There is a row of multicoloured, late-blooming snapdragons at the entrance to the park where I run. Their effortless exuberance seems to mock me as I begin the clumsy cycle of awkward, desperate movements that constitute my running style. It's a wonder I get anything done, with the number of people who keep stopping me to ask how I manage to combine leaden stumbling and uncontrollable flailing at the same time.

Still, I keep telling myself, things are improving - 2, 4, 1, 1.5 and 2.25, 4, 1, 1, 1, 2 are not in fact the vital statistics of Paris Hilton and Victoria Beckham but the timings in minutes of my past two runs. Yes, I can now break out of my customary amble for up to two minutes without dying, and have twice managed to breach the four-minute barrier. Admittedly most of it was downhill and with a following wind, but if I squint hard enough, it can look like progress.

I do hate it though. It's painful, boring beyond measure, and the paltriness of what I have just over-generously described as progress makes me despair. I don't feel any better "in myself" as they say - in fact, I usually have a headache for hours after I've finished and am in a vile mood at the crushing futility of it all.

I keep waiting for the fabled endorphin rush or, failing that, some sweet cessation of the burning agony that sets in 18 seconds after I start. But there is nothing. I don't even feel the brief glow of virtue afterwards. What, after all, can I tell myself? "Well done, Lucy. You have managed to move at just above walking speed for literally a few minutes at a time," is not enough to flush me with a feeling of success, to keep me pounding ever onwards in search of that elusive goal of fitness.

All I can say is that it's a salutary lesson in the cumulative effects of sloth. I've never smoked, never drunk (consistently) to excess, and don't eat convenience food. My only (ha!) problem is that I have been inert since the day compulsory school sports ended, heedless of the consequences. No wonder the snapdragons mock.

· Next week: Tim Dowling goes skydiving - without the aeroplane.