Tushes are flattening by the minute. Backs are gnarling up. Spinal cords are compressing.

The culprit: the evil office chair.

Sitting — yes, sitting — is a proven workplace hazard, and employees are ready to take a stand.

Nine out of 10 office workers, anchored to their desks for most of the day, report end-of-workday aches, pain and fatigue, says a study by WorkRite Ergonomics, a Calif.-based company that sells work centers for the office.

Fifty-seven percent of employees say that if given a choice, they would prefer to stand.

"It really takes a toll on the behind," says Mindy Spreitzer, an insurance claims adjuster from Indianapolis. She spends her entire workday — 8 a.m. to 4:30 p.m. — sitting.

Her company recently switched to a paperless system, meaning no copy or fax machines — and no reason to actually walk away from the computer. "There is no getting up now," Spreitzer says.

She does sneak an extra trip or two to the bathroom, just to stretch her legs. She says standing up to work for a few hours a day would be a relief.

With the move to paperless office environments, teleconferences and e-mail — which don't require workers to walk away from their desks to talk to co-workers — sitting is practically the new job requirement.

Nearly 60 percent of workers say they are planted in chairs for more than six hours a day.

"You're holding a position all day long that is static," says Derek Timm, technical services manager with WorkRite. "You're forced into a position that doesn't fit your body shape. This is comparable to walking around in ill-fitting shoes or sleeping in a bed that's too small."

Sit too long, and you'll find your body giving signals.

"You'll feel a need to start fidgeting," Timm says. This is the body's way of telling you it needs more oxygen. You'll feel discomfort and soreness. You'll feel fatigue. Your body actually is tired of sitting.

It's not that sitting itself causes harm. But holding that position over time is detrimental, causing repetitive strain injury.

He suggests companies invest in workspaces like the ones his company sells.

The Sonoma Premium, for example, is a height-adjustable work center that allows sit-to-stand flexibility. That means you can sit for an hour, then push a button that moves the desk to a standing position. Those stations cost $1,539 to $3,522.

In the meantime, here are some tips from the American Council on Exercise: