In my opinion the words “fun run” are up there with the oxymorons “happy birthday” and “easy childbirth”. If you don’t agree, a brief glance at the bulging calves, the sweat-soaked singlets and the contorted faces of the 35,000 or so finishers in today’s Flora London Marathon will settle the matter.

Do they look as if they’re having fun? No. Do they look as if they are in the panting throes of an all-consuming, possibly life-threatening, obsession? Yes.

It is all too tempting to have a go at the runners, so I will. Like you, I’ve had one matey letter too many telling me at length about some acquaintance’s crazy decision to compete and his every running-related injury from patellar tendonitis to problems with his big toenail. On and on they go, basically letting us know in the sweetest, most self-deprecating language imaginable how if they make it to the finishing tape it will be a triumph of grit over idleness.

Not being one myself, my guess is that marathon men and women fall into three categories. They are either exercise-orexics, like the many I know who spend their lives in Stella McCartney for Adidas sportswear running between Pilates, army training, tennis lessons and yoga. Or they are “slack bobs”, that is, people who have decided to heave themselves off the sofa, which is great – the World Health Organisation said last week that overall physical inactivity is estimated to cause 1.9m deaths globally each year – but these former slouches now want everyone else to share every second of their fitness journey with them. The third category are professional athletes, an elite. And in my book, all three groups are running . . . mainly for themselves.

Still, they get away with all this attention-seeking, with being unavailable for months “because I’m training”, because it’s for charidee. At the end of the letter/e-mail there is always the bashful link to a donation website, which makes the rest of us feel even more flabby and mean-spirited. It’s not enough, one gathers, for these marathon runners to be celebrated for pounding 26 miles of pavement in four hours and for deservedly earning a sense of lifetime achievement. We have to fork out and fund their high for them, too.

They are a bit like those people who go on charity bike rides in China. We know, and they know, that the reason they need our money is to pay for their lovely free long-haul holiday in China. The charitable motive is a distant second. It’s totally maddening.

So I am convinced that people who run marathons or bike down the Great Wall of China are really doing it for themselves. After all, according to the latest issue of the British Journal of Sports Medicine last week, women who exercise aerobically and regularly slow down their biological ageing by 10 to 12 years. Now that’s got to be a good incentive for exercise. Doing sport for 20 minutes three times a week also cuts down stress by 33%. “The results indicated the more activity a person indulged in, the lower were their chances of psychological distress,” the BJSM said.

Okay, so now it’s time to give credit where it’s due. I’ve had my ungenerous whinge and I’ve shared all my reservations and I would like to reverse thrust. All those who run marathons? Today is their day. And so it should be.

However annoying it is receiving all those letters and requests for sponsorship, the fact of the matter is that 68% of those who entered the Flora Marathon, which raised a record £46.5m last year, really did do it for charity as well as for themselves. Let’s hear it for Dale, 40, whose three-year-old son Jack has microcephaly, epilepsy, oesophageal reflux and cerebral palsy; Dale is running to raise money for Jack’s hospice. You would have to have a heart of stone to be cynical about Dale, Jack and their like.

What they do is wonderful, grrrr! “I really didn’t want to do the marathon,” said Rosie Millard, my colleague. “I’m a 42-year-old mother of four and I’ve got up at dawn, before dawn, to run 16 miles, day after day, and I’ve dropped two dress sizes – ” I interrupted her to say, “You see, you see? You’re doing it for you!” Rosie ignored me and went on calmly: “I’m doing it for Help the Hospices, after a dear friend died in one, aged 41. You never feel more alive than when you’re collecting money for children who, unlike you, will never live to see the age of 21.”

So I take my hat off to them, to Rosie, to Candida, to Jasper, I do, but here’s my tip for the next time: tell your friends that you’re running to help to raise money for (fill in your charity of choice). Also admit, though, that you are doing it because you want to lose weight, to destress, to look hot and 10 years younger.

You won’t get as much sponsorship cash but you might get extra Brownie points – for honesty.

I don’t get blogging. It’s not only that I’m reluctant to write for nothing. There are all those people who ask, “Do you blog?” at parties (our own sad neutered version of the “Do you swing?” question), and who warble about “wikis” and “web presence”. Still, a few weeks ago I started to write one. It’s very easy - even a middle-aged woman can do it. I wrote about what I was making for supper that night. And food shopping in the Portobello market. Then I checked to see the global response to my debut. Nothing. On my next five posts? Zero comments.

Anyway, last Sunday I went to watch the Olympic torch relay up the road. I witnessed the men in blue and the Met surging up and down Ladbroke Grove and skinny little athletes in their white logoed tracksuits trembling in the snow. I watched Konnie Huq run gamely past, holding the torch, and I watched that angry gingery man try to grab the torch and I watched men in uniform try to stomp on his head.

Then I really pulled out the stops. I wrote about how my husband shouted, “Free Konnie Huq!”, and I gave an eyewitness account of how a former Blue Peter presenter, that is, a celebrity, was actually touched by a civilian. And after all that unpaid work, was the web on fire? Once again – nul comments.

I don’t get it. There are the blogs that work – such as Judith O’Reilly’s brilliant blog turned book Wife in the North, or the riveting Petite Anglaise, or our own Alpha Mummy (on Times Online; a treat) – where you sense that the authors are releasing themselves with feeling into the ether. This is because blogging is about regularity, I presume. You have to post every day. You have to be totally committed.

In California people have started to blog themselves to death and The New York Times is reporting stress, sleep disturbance and exhaustion among the “blogging community”.

Well, there is no danger of me having a coronary at my laptop triggered by exhaustion and anxiety about page hit rates. It’s quick and easy to start a blog, as I’ve discovered. It’s even quicker and easier to stop.

rachel.johnson@sunday-times.co.uk

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