Pittman-Rawlinson has twice captured the world title in the 400m hurdles
Jana Pittman-Rawlinson will not defend her 400m hurdles title at next month's World Championships in Berlin after succumbing to a back-related injury.
The Australian has only raced twice since returning to the track last month after a year-long lay-off due to complications from a toe injury.
And the 26-year-old has now suffered soreness in her hamstring as a result of a bulging disc in her back.
"I haven't trained properly for six weeks and I am in pain," she said.
It is another major blow to Pittman-Rawlinson, after injury forced her to miss last summer's Beijing Olympics.
But she admitted her preparation has been so hampered by the latest setback she will now be focusing all her efforts on getting fit for London 2012.
"When I compete I want to do both myself and my country justice by competing at a world standard, but sadly this won't be the case at the upcoming World Championships," she said.
"I will now continue treatment over the next few weeks before I head back to Australia, where I hope I can recover from this latest setback and get back on track for my long term goal and dream - winning Olympic Gold in London in 2012."