ATHLETICS: Can a human run a marathon in under two hours? It is one of the last great barriers in athletics. In the meantime, we'll settle for a qualifier for London

BEFORE INDULGING in another feast for the endorphins, here’s a quick challenge: those of you with access to a treadmill, see how long it takes to work the thing up to just over 13.1 mph – or 21 kph – and then see how long you can hold it.

You might want to buckle up.

Truth is, I tried this a few days ago, on a custom-built treadmill in the shed. Let’s just say the thing was soon smoking – and with that completely blew the fuse box, leaving the entire east side of the Dublin Mountains without power for the rest of the afternoon. Pat in the Blue Light later told me he was limited to serving bottles of cider for a while, and that did not go down too well.

Anyway, the point of the challenge is to experience what it would feel like to run a marathon in just under two hours. That’s 26.2 miles, at around four minutes and 33 seconds per mile – and if you managed even one mile at that pace you must be a Kenyan, born and raised in the mountains, and used to running several miles to and from school.

In case you need reminding, the world record for the marathon is two hours, three minutes and 59 seconds, run by a certain Haile Gebrselassie, in Berlin in September 2008. That works out at about 12.7 mph, for 26.2 miles, and really is smoking the shoe, as we say in the business. He’s the only man to run sub-2:04, and only seven other men have run sub-2:05. In case you need further reminding, the marathon world record has been broken only seven times in 25 years, and the first sub-2:07 achieved as recently as 1988.

And yet, around this time every year, the sub-two marathon debate seems to surface, as if man – or indeed woman – is ready to take that one small step in distance running history, when in fact it’s more like a giant leap. It is one of the last great barriers in athletics, or at least one of the most intriguing.

There are definitely two sides to the debate: those who believe a sub-two marathon will happen, sooner or later, and those who believe it will never happen. I know which side I’m on. It effectively requires a four-minute improvement on Gebrselassie’s 2:03.59, which has already stood for nearly three years. Before that it took 24 years to lower the world record by four minutes, from the 2:08.05 Steve Jones ran in 1984.

But this debate is not really about how soon a sub-two marathon might happen: it’s about the limits of human speed and endurance.

This weekend marks the peak of the so-called Spring Marathon season, with mass participation races in about 20 cities, including London, Madrid, Zurich, Vienna, Belgrade, Salt Lake City, and the grandaddy of them all, Boston, which takes place on Monday. London, typically, has also assembled a stellar, elite field, including seven men who have run sub-2:06, and another two who have run sub-2:05. With that in mind, BBC Radio 4 aired a fascinating documentary last Monday, aptly titled The Sub Two-Hour Marathon: Sport's Holy Grail,featuring opinions from the likes Gebrselassie and Paula Radcliffe, who in 2003 in London made a giant leap in women's marathon running history with a world record of 2:15.25.

“No question,” said Gebrselassie. “The first sub two-hour marathon will need 20 to 25 years, but it will definitely happen.”

Radcliffe agreed, although she reckoned it would be a more mental than physical barrier: “Records are there to be broken and people are going to be shooting for it, but someone is going to have to run really hard to beat this one. That’s the kind of mindset it will take.”

Dave Bedford, the London marathon director, told them we’ll see the first sub-two marathon in the next 20 years.

Some people are more scientific about their predictions: in a study entitled ’Mathematical Analysis of Running Performance and World Running Records’, Francois Peronnet and Guy Thibault of the University of Montreal predicted the first sub-two marathon will be run in 2028, but that it is physically impossible for a man (and presumably a woman) to run a marathon faster than 1:48:25.

Incidentally, I once had this debate with Kenya’s Paul Tergat, who in 2003 ran a world record of 2:04.55 – which was also the first sub-2:05. Tergat looked me squarely in the eye and began shaking his head. “Impossible,” he said. “A sub two-hour marathon will never happen” – and I’m inclined to agree with him.

There’s a slightly different debate in Irish marathon running, and that’s whether we can get a man to run sub-2:15 – which yesterday was announced as the A standard for next year’s London Olympics. This is quicker again than the sub-2:16 Athletics Ireland are demanding to qualify for the World Championships in Daegu this August, although some would argue that if you can’t run sub-2:15 these days you really don’t belong in the Olympics – and that’s probably true.

John Treacy’s Irish record of 2:09.15, set when finishing third in Boston in 1988, has stood for 23 years, and only one Irishman, Martin Fagan, has run sub-2:15 in the last eight years: the 2:14.06 he clocked in Dubai in January 2008, which also qualified him for the Beijing Olympics. Incredibly, no other Irish man had qualified for an Olympic marathon since 1992, in Barcelona, when Treacy, Andy Ronan and Tommy Hughes all made it.

In other words, Irish runners haven’t exactly kept pace with the rest of the world. Mark Carroll’s 2:10.54, our second-fastest, was run in New York in 2002, and Andy Ronan remains our third-fastest, with the 2:11.27 he ran in 1991, also in Boston. Likewise, Catherina McKiernan’s women’s record of 2:22.23 has stood since 1998, and, believe me, will stand for a long time yet.

There are signs this sad scenario may be about to change, at least on the men’s front. Last Sunday, in Rotterdam, Seán Connolly ran 2:17.23, the fastest by an Irishman since Fagan’s 2:14.06, and an encouraging debut. Tomorrow in Vienna, Mark Kenneally hopes to go even better, and is targeting something around 2:15. Coached by Mark Carroll, Kenneally certainly has the engine to go the distance, although the Olympic qualifier, in his marathon debut, might just be beyond him.

So to Alistair Cragg, who on Monday lines up in Boston, targeting something significantly quicker than 2:15, at least in his mind. Now 30, Cragg has inevitably turned to the marathon in an effort to revive his career, which had, quite literally, gone off track in recent years. Earlier this week the Boston Heraldgave him a half-page spread under the headline "Cragg goes long: Irishman uses Boston for debut marathon", and he's certainly talking up a big race. Why not? Cragg ran an Irish half-marathon record of 60:49 in New York last month, and if everything goes right on the day Treacy's Irish record could well be beaten.

What we’ll take for now is at least one qualifier for London: one small step in distance running, perhaps, but one giant leap for Irish marathon running.