People may be on the lookout for an exercise-free fitness regime, but if the alternative involves electrodes, then I'm happy doing a few sit-ups. The folk at Ultratone, however, insist that "bio-stimulation", as they call it, is actually better than exercise. They produce a leaflet quoting Professor Gerta Vrbova, who says that electrical bio-stimulation can target muscles that are not triggered by normal exercise.

I am persuaded enough to try it. The Ultratone clinic waiting room is a beige-on-beige oasis of calm, decorated with posters which seem to indicate that bio-stimulation is a therapy that largely appeals to female underwear models. My therapist, Liz, admits that they don't get many chaps in. I sign a form promising I am not pregnant, and am soon standing in my pants while Liz applies sticky pads with wires coming out of them to my back, arms, chest and stomach. I ask how many pads there are in total.

"Twenty," she says. That's a lot. What, I wonder is the most you can safely put on a person? "Twenty."

Then I lie down while Liz turns up the juice. When she does my left biceps my hand rises up and gently chucks me under the chin. I suddenly realise the power she has: I'm sure she could make me punch myself to death by twiddling the right knobs.

She leaves the room as the programme begins, firing my upper-body muscles in precisely choreographed patterns. "Relax," she says, but that is not really up to me anymore. Under the towel I am jiggling faintly, like a reanimated corpse.

While not unpleasant, there is something extremely lonely about lying still in a darkened room while a machine contracts your muscles. In the other room I can hear Liz on the phone, making evening plans. If you think half an hour on a treadmill is a soulless pursuit, I suggest you try this.

Two days later, my right biceps ache at a point deep in their centre, but otherwise I don't feel any different. It seems bio-stimulation has found a tiny bit of muscle I never even knew was there, and made it hurt. Progress.

Next week: Lucy Mangan tries some diet shoes for size.