Orthopedic surgeon Nomi Kahn says:

“Most of us do not sit well, and we’ve certainly been putting a lot more stress on our spines,” says Khan, who operates on spines at Sutters Health’s Palo Alto Medical Foundation.

If we change the way we sit, Khan says, it will help to decrease back problems.

“We should sit less, and we should sit better,” he says.

Over the past century or so, many Americans have lost the art of sitting, he says. Most people in the U.S. — even children — are sitting in one particular way that’s stressing their backs. You might not realize you’re doing it. But it’s super easy to see in other people.

Here’s how: Take a look at people who are sitting down – not face-on but rather from the side, in profile, so you can see the shape of their spine.

There’s a high probability their back is curving like the letter C — or some version of C. Or it might make you think of a cashew nut, sitting in the chair. There are two telltale signs: Their shoulders curve over and their butts curve under. That posture is hurting their backs, Khan says.

“Most people tend to round out their backs when they sit,” Khan says. “Their spine is in an improper position, and they will tend to have more back problems.”

Back problems crop up because sitting like a C — or a cashew nut — can damage the little shock absorbers in the spine, called the intervertebral disks.

“You can think of a disk as a jelly doughnut,” Khan says. “Sitting like a C puts a lot more pressure on the front of the doughnut than on the back.”

And what happens when you press down on one side of a jelly doughnut but not the other side? Jelly can squirt out.

Your spinal disks aren’t much different. Sitting in a C-shape, over time, can cause disk degeneration. Or one side of a disk can start to bulge. “The disk can then push against nerves, or it can rupture,” says biomechanists who direct the Spine Research Institute at Ohio State University.

“When the disks get messed up, you’ve got real problems,” Marras says. “So everything we do in biomechanics is to try to protect the disks.”

Are there experiments you can do? Take a look at the people around. Look for the “C.” Read the full article and hear the audio here.