A week on from the London Marathon and the aches and pains of the 35,674 finishers may be fading fast, but are any of them ready to run, not 26.2 miles, but 62?
For those who balk at taking on the marathon, running 62 miles - the distance between London and Cambridge - seems like something for masochists.
It's not, it's called ultra running.
Great Britain coach Norman Wilson has already begun sifting through the list of London competitors in search of those tough enough to become an ultra runner.
Britain's Lizzy Hawker was crowned world 100km champion in 2006
Being tough enough means taking part in challenges on the track, road and mountainside, even running through the night.
In other words, just about anything that fits the International Association of Ultrarunners (IAU) slogan: "Beyond the Marathon."
"After London I will be contacting several athletes to encourage them to step up beyond the marathon," Wilson told BBC Sport.
"I worked with 130 athletes last year and we now have a nucleus who are capable of jumping up to 100km (62.13m) within two years."
In 2005, Wilson spotted Lizzy Hawker in a 40-mile track race in Wales. By 2006, the Cheshire runner had become world 100km champion.
"We saw her ability but did not anticipate she would be world champion less than two years later," says Wilson.
Hawker, who took gold by completing the 100km race in Korea in seven hours, 29.12 minutes, says her dramatic rise was unexpected.
"I fell into ultra running by chance," she admits.
"I've always run to keep fit for when I'm in the mountains, but I have no history of racing or training for a club. It has all happened so quickly."
Although Wilson describes Hawker, an adventurous mountaineer and skier, as unique, the raw qualities he saw in her are required by every ultra runner.
Physically, potential recruits must have plenty of in-built stamina and a talent for endurance running.
What does it feel like to run 60 miles? Perhaps little different to six
In terms of performance that means men being able to run a marathon in two hours, 30 minutes and women in three hours, five minutes.
Of equal, if not greater importance, is mental strength, an ability to narrow the mind's eye into tunnel vision.
"Running a 100k is no different to running 10,000m on the track," says Wilson. "You still have to be focused on winning the race, covering the breaks and staying with the leading group."
Hawker, who was the 14th woman home in this year's London Marathon, goes further: "What does it feel like to run 60 miles? Perhaps little different to running six miles.
"What I mean is that if you are running, then the time just passes. My mind becomes a form of moving meditation.
"The most important aspect of ultra running is your mind-set. You have to run with your heart and your soul and not just your head and your legs, otherwise you will fall apart."
After running a marathon, the average person will lose two centimetres in height, shed up to five kilograms in weight, sustain muscle tears and suffer from blisters and damaged toe nails.
It seems safe to assume then that running nearly two-and-a-half times that distance will wreak further damage on the human body.
A pinnacle for ultra runners is the 158-km trek on the Tour du Mont Blanc
"It is daunting to run 62 miles compared to 26 but in my experience ultra runners have recovered far quicker than those running the London Marathon," counters Wilson.
"Because they are running that little bit slower, the recovery seems to be quicker.
"When Lizzy won the world title, her pace was around seven minutes 12 seconds per mile. In the marathon, she runs six-minute miles."
Ultra running is recognised by the governing body of world athletics, the International Association of Athletics Federations (IAAF), as well as UK Athletics.
The IAAF financially supports the IAU 100km World Cup and the 24-hour World Challenge while UK Athletics backs the major domestic championships.
Hawker, 31, has been offered high-altitude winter training, access to physiotherapists and masseurs by UK Athletics if she decides to defend her world title in Holland this September.
She has yet to decide but says: "Anything over marathon distance tends to get forgotten and doesn't get the level of support in the UK that the marathon does.
I have tried for an Olympic demonstration for 2012 but the feasibility of that happening is almost nil
"There is no lottery funding. I don't know whether that will change in the future but at the moment it's not there."
Wilson is at the heart of plans to raise the profile of ultra running on a global stage. The ultimate goal is to win a place at the Olympics.
He will put a proposal to the Commonwealth Games Federation on 10 May to stage four ultra running demonstration events - 100km and 24-hour races and two mountain running competitions - in 2009 in the Lake District.
"We have 15 Commonwealth countries who support the event," says Wilson. "If it is a major success we anticipate it would be considered for the Games in 2014.
"The Olympics is a long-term goal. I have tried for an Olympic demonstration event for 2012, but the feasibility of that happening is almost nil.
"But we have a world champion in Lizzy and we can provide high-class competition.
"The time is right for ultra distance running to be recognised as any other sport."