Revealed: Why Portsmouth's stars run longer and shoot harder

A bit more bite in Sean Davis's challenges, perhaps? An extra yard of pace from Benjani Mwaruwari maybe? Even more power in Niko Kranjcar's shot?

All these things might actually be true — and it's down to the shirts they are wearing. Portsmouth are the only English club to latch on to a trend that was the talk of the rugby World Cup — ionized shirts, or 'wearable steroids' as the marketing bods soon dubbed them. South Africa were one of the rugby countries to use them and they won it.

Developed by New Zealand kit firm Canterbury, the 'IonX' shirts are made from a fabric that contains a negatively charged electromagnetic field. This means the process of ionisation, which produces electrically charged atoms long understood by former Eastern Bloc scientists to improve sporting performance, can occur in the body during training and even competitive matches.

It is claimed to increase blood flow and oxygen levels, leading to improved performance.

Portsmouth seem to think it has an effect. Paul Bell, the club's commercial director, said: 'It's something we believe is delivering a tangible, positive effect on our players.'

Tests carried out at Loughborough University appear to back this up.

Professor Mike Caine, head of sports technology and innovation at Loughborough, compared the performance of athletes wearing IonX garments with those in normal gear and saw a difference. 'There seems to be a small but significant improvement to repeated power output during high intensity exercise,' he said.

Professor Caine found a 2.7 per cent improvement in 'mean power' — so, does this mean that Portsmouth's players can shoot 2.7 per cent harder wearing their new shirt?

He wants to carry out more research before going that far (and has just started to do so) but says: 'If you ask me "could it make a performance benefit?" Yes, I believe it could.

'If you look at professional sport, certainly at international level and almost certainly at Premier League level, would a coach or a fitness and conditioning manager bite your hand off for a 2.7 per cent increase in strength , power, agility, flexibility, reaction time? Yes they would.'

While the shirts were being tested by the likes of South Africa , Australia and Scotland prior to the rugby World Cup, several other countries (believed to include England and France) sought clarification over the legality of IonX.

The International Rugby Board asked the World Anti-Doping Agency for a ruling. They replied that they were happy — for now. Spokesman Frederic Donze said: 'Since there is no scientific publication supporting claims that changes in the body ion charges or magnetic field distribution enhance performance, and since such technologies do not contain prohibited substances, these technologies should not be considered as a banned method to date.'

Portsmouth are so keen they have done a deal preventing other Premier League sides from using IonX for 'the immediate future' — thought to be several seasons.

Bruce Vandenberg, the club's chief executive, said: 'It was very important to us that we were the only football club that could wear IonX so we sought to create an exclusive window.'

It has taken football a long time to discover a science that has been known for centuries.

The Japanese long ago realised that standing next to a waterfall, where ionisation also occurs, makes people feel better and German scientists in the 1930s used ionisation chambers to train bomber pilots to stay awake longer and be more alert. That technology was then applied to athletes in the former East Germany and Soviet Union.

It took an American textile company, who made protective suits for the Chernobyl clean-up operation as well as Ian Thorpe's 'shark-skin' swimming outfit, to work out how to incorporate the technology into fabric. Canterbury have a 25-year agreement with that firm.

Joe Middleton , chief executive of Canterbury UK, said: 'With this kit elite athletes can recover more quickly between training sessions and probably train half a day earlier. That's the feedback we're getting from these guys. So, it's big.' Even Harry Redknapp is said to be a convert.

Those negative ions must be a powerful force if they can win over a traditionalist like the Portsmouth manager.