If one more person asks me to make a donation to their Just Giving page, I think I might scream; at them, at the page and at the chutzpah. Is there suddenly an epidemic that is infecting everyone, transforming them into marathon runners, bike riders, moon walkers and triathlon competitors?

Why does your exercise and participation in charity runs make me feel the opposite - uncharitable? Perhaps it's your incessant updates that sour otherwise good intentions. Do we really need to know Dan has finally run 5k in 20 minutes? Somehow it feels less about supporting the charity and more about an unspoken obligation to support friends who are running?

Raising money for charity should be commendable but perhaps this type of fundraising uncovers an ugly truth about our need to both advertise and publicise our endeavours in a distasteful, self-aggrandising way. My virtual world is saturated with pleas for sponsorship, signifying to me that people want my support for their feats of exercise not for their chosen charities. "Who are you running for?" I ask. Wouldn't it be lovely if for once someone answered honestly saying: "For myself." I'm tempted to set up a Just Giving page and do nothing, no bike ride from Borehamwood to Brighton, no half-marathon and certainly nothing that includes mud in the title. Why do we have to compete to justify the giving?

Charities have worked out our desire to be heard, congratulated and adored, latching on to the trend of obsessive social media updating. When a Cancer Research radio advert declares it is "my duty" to take part in an event, demanding I must join the fight to cure cancer, I momentarily feel a call to arms and the desire to dust the cobwebs off my unloved trainers. The implication that by fulfilling my duty I will be able to eradicate cancer is irresistibly powerful.

But, is it really my duty to do any of those things? I am not a terrible, uncharitable, unfit human because I am not currently taking part in a half-marathon, nor will cancer be any more quickly cured if I don't beseech you to sponsor me.

Does this heavy-handed approach take away from the philanthropic nature of giving? Cancer research feels like a multi-million-pound Jewish Mother buttering guilt on to our challah, but should we bite?

Fun runs are so popular now that the annual figures of voluntary aid could rival any big business. Cancer Research UK is the third largest charity in the country, with people consistently picking this one over others because as the nice boy who rang my doorbell this week explained - while imploring me to sign up for monthly donations - one in three of us will be touched in some way by cancer.

Not just content to be lone runners we are beginning to include our children, too. It must be their duty to cure cancer as well. The guilt driving us to donate is greater when Ella has worked hard to run the 5k for Norwood. Does this teach our children that physical activity is of no value unless it is being done for charity?

Maybe it's not the racing and raising that perturbs me so much as the public documentation of it - why do anything any more without instagramming it. Perhaps it's a deep-rooted prerequisite to prove we are all at our core altruistic beings. We've just been swept along in the wave of social sharing.

When Dan posts his recent run, is he just looking for a virtual pat on the back and in doing so kicking away his right to privacy and instead placing more importance on his need to be ''liked''. I just wish I didn't feel like virtually tripping him up every time I see his posts.

What seems unjust is the potential for charitable giving to be overrun by this crude breed of self-publication that can eclipse the very real fact that people are suffering and dying and that your charitable donations can help. Let's not lose sight amid the throngs of bikers and triathlon tri-hards that there are those that would not normally be participating in organised events, but are doing so purely to raise money and to commemorate a life.

Let's not let them become diluted in the mass of look-at-me joggers because their achievements should be supported, cheered and clicked on.

Maybe Cancer Research is right after all and we do have a duty - only be assured that you don't have to perform a run for the money, nor do you have to broadcast it.

Sometimes it really is good enough to just give.