Boxercise: The workout that pulls no punches

Perhaps it was Lennox Lewis' reign as world heavyweight champion; certainly Audley Harrison's Olympic success won't have done any harm. Whatever the reasons behind the surge of interest in boxing in this country, "boxercise" is feeling the benefits.

Boxercise takes the core of the sport but combines it with aerobics and fitness training. As with boxing, you wear gloves and hit a punchbag – but instead of then getting thumped in the ring by an opponent, you do a couple of rounds with a trainer wearing focus pads (about 30cm in diameter, worn on the hands like gloves). He will still corner you, pin you against the ropes and cuff you, but at least you won't actually get a battering. So, the thrill of the ring, with fewer bruises, and a great workout to boot.

Above a pub in Herne Hill, south London, lies the gym of the McKenzie brothers, Clinton and Duke. A family of true boxing pedigree – Duke was world champion at flyweight, featherweight and bantam-weight, his brother Clinton the British, European and Commonwealth champion at welterweight. It was Clinton who would be my boxercise instructor for the afternoon.

"No doubt about it, boxercise is the hardest but the best form of fitness training. You experience what a real boxer goes through," he said. That is exactly what I was worried about as I stepped into the ring for my first date with boxercise. After a couple of years of very little exercise, the only thing I had been fighting was fat.

The first stage was simple enough. A bit of light jogging in the ring, air-punching out in front of me and up above. Then some stretching, loosening up calf and quad muscles. Next came a tougher test, the punchbags. First, Clinton bandaged my wrists and knuckles, and then I donned the gloves.

I soon realised punchbags aren't just about improving technique; more importantly, they test levels of fitness and endurance. Advanced athletes train anything up to 12 rounds on these bags, but I found my fitness levels waning after just a couple. The bag-work, indeed all of boxercise, mimics the rhythms of a real bout: you go for rounds of three minutes, taking rests of one. I think I managed about three rounds; by the end my right hook was still strong, but I was virtually pushing away the bag with my left jab. The energy a few minutes of punching had used up was revealing – as a cardio- vascular workout, the punch- bag alone is hard to beat.

Though my energy was drained, my enthusiasm was quickly restored by the next exercise: the focus-pad work. Stepping into the ring with Clinton McKenzie was intim-idating, but fortunately boxercise differs from boxing in one important respect: you don't get hit back. On the focus pads you get to hit and move like a real boxer, placing jabs, hooks and uppercuts as your trainer makes the pads your targets – and this is certainly the most fun and authentic part of boxercise.

Next it was skipping. I quickly learnt why this is such a key element of a boxer's training – the energy in my shoulders was sapped within a minute of less than technically competent rope- work. The session was rounded off with more traditional gym work, 10 minutes each on a step machine and bike.

With boxercise, you also get to work towards certain goals. And what a goal have the McKenzie brothers for you. After a few months at their gym, you get a letter through the post. In big bold letters it says 'Judgement Day', below it a date and a time.

You must turn up. And when you do, you face three rounds of "hell in the ring" with either Clinton or Duke McKenzie. And they will know if you've been slacking on the bags...

McKenzie Bros Gym Half Moon Public House, 10 Half Moon Lane, London, SE24, 020 7737 2338; Holmes Place (020 7954 100) and LA Fitness (020 7366 8080) also run boxercise classes