This story was first published on April 5, 2010

The greatest distance to cover in any race is the distance between your ears. Strength does not come from physical capability, but from an indomitable will.

So says Yong Yuen Cheng, fastest finisher of the 218-km Run Round Singapore in 31hr 28min 51sec.

Of course, many people think he has lost whatever was between his ears, judging by the distance - equivalent to more than five marathons - he covered on March 28 to mark Nanyang Technological University's 55th anniversary.

Why would anyone want to put themselves through an experience littered with low points like cramps, diarrhoea, dislodged toenails, blisters, heat, sleepiness and excruciating leg pain - and end up in a wheelchair after? Crazy!

Yong, 38, agrees.

"If one is not well-trained, conditioned, prepared, experienced or supported," says the ultra-runner, who is in the business of logic (he is a Hwa Chong Institution physics teacher), "then yes, running 218km is crazy."

But he will tell you that he built up his mileage gradually since last May, down to the nitty-gritties of date, distance and time (his reply took a full page).

Races and other organised mass running events doubled up as long training runs - a good way of "setting short-term goals in terms of preparation", he says.

Twice - in the span of two weeks at the end of last year - he ran five marathons in five days to condition his body to the 218km distance.

He will tell you that he is neither a fast nor talented runner.

In his Secondary 1 fitness test, he took more than 16min to run 2.4km. In his first road race as a 17-year-old student at National

Junior College, the school canoeist came in 148th. He trained his heart out the next year, but managed only 24th.

His first marathon in 1992 is his fastest to date (3hr 52min). It was only at the 2004 MR25 Ultramarathon, where he ran 84km in 10hr 36min and was fifth, that he realised he was "not bad" at ultras.

To those who still don't understand why Yong does what he does, he will tell you he was a sickly child. In Primary 2, he weighed just 19kg, in P6, just 26kg (the average boy would be 40kg by then).

Running for him is a blessing.

"Actually, I expected little from the run in terms of placing because I know how much slower I am compared with most of the other runners," says Yong, who rested just one day before going back to work last Tuesday.

"But I feel lucky that this has become a good lesson for my students."

And, that is, that anyone can achieve the extraordinary.

Clickhere to read about Mr Yong's progress in the Go50 Run project to mark Singapore's 50th birthday.