I had been doing the exercises the yoga instructor gave me for two weeks - which is to say I had done them twice - when I decided I was ready for a class. He had promised yoga would bring me joy, and I was so focussed on this that I failed to consider that it might also be humiliating.

Normally I would start going red with embarrassment about 48 hours before the class, but this time the full realisation of what I was embarking upon didn't hit me until I opened the studio door and saw a dozen women stretching in leotards and leggings. "Oh, God," I thought. "I'm auditioning for Les Mis." Then it became apparent that I was going to have to remove my shoes and socks in public.

I picked a spot in the back row but this attempt to avoid being noticed was thwarted by the large mirrored wall in front of me. Anyone who cared to look could see that my Downward Facing Dog more closely resembles Teen Being Sick On Pavement. Having no idea what I was doing was less of a problem than I had anticipated. I'm not supple, my balance isn't great and I was born without an ounce of grace, but I'm good at imitating people if I think it will help me blend in. While the positions themselves are strenuous, the pace is fairly gentle and repetitive enough that I was beginning to think I might eventually get the hang of it.

I'll tell you what, though: these yoga people don't stop - not for a break, not even to drink water. It's one continuous exercise lasting an hour. Five minutes in, I started to perspire intensely, which I put down to a combination of embarrassment and exertion, but it got worse. Sweat soaked through my shirt and gathered in the runnels of my ears. Soon it was dripping off my nose on to my mat. As far as I could tell, this wasn't happening to anyone else. In the mirror I saw four neat rows of women doing the splits and one guy standing at the back who looked like he had just come in from the rain.

By the end of the session, any residual humiliation was dispelled by the rush of exhilaration that comes from being allowed to stop doing something you're not very good at. If you wanted you could even call it joy.

· Next week: Lucy Mangan learns to vibrate like Madonna.