But every Tuesday you can catch them standing barefoot in a back garden in Fulham, west London, engrossed in a yoga class. Pat Benzie, 27, closes his eyes, breathes deeply and raises his arms high. John Reynolds, 29, positions his feet slightly apart, bends forward, and slowly arches his back. Oliver Griffiths, 25, stands barefoot, on his tip toes, and rocks gently back and forth.
Yoga is the new sport for lads. It boasts a string of superstar fans, including Woody Harrelson, Robbie Williams, Sting and David Ginola. It is even part of the school curriculum at Dulwich College, where boys are taking lessons in the technique that promotes flexibility and strength.
According to Dr Robert Munro, 67, director of the Yoga Biomedical Trust at the Royal London Homeopathic Hospital, yoga is particularly beneficial for men. The trust trains yoga teachers to treat medical problems. "Yoga can help combat the typical symptoms of middle age among men," Munro says; "stress, heart problems, high blood pressure, impotence, fatigue and back pain."
Sophie Jones, 24, from north London, teaches the class of lads in Fulham. "Even if someone is severely disabled, yoga is still beneficial", she claims. "It can help the old, frail, sick, young and athletic."
Her star pupil, a banker, Pat Benzie, took up yoga in June. He started having 40-minute one-to-one tuition in Viniyoga - a variant thatemphasises breathing techniques. "I was running maybe five or six times a week and wanted an alternative to high-impact exercise," says Pat. The idea was a big hit with his mates and he is now joined by four or five of them every session.
The evening I joined them, neighbours James Boden, 12, and his brother Edward, nine, who had longingly watched the classes from their next-door window for many weeks, had plucked up the courage to attend the class for the first time.
So what is the attraction for young men? Is it the hope of meeting a star? Or the thrill of watching a personal trainer contort herself into fantastical positions? It may be Sting's promise of sinewy muscles (and a wonderful sex life).
Or is it that men are sickeningly good at it and, with practice, are better than most women? "Men are responsive," says Sophie Jones, who coaches equal numbers of men and women. "They have an open mind and are often surprised by their own ability. Women read too many magazines, and think they know it all."
Sophie believes that the psychological benefits of yoga help explain its pulling-power. "Most of my male clients are businessmen who need help with insomnia and stress management", she says. "Yoga teaches them to find a quiet space, a bit of tranquillity in their hectic lives."
This is certainly true for John Reynolds, a fund manager, who is attending his first class tonight . "I am under a considerable amount of stress both at work and personally", he states. "Normally I like to unwind on my own by listening to music, but I thought I'd give this a go."
Oliver Griffiths, a lawyer, is recovering from a slipped disc. He spends most days seated at his desk and needs to improve his posture. "I have been doing a lot of stretching to help my back injury," he says. "I am hoping that yoga will be an extension of that."
Then there's the glamour factor. Derek Sulger, a 27-year-old banker, is a dedicated member of the class - after being told that Sophie also tutors the lad idol Robbie Williams. The garden has yet to be visited by Robbie, but the lads live in hope.
Aside from the mental and physical benefits, the Tuesday sessions are very much a social occasion. Most lessons end with a barbecue in the garden or down the pub. The teacher even approves. "Beer and yoga are not mutually exclusive," Sophie insists. "Lads can still be lads and do yoga. People have this idea that you can't drink, smoke or have sex... They think you have to be dull, and read a lot. This is not true. Yoga does not water you down in any way. It simply enhances your life and adds nourishment to it."
Which yoga is best for you?
For sinewy muscles: Ashtanga Vinyasa Yoga, a dynamic, high-energy variant that synchronises breathing with movement.
For beginners: Sivananda Yoga exercises the muscles and encourages correct breathing.
For executive stress: Viniyoga emphasises breathing techniques. All teachers have a minimum of six years' training.
For sore backs and bad posture: Iyengar Yoga uses foam blocks and canvas belts so students can practise without strain or injury.
For a practitioner in your area, send an SAE to the British Wheel of Yoga, 1 Hamilton Place, Boston Road, Sleaford, Lincolnshire NG34 7ES. Call Sophie Jones at Active Real Training: 0171-736 3590 or 07050 155 265
It Does It For Them
Jude Law: The star of Wilde and Gattaca (top left) practises yoga every morning in his front room. It makes him feel "clean and serene".
Woody Harrelson: The actor (top right) was inspired to take up yoga after a visit to a lost Inca city in Peru. He later gave up drinking and womanising:
"I started to turn a corner from being an out-and-out hedonist to some sort of spirituality."
Frank Bruno: (bottom right) Yoga was an important part of the boxer's training. After
taking up the technique, he said: "I feel the strongest, the fittest, the best I've ever felt. If you're fit you can chase your wife round the bedroom."
Sting: A self confessed yoga fanatic (bottom left), the singer spends two hours every morning in the lotus position. He boasts that as a result he can make love for five hours, "although that includes dinner and a movie". He claims: "I can do things with my body now that I wasn't able to do as an 18-year-old."
STRIKE A POSE
1) Position your feet a few inches apart
2) Hang your arms by your sides. Turn your palms outwards towards the front
3) Inhale deeply and slowly and raise your slightly bent arms to above your head
4) Exhale slowly. Then lower your arms
5) Repeat four to six times