When Andrea Martin became pregnant with her son in 2012, the chair at her then-desk job made her back ache.

“I had heard of other pregnant women switching to an exercise ball, so I gave it a try,” says Martin. “Not only did it help keep me comfortable, it was fun to sit on.”

Once banished to the gym, exercise balls are popping up in place of chairs in cubicles, with the promise of a more engaged core.

“Sitting at a desk affects the neck, upper back, and shoulders,” says Dr. Ray Moore of Physical Therapy First in Roland Park.

Over the course of a workday, it’s natural to fall into a “slump” posture, with a rounded back and protracted shoulders. That’s where, according to some experts, the ball comes in.

“It really allows you to choose the position your spine is in while you’re at your desk,” says physical therapist Lizzie Cavanaugh Bellinger of Spine and Sports Rehabilitation Center in Timonium. “Most office chairs choose your spine position for you by supporting you into a very specific posture.”

Although it may not be practical for an entire eight-hour workday due to muscle fatigue, it can be beneficial in shorter periods, says Bellinger.

While the ball and standard chair come out neck-and-neck in clinical studies, users like Martin swear they can feel the difference. “I wouldn’t go back to a traditional desk chair,” she says. “I credit the ball with helping me get my core back in shape after having my son.”