I don't think I would've thought a mile as a "long run", but until age 30 it was further than I'd ever run without having to stop to rest. If you don't run regu

I don't think I would've thought a mile as a "long run", but until age 30 it was further than I'd ever run without having to stop to rest. If you don't run regularly, running for any length of time is hard, even if you're in good shape. (I was biking ~70 miles a week when I first started running, but unless you're really pushing, that doesn't work your heart of lungs anywhere near as hard.)