Have you noticed anything unusual about Portsmouth players this season? No, not just their lofty Barclays Premier League position.
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, 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.
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 (2.7%) to repeated power output during high intensity exercise,' he said.
'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.'
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.'