Kickboxing. Is. Hard. I haven't sweated like this since we had to create a Joan of Arc tableau at primary school (with moi as Jeanne, naturellement) and Jimmy Jarvis took his role as Chief Firesetter rather too literally and applied his dad's Dunhill lighter to the scrap paper at my feet.
Dee, the teacher at London's KB Fitness Academy, is tremendously positive - "If you want to lose weight, I'll get you there. If you want to get fit, I'll get you there. If you want to do all the grades, I'll get you there," - and manages to keep us all bouncing on the spot between kicks and punches long after the sensible thing would have been to lie down and gasp for a stretcher. She has an assistant who roams around, adjusting individual stances, straightening punches and mopping up the pools of perspiration at my feet.
My friend Anna came with me. Neither of us had kickboxed before, but we agreed that it always looked cool on Ally McBeal. What I hadn't appreciated, however, is that a person needs two innate qualities to be a successful kickboxer.
One, you need to be relatively well coordinated. "Kick, step, turn, punch" looks like a simple set of instructions on the page. Actually, the words are tiny markers on the road to hell. At least for me. Anna turns out to have some natural aptitude for synchronised movement of which I was previously unaware - probably because I so rarely see her sober.
Two, you must possess some natural aggression. As the hour passes, the class divides into those who are experiencing no rush of adrenaline to keep them going but are getting through the exercises as best they can, and those who are getting a huge, self-fuelling buzz out of the yelling, jabbing and punching and have to be restrained from kicking in the heads of their more hapless companions. Anna is firmly in the latter camp, and I have the contusions to prove it.
When we leave, I decide I can only drag my exhausted limbs as far as the bus stop. I wave to Anna from the window as bloodcurdling cries of "Hi-yah" rend the air as she scissor kicks her way home. She can't wait to go back.
· Next week: Tim Dowling takes an infra-red sauna