DD said it was a mix of calisthenics — and yes, running — though a watered-down version of regular PT. She also said there was a broad range of fitness, from sports studs to the, ahem, cardiovascular-challenged. Don’t worry about it for now. Just do your best, knowing that others may be in worse shape. There’ll be some things, outside of fitness, in which you’ll be better than most of the others.
BUT, should you decide that an academy (any of them, or ROTC) is something you want to pursue, get cracking on your fitness. The CFA you take at SLE will provide a very good idea of what you’ll need to work on. Good luck.