INDIANAPOLIS (AP) _ Michael Phelps withdrew from the World Short Course Championships on Friday night with a back injury.
Earlier in the day, Phelps pulled out of the 400-meter individual medley to seek treatment. He had planned to swim in the evening's 800 freestyle relay final, but was advised against it.
``I'm done here for good,'' he told The Associated Press before the evening finals. ``I've decided not to chance anything.''
Jim Johnson, the meet's medical director, said Phelps had a ``slight back injury.'' He declined to be more specific or reveal what part of the back was involved.
``We just don't want to take the risk of it worsening over the next three days,'' Johnson said. ``He gave it all he had last night and swimming made it a little worse.''
Johnson said Phelps would return home to Baltimore for further evaluation and treatment.
``I don't think this is a big issue,'' Phelps said. ``I just want to be extra cautious and extra safe.''
Phelps' back has been bothering him for 1 1/2 weeks. The winner of eight Olympic medals in Athens, including six gold, Phelps was using physical therapy and ice to treat the soreness.
``It's something we don't want to play with because my sister had a back problem and it put her out of swimming for good,'' he said. ``Hopefully in a few weeks or days this will all be over with.''
Phelps blamed the problem on traveling by bus and sitting for several hours a day during a post-Olympic promotional tour with fellow Olympians Ian Crocker and Lenny Krayzelburg.
``It felt decent coming into the meet,'' Phelps said at a news conference. ``Sitting on the plane for a few hours coming here, I don't think it helped.''
The teenager won the 200 freestyle on the first night of competition Thursday. He had been scheduled to swim five individual events and some relays during the five-day meet.
``You can probably tell this is one of the most disappointing things I've had happen,'' Phelps said.
The short course championships was the last major meet of the year for Phelps, who plans to move to Ann Arbor, Mich., next month to be with Bob Bowman, his personal coach who is the new coach at the University of Michigan.