However, it's not just sports stars who are accessorising with the bands. Actor Russell Crowe was openly wearing one when he visited Marysville three weeks ago to discuss a building project for the bushfire-stricken town. Power Balance says the holograms on either side of the wrist react with the body's energy flow and tune its frequency to the ideal 7.83 hertz required to power the body. The Australian Medical Association, however, yesterday dismissed this alleged benefit as ''biologically implausible'' and suggested the advertising regulator should investigate the claim. Power Balance's Tom O'Dowd says if the bands - which are said to increase an athlete's core strength and power by up to 500 per cent - didn't work, people wouldn't wear them. Mr O'Dowd said about half the players in the AFL and the NRL now use them, but spokesmen for both codes could not confirm this.

High-profile players who proudly sport the bands include the Brisbane Lions' Brendan Fevola, a product ambassador paid to wear one, and the NRL's Benji Marshall. The players are reluctant to explain why they use them but sports psychologists say the bands have a placebo effect - the players think the bands will improve their performance on the footy field, so they feel more confident and play better. The AFL's Patrick Keane says the code has no problem with players wearing the bands as long as they are not a danger to other players. ''The view of our medical commissioners is that they have no issue with them,'' Keane said. ''If the players think they're getting some sort of benefit, that's fine. There's no performance enhancing rules that they're breaking.'' The Sunday Age understands the AFL's medical staff do not believe the bands can turn ordinary men into super humans.

And the two men who would best be able to shed some light on any transformative powers the bands may have, Riewoldt and Fevola, declined to discuss their new wrist accessories with The Sunday Age . According to a Brisbane Lions insider, Fevola swears by the bands and has been trying to convince a number of his teammates to try them. A Tigers spokesman said Riewoldt had only recently decided to experiment with the band and it was too early for him to talk about its affect on his strength. He planned to wear one again last night against Fevola's side, the Brisbane Lions. Australian Medical Association vice-president Steve Hambleton said the bands were ''biologically implausible''. ''My suspicious antenna goes up immediately when you hear the claims being made about these wristbands,'' Dr Hambleton said. ''My first feeling is that no one is going to believe it.

''Surely the advertising laws in this country would have the regulators wanting to take a look at these claims to see if they are real.'' A federal Health and Ageing Department spokeswoman said the bands were not registered with the Therapeutic Goods Administration because they did not meet the definition of a medical device or therapeutic good. However, Mr O'Dowd who refused to release sales figures for the bands, believed to be in the tens of thousands, said about 30 per cent of sales were to the medical profession, mainly osteopaths and chiropractors. Mentone chiropractor Dr Matthew Bateman said from his experience with the product, which comes with a 30-day money back guarantee, many clients felt an ''amazing benefit'' from wearing it. Developed in California, the bands went on sale in Australia in August last year for $59.95 and have become popular through clever marketing.

Not only are several of the world's top athletes paid to wear them, Power Balance has poured money into different sports through sponsorships to lift its profile, and has posted videos on YouTube showing wristband users growing stronger. People would stay upright when pushed and turn further around than they thought they could when wearing the band. However, Australian Skeptics spokesman Richard Saunders said this was just a trick using applied kinesiology which relies on the way muscles react to forces in different directions. He said the bands had no real beneficial effects at all. ''There is no science behind them,'' Mr Saunders said. ''It's a bit of plastic and two holograms which reflect light. It doesn't have magical powers.'' He said spending $60 on something that should cost $3 was a waste of money.

The NSW rugby league team probably agrees with him. It requested a box of 40 wristbands before last Wednesday night's State of Origin clash with Queensland. NSW lost 34-6. NRL spokesman John Brady said medical staff had approved their use but he did not know how many players wore them on the night. He said the product was not endorsed by the NRL or any club. Power Balance is a sponsor of both the West Tigers and St George Illawarra. Surfing Australia's website has a link to the Power Balance website, which promotes an exclusive Surfing Australia aqua and white colour wristband. For every band sold, $20 is donated to Surfing Australia. Surfing Australia's high performance centre manager, James Egginton, said the deal with Power Balance was brokered about six weeks ago but the surfing organisation had yet to receive any money. Mr Egginton said a number of top surfers, including Andy Irons, had endorsed the product but he could not say if Surfing Australia believed in the band's powers.

Reigning world champion Mick Fanning trialled the band in March when competing at the Quiksilver Pro on the Gold Coast and suffered a shock third round loss to fellow Australian Kai Otton. Fanning's manager, his mum Liz, said the Power Balance distributors wanted to sponsor Mick to wear the band all the time but he decided against it. ''He didn't have any negative things to say about the product. He found it helpful but preferred to wear it when training and not in the water,'' Mrs Fanning told The Sunday Age. Mick Fanning was in Indonesia last week and could not be contacted. POWER BALANCE WRISTBAND USERS Brisbane Lions' Brendan Fevola

Richmond Tigers' Jack Riewoldt St Kilda's Nick Riewoldt Wests Tigers NRL player Benji Marshall Parramatta's Timana Tahu St George Illawarra's Matt Cooper

Jockey Damien Oliver Wallaby James O'Connor Surfer Andy Irons Real Madrid's Cristiano Ronaldo Basketballer Shaquille O'Neal

F1 driver Rubens Barrichello Actor Russell Crowe The Biggest Loser trainer Shannan Ponton