The world’s best marathon runners are just 177 seconds from breaking the two-hour barrier: what will it take to get there (apart from drugs)?

Shortly before nine on a bright autumn morning in Berlin, Geoffrey Kiprono Mutai prepared to run a marathon faster than any human being – even he – had run before. It was a wild, audacious proposition, to propel one’s body to such a ragged extreme, and he felt the walls of his quest closing in on him.

Mutai is 170cm tall and weighs 57kg. He has a wide, expressive face, with a high forehead, elfin ears and long, gleaming teeth. Most often, you find him amiable, amused, desirous of news and gossip, a flashy smile close by. But now he looked as vulnerable as a foundling.

There were two dozen professional athletes on either side of him on the start line, and around 41,000 runners behind. Penned together, they bobbed and lilted like a gentle sea against a harbour wall. Mutai said his habitual prayers – for clemency, for strength and courage, for his stringy legs, veterans of tens of thousands of miles of training, to carry him another 26 miles and 385 yards.

The official marathon world record on that September morning in 2012 was two hours, three minutes, 38 seconds, set the previous year in Berlin by Patrick Makau of Kenya. But Mutai was not interested in 2:03:38. Although he made no announcement of his intentions, he wished not only to break Makau’s world record, but to annihilate it.

His grievance stretched back to eighteen months before, when he had won the 2011 Boston marathon in an astonishing 2:03:02 – a course record by nearly three minutes. But it wouldn’t stand as an official world record: despite being the oldest continuously contested marathon in the world, Boston does not count for world record purposes. (A world record must be run on a looped course, with the start and finish separated by no more than 50% of the 42.2km distance; the net downhill must be no greater than one metre per kilometre.) Mutai believed something precious had been stolen from him.

Facebook Twitter Pinterest Dennis Kimetto posts a world-record time in Berlin, in 2014.

As he stood at the head of the vast herd, high banks of loudspeakers began to play the kind of jangling electronic string music you hear in game shows. Over these shifting arpeggios came the sound of a stout man with a microphone, counting down the final seconds before the gun. “Ten!” he shouted, in English. “Nine! Eight! Seven…” Mutai stood still, his chest pushed forward in anticipation of movement.

***

For the past two decades, athletes from Kenya and Ethiopia have utterly dominated the professional marathon. In the Nandi Hills of Kenya, or on the training trails of Addis Ababa, athletes know each other not just by name but by personal best. That guy is a two‑oh-eight. This one is a two‑oh-five.

Just how low will those numbers fall? Right now, the world record for the marathon is 2:02:57, set by Dennis Kimetto of Kenya in Berlin last year. Is a sub-two-hour marathon possible? In 1986, a medical student called Mike Joyner began considering this question. He’d been working on papers that investigated how measures such as lactate threshold, running economy and lung capacity (all of which have a limiting effect on running speed and endurance) related to athletic performance. What would it be possible for a human being to run, he wondered, if he had the best possible physiological values? If his heart and lungs and legs were the strongest and most efficient they could be? He drew up a model and came to a surprisingly specific number. Given ideal conditions, and the ideal runner, Joyner concluded that the best time in which a marathon could be completed was one hour, 57 minutes, 58 seconds.

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He wrote up his findings and eventually his paper, peer-reviewed and rubber-stamped, appeared in the Journal of Applied Physiology in 1991. At the time, the world’s fastest marathon was 2:06:50, and the two-hour mark existed only at the far reaches of the imagination: the Narnia of distance running. But Joyner’s paper became the seminal document in the debate. He is now a professor of anaesthesiology and has been working at the Mayo Clinic in Rochester, Minnesota, since 1987, on a wide range of topics, from gene studies to cardiovascular disease; but none of his work has stuck to him as much as his famous 1991 paper.

Why does it matter whether the sub-two-hour marathon is possible? And, if it is possible, what will it mean when the first 1:59:59 marathon is run? At one level, the achievement will signify nothing. The marathon length is a scruffy figure, fixed by the Olympic Committee only in 1921, to match the course of the 1908 London Olympic marathon, which was itself designed to accommodate the peculiar viewing demands of the British royal family. (The royals wished to see the race start underneath a terrace at Windsor Castle, so their children could watch; for their benefit, the race was also stretched at the other end to include a full lap of the old White City stadium.) Why should we care if some extraordinary person can run this arbitrary distance in just over, or just under, two hours?

