TAMPALawyer Colleen Fitzgerald slips off her patent black heels and pulls on a pair of old running shoes.In the middle of her office, a treadmill whirs to life. Unlike the treadmills in the gym (or the ones gathering dust in your spare room), this one is fitted with a desk where you'd normally find the speed and incline controls.The platform looks like any other workspace: two monitors, a keyboard, yellow sticky notes and the obligatory coffee cup. Fitzgerald climbs on, picks up her phone and joins a rising workplace trend.When the downtown Tampa law firm GrayRobinson started encouraging its employees to embrace standing and treadmill desks, buying a walking workspace was a no-brainer for Fitzgerald, 43. Heart disease runs rampant on her mother's side of the family. Her mom and her maternal grandfather died in their 50s."My motivation is to try to defeat my genetic fate," she said while holding a steady pace.Prolonged sitting has been associated with significantly higher risks of everything from cancer, diabetes and heart disease to obesity and depression. Some researchers say our comfortable, ergonomic chairs are worse for our health than cigarettes. Even our early morning runs or evening gym sessions may not compensate for the damage we do sitting for hours on end at our desks.Experts say we should move around or stand for at least two hours — ideally four — per eight-hour shift, according to a statement recently released in the British Journal of Sports Medicine. Standing desks also have been shown to increase activity, concentration and focus.Woodrow "Woody" Pollack, 40, was one of the first at GrayRobinson to take the standup desk plunge a little over two years ago. A dull ache in his lower back prompted the patent attorney to re-examine his workspace. He considered plunking down $1,000 for a fancy new desk chair but wondered if it was time for more drastic measures.Pollack grabbed some discarded bankers boxes, laid his law school books on top and made a makeshift standing desk. In three weeks, his back pain disappeared.He has since traded the books and boxes for an official standing workspace. Now, he spends his 10- and 11-hour days at an adjustable-height table."I have not sat in a desk chair for two and a half years," Pollack said. "I highly recommend it."Like any change in routine, there's an adjustment period. Standing for long hours puts strain on your veins, joints and back. For a few weeks, your legs are sore. Your calves hurt. You might find yourself leaning against the desk for support.Lawyer David Hendrix's back hurt at first. He bought an antifatigue mat, a thick pad that cashiers, restaurant staffers and other workers who stand all day use to take the pressure off their joints. Hendrix, 53, now stands for the majority of his 10-hour days in the office."I feel more productive," he said. "I think better on my feet."Fifteen people at the GrayRobinson office now have standing or treadmill desks. The firm splits the cost of the standing desks with employees. Treadmill desk owners pay for their own equipment. The move is part of a larger firm wellness initiative that includes reimbursement for smoking cessation programs, subsidized gym memberships and annual flu shots.Employees at GrayRobinson aren't the only ones embracing the standing desk trend. At Bright House Networks, project manager Eli Pagan spends about a third of his workday standing. He said he's one of at least three people in the Riverview office with an alternative workspace.Pagan started using a standing desk at home two years ago to help ease the pain of a bulging disc. Shortly after joining Bright House in April, he put in a request for a standing desk. While waiting on the company to order it, he does his work from a coffee table propped on top of his regular desk. Not only has standing eased his back pain and increased his productivity, he said his makeshift desk also helped him meet people when he first started at the company this spring. People came by constantly to ask him questions about his setup."They were very intrigued by it," he said.Back in the GrayRobinson office, Ashley Runnells, 32, eyes Hendrix's setup admiringly from the hallway. The business development coordinator joined the firm in April. Lately, her back has been sore at the end of the day, and she's unimpressed with the daily activity tallies on her Fitbit."I think I'm going to have to ask about getting one of those," she said as she headed back to her desk chair.Contact Helen Anne Travis at [email protected] Follow her @helen_anne.