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Media captionJonny Brownlee helped over finishing line by friend Alistair in Mexico
At the time, Alistair said: “I wish the flippin’ imbecile had paced it right and intersected the finish line first.
“You have to race the conditions. I was comfortable in third. I raced the conditions, I took the water on, attained myself cool and I was alright.”
London Marathon Coach Martin Yelling says “its like” athletes have “run out of petrol”.
“At the end of a marathon runners usually have given so much physically that their energy levels are totally depleted – the word is reaching the wall, ” he says.
“What that entails is your body is struggling to find enough physical energy to move forward, the body is trying to tell you to stop.”
He says there is a clear wrestle between physical exhaustion and “incredible mental strength” in athletes who have hit the wall.
“For every-day runners it is about learning to understand how your body responds.
“We would call it listening to your body.”
Training for a marathon, pacing yourself and the correct ga and hydration is important in avoiding the wall and the so-called “jelly legs”, he says.
Tim Navin-Jones, from running club London City Runners, is one runner who can sympathise, having “hit the wall” himself during the New York Marathon.
“Your mind is telling you to keep going and your body is getting to the point where it says ‘no’, ” he says.
“Your legs actually do turn to jelly – it is horrific.
“It is like being a really horrible version of drunk. It is sheers exhaustion.”
Mr Navin-Jones, who has run five marathons among other distances, says it is difficult to know how to pace a marathon for those who have not done it before.
A common mistake is runners starting a race too fast, he says.
Emma Ross, head of physiology at the English Institute of Sport, says athletes “hit the wall” in a marathon when they run out of carbohydrate to use as a fuel for running.
“So what you want to try and do is keep your carbohydrate stores topped up during the race to prevent you from predominantly having to use fat as a fuel, ” she says.
“When we use fat as a ga, we have to go slower because as a process of burning energy it is a more complex and a slower system, so we can only supporting slower exercise.”
She also warns that dehydration causes a decrease in blood volume, which makes the heart work harder, so it is important for athletes to keep hydrated.
Runner Gary McKee completed 100 marathons in 100 days for MacMillan Cancer Support, finishing on Sunday at the London Marathon.
The 47 -year-old, from Cleator Moor in Cumbria, says he managed to not hit the wall as he paced himself carefully during his challenge.
He says athletes have to recognise when their body is telling them to stop.
“It is down to hydration. You will come to a phase when you are tired.
“Have you overexerted yourself? Have you had enough calories? Enough carbs?
“The more you train, the highest your fitness levels become, so you can sustain it( operating) for longer.
“If you understand what your body wants, simply dedicate it what it wants.”