One more note that popped into my mind after I posted, this was a real eye opener for me. I have tons of backpacking and mountaineering experience. That said, much of that is confined to well defined paths/trails clear of obstacles. Off trail trekking, especially through blow down takes a toll. Even after you're acclimated, traversing blowdown will wear you down, even with a light pack on. Work out your legs, especially on steps, box jumps, hill repeats etc. You'll be glad you did. If someone already mentioned this, I apologize for double tapping it.