Despite a complete recovery from the irregular heart rhythm that cut short his World Cup, Ireland and Ulster prop Simon Best has announced his retirement from professional rugby.

Best has been closely monitored by medical staff since falling ill after Ireland's third group game against the hosts in September and while the former Ulster captain, who has just turned 30, suffered no long-term effects from the illness, he has been advised further high intensity training could provoke a relapse.

"It is with great sadness that I am forced to retire from the game at this stage in my career," said the man from Poyntzpass, Co Armagh, today.

"However, I have no regrets and feel immensely proud and privileged to have represented both Ulster and Ireland for the past nine years. I am grateful to have had the opportunity to work with coaches, management and players that I have had the utmost respect for and have formed lifelong friendships with many.

"I would like to thank the Ulster and Ireland supporters and my friends and family for their loyalty and support throughout my career and during this difficult time.

"I would also like to take this opportunity to thank the IRFU and their medical team for the extremely high standard of care that I have received.

"Finally, having grown up as a supporter of Ulster and Irish rugby I would like to wish the players and management of both squads all the very best for the rest of the season and the coming years, I will continue to support and follow their future successes with great interest," added Best, who debuted for Ireland against Tonga in June 2003.

Best went on to be selected in the Ireland squads for the 2003 and 2007 World Cup campaigns. In 2006 he led Ulster to a Magner's League title and captained Ireland twice on tour to Argentina in the summer of 2007.

His international coach Eddie O'Sullivan said today: "Simon has been an integral member of the Ireland squad since he won his first cap in 2003. He was an incredibly honest, talented and hard working player in every aspect of his participation in the game and a model professional.

"In addition to that, he was and still is an extremely popular guy with all the players and it is very unfortunate that his career has been cut short by this condition when he still had so much more to offer Irish Rugby. I would like to wish Simon and his family the best of luck for the future".

Ulster Rugby Chief Executive Michael Reid described Best, whose brother Rory is an Ireland and Ulster hooker, as "a hard and uncompromising prop forward on the field" and "the epitomy of the model professional off it".

He added: "We look forward to seeing Simon regularly at Ravenhill cheering Rory and the rest of the boys on."