In Kenya, athletes know each other not just by names but by personal bests: 'He's a two-oh-eight. He's a two-oh-five'

Nobody finds the marathon easy – even professionals, especially professionals. The distance is democratic. It has become an event against which hordes of people – fat people, thin people, people crooked by time and people sprightly as foals, rich people and people in need – test themselves. There are now more than 500 marathons all over the world, and more competitors than at any time in the history of the sport.

The two-hour debate is irresistible. It arises every time a man breaks the marathon world record. In 2003, the Kenyan Paul Tergat crested the tape at the Berlin marathon in 2:04:55. (Before that race, only “world bests” were recognised. Tergat’s time, which crushed Khalid Khannouchi’s 17-month-old world best by 43 seconds, was the first ratified marathon “world record”.) At the post-race press conference, Tergat was asked the question: could someone break the two-hour barrier? “I believe records are set to be broken, and to fall lower is possible,” he said. “But what remains impossible is running a marathon in under two hours.” He smiled, and added: “Maybe time will chide me.”

Facebook Twitter Pinterest Former world record holder Paul Tergat (fourth from left) trains at altitude in the Ngong Hills in Kenya, in 2007. Photograph: John Gichigi/Getty Images

If Tergat was sceptical, you could see why. He was reflecting on the abyss into which he had just pushed his own body in order to run 2:04:55. The prospect of running a whole five minutes faster than this was unfathomable, too much slack for the brain to handle. But nobody was suggesting a 1:59:59 marathon would be reached in one giant leap. Patrick Makau’s 2011 world record, 2:03:38, beat Haile Gebrselassie’s 2:03:59 from 2008 by 21 seconds, which in turn beat Gebrselassie’s previous best from 2007 by 27 seconds, which beat Tergat’s landmark of 2:04:55.

Tim Noakes, one of the world’s leading exercise physiologists, and the author of the influential book Lore Of Running, believes that these incremental advances are connected to how the brains of top athletes communicate with their bodies. “When you start running,” he says, “you know what the world record is, so you don’t have to run 10 minutes faster than the world record. Your whole focus is to run one second faster than the world record. That’s what your brain is keyed in on. And that programming occurs all the time in running and is terribly important.”

The brains of elite athletes are only as obstructive as they are programmed to be – as one recent experiment showed. In 2011, Professor Kevin Thompson of the University of Northumbria assembled a group of enthusiastic bike riders for a laboratory test. These cyclists were placed on stationary bikes in front of screens, hooked up to oxygen monitors, and asked to race a computer-generated cyclist avatar. Each rider had previously set a personal best for a 4,000m time trial on the machine. The avatar they were now racing represented that personal best.

'Records are set to be broken,' Tergat said, 'but what remains impossible is running a marathon in under two hours'

Or so these guinea pig cyclists thought. In fact, Thompson was lying. He had set the avatar to race 2% faster than their personal bests, because he wanted to know if an athlete’s body could be tricked into performing better. It was his belief that even world-class performers, who thought they were regulating their energy output to their absolute maximum, possessed a “reserve” of around 2% that could be tapped into, given the right motivation (or a little deception).

Thompson was right. Almost all the cyclists finished ahead of the avatar.

If the sub-two-hour marathon is reached, it will be in such baby steps – each one taken by a member of the tiny, elite fraternity of athletes with the talent and industry to inch the sport closer to the impossible marathon, world record by world record.

***

Within 5km of the start line in Berlin in 2012, a disaster occurred: the display on the pace car froze. It showed 2:50 per kilometre – a two-hour marathon pace. In fact, the leading runners were clocking nearly three-minute kilometres, which would be good enough only for a 2.06 finish. It was a tiny difference, and Mutai and his fellow runners soon understood the problem, but the elite marathon is a sport of tiny margins. The fastest times are achieved when races are run at an even pace from start to finish, or with a “negative” split, with the second half slightly faster than the first. Start the race too fast and you’ll kill a record attempt stone dead. Start too slow and you’ll have to make up too much ground.

