It's a curiosity that so many memoirs by runners emphasise the pain rather than the pleasure of an activity that is, after all, wholly optional.
There are exceptions, such as Haruki Murakami's gentle, ruminative What I Talk About When I Talk About Running, but Robin Harvie belongs firmly to the "no pain, no gain" camp. Whether it's stumbling along frightened and lost, nipples bleeding and blisters swelling, or collapsing after running 85 miles in 17 hours, he is driven to extremes.
It is no surprise that he counts among his heroes the doomed explorer Captain Scott and mountaineer George Mallory, because he almost seems to have a death wish himself as he pushes his body towards ever tougher tasks, culminating in the Spartathlon. This race recreates the legendary feat of Pheidippides, who supposedly ran the 152 miles from Athens to Sparta non-stop to enlist the aid of the Spartans against the Persians.
It proved too much for Harvie, but by the end of the book he is contemplating another attempt, despite having promised his wife he wouldn't.
The answer to the question posed by the title remains elusive. Harvie talks of how running helps him on his "journey into adulthood", without quite specifying what that means, and offers gnomic clues through the words of others, such as: "There is only one antidote to mental suffering, and that is physical pain" (Karl Marx); or "Beyond the extreme of fatigue and distress, we may find amounts of ease and power we never dreamed ourselves to own" (William James).
He concludes that running "is simply about becoming a more sentient person, living what the novelist Alice Munro called a more authentic life", which didn't leave this reader much the wiser. Yet however unresolved the ending is, his journey is undeniably a compelling one.
Published in paperback by John Murray, £12.99