Ultra-crazy: What drives runners to attempt longer and longer distances?

Running as a leisure pursuit is proving more popular than ever, with races and charity runs taking place across Scotland every week. This year's Edinburgh marathon festival, for example, saw a record 30,000 runners taking part over various distances. Yet for the vast majority of us, the idea of running 26.2 miles remains almost unfathomable. That was certainly my view when a friend suggested taking part in a marathon.

I'd vowed never to do it. Though I'd always enjoyed sport - I was that kid whose mum had to physically drag him off the imaginary pitch during jumpers-for-goalposts kickabouts - running marathons had always seemed to me a form of self-flagellation.

Last summer, however, I agreed to go out with two friends, both keen runners. It was a tough five miles but I managed to keep up. "You've got the perfect physique for it, tall and slim," they told me. "You should really look into doing a marathon."

I decided that if I was ever going to complete a marathon - and that was a very big if - then it would have to be somewhere nice. Paris came to mind because I remembered reading that the route passes by the Eiffel Tower. I looked up the website and found the race date, April 12, 2015 - my 35th birthday. It was fate, or something like that, and I booked it right away.

The training was difficult, at times brutal, and when I crossed the line, in three hours 46 minutes, my tank was empty - my race, as they say, was run. Once I had stopped I could barely make it to the athletes' exit area.

How, I wondered, did anyone manage to run this distance not on flat city streets, but over an Alpine mountain ... and then not stopping, but completing another 26 miles on the mountain, and another, and one more for good measure? You'd be running through the night, in the pitch dark. And because you'd be in the Alps, the air would be thin, so getting enough oxygen into your lungs wouldn't as easy as it is at sea level.

This isn't some dystopian vision of hell, it is a phenomenon called ultra-running and, believe it or not, it is a challenge that some people enjoy. Lizzy Hawker is one of those people. In her book, Runner, she describes how in 2005 she turned up as an amateur runner at the Ultra-Trail Mont Blanc, a 158km race through the Alps including ascent equivalent to running to the summit of Mount Everest.

Like you and me, she thought the idea of running for more than 100 miles up and down mountain trails was pretty excessive. It was a challenge, though, and Hawker, inspired by the thought of running in this picturesque Alpine environment, wanted to test herself - to see how far she would get before the cut-off time of 46 hours hours ran out.

It didn't run out. Not for her, at any rate. Hawker started near the back then slowly but surely passed every other woman in the field, and quite a lot of the men too. She finished the race as first woman and 24th overall in an almost brain-scrambling 26 hours 53 minutes and 51 seconds of perpetual motion. Since then, Hawker has won the event five times and has entered into the world of elite ultra-distance running.

Anyone trying to comprehend what Hawker puts her body through will be asking the same question: why? Why would anyone run for such a sustained period over unforgiving terrain - running to the point of being physically sick, where blisters cover the entire sole of your foot and your joints scream at you to stop?

Hawker admits she's not always been good at answering that question. "Fear and excitement, anticipation and trepidation. Racing has the power to evoke a kaleidoscopic medley of emotions," she says in Runner. "Within a race I can experience all extremes - passion, beauty, heartache, pain, tears and joy. This is part of its appeal. It reminds me of my fragility and my vulnerability. And yet I learn also to feel my strength and power. Racing can give me focus. I'm forced to focus on what I am feeling, on what I am enduring in the here and now. Sometimes during a race I experience the moment where I am resting in stillness; I've stopped doing and I'm focused instead on being. That is when I feel free."

Hawker clearly has a deep, even spiritual, love of running. Her daily routine involves covering a distance many people would think twice about commuting to work ... and that's with a car. But every day people do things that others might find excessive, odd even, because they have a passion for it.

So perhaps the question isn't so much why as how. How can one person endure so much? Could it be that ultra-distance athletes are genetically unique, born with the ability to continue beyond the limits of us mere mortals? I put that question to Dr Stuart Galloway, a Stirling University sports scientist who specialises in sports nutrition and exercise metabolism, and has conducted research aimed at identifying genetic markers among elite long-distance athletes.

So far, he tells me, attempts to identify a genetic component have been unconvincing. "That is maybe because the analysis is very simplistic," he says. "It is looking for specific genes that maybe be defined as unique in these elite runners. It is going to be far more complicated than that and it is probably a combination of elements."

There has been a huge amount of research into how East African distance athletes came to dominate the sport of marathon running. From lifestyle and environmental to diet and cultural components, I ask Dr Galloway what factors are important.

"I think all those factors play a part," says Dr Galloway. "First of all it takes a certain type of person but I think lifestyle has been a big part of that [East African marathon] success.

"One of the big things is their running to school. I was at a talk in December where Haile Gebrselassie (Ethiopia's long-distance running legend) said his favourite distance is still 10k because that is the distance he ran to school and he knows that distance very well.

"Apparently when he is running he still has one arm held differently from the other because that is where he used to tuck his books under his arm. And so even though he is not carrying books he still runs with that gait."

