Michael Phelps recently announced that he is coming out of retirement and returning to competitive swimming.

The Olympic competitor has won 22 Olympic medals, 18 of them gold, and has not raced since the summer Olympics of 2012 in London. His retirement lasted 20 months.

Phelps will swim the 100-meter butterfly at the Arena Grand Prix on Thursday, which will be his first race since winning gold in the 400 medley relay in London with team mates Matt Grevers, Brendan Hansen and Nathan Adrian. He will be racing alongside fellow American and rival Ryan Lochte. Phelps currently holds both the American and world records for this event.

According to the Associated Press, Phelps decided to come out of retirement because he missed the sport that has been a part of his entire life. He has been training at North Baltimore Aquatic Club, in the city that he is from. He has had to train especially hard to get back into prime shape, and has slimmed down from 225 pounds to 194.

Phelps has said he is not worried about tarnishing the career he built, because he just wants to enjoy swimming competitively.

There’s no word yet on whether or not Phelps plans to compete at the 2016 Olympics in Rio.

“I’m doing this for me,” Phelps told the Associated Press.