You’ve probably heard a lot over the years how sitting all day isn’t doing you any good. Too much time spent on your butt can mess with your back, cause you to gain weight, and even age you by eight years.

So is forgoing the chair and standing all day at work the answer? Maybe not, as a new study published in the American Journal of Epidemiology suggests.

In the study, researchers analyzed a survey of 7,320 people who worked 15 hours a week or more, and analyzed their occupations to determine how long they would spend sitting, standing, or walking around. They found that guys who mainly stand all day at their jobs—say, standing behind a counter all day at the bank or behind a cash register at a store—are twice as likely to have heart disease than guys who mainly sit.

The reason for that increased heart risk is actually pretty simple, says Peter Smith, Ph.D., lead author of the study and scientist at the Institute for Work and Health in Canada.

“When you’re standing for a prolonged period of time, the blood tends to pool in your legs, and it’s hard for your heart to pump that blood back up to the top of your body,” he said. That can increase your risk of heart disease.

Standing all day, which can put your body in an uncomfortable position for a prolonged period of time, he says, can also increase oxidative stress, a process that can damage cells in your body and increase inflammation. Again, not good for your heart.

So Is Your Standing Desk Hurting Your Health?

No need to shelve your standing desk and go back to spending the rest of your workday parked on your butt.

“One of the things about [standing desks] is that they enable people to be able to stand when they feel uncomfortable sitting, and vice versa,” Smith said. “I think the key here is that workers have the flexibility to be able to move their bodies when they want to.”

And it's that movement that may be helping your heart—you're neither sitting nor standing for hours on end.

So make that your workday goal: In fact, the study found that workers who did a combination of sitting, standing, and walking had about a 40 percent reduced risk of heart disease compared to those who only stood all day.

"It’s as simple as just providing a chair to workers, or rotating their shifts so that they’re not forced to stand for prolonged periods of time," Smith said.

If you need to stand all day, at least make sure you walk around a little to get your blood moving. And if you sit all day, get up, stand, and move when you can. By simply switching between sitting and standing every few hours, or getting up to go for a quick walk or two to get your blood flowing throughout the day, you can lower your risk of heart disease.