London: Organisers may think the most closely-guarded secret of the 2012 Games is the one who will light the Olympic flame, but of far greater interest to the wider sporting public is the condition of Usain Bolt's right hamstring.
The Jamaican triple gold medallist from Beijing is the number one attraction of the London Games, but the question mark over his fitness has added an extra layer of intrigue to what is already an eye-wateringly exciting 100 metres race.
Bolt needed some stretching and massage treatment for a tight hamstring following his 200m defeat by Yohan Blake in the Jamaican trials at the start of the month, having also lost to Blake in the 100m days earlier when he looked to be nursing the injury with a tentative start.
He immediately withdrew from last Friday's Monaco Diamond League meeting where he was due to run the 200m in a last race before the Olympics.
Bolt then travelled to Germany to see renowned German sports doctor Hans-Wilhelm Muller-Wohlfahrt, though his agent Ricky Simms said the trip had been long-scheduled as part of his regular "prehabilitation" regime.
The 6ft 5ins (1.95m) sprinter suffered from hamstring troubles early in his career, a problem linked to a curvature in his spine, and has to put himself through a gruelling stretching and conditioning regime to prevent any recurrence.
"He had a slightly tight hamstring during the trials and that's why possibly he didn't push as hard as he could have," Simms said recently when assuring the public that his man would be in good shape for London.
ON PUNISHING REGIME
"He was just protecting that. The main thing at the trials was to get through and get on the team for the Olympic Games.
"His coach decided that he needs to get a little bit of massage and treatment on that and rest up, and then train again hard next week so that he's ready for the Olympic Games."
Bolt, like the rest of the all-conquering Jamaican athletics squad, is training behind closed doors in Birmingham, around 100 miles north of London, before moving south for the start of the track and field programme on August 3.
Running with aches and niggles are part and parcel of an international sprinter's life but winning a multi-round championship with an injury is another matter all together.
Bolt, who has been given a specially-made 7ft bed in his Birmingham quarters, will also be defending his 200 metres title and will hope to help Jamaica defend the 4x100 gold they won in world record time four years ago.
That programme represents a minimum of nine separate races in eight days and while some of the heats will be running on cruise control, the semis and finals will be at full bore.
That is a punishing regime for a fully fit athlete but an impossible one for a sprinter with the slightest question mark over a hamstring.
Team mate and former world record holder Asafa Powell withdrew from the London Diamond League meeting on July 13 with a groin injury while Tyson Gay, the second-fastest man in the world, needed treatment for a minor groin strain after winning that race in cold and wet conditions.
Gay failed to make the 100m final four years ago as he ran with a groin/hip problem which eventually needed surgery and will be desperate to toe the line fully fit this time.
Should Bolt, Gay, Powell and Blake all start the heats on August 4 it will be the first time since the introduction of electronic timing in 1968 that the four current fastest men in the world will all be racing each other for Olympic Gold.