Accompanying me on a fleeting recent trip to the United States was my good friend Patrick, who was in health and fitness clubs in a pretty big way until he sold up a few years ago. He still proselytises on behalf of the divine Multigym, and indeed on our first morning in the States, as I woke up bleary-eyed, jet-lagged, and looking forward to an all-American breakfast, there he was on the carpet, powering through his habitual 70 sit-ups.

I got home four days later determined at least to hang up the punchbag that I bought three months ago at Walsall market. I have extolled the joys of Walsall's Sunday-morning market before in this column: it is the only place I know where you can stock up on chicken thighs, SIM cards, sports socks, azaleas, bin bags, pillowcases and apricots without walking more than about 50 yards, although actually, for breadth of stock, I should also put in a word for Gilbert's in Bromyard, here in north Herefordshire. Waiting to be served I once stood behind a woman who solemnly read her shopping list – a pound of grapes, six-inch screws, a wok, tulip bulbs, paperclips, a mole trap – while Mr Gilbert just as solemnly fetched every item, doubtless with only me of the three of us thinking of The Two Ronnies' classic "Four Candles" sketch.

I could probably have got my punchbag from Gilbert's, come to think of it, but at Walsall market it cost half the recommended retail price even before the obligatory haggling started, and now, finally, it hangs in the attic. As soon as I have recovered from the cricked neck I incurred while putting it up I intend to begin daily sessions. I'm told it's an excellent way of keeping fit, and it's just outside my office, so every time I get an annoying email I can go and belt it.

Also, with there being a rowing machine out there already, not to mention plenty of digging still waiting for me in the vegetable garden, and a weekly game of admittedly slightly pedestrian tennis with three friends similarly grappling with middle age, I can claim to be doing my bit on the fitness front. On the other hand, I can't remotely match Patrick's regime, or my dear wife's for that matter. Jane joined a gym in Hereford two years ago, and still goes at least twice a week, either to swim 100 lengths of the pool in the time it would take me to get my trunks on, or to do an hour's circuit training. And she gets to exercise her willpower, too, because there's almost always something she would rather be doing than sweating cobs on a treadmill.

There are disadvantages to gym membership, however, and one of them is the potential it offers for acute embarrassment. There are a number of women in the Hereford area whom Jane knows only from the ladies' changing-rooms, so scarcely ever sees except in bra and knickers, or less. She tells me that there is one woman in the habit of blow-drying her hair while standing proudly naked in front of a mirror, and I have spent enough time in male changing-rooms down the years to know that letting it all hang out is a quirk also shared by some men. Not that I'm counselling extreme self-consciousness, which can be just as disconcerting, but there's something decidedly unBritish about look-at-me nakedness.

Anyway, we were at a charity dinner a few months ago when Jane spotted, dressed up to the nines, one of the women she knew slightly from the changing-rooms, a woman with whom she had once or twice exchanged smiles at the bra-and-knickers stage of proceedings. The woman was sitting at a table, talking to her friends. Passing by, Jane instinctively tapped her lightly on the shoulder. "Hi," she said, gaily. "I almost didn't recognise you with your clothes on."

The woman turned, and in the split second that followed, Jane realised to her horror that the returning volley of banter she had anticipated was not on its way. "I'm sorry?" the woman said, while around her, chatter at the table suddenly ceased. Jane felt her cheeks flushing magenta. "Erm, I normally see you at the gym, erm, getting changed," she said. The woman gave only a half-nod of understanding. "Oh, I see," she said. "Have a good evening."

I can at least be sure that no such embarrassments will befall me, alone with my punchbag.