WASHINGTON — At work, Pam O'Donnell types at her computer, talks on the phone and, every so often, bounces a bit on a big blue ball.
O'Donnell has an office chair, but this doesn't mean she uses it. She prefers to sit on an exercise ball.
Although some posture experts are leery of the practice, she and others say sitting on the balls lets them add a little workout into their work time and strengthen their legs, abs and back muscles.
The inflatable balls, typically the size of a big beach ball but made of tougher plastic, have migrated to offices from health clubs and physical therapy clinics.
The lack of armrests, back support or other attributes of a chair, except for a spot on which to sit, makes her pay more attention to posture, said O'Donnell, director of member service for the International Health, Racquet & Sportsclub Assn., a Boston-based trade group.
"It makes me sit up straight," which gives a ball some advantage over a chair, she said. "When you are sitting at your desk, especially at a computer or keyboard, you tend to hunch over."
"What we are trying to promote is active sitting versus passive sitting," said physical therapist Cheryl Soleway of Vernon, Canada, a consultant to Ball Dynamics of Longmont, Colo., which sells the products.
"You get a low level of neuromuscular activity -- your abdominal and trunk muscles are contracting to some degree. Without that activity, you would fall off."
To Soleway, there is even an upside to the fear of falling down. The natural urge not to slide off the ball should help to train the balance system, reducing the risk of falls, she said.
Position counts in ball work. Soleway said the ball should be big enough to allow the legs to slope slightly downward at not quite a right angle from the thighs.
However, she conceded that there are many unknowns in the physiology of ball sitting as an office exercise. "I'm not sure anybody has spent a lot of dollars researching this," she said.
Sitting on a ball at work should improve muscle tone, but a risk of injury could await people who do it for a full day, said Dr. Henry Goitz, chief of sports medicine at the Medical College of Ohio in Toledo. "Twenty minutes is good, 30 minutes is great, but eight to 12 hours, some time in that span, you may have fatigability," he said.
Still, exercise balls in offices have raised concern in some parts of the world.
"Providing fitness balls in a workplace may place the employer at risk of introducing a hazard," according to a statement posted on the Internet by workplace safety officials in the Australian state of Victoria.
And an expert in office ergonomics -- the fitting of office functions to the strengths and limits of human bodies -- has doubts about the wisdom of substituting a bouncy ball for an ergonomically designed chair.
"I don't think this would be anything I would use to reduce my exposure to musculoskeletal disorders," said Peter Budnick, chief executive of Ergoweb, an ergonomics training and equipment sales company in Midway, Utah. "It's not an ergonomic device. It does not offer the full support you would expect from an ergonomic chair: stable base, adjustable height and back support."
Just the same, "I have to say it sounds like fun," Budnick said.
If exercise balls encourage fun -- or a less stressful workplace -- companies should encourage balls, said Nancy G. Lynch, an adjunct professor of human resources management at Canisius College and president of Human Resources Consulting Associates in Buffalo, N.Y. Companies in which employees look like they are having fun will find it easier to attract new hires, she said.
Activities that get people moving also are good for "thinking and problem-solving," Lynch said.
O'Donnell said fun was only one of the advantages to using a ball. "Every so often, you do sort of roll back and forth or bounce a little," she said. "I have a little radio on, and if there's a good song that comes on, I might bounce a little."
As for group activity, O'Donnell noted that some workers in her office use exercise balls. "We haven't had any hippity-hop races around the office at this point, but that might be a good Friday event."