Mutai was now in the second category. He reached halfway in 62:12. By his own recollection, it was only then that he seriously considered the scale of the challenge confronting him. Having run the first half 42 seconds slower than he had hoped, he understood dimly that the sub‑2:03 marathon was gone already. But he still believed he had a shot at Makau’s world record of 2:03:38. In order to break it, he would need to run the second half of the race in 61:26. Only two men in history had run that fast in the second half of a marathon: the Brazilian Ronaldo da Costa, in Berlin, in 2003, after a sluggish first half; and Mutai himself, in Boston, in 2011. The question was: did Mutai have the legs?

In the next 10km, just as the course rose slightly in gradient, he caught fire. At 25km, as planned, two “rabbits” (athletes who for reasons of schedule, finance or talent are paid a few thousand dollars to run a limited section as pacemakers) dropped out, leaving the lead group paced by only one man: Victor Kipchirchir, a training partner of Mutai.

The pace quickened. Jonathan Maiyo felt tight and began to weaken. He was soon dropped from the lead group. Geoffrey Kamworor also failed to respond to the rising pace in his first marathon and lost touch with the leaders shortly afterwards. At 30km, the final rabbit, Kipchirchir, made his scheduled exit.

Now it was only Mutai and his training partner Dennis Kimetto, head to head for the final quarter of the race. As they had done many times together, at an altitude of nearly 9,000ft (2,700m) on the rough hills around their base in the forests of Kenya, they drove each other on. From 30km to 35km, the pair ran a 14:18 split, which is absurdly fast. (A whole marathon run at this pace would finish in two hours and 40 seconds.)

Mutai's heart pistoned at over 160bpm. His lungs bellowed half a gallon with each breath. He took three strides a second

As Mutai led the charge, he dipped his head in trademark fashion and a hint of a snarl appeared at the corner of his mouth – a look he refers to as, “Now, business.” Within his body, there was a tumult of exertion. His heart pistoned at over 160 beats a minute. His lungs bellowed half a gallon with every breath. He took three strides a second. In his cells, the complex process powering his heart and lungs and legs – the burning and resynthesising of adenosine triphosphate – created three times as much heat as energy. And so he was hot, too hot. His body, losing around three litres of sweat an hour, grew slick with moisture. Lactic acid began to singe his muscles. Everything but his conscious mind screamed, “Stop!” And still he ran.

How does it feel to travel so fast, so late in a marathon? Mutai described the sensation as “fighting inside”, as if your body is at war with itself. Another former runner said it is like putting your hand in a bowl of hot water: you have to keep your hand in, while the water just keeps getting hotter and hotter – take your hand out and you lose the race.

Mutai is, of course, accustomed to these sensations. He later told me that he drew strength from the crowds that lined the roads. He could feel that “people love me” and he was determined to repay that affection with a Herculean effort, to consciously override the signals his body was sending him. “I sacrificed myself,” he remembered.

***

There are many observers who look at the times now being run in the marathon with a raised eyebrow. Dope infects almost all professional sports. For every athlete who wishes to ascend to the highest plane of competition under his own steam, there will always be athletes who desire a short cut. Marathon running is no different. (Tom Hicks won the St Louis Olympic marathon jacked up on strychnine and brandy, and it nearly killed him. That was in 1904.)

There was once an Elysian view of the sport of distance running that wilfully exempted east Africans from the temptations of others. Journalists saw the humble manner in which Kenyan and Ethiopian runners lived, and concluded that cheating in such circumstances simply wasn’t possible. This myth has now been exploded. In the past two years, several east African distance runners have tested positive for banned performance-enhancing drugs, including steroids and the hormone erythropoietin, or EPO, which stimulates red blood cell production and the transport of oxygen into the bloodstream.

