Denethor's plunge

[William Cloud Hicklin]

It is simply a physical impossibility that an untrained individual can run the equal of 1.6 marathons three days in a row.

It's the 'marathon' model that's leading you astray. Running 26+ miles in three hours or so is indeed a killing endeavor (athough triathletes seem to have energy left over).

But this is not what the Three Hunters did. They travelled from dawn to dusk (actually before dawn the first day). At the end of February in a northern latitude that would mean 9-10 hours/day of travel time. This means an average speed of 3.5-3.9 mph: that's a walking pace.

Perspective: most experienced backpackers will do 3.5 mi/hr in mountains, and 4 on the flat. Why on earth is it 'impossible' for the 3H to have done this over the rolling plains of Rohan? As to 'untrained": Aragorn is supposedly the greatest traveller in the world, and is moreover of the Line of Elendil. Legolas is an Elf, not given to human weariness, and (we are told) capable of sleeping on the move. This isn't exactly a human physiology! And Dwarves, within Middle-earth, are legendary for being stone-hard and enduring.

And you claim that these 3 explicitly superhuman individuals couldn't do what Stonewall Jackson's 'foot cavalry' did many times?