That's the large and small of it.
Granted, the 14 year old nephew with me was panting almost as bad as I was, and he is not fat at all.... but he got his air back faster than I did, I was still pulling leaves from the trees with my gasping inhales minutes after he was OK. Uncle Broke had to sit down and suck down another Marlboro
I thought the trip up the hill was going to kill me. Really. I thought this would really suck to be out here and have the ticker freeze up on me in the middle of the woods.... but after the funny noise in my ears stopped, and the twinkly spots disappeared from my vision I was OK.
OK enough to know I'm not going down that frickin' hill again.... we shot farther up, closer to the truck.
It IS absolutely crucial to moving and shooting, which is what some are prepping for... so you're 100% correct in it being crucial in that aspect.
If you have to move fast, carrying a load, amped up from having to move fast to start with (chasing something or being chased), physical fitness will become key.
Not to Uncle Broke though... I'll just make a stand where I am I reckon... Donato's Big Don Italian sub in one hand, the other pulling the trigger on whatever has ammo left in it.
If I finish the Big Don before I die, I win.