Usain Bolt is calling it quits for 2010, cutting his season short because of tightness in his lower back.
The announcement comes less than a week after he lost to American rival Tyson Gay in the 100 metres.
Bolt's manager, Ricky Simms, wrote in an e-mail on Tuesday that the world record-holder in 100 and 200m will have treatment to loosen his back, and then rest, skipping IAAF Diamond League meets in Zurich on August 19, and in Brussels on August 27.
Bolt had been scheduled to face Gay and Asafa Powell — bringing together the three fastest 100m runners in history — at this year's final Diamond League meeting in Brussels on 27 August.
"I am very disappointed to miss two of the top meetings on the circuit ... but trust that it is better for me not to take any risks this year," Bolt said, according to Simms.
"2011 and 2012 are very important championship years and I hope to be back fully fit and healthy.
"I would like to thank everyone for their support and look forward to coming back stronger next year."
Simms said Bolt was examined by a doctor in Munich on Monday.
"He has tightness that restricts his ability to generate power in his stride. Continuing to race in this condition could risk injury to his hamstrings or calf muscles," Simms wrote. Bolt's manager said the decision to take a break was made "with a view to his future career".
Simms also said that an MRI examination showed that a previous left Achilles’ tendon injury is healed.
Bolt hadn't lost an individual race in two years until Friday, when Gay beat him at the DN Galan meet in Stockholm. Gay ran 9.84 seconds, and Bolt finished in 9.97.
In fact, Bolt's only other defeat in the 100m came at the same Stockholm Olympic track in 2008 when Jamaican compatriot Powell — who is also now struggling with a back complaint — took victory.
Since that reversal, Bolt enjoyed 14 successive wins.
After the latest loss at Stockholm, even Gay acknowledged he wasn't racing against a fit Bolt.
"I'm really happy with the win," Gay said at the time, "even though Usain Bolt isn't in the best shape."
When Bolt is at his best, no one comes close to him. He stole the show at the 2008 Beijing Olympics, winning gold medals and breaking the world records in the 100 and 200 sprints, as well as the 4x100 relay.
None of the finals in those events was even close, and Bolt began his celebration in the dash before it was done, stretching out his arms with palms up, then slapping his chest.
He followed that up at last year's world championships in Berlin by lowering his marks in the 100 to 9.58 seconds and in the 200 to 19.19.