If you bought a stability ball to use at your pandemic home work station, or dusted off the unused one in the basement, you might want to sit down for this reality check — on a traditional chair. Claims that stability balls will strengthen your core have little backing in research. In fact, sitting on a stability ball, also known as a balance ball, exercise ball or Swiss ball, could have detrimental effects.

Manufacturers often promote stability balls as both workout equipment and furniture. Advertisements assert that although the products can be used to make exercises more challenging — by doing sit-ups atop the balls, for example, or propping your feet on them to do push-ups — simply using them as desk chairs improves posture and facilitates a core-strengthening workout.

The hype seems to have worked. Sales of balance balls grew 67 percent from January through July 2020, compared with the previous year, according to figures gathered by the NPD Group, a market research company. An NPD spokeswoman said sales grew the fastest in March, April and May, corresponding to the time when many gyms were closed and Americans were starting to work from home.

Balancing on an unstable surface does require engagement of your core — your abdominal, lower back and pelvic muscles. And engaging your core helps it grow stronger, which should improve posture and lessen back pain. That’s why people do exercises on top of stability balls. Thus, the idea that office workers could gain similar benefits by using balance balls as desk chairs doesn’t seem that far-fetched.  

But it’s not a theory backed by science, according to Brian Lowe, a research industrial engineer at the Centers for Disease Control and Prevention’s National Institute for Occupational Safety and Health. He and his colleagues were concerned when they saw workplace wellness campaigns bearing images of employees sitting on stability balls, because they weren’t sure sitting on a free-rolling stability ball was “an appropriate general workplace recommendation,” Lowe wrote via email.

After examining the issue, they published a commentary in the American Journal of Health Promotion in March 2016 that ended: “Although the existing body of literature is small, and the studies have limitations . . . the literature to date does not suggest significant health benefits to justify unstable sitting as a health promotion practice.” Until studies showed more conclusive benefits, they added, workplace recommendations involving stability balls should be viewed skeptically.

Diane Gregory, an associate professor in the Department of Kinesiology and Physical Education at Wilfrid Laurier University in Waterloo, Ontario, was an author of one of the studies cited in the commentary. That paper, which compared balls with office chairs, concluded that “prolonged sitting on a stability ball does not greatly alter the manner in which an individual sits, yet it appears to increase the level of discomfort.” She also was a co-author on a 2013 study, which found that gradually acclimating to sitting on a stability ball might ease the lower back discomfort caused by the balls, but again did not see an improvement in trunk strength or posture.

“The amount of movement that these unstable surfaces allow for really is not so much more so that the benefits outweigh the potential consequences,” Gregory said in a telephone interview.

Discomfort is not the only potential problem. Another negative found in one of the studies cited by Lowe is “spinal shrinkage,” a decrease in spine height due to flattening of the discs between the vertebrae. “Increased movement of the spine, if beneficial, should reduce disk shrinkage because the beneficial movement would increase fluid exchange within the intervertebral disc,” Lowe said. “The loss in spinal height, due to intervertebral disc shrinkage calls into question any benefits on the spine.”

Lowe also said there is “anecdotal evidence among ergonomics professionals of people falling from the free-rolling stability balls”; balls that are set on a base with a backrest should lower that risk.

And what about the idea that balancing on a stability ball will help you burn extra calories, which is sometimes cited as a benefit? Two studies that measured the difference between sitting on a regular chair and on a stability ball concluded that the difference was approximately four calories per hour, Lowe wrote, which works out to only about 30 calories over an eight-hour workday.

None of this is to say that stability balls don’t belong in fitness routines. (The question of stability balls as an aide for hyperactive students is also a separate issue.) “Physical therapists often incorporate these devices in dedicated exercise programs and that may be appropriate — particularly in a supervised exercise program,” Lowe said. But, as Gregory points out, no one is expected to participate in any workout that requires core activation all day. “We don’t want to have a muscle activated and then stay activated for a period of time,” she said.

Tessa Elliott, a physical therapist who works for Emory Healthcare in Atlanta and did research on balance balls as a doctoral candidate, says the balls can help patients build endurance in their deep abdominal muscles. “Using an unstable surface allows those muscles to be turned on,” she said.

Elliott was part of a team at Armstrong State University in Savannah, Ga., that compared stability balls with desk chairs. The 2016 study, published after she graduated, concluded that sitting on a stability ball did not reduce lower back pain, though it did improve endurance in the muscles that control forward and backward movement. Still, Elliott said, sitting on a ball all day isn’t something she would recommend as a strategy “to specifically target core endurance.”

“The bigger picture is that a healthier way to sit is varying what we sit on,” she said. So, she suggested, an at-home worker could switch between, say, a traditional chair, a stability ball, a backless stool and standing. (Standing all day, however, is also detrimental to the body, she pointed out.) “It’s also important to pay attention to posture and get up and move as often as possible, even if it is just for a few seconds,” she added in an email.

Gregory isn’t averse to people using the balls for short periods of time if they’re really interested in doing so. “I would say, maybe work up to an hour,” she said, “but at the end of the day, I don’t think anyone should be sitting longer than an hour, even in a fancy office chair.”

Get up and move around often, she added. “That’s going to be so much more beneficial than anything you’re sitting on to begin with.”