Facebook Twitter Pinterest Urine samples are tested for EPO or the hormone erythropoietin in a Swiss laboratory. Photograph: Fabrice Coffrini/AP

Some of the busted athletes have been well-known figures, but most have been nobodies. Three years ago, I sat in the twin room of a four-star hotel in which two low-level Kenyan runners were preparing their vests and bibs for the following day’s marathon. They wanted to talk to me about drugs, and spoke on condition of anonymity. Their personal bests were relatively modest in Kenyan terms, and they barely covered their expenses to travel to a race in a bleak European capital with only a few thousand euros in prize money. They talked for a long time as they sat on their beds, with the burble of the television and the sound of rain against the windows in the background.

The two Kenyan runners, whose personal bests were above 2:10, said anything below 2:06 was 'suspicious'

The two runners said that, in Kenya, there were “so many bad doctors, you can’t count them”. They described a system whereby these “doctors”, who were mostly quack pharmacists based in the town of Eldoret, would sell an athlete a course of performance-enhancing drugs in exchange for either cash or a share of their winnings. The drug in question, although they didn’t name it explicitly, seemed to be EPO. (They referred often to a drug for “the blood”.) And the relationship between the athlete and the “doctor”, said the two runners, was “24/7”: they were always on hand to provide masking agents, should the testers come calling.

Most of this information was talked about openly enough, especially among European agents and coaches (although before my meeting with the two athletes, I had never heard such a detailed description of the process). Some Kenyan stars also discussed the problem in a roundabout way. In the narratives of many high-profile athletes, doping was seen as something that “lazy” runners did in lieu of training. This was a wilfully wrongheaded view. As the Tour de France scandals showed, drugs are used for precisely the opposite reason: to train and race harder.

The two athletes in the hotel named almost every star in Kenyan marathon running and accused them of doping. The allegations were shocking, though the basis for their specific charges seemed thin. They simply didn’t believe it was possible to run the spectacular times that had now become commonplace on the marathon circuit without illegal assistance. These two runners, who had personal bests above 2:10, said anything below 2:06 for a marathon was “suspicious”.

One of the runners laughed when I expressed surprise. “You think you can run two‑oh-three, only with blood?” he asked. Well, yes, I did think that. I still do.

From a layman’s perspective, it’s not obvious what kind of edge EPO would give a Kenyan who has already spent his whole life running at altitude. The number of red blood cells in his system is already likely to be high, and there is a limit to how many a person can have before he or she is at risk of a heart attack or stroke. (This dangerous abundance of red blood cells is known in medicine as polycythaemia.)

But this apparent common sense is wrong: EPO does help altitude-born-and-raised Kenyans. A recent study by the University of Glasgow conducted tests on a group of Scottish runners, and Kenyan athletes from running country, and found that their performances benefited equally from a course of EPO.

If there were a wonder drug for distance runners, it would be one that aided recovery. Marathoners have always logged extraordinary mileage, and their biggest problem is staying healthy for races. The “high volume, high intensity” philosophy requires a mixture of speedwork sessions lasting an hour or more in order to build resistance to a fast race pace, and long runs at a high tempo. Being able to complete such punishing sessions day after day is the key to staying competitive. So it is in the field of recovery that the marathon is most vulnerable to cheating. In theory, athletes could stop taking illicit substances weeks before a race, and show up to a marathon clean – with hundreds of high-quality, ill-gotten miles in their legs.

Some former runners believe the elite have been doping for years. These views come from surprising places. In 1999, for instance, Mo Farah’s coach, Alberto Salazar – currently under extreme pressure after the BBC and ProPublica linked his athletes to banned substances – gave a presentation to the Duke Conference on Doping in Sport in which he made several fascinating remarks, not least this one: “I believe that it is currently difficult to be among the top five in the world in any of the distance events without using EPO or human growth hormone. While some of the top athletes may be clean, so many athletes are running so fast that their performances are suspect. This is compounded for me by the fact that the times these athletes are running just happen to coincide exactly with what top exercise physiologists have calculated taking EPO would produce.”

In 1999, you could have an argument about who the top five distance runners were, but there was no doubt about the top two: Haile Gebrselassie of Ethiopia and Paul Tergat of Kenya. Was Salazar saying he believed they were dopers? (Salazar told me last year that he no longer stands by the comments he made in 1999, and that he “did not reference the athletes you call out”.)

