New research is helping medical experts devise formulas for how long a typical office worker should spend sitting and standing.
Studies have found that sedentary behavior, including sitting for extended periods, increases the risk for developing dozens of chronic conditions, from cancer and diabetes to cardiovascular disease and nonalcoholic fatty liver disease. Some ergonomics experts warn that too much standing also can have negative effects on health, including a greater risk for varicose veins, back and foot problems, and carotid artery disease.
“The key is breaking up your activity throughout the day,” said Alan Hedge, a professor of ergonomics at Cornell University. “Sitting all day and standing all day are both bad for you,” he said. 
For every half-hour working in an office, people should sit for 20 minutes, stand for eight minutes and then move around and stretch for two minutes, Dr. Hedge recommends, based on a review of studies that he has presented at corporate seminars and expects to publish. He says standing for more than 10 minutes tends to cause people to lean, which can lead to back problems and other musculoskeletal issues.