Replace Your Chair We don't care if it adjusts or has amazing lumbar support -- lose the office chair, and invest in alternatives. The first option is a stability ball, which requires you to engage your core muscles just to sit, helping burn calories and tone your abs and back, says Michelle Ross, certified fitness trainer at E.W. Training. Just don't sit on the ball to work for more than a total of 60 minutes a day, says Amir Pozderac founder of Executive Fitness Consulting LLC. "Your core muscles will get tired and relax, so your body position will alter and cause your back to bend forward." To rest your core, work while standing or use another chair in between. Health expert Susan Schenck suggests propping a rocking chair at your desk as a respite, or use one on its own. "Rocking burns 150 calories an hour," she says.