As i said possible, squaddies do it, quite regularly, but they have a rest inbetween, and take transport to save energy. I know about the 10lb tents etc, but precicely how far did you carry them ?
If squaddies are in the desert for 20 days there kit includes 10 gallons of water, ammo weapons food kit fuel etc far exeeding 80lbs, but thats for a static camp. Carried in in stages like the miners mentioned earlierhttp://www.express.co.uk/news/uk/188986/British-soldiers-suffer-injuries-from-too-heavy-weightshttp://www.seattletimes.com/nation-world/weight-of-war-gear-that-protects-troops-also-injures-them/
And this is from people who are used to carrying weight. Be warned ! A knee injury when you cant apply weight is painful.