Usain Bolt says he was troubled by recent back and hamstring problems but he's ready to go in his defence of the Olympic 100m and 200m titles.
"I'm always ready. "It's all about championships. I've had slight problems, but I'm ready to go," said Bolt.
The 25-year-old track superstar was buoyed on Thursday by his appointment as Jamaica's flag bearer at the Friday's Games opening ceremony.
"Carrying the flag is an honour. For my country Jamaica, I'll do anything," said Bolt.
At the 2008 Beijing Olympics, Bolt set world records in winning the 100 and 200 metres. He also helped the Jamaican team set a world record in the 4x100 relay for a third gold medal.
But he will enter the London Olympics after losing to teammate Yohan Blake in the 100m and 200m at this month's Jamaican trials.
"My back was a little stiff and it affected my hamstring but I'm over that. I've been training for the past two-and-a-half weeks and everything is alright," he said.
Bolt insisted he wasn't feeling overwhelming pressure to win.
"I don't think it will be the end of the world if I lose.
"I would definitely be disappointed if I was second. Mentally though I am always strong. I have a great team around me who keep me on track."