Eight at night, it’s been a long day, and a personal trainer is taking down my particulars. How old am I? How tall? How heavy?

Like a suspected drink-driver pulled over by a Texas Ranger, I am then told to balance on one leg. Every time I wobble a bit on the incredibly sensitive high-tech balance board, an arrow on a TV screen zigzags.

When it is over, I have failed to impress. “Balance obviously wasn’t your cup of tea,” says my trainer. “Do you find yourself tripping over when you’re walking?” With a drum roll, I am then told my WiiFit age. I am 44, or 11 years older than I am in the real world.

This, says my WiiFit machine, is not good. For my trainer is not actually a person, but a video game console.

It appears that my muscles are much weaker than they should be. Tact is not the Wii’s strong point. Confusingly, it has also calculated that my body mass index is 22.18 (“ideal”, it says, so why all the doom and gloom?). It then tells me we should set a goal right away.

“Willamina,” it says because that’s the name I accidentally gave myself when I was trying to find out if Matt was an option. “Willamina, although your BMI is in the ideal range, how would you like to set a BMI of 22 as your goal?”

It has finally happened. The machines have taken over. Or they will have by the end of the month. I don’t want you to panic though, because H G Wells got it wrong: the machines don’t want to kill you – they just want to make you fitter.

Wii, Nintendo’s video games console, was already popular but in April, with the launch of its new exercise game, WiiFit, things got out of hand.

In the first two weeks of the launch, spurred on no doubt by the endorsement of the Girls Aloud superbabe Sarah Harding, Nintendo sold 338,000 (complete with that flashy balance board) in Britain and Ireland alone.

One month on, you cannot get hold of one for love nor money. Well, money, yes. The retail price is £69.99 but if you’re prepared to splash upwards of £130, eBay will oblige. That’s after you’ve already spent £180 on the Wii console you need to play it on.

According to the Office of National Statistics, booming sales of WiiFit (along with shoot-’em-up game Grand Theft Auto IV) softened the blow of the spending downturn on the high street in April. While other sectors reported declining sales, entertainment shops saw a 5.3% increase. In these dire times of credit-crunching gloom, one assumes food might be the last thing to go. It isn’t: it’s the WiiFit.

This, then, is a seriously crazy craze. And, weirdest of all, it involves us getting off our fat behinds and doing some exercise. Sort of. Anecdotal accounts of epic WiiFit weight loss are springing up across cyberspace. Suburban streets are hushed but for the swoosh of housewives Wiiing. And one hospital is even planning to use the WiiFit to treat stroke patients.

Could a computer game that claims to make exercise fun be the panacea for our sloth-like age? Will playing the WiiFit guarantee to turn you from couch potato to spring chicken? Or have we all gone stark, raving mad? FOR those of you not yet gripped by the cult of Wii, let me explain how it works. Launched in 2006, the Wii itself is a games console with one big difference. Instead of sitting on the sofa zapping things, you hold two wireless controllers and act out the game. For real. And virtually. At the same time.

In the Wii boxing game, for instance, the punches you throw are shadowed by your cartoon representation on the television screen. In golf, you take a swing and then watch the ball fly off down the virtual fairway. The console picks up your movements from the controllers and interprets them into the game. It is an astonishingly clever piece of technology.

WiiFit goes one step further. With the wireless balance board, it can sense your precise weight distribution. Along with the handheld controllers, it then perfectly recreates your movements on screen as you work your way through a variety of exercise-based games such as hula-hooping, slaloming, tightrope-walking and, less rivetingly, jogging.

You can do a yoga session, aerobics and muscle workouts (the press-ups are just as hard as ever). The more you do, the higher your score, the more levels of the game are unlocked.

Nintendo only goes so far as to describe it as “an easy, simple and enjoyable way for every member of the family to incorporate exercise into their daily routine”, although in the dialogue of the game itself the recurring, hypnotic theme is that by playing it regularly, you are improving yourself.

The government is certainly getting very excited about Wii. In January, even before the latest fitness-specific game was launched, it was considering putting Wii consoles into school gyms as a way to make games lessons fun. By inference, it has accepted that it does have health-giving properties.

There are plenty of online accounts of people using WiiFit as their main or sole fitness regime. One blog full of unsavoury then-and-now photos reports a man losing 11lb in 35 hours on the Wii, allowing him to wear a very strange tuxedo to his wedding (I’ll spare you the web link).

More academic studies are less positive. Liverpool John Moores University last year concluded that if you played Wii sports for 12.2 hours a week you could lose 27lb in 12 months. That’s not a great ratio. It also concluded that children playing Wii games burnt only 2% more energy than children wasting their lives on other games consoles.