Lizzy Hawker can't cite any outstanding sporting feats from her childhood. "There was never any sporting talent noticeable at school," she says, "and I have no history of competition in the family. Endurance has always been built in, however, because I am just a bit stubborn. Even as a child I would prefer to walk rather than take the bus because I preferred moving under my own steam. So my success really came from endurance being the way that I live rather than any particular talent at running.

"The physical conditioning, obviously, has to be there but with the longer distances it is mental as much as anything else. You could be in top form but if your head isn't in it then there is no way that you will make the finish. And at the same time, it's amazing what you can run through. I have fallen in races and had a puncture wound in my knee five miles into a 50-mile race and managed to still finish. So it is amazing what the mind can pull the body through."

I am about to discover what she means. Two months after completing the Paris marathon, I am standing at the start line of the Caledonian Challenge, a 54-mile race that starts just outside Fort William and continues along the hills and glens of the West Highland Way.

Initially, I thought this event was mainly a walking challenge, and figured that if I can run a marathon I can walk two. Somewhere along the line, however, I found out that many competitors run this race and, partly inspired by Hawker's account of ultra-running, I knew I had to also.

I realise, now, what Hawker means when she talks about getting into the right frame of mind. Despite never having attempted anything of this magnitude, I know I will complete the race within the allotted 24 hours. Where this confidence comes from, I have no idea but, standing on that start line, I feel totally calm, eager to get moving and out on my own.

I have learned from Dr Galloway that psychology is a component to ultra-running. "You'd have to be mentally prepared for that [type of race]," he says. He also talks about the importance of pacing and nutrition: compared with elite marathon runners, "endurance athletes will be running at a lesser pace for longer, so the demands are slightly different".

Eating the right amount at the right time during a run is crucial. "Quite an important aspect is when you start taking on food and what the interval is between taking it, so that you are optimising the carbohydrate delivery. If the interval is too long between eating then you will get a spike in your blood glucose and, subsequently, a big dip in blood glucose below normal," he says. "When you are taking on carbohydrate like that your body switches off fat metabolism and switches to metabolising carbohydrate. If you don't eat often enough, you're going to end up in a bad way. Quite often people end up crashing or 'hitting the wall' because they have taken on some food but have not feed frequently enough or at a high enough rate."

I found that out to my cost during the Paris marathon, when I suffered fairly severe cramp three miles from the finish because I had sweated out all my electrolytes in the 20C heat. Keen to avoid that mistake during the Caledonian Challenge, I packed electrolyte tablets as well as isotonic sports drinks and followed his advice of eating small amounts regularly.

And it seems to have worked. When I cross the finish line, in eighth position, I feel remarkably good physically.

Self-flagellation? It didn't feel like it. But am I any closer to understanding the science and psychology of ultra-marathon running?

I have certainly learned about cardiovascular fitness. In athletes, Dr Galloway explains, this is tested by gauging their VO2 max: a measure of the maximum volume of oxygen they can process while exercising. The harder an athlete exercises, the more oxygen their body consumes until it reaches a point where oxygen consumption plateaus and does not increase any further. which allows ultra-distance runners to run at a set intensity for very long periods of time.

I wonder if Lizzie Hawker has ever had her VO2 max tested. "I think I had it done once or twice, but I can't even remember what the results were," she says in that understated way that many supremely talented individuals talk about themselves. "I certainly didn't take any note of them or use them. I don't think there was anything outstanding, otherwise I probably would remember."

So if the secret to Hawker's ability doesn't lie in childhood, genetics or cardiovascular capacity, what else could explain it?

In a small but perhaps telling aside in her book, Hawker mentions that she has the ability to drink tea at almost boiling point. Is this an indication of a high pain threshold? Can she literally not feel the pain in the same way that you or I do and can therefore endure more of the inevitable agony?

"I have got a high pain threshold," says Hawker. "But I very often wasn't running in pain. Ultra-marathons don't have to be painful. I didn't ever get aching muscles after it, simply because my body had adapted, so it was what was normal for my body to do. So often when I was racing I didn't actually run as hard as I could. I was always within what was comfortable, so I could often finish a 100-mile race and be running again the next day."

Anyone who has run for any length of time will no doubt find it remarkable that someone could run 100 miles in one go and then feel fresh enough to go again the next day. Rather worryingly for me, more than a week after running 54 miles, my shins make a broken wood-type creaking noise every time I moved my feet.

I ask Hawker why she thinks she didn't suffer from the dreaded DOMS (delay-onset muscle soreness).

"I think it is the adaptation. Everything is relative and I just got used to running long distances, not particularly fast. So for me a 10K run is sometimes more of a challenge because that feels like a sprint. Everybody is different, but I just enjoy the movement of running so it is quite natural for me."

It seems then that there may not be one key element that makes up an ultra-distance runner or elite athlete and everything comes into consideration, from hydration and nutrition to psychology and lifestyle factors.

All of this is bad news for those using the excuse that these athletes are genetically gifted as a reason not to get off the sofa. While you might not be the fittest person on the planet, or have a family history of sporting success, if you are determined enough and spend enough time training, there is nothing stopping you from competing in a 100-mile mountain race ... that is, of course, if you, like me, are crazy enough to ever want to.