Facebook Twitter Pinterest In 1999, coach Alberto Salazar (pictured flanked by Galen Rupp and Mo Farah) said he thought it ‘difficult’ to be in the top five for any distance event without using banned substances. Photograph: Michael Steele/Getty Images

Salazar has long been the subject of scrutiny about his methods. In 2013, a Wall Street Journal investigation into his (and his sponsor Nike’s) relationship with a doctor named Jeffrey Brown found that many of Salazar’s athletes had been treated by Brown for a syndrome called “hypothyroidism”. Galen Rupp, Mo Farah’s training partner and 10,000m Olympic silver medallist in 2012, was one such patient. Treating athletes for hypothyroidism is not illegal, and it’s also not clear what kind of benefit it would give an elite runner. (The treatment is a synthetic hormone called levothyroxine – not a banned substance, though it has been suggested it helps with swift weight loss.) But the very fact that so many of Salazar’s charges have been diagnosed with the condition has caused suspicion. After Jos Hermens, who manages many of the best east African runners, watched his athletes being trounced at the 2012 Olympics by Salazar’s, he told a Dutch journalist, “Science has triumphed over nature.”

But what of the supposedly widespread nature of doping in east Africa? Should we consider every fast marathon as suspicious? What counts as suspicious? 2:06? 2:04? 2:02? In 1991, Joyner estimated a physiological ceiling for running a marathon: 1:57:58. So what extra time on top of that should we allow today’s best runners?

For Kenyan runners, most of whom grew up poor, the prize money for one win can change a life

The fastest men fall under the most suspicion, which may not be fair. There is as much motivation for a middling talent to dope as there would be for a supreme one. This is true particularly for Kenyan runners, almost all of whom grew up dirt poor. The prize money for one win, even in a low-grade marathon, can change a life.

Geoffrey Mutai has fallen under more suspicion than most, because he has run fantastic times in an aggressive manner. But in the three years I spent following Mutai, staying in his training camp and watching him at home and at races, he was tested many times for blood and urine. He has never given a positive test, and I had no reason to suspect him of doping.

Troubled by the reputation his country’s runners were attracting, Mutai said he wanted more testing, more often, to prove his innocence. “I am clean,” he told me. “I want all athletes in Kenya to remain clean. Any time, anywhere, I am ready for testing. It gives me pain when people see me run fast and say I have used drugs. If I have used them, then God take everything from me – I cannot enjoy it.”

You can be sure that if and when a man breaks two hours for the marathon, the whiff of disbelief will hang around him every day of his life.

***

At the 35km mark in Berlin, Mutai’s sacrifice appeared to have paid off. Despite the botched beginning, both he and Kimetto were now inside world record pace. All they had to do was hold on. If they ran a 2:56/km pace for the final 7.2km of the race – which seemed, given their earlier pace, possible – the world record would fall to one or the other.

The path that had led Mutai to this position would have broken lesser men. The eldest of 11 children, he had suffered not only deep poverty, but a fractious relationship with his father, periods of insecurity about shelter and food, and a hair-raising brush with the tribal violence that scarred Kenya after the disputed 2007 elections. Before he had become a professional runner, he had worked in back-breaking jobs: smashing rocks in a quarry and cutting down trees. As a pro, he had run 125 miles a week, up and down hills, at altitude.

Now, here he was, at the quickest marathon in the world, with a chance to break the world record. The opportunity might not come around again. The elite marathon is a brutal sport. The best runners compete only twice a year at the full marathon. There are only a handful of courses, and a handful of days, upon which to run fast. This was one of them. He and his training partner, Kimetto, were half an hour from glory.

Facebook Twitter Pinterest The fastest men on Earth: marathon world record holders over the years. Photograph: AFP/Getty Images (4); EPA/Getty Images; Reuters

Perhaps inevitably, they couldn’t do it. The prodigious acceleration just after halfway took its toll, and by 40km, slowing markedly, both athletes were eight seconds outside world record pace, and spent. Mutai’s right hamstring began to tighten. The pain moved to his hip and back. Kimetto – high-shouldered, and seemingly in better shape – ran at his back.

