He can work it out: Tim Dowling being himself, only better. Photograph: David Levene.

Now they tell us: the scientists who developed the fitness guidelines for adults, the guidelines adopted by the World Health Organisation, have decided to "clarify" their advice. They would like to point out that when they where they said "moderate" exercise, they meant "vigorous", and that where they implied that a minimum level of fitness could be maintained through one's normal daily routines, they now wish to include "in addition jogging and two weight-training sessions a week". If you're not regularly breaking a sweat, they say, you're not doing enough.

This new advice come just days after the release of a study that said that even low levels of physical activity - say, three brisk walks a week - could lower the risk of heart disease in people who took no other exercise. What are we supposed to believe?

In hindsight, the old guidelines always seemed too good to be true. To suggest that doing the hoovering and using the stairs counted as exercise was to give almost everybody the idea that they were already immensely fit. People could congratulate themselves for simply negotiating the dull routine of daily existence. I had taken to including the sweat I broke into whenever a tax demand arrived as part of my overall exercise regime.

Everybody knows that maintaining fitness involves a certain amount of bother, and that improving fitness requires a degree of discomfort. If you're only walking between the sofa and the fridge, you're better off not exercising at all.

Perhaps the health officials have they taken their revisions a little too far. How many minimally fit people have been reclassified as dangerously unfit by this shift in emphasis? Lots of us do a bit of regular, actual exercise - beyond the realm of vigorous ironing or trudging to the bus stop - but how many of us do two weight-training sessions a week? I've done two weight-training sessions full stop, and it seemed like more than enough to me.

But then I don't have to worry about fitness, because I lift myself out of the bath every day, rain or shine.