We have all received one of those begging emails in our inbox. "Three months ago the walk to the bus stop tired me out. I was so unfit!! Now I'm running a marathon for [insert worthy charity here]. All 26.2 miles! Please sponsor me." I sent one myself a few years back, simultaneously confounded that I had agreed to do something so apparently insurmountable, and excited about the sense of achievement I would feel on crossing the finish line.
Was I special? Decidedly not. The participation in serious endurance events such as marathons and triathlons has soared over the past five years – there are around 850 races a year compared with 350 five years ago – leading to a fitness phenomenon where these days every man is an amateur athlete, if not quite an Olympic medallist.
The popularity of the UK's highest profile endurance event, the London Marathon, bears this out. Every year, 120,000 applicants compete for a ballot place in the race. The 2011 event was the most oversubscribed ever. Of 35,000 places, around 15,000 go to charities, so those 120,000 runners were competing for 20,000 places, and the lot of them signed up in a record three days.
There are so many marathons, half marathons and races of shorter distances around the UK each year, and no umbrella organisation, that it isn't possible to estimate how many people are taking part. The London and Edinburgh marathons both have major profiles, but last year Brighton held its first marathon, for 12,000 runners, and this year Liverpool hosted its first in 20 years. Experts say there is room for more. Triathlon is booming too. Membership of the British Triathlon Association has increased 119 per cent in six years, and in 2010 there were 132,000 triathlon race starts.
"That is a phenomenal number of people tackling an event of any distance," says Zara Hyde Peters, the chief executive of British Triathlon. "At Hyde Park this year, where you ride the Olympic course which is quite something, it was 60 per cent novices."
"Had you asked someone on the street 10 years ago what a triathlon was, they would have probably guessed it as some sort of multi-sport. But they wouldn't have known exactly what it was, let alone thought about doing one." In case you don't know, it's a run, swim and cycle event with a variety of distances for different abilities.
Hyde Peters was a novice herself three years ago when she landed the job at British Triathlon and decided she needed to "sample her own product". "I'm 48 and I'm quite proud to say that I can swim a mile in front crawl."
Fitness expert Gareth Cole, who is head of education at The Third Space gyms, says that training for endurance events is the most effective way to maintain motivation for a fitness regime. This is why he persuades clients into signing up for a five or 10k run or a longer event as often as possible. "I use events to keep people on the fitness wagon. Training for an event is completely different than training for aesthetics, where there is no end goal. If you just want to look better, you'll never be satisfied with the results.
"If you sign up to an event, it is so much easier to find motivation because there's a beginning, a middle and an end, and on race day there is an enormous feeling of achievement. It is also a way of underlining the year, because you can say, 'I ran a marathon or did a triathlon in that year.'" First-timers realise that they love the flush of a bit of competition and sign up to further and more challenging events to beat their own times or race against friends.
The stories of virgin endurance athletes bear this out. Pete Carr began running in October 2009 and has since lost 6st. He ran a half marathon in March and a full marathon a few weeks ago. "After the half marathon I felt like I hadn't reached my limit," he says. "My new interest in running made me wonder how far I could really push myself. I was curious to see if I could run a full marathon, to see what my body could do."
Michael Spencer-Chan, who says he was "no kind of athlete" before signing up for a triathlon, completed two sprint distances, in August and September. Beginners were asked to put their hands up at the starting line, and more than 50 per cent turned out to be novices. He admits he didn't train much between the two and really struggled on the second swim. Nevertheless, he completed the race and is planning on undertaking the longest triathlon distance at next year's London Triathlon.
Another novice, Pete Tutton, completed the 2011 London Marathon to fulfill a long held ambition, despite a series of injuries. He says it was a one off, but is tempted to see how fast he could run with proper training. Journalist Julia Buckley has turned her running hobby into a career, and since completing her first long distance event four years ago, she takes part in about ten races a year, writes about the sport and doles out tips to 10,000 Twitter followers.
When you tire of marathons and triathlons, what's next? An Ironman is basically an ultra-triathlon, demanding a swim of 2.4 miles, a cycle of 112m and a run of 26.2m. Last month, the Ironman world title went to British woman Chrissie Wellington for the fourth time. It's an arduous challenge, but Ironman UK's commercial director, Patrick Alexander, says that interest is booming. About 10,000 competitors take part in an Ironman in Britain each year, and two new events were set up in 2010. This includes beginners. "A lot of people who have never even done a 5k sign up," says Alexander, "because it is seen as the ultimate mass participation event for normal people. It is such a big challenge that it turns your life around."
According to Gareth Cole, the life-changing benefits of endurance events reach further than you might expect. He says there is a great social aspect to the training and participation. "You're pretty exposed when training. You're in your swim gear and you let the barriers down, and then away you go!" He is very proud that of his own clients there are now three triathlon-loving couples.