Seven miles seems so little, but it's not, believe me. With a pack, even for fit people it is not.
You know what it's like when you're at a zoo or an amusement park with a small child who won't walk another step? You hoist him lightly onto your shoulders and for a while-- for a couple of minutes--it's actually kind of fun to have him up there, pretending like you're going to tip him off or cruising his head towards some low projection before veering off (all being well) at the last instant.
But then it starts to get uncomfortable. You feel a twinge in your neck, a tightening between your shoulder blades, and the sensation seeps and spreads until it is decidedly uncomfortable, and you announce to little Jimmy that you're going to have to put him down for a bit . Of course, Jimmy bawls and won't go another step, and your partner gives you that disdainful, I-should-have-married-the-quarterback look because you haven't gone 400 yards. But, hey, it hurts. Hurts a lot.
