy."

In reality, the popularity of fitness balls — also called stability balls, gymnastic balls and Swiss balls — sprang from their longtime use in physical therapy, sports medicine and sports-specific training, says Bill Macy, director of Avamere Health & Fitness Club in Medford. Elite athletic trainers like Macy employ fitness balls for total body strengthening.

"It's an extremely advanced form of exercise," Macy says.

As with all exercises, beginners should seek advice and assistance from a fitness professional, ideally working one-on-one with a personal trainer to start, Macy says. Novices can benefit from a slightly deflated ball and may need to practice balancing while staying seated for several sessions before adding any movement, he says. More advanced exercises with a fitness ball may take months to master, he adds.

Superior member Virginia Graber used a fitness ball haphazardly before joining Oppelt's class, which proved the importance of sizing a ball to one's frame. Starting out with a 65-centimeter fitness ball, Graber couldn't understand why Oppelt's workout seemed so extreme. Trying to bounce the ball along with other class participants revealed the hard truth: Hers was weighted with sand.

So the 5-foot-1-inch Graber purchased a 55-centimeter ball — without stabilizing filler — and made Get on the Ball part of her Superior routine, which also includes yoga, Pilates, dance and weight-lifting. Exercising with her fitness ball is a welcome change of pace, the 63-year-old Central Point resident says.

"I think you need to mix up your routines," she says. "The older you get, the more you need.

"It helped with balance," she adds. "Balance is a big thing for somebody my age."

At 78, Steve Sanford could barely walk on a collapsed arch, much less balance on one foot. After a trainer at Avamere introduced him to fitness balls, the Medford resident is regaining mobility and straightening his spine in an unconventional way.

"The height of the ball, it turns out, is just perfect," Sanford says. "I use it as a chair."

Sanford perches on the ball, legs akimbo, while working at his home computer. Wiggling his hips moves the ball around his desk. Still not fit for more strenuous ball exercises, Sanford has lost 50 pounds and strengthened his back by swimming. He's convinced Avamere's fitness-ball class will help him accomplish a goal of walking five miles at a stretch by the time he's 80.

"I can see a lot of potential for it."