The secret of Portsmouth's success last season has been revealed - magic shirts!

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.

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, told the Daily Mail: "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?

"If you ask me 'could it make a performance benefit?' Yes, I believe it could."

Portsmouth are so keen they have done a deal preventing other Premier League sides from using IonX for the immediate future,â€" 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."