Add Yahoo as a preferred source to see more of our stories on Google. Do you remember hula hooping when you were a kid? It was so much fun it never seemed like 'exercise.' But to do it now? Really?

Hula hooping is so commonplace that we may overlook some interesting questions it raises: 'What keeps a hula hoop up against gravity?' and 'Are some body types better for hula hooping than others?' A ...