In a leafy suburb of Washington DC, 20 leotard-clad adults are locked in an airtight room with heaters blazing. They have chosen to stay there, striking poses and sweating for 90 minutes. Madness? Self-flagellation? Possibly.
These are devotees of the Beverly Hills yoga guru Bikram Choudhury, and all believe that "hot yoga" is going to do them some good. They claim that it can cure anything from kidney failure to a slipped disc; asthma to acne. And it is also, they believe, the best way to achieve spiritual harmony and a bottom as tight as Geri Halliwell's. Bikram Yoga is performed in a room heated to about 105 degrees Fahrenheit, with a humidity of 60%. Its founder claims that it will "melt you from the inside out", via a series of moves designed to "warm and stretch muscles, ligaments and tendons in the order in which they should be stretched".
The British are, it seems, reluctant to get off their backsides, especially if it involves discomfort of any kind. We spent about £1.25bn on joining and attending health clubs last year, yet slothful recidivism is, it seems, our only reliable trait. Of those who join a gym, 80% give up training within a few months. Why? Boredom, largely.
In America, the message has sunk in, and the trendiest fitness clubs are doing all they can to take people's minds off the fact that exercise is often moronically tedious. The list of classes now on offer in clubs across the US sounds, if not scary, then certainly embarrassing. From New York to LA you can now raise your heart rate in "Karaoke Spin". (You pedal an exercise bike while yowling into a microphone, burning - presumably in blushes alone - about 900 calories an hour.) Step class lost its spangle? You can now do "Gospel Aerobics" instead - the standard moves, but instead of Madonna, you march to the rousing accompaniment of a live gospel choir. And if God isn't enough to get you down the gym, then how about defying gravity? "Circus Sports" raised its flamboyant head this year in Manhattan: an acrobatic class that will, apparently, build up your flexibility, strength and fitness while you fantasise about life in the big top.
Or you could try something a little more down to earth. A Saturday morning trip to the park in contemporary America is no longer complete without the sight of a large man chasing grown women in their gym kits through the mud. This is what's known as "Boot Camp".
"It's just a form of circuit training," says one fitness expert, Sam Jenkins,"using your body weight as resistance". Sit-ups, pull-ups, squats and running are the basics, and why not? As Jenkins points out, "some people respond well to being shouted at by men in big boots".
Boot Camp is said to have brought exercise beyond the gym again, and "outdoors classes" are booming. Group treks and hill runs led by trainers are propelling more and more Americans into their "fat burning zones" and go hand in hand with rainy-day activities such as "PE 101" or the "Recess Workout". Again, the aim is simple: get your heart rate up, build stamina, flexibility and strength and avoid boredom.
If this sounds too traumatic, then you could try "Super Slow" instead. It is a controversial exercise trend "invented" by a fitness trainer, Ken Hutchins. Devotees claim to have shed pounds by working out only once a week for 20 minutes. It's an old weightlifter's technique. Essentially, you lift weights very slowly - pushing each muscle until it fails. As the muscle recovers over the next few days it thickens. This new muscle tissue needs more food to keep it going, so by the time you've added three pounds of muscle, your body is burning up an extra 9,000 calories a month. Critics of "Super Slow" say this is not only hard to achieve, but doesn't give you the cardiovascular workout that your heart requires to stay healthy. The other danger, of course, is dying of boredom.
The kind of person who likes "slow training" may also want to snap up the fitness gadgets now popular in America. Digital assistants that track your heart rate and give nutritional advice are a must for those who find the aim of "getting slightly out of breath" too nebulous. You can, for example, wear a device called a "Sport Brain" to calculate your daily activity in terms of fitness. Or, if you travel a lot, you might shell out for a "Pocket Gym" - a "fitness system" that looks like a bicycle pump and claims to be "the world's smallest gym", enabling you to exercise anywhere.
But geeks and weightlifters beware. Baby-boomers are now influencing US fitness trends (which, inevitably, will filter across the Atlantic soon enough). Ex-hippies, it seems, would rather do low-impact "mind-body" activities than rig themselves up to milometers. Water aerobics have never been more popular and, in California, you can't go far without encountering variations such as "water t'ai chi" or "underwater massage".
If this sounds namby-pamby you can go for the burn underwater, too. "Hydro Ride" made its debut last year at New York's Crunch fitness club. It is underwater "spinning" - don't worry, your head is above the water level - and apparently works miracles on flab because water resistance is 12 times greater than air resistance.
The bottom line, says Jenkins, is that "all these people are doing roughly the same thing" - that is, inventing exercise classes that combine cardiovascular work with strength and flexibility training. The only real difference, he says, is in "how you dress it up to get new members and keep people coming".
Needless to say, the first signs of all this are popping up in Britain. You can now do stripercize in Soho or Boot Camp in Bognor. There is at least one British fitness club offering "Gospel Groove", and you don't have to look too far to find a room full of sweating yoga enthusiasts in virtually any corner of the UK. So whether you want t'ai chi, qi gong or a romp in your gymslip, there's a class out there for you - or there will be soon. So there's no excuse, right? The sofa, I'm sure you'll agree, has never looked more alluring.
