You spend all day sitting at a desk. Then, you plop down on the couch to relax, watch TV, read a book or play computer games. Maybe you sit at the dinner table for a while, too.    

If you’re like many Americans, you’ll spend more than eight hours of your day seated. But did you know that sitting for long, uninterrupted stretches can put your health at risk — even if you exercise regularly?  

“There is some evidence...