I have a confession. I am addicted to a punishing device that pulls, pushes and whooshes and leaves you hot, sweaty and aching all over. Three or four days out of seven, I give in to the urge. I strip off, strap in and get down to it. For the rest of the week, I suffer withdrawal symptoms.

The name of my metal mistress is the Concept 2. It is a rowing machine, and it lives in the gym a few minutes’ walk from my office. I have always tried to keep fit, not least because I fight a constant battle against a metabolic rate and an appetite that agree I should be a lump of lard. So I have tried them all - cycling, swimming, jogging. Then, as I turned 60, I joined a gym and tried most of the cardio-vascular machines, including the arm and leg gadget that makes you look like someone trying to walk up the Cresta Run.

In the end, though, I settled on the rowing machine. It supports your weight - important when you are over 60 and the knees are crying out for mercy - and it exercises the whole body.

The Concept 2 is a model you find in many gyms. It has a lever to vary the resistance and a digital read-out that tells you what you want to know - distance covered, average time per 500 metres, total time, calories burned. It has a sliding seat, like a proper racing shell, and real athletic rowers train on it - most rowing clubs, rowing schools and colleges have these machines.

You might think rowing for, say, 20 minutes, and getting nowhere might be boring. In fact, it is surprisingly full of possibilities. You can hone your technique, and search for the best stroke rate, and you can watch the digital readout, setting yourself lots of targets along the way.

The real attraction of the Concept 2, though, is that it is more than just a device for keeping sad loners off the streets. It is, in fact, the focus of a sort of worldwide Internet rowing club. There’s this huge Concept 2 website with training schedules, fitness advice, and the rankings and perormance records of 14,000 indoor rowers from 50 countries, broken down in all sorts of ways - men, women, heavyweight, lightweight, every age group from children to real veterans. (The oldest person on the site is 93.) You can keep a log of your own times, and post them alongside the thousands of others. There’s a range of distances, from 2,000 metres, which is the blue riband distance of indoor rowing, upwards.

I am a heavyweight (of course) in the 60-69 age bracket. For my favoured distance, 5,000 metres, the website lists 25 men in the UK in my age and weight category. At the top is one Noel Frost of the Upper Thames Rowing Club (I told you proper rowers did it). At 60, he can do five kilometres in 17 minutes and 30 seconds. (Imagine it! I bet he’s all craggy, with pepper and salt hair and a flat stomach. No, I’m not a bit jealous.) My own current best time of 20 minutes and 50.1 seconds puts me at number 11 out of the 25. So watch it, Noel. I’m on my way, boy. That’s me scattering the ducks in the distance.

There are lots of indoor events at which rowers gather to compete. World-class rowers do 2,000 metres in under six minutes. Top rowers in my age bracket do well under seven. My own best time is seven minutes 57. But the short distance bothers me. I just think that seven or eight minutes flat out is too explosive an effort for an older person, and I instinctively hold back from finishing in a state of complete exhaustion.

In any case, so the website says, a much longer effort at a lower heart rate is better for keeping the weight off.

So, I warm up, do my five kilometres, walk on the treadmill a bit to loosen up, maybe do some weights, have a shower and then get back to the computer. It’s safe, satisfying and it does you good - and there’s this feeling of tapping into a worldwide community of maniacs, pulling like stink and getting absolutely nowhere. As you get older, you realise the whole thing is actually a good metaphor for life itself.

www.concept2.co.uk