Good guess is 'on their feet' with their legs working above them. I guess you are talking abut real running not going in a car, bus or train.
Why five miles? Why not two? Or the Marathon twenty-six?
When we are young and fit it isn't difficult to run five miles once we've trained up to it. But training up to it is important. You'll become lean and develop great lung-capacity. By running five miles a day, say, three times a week you'll become super fit. But don't try it on straight off. To reiterate, if you are able, train up to it.