Still, some men in white coats are willing to give WiiFit a shot and university staff at St James’s hospital in Dublin are even optimistic it could have benefits for patients. They’re planning to use a WiiFit to treat stroke victims, suggesting it could be a sturdier, cheaper and more entertaining alternative to standard medical equipment.

Joseph Harbison, a consultant at the hospital, says: “We’re considering the WiiFit in the first instance to assess and rehabilitate patients’ balance, as trying to restore a stroke patient’s standing balance is the first stage in getting them to walk again.”

Before installing the console, the unit was trialling a medical device designed specifically to rehabilitate stroke sufferers. The equipment costs eight times the price of the WiiFit. Harbison said that as well as being more expensive, it had only a fraction of the versatility of the Wii, was less robust, less adaptable to the individual and “frankly less interesting for the patient to use”. Meaning, presumably, that it didn’t have a tightrope walk.

Boredom is the biggest complaint made by patients in the hospital’s rehab wing. The plan is that the Wii will counteract this.

Even Darren Campbell, the Olympic-gold-medal-winning sprinter, has got a blimming WiiFit. You would think he wouldn’t need to bother but he is philosophical about why he plays it with his children: “The reality is that games consoles are now part of our lives, and a console where there is a little bit of exercise is not a bad thing. For keeping fit though, I don’t think anything can substitute running on the treadmill, or swimming. I am not going to throw away my gym membership yet.”

T J Salih, chartered physiotherapist and former team physio for Tottenham Hotspur, the Premier League football club, is less enthused, describing the WiiFit as nothing more than a gimmick.

“It’s okay for people trying to relearn their balance. It’s a good visual cue. But because the main measure is the pressure from your feet, you could be doing anything with your upper body to pass the test.”

He goes on to explain that it is almost impossible for us not to cheat when our brains have visual clues. “I often get patients to close their eyes for an exercise, but you can’t do that with the Wii. So the temptation is to do the exercises wrong. I’m pretty sure I’ll be seeing people hobbling into my clinic who’ve been rocking about on their knee, ankle and hip joints for hours.”

Even before the arrival of the balance board, there have been concerns about injuries caused by excessive Wiiing. In January, a group of British osteopaths even coined a new condition, “Wii syndrome”, in response to the rising number of parents turning up at clinics with game-related neck, shoulder and elbow injuries. BACK in my front room, I’m finding that cheating pays dividends. I have become brilliant at the jogging game, mainly because I’ve worked out I can stand motionless and just waggle the control about. It’s so much easier than actually running.

Within seconds, my Mii (my virtual representation on the screen) has run ahead of the Wii pacemaker and the computer is panicking that I’ll do myself an injury. That I might sprint off through the patio doors. It has no idea I’m just standing there giving the stick a cheeky waggle.

For the next hour, I cheat ata lot of things and progress to previously unimaginable levels of sporting prowess. But after five hours, I’ve hardly brokena sweat. Wii, I’m afraid, is not the solution to everything.

Still, I’ve just been on again for another session (if nothing, it’s addictive). And it’s just told me my WiiFit age has plummeted to 38. That might be because I’ve learnt how to cheat in the balancing bit. It might also be because I have fewer clothes on.

I like to think it’s because I have become six years younger overnight. I’ve virtually convinced myself of it.

No need to break sweat with these gizmos

Vibrating belts
More use for Carry On film comedy than weight loss, vibrating belts operated on the entirely unsound principle that if you wiggled flab about enough it would eventually disappear. After a brief heyday, the machines, rather than the fat, vanished.

The electric six-pack
Strap on a charged-up belt and – while you sit back to watch TV – the electric shocks will exercise your stomach muscles until Calvin Klein is hammering down your door, begging you to expose your sculpted abdomen on the side of every bus in Britain. A tempting proposition and one that sold an awful lot of electric belts – but there were flaws. Mainly that most users found their newly rippling muscles were invisible because they forgot to lose the fat that obscured them.

Power Plate
The latest and flashest addition to any self-respecting gym: a large vibrating plate. All you have to do is stand on it and then hold a series of low-impact positions. If it was once good enough for Russian astronauts at risk of weakened bones and muscles, it’s almost certainly good enough for you. But whether, as claimed, it can give you an hour’s work-out in 15 minutes – unfortunately only time will tell.

The dumbbell phone
It exists, it really does – a weighted receiver that helps you to build those biceps while you chat. With free weekend calls you will be Arnold Schwarzenegger at no cost – and at least cramp is a good reason to hang up on your mum.

Pedometers
When fast-food chains started giving these gadgets away, people should have realised that they were about as useful as the free plastic stirrers that don’t actually move your coffee. Knowing how far you’ve walked all day doesn’t necessarily get you very far. Did you stroll? Did you stop for a burger? Did you gobble 1,000 calories while picking up that pedometer?

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