Imagine you’re in the thick of marathon training and your 18-miler falls on the weekend you’re going to be on vacation with your family. You have a 9 a.m. tour planned, so you figure you can get in a solid 10 miles beforehand, then log the remaining eight miles that afternoon when you get back to your hotel. Or, maybe you have a small injury that starts bugging you around 13 miles in, so you call it at 13, then log the remaining five later that day when you are feeling better. Splitting up your long run within the same day is pretty much the same thing as logging continuous miles, right? Not so fast. “The whole point of a long run is to get your body used to being on your feet for hours at a time, and that’s something that your body has to adapt to,” says Kara Dudley , an RRCA-certified run coach and founder of Rerouted Running . The good news is this means that slowing to a walk for a few seconds or minutes during a long run is totally okay.…