INDIANAPOLIS — Michael Phelps' sore neck is feeling better and the 14-time Olympic gold medalist is back in the pool practicing.

Phelps swam 4,000 yards Saturday in what coach Bob Bowman called a "light workout" at the Indiana University Natatorium.

He withdrew from the 100-meter freestyle at the U.S. national championships on Friday after waking up a day earlier with a kink in the left side of his neck.

Phelps said he swam through the pain while setting a world record in the 100 butterfly Thursday night. He has qualified for the world championships later this month in three individual events, and he'll likely swim all three relays in Rome.