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Patrick Semansky, File, Associated Press
In this July 31, 2014, file photo, Michael Phelps pauses before a training session at Meadowbrook Aquatic and Fitness Center in Baltimore. The winningest athlete in Olympic history is facing DUI charges for the second time after being arrested early Tuesday, Sept. 30, 2014, in his hometown of Baltimore, where police said he was clocked going nearly 40 mph over the speed limit and was unable to perform a series of field sobriety tests.

After his second DUI arrest, Michael Phelps says he will take a break from swimming to attend a program "to better understand myself."

The winningest athlete in Olympic history made the announcement in a series of tweets Sunday morning.

The 29-year-old Phelps was arrested early Tuesday and charged with drunken driving. Police said he failed a series of field sobriety tests and had a blood-alcohol content of 0.14 percent, well above the legal limit of 0.08.

Phelps retired after the 2012 Olympics in London, having won a record 18 gold medals and 22 medals overall. But he returned to competition this year with the goal of making the 2016 Rio Games. His comeback has produced encouraging results, including three golds and two silvers at the Pac Pacific Championships in August.