In which my fitness career is in the bag

It was all going fine until they gave me the rucksack.

"I can be a gym person," I had told myself. "I can wear a trainers in public. I can get up early at the weekends to go to classes with words like "pump" and "crunch" in the title. I can consider a banana 'a snack', without the addition of toffee, whipped cream and buttery biscuit base. I definitely can."

It started two weeks ago, when I walked past tracksuited men handing out fliers on Muswell Hill Broadway Just before I could whip out the standard "not today thank you" response for leafleters, clipboard-bearers and those people who want you ask you a few questions about your hair (to which I like to reply "a lady never tells," with a knowing smirk), they threw me with a piece of genuinely useful information.

"Did you know there's an LA Fitness round the corner?" they said. I did not know. "That's near your house. Near enough that you might actually manage to go there sometimes. It's the same distance as Whistles and you make it there often enough, don't you?"

The trouble is, am a health club marketer's dream. I begin every Monday full of muesli and good intentions, and end every Friday face down in a tub of brownie bites. I have had two exercisey spurts in the last five years - one during my finals, when I realised that swimming was the ultimate form of procrastination because kudos for the exercise cancel out guilt for the not revising, and the other last summer, when I started getting up an hour early to go jogging before work. I'm pretty sure this second phase did really happen (I have the sodden ball of workout gear in the bottom of my wardrobe to prove it) but from where I'm sitting it seems like the giddy behaviour of a sun-soaked moron.

"So what do you want to achieve from joining?" asks the tracksuited man when I go for my tour.

Um. To lose the permanent indentation round my stomach where my control pants dig in? To not get out of breath singing in the shower? To learn to view sweat as a badge of honour rather than a reason not to use my hairdryer in summer?

"Just to improve my general fitness," I say.

Then a quick chat and a whizz around with my bank details later, he presents me with The Rucksack. Up till now, when he's mentioned "your bag" I was picturing a purple plastic number with drawstring. But no, it turns out "my bag" is a hardcore, padded-straps-gortex-panels-clippy-bit-to-do-up-round-your-middle-whilst-climbing-a-mountain rucksack. Which isn't my bag at all. I've spent my whole life ensuring that I never have need for a rucksack, and now I've actively bought myself a rucksack for the princely sum of £49 a month plus a £25 joining fee.

So here we go, exercisey spurt number three. I am going to find my swimming costume, fill up my water bottle, grab a banana and crunch and pump for all I'm worth.

But if all else fails and I never go, at least I can recoup a little by selling the rucksack.