this seems highly spurious

I looked at a variety of sources for the Roman march, I didn't find one reference stating 1.5 marathons per day (40 miles). Most sources say something like "During the summer the soldiers had to march 18.4 miles (29.6 km) in five hours.".
http://en.wikipedia.org/wiki/Roman_army / The largest distance I could find was a reference to 25 miles, and nothing about 40 miles.

Soldiers still do this stuff when required to. EG:
"After disembarking from ships at San Carlos on East Falkland, on 21 May 1982, Royal Marines and members of the Parachute Regiment yomped (and tabbed) with their equipment across the islands, covering 56 miles in three days carrying 80 pound loads."

http://en.wikipedia.org/wiki/Loaded_march

Finally, think of the tough nuts who existed at the start of the 20th century. No interweb or microwave meals for them. Could they really run faster than Usain Bolt? It's simple to check the speeds and athletic records from that time and find that this man is a delusional nut case.

I think this author has a chip on his shoulder about something or other.

For some reason as I read that I began to think of Christopher Walken's lecture to Butch about his dad's watch, in Pulp Fiction.

So I began to have a terrible suspicion that the desk had been smuggled into America up someones ass.