Facing the final 2km, the pair ran into the breeze, rather slowly. They seemed headed for a very fast time, but not a world record. As Mutai and Kimetto ran through the Brandenburg Gate shoulder to shoulder, 400m from the end, the spectators raised their voices in anticipation of a sprint finish.

But the kick never came. In a finale in which a burst from either man would have sealed the race decisively, Kimetto finished the race as he had run most of it: just behind his colleague. Mutai raised his arms weakly as he crossed the line in a time of 2:04:15. Seconds later, the two men shared a limp, exhausted hug.

Why no sprint? There were half a million reasons why. If Kimetto had beaten his training partner, Mutai might have lost the $500,000 World Marathon Majors jackpot he was in line to win after his runs in Boston and New York the previous year. (Kimetto had no chance of winning that money himself, this being his first marathon.) Meanwhile, Kimetto was not just Mutai’s training partner. For the previous few years, like many in the village where he trained, he had been fed and housed by Mutai. If he had sprinted past his boss under the Brandenburg Gate, everyone in that village would have lost. Marathon runners are not just athletes; they are economies.

Any kind of arrangement between the two was vehemently denied by the athletes themselves, while their manager, Gerard Van de Veen, told journalists, “There was no deal.” Mutai told me that he and Kimetto were dog tired: neither man could have done anything more.

Facebook Twitter Pinterest Geoffrey Mutai and Dennis Kimetto cross the line at the 2012 Berlin marathon, during the former’s failed bid to break 2:03. Photograph: Markus Schreiber/AP

Mutai’s finishing time of 2:04:15 was the fastest that anybody ran in 2012. For the second year in a row, he was the quickest marathoner on the planet. These statistics brought him little comfort. He signed autographs and smiled for photographs, but left Berlin with the sense of an opportunity lost, of a tide untaken.

In September 2014, Kimetto returned to Berlin and achieved what Mutai had failed to do: he ran the first 2:02 marathon. Kimetto does not have Mutai’s grace – his stiff-backed style makes him look haughty and a trifle uncomfortable – but his effort was extraordinary, and his finishing time would have been science fiction to runners of the 1990s.

The world record is still two minutes and 57 seconds away from the two-hour mark. What’s 177 seconds? It’s a pop song, a long commercial break. In marathon terms, however, those 177 seconds are a lifetime. A marathon run in two hours dead requires an average of 4:35 per mile, or 2:50 per kilometre – nearly a 3% improvement. In the abstract, this difference seems trifling. In reality, it’s a chasm.

The chasm can be bridged, but it may take a reimagining of the sport to do so. What may need to change is not the shape of the athletes’ bodies, but the shape of races. If you really wanted to see how fast a man could run 26.2 miles, you would take them off the roads and on to a more forgiving surface. You’d allow pacemakers to come in and out of the race, right until the finishing line. You’d make sure the temperature was very cold, to combat the extreme heat that elite marathoners generate, and that the course was flat and entirely sheltered from the wind.

The world record is still 2mins 57 seconds away from the two-hour mark. It seems trifling, but it's a chasm

Several deep thinkers – including Mutai – have already considered what such a race could achieve. It might take a rich man with a flair for publicity (Richard Branson, perhaps) or a shoe company with a motive (Adidas, Nike) to see it happen. But that’s the way to break two hours. “Organise it like that,” Mutai told me, “and people can run crazy times.”

As a species, we are interested in outlandish feats, and our brains cleave to landmarks. The two-hour quest has become the sport’s Everest. Those final 177 seconds will not fall easily. But somewhere there is a runner alive, right now, who has glimpsed the mountain top, and who will set his mind upon its conquest.

• This is an edited extract from Two Hours: The Quest To Run The Impossible Marathon, by Ed Caesar, published next month by Viking at £16.99. To order a copy for £12.99, go to bookshop.theguardian.com, or call 0330 333 6846. (Free UK p&p over £10, online orders only; phone orders £1.99 minimum p&p.)