What pack ?
I think that some confuse what can be and what should be done.
In Nepal I noted how the porters,(all much smaller than me and I am only 5'7" ,150 lbs...) could carry all day loads that are twice or more than what I do.
For example this "external pack" was around 60-70 lbs, I walked with it on flat ground for about 200 yards, and that was enough for me. The porter in charge of that came down slippery slopes the day before, he was about 5'3" and provably 125 pounds.
However at 35 he looked as old as me at 53...
Note that when you read about folk that can only hike with the use of painkillers you typically find that they used to carry heavy loads and/or put in huge mileage.
Franco

150 lbs, 5"7", 5-7 days with food around 25 lbs.
Note also that some packs can carry 30 lbs the way others carry 20...