I have coronary heart disease, and my doctor has told me to avoid certain physical activities to avoid putting more stress on my system. I work as an administrative assistant at a real estate agency. Most of my job involves scheduling, completing paperwork, and keeping client files up to date; I do most of it sitting at my desk. Occasionally, however, I'm asked to do something more physical, like replacing large water bottles or carrying boxes of files or paper. Rarely, I have to help with a last minute staging job, which might include moving furniture and accessories. These physical tasks are painful, but they are part of my job. Can I ask my employer to allow me not to do them?