Michael Phelps

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An official watches Michael Phelps turn as he swims the 100-meter butterfly in the preliminary round at the Arena Grand Prix swim meet in Charlotte, N.C., Friday, May 16, 2014. (AP Photo/Nell Redmond)

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Michael Phelps swims the 100-meter butterfly in a preliminary round at the Arena Grand Prix swim meet in Charlotte, N.C., Friday, May 16, 2014. (AP Photo/Nell Redmond)

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Michael Phelps swims the 200-meter freestyle in a preliminary event at the Arena Grand Prix swim meet in Charlotte, N.C., Friday, May 16, 2014. (AP Photo/Nell Redmond)

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Michael Phelps prepares to swim in a 200-meter freestyle, preliminary event at the Arena Grand Prix swim meet in Charlotte, N.C., Friday, May 16, 2014. (AP Photo/Nell Redmond)

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Michael Phelps swims the 200-meter freestyle in a preliminary event at the Arena Grand Prix swim meet in Charlotte, N.C., Friday, May 16, 2014. (AP Photo/Nell Redmond)

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Michael Phelps answers a question about swimming in the upcoming Charlotte Grand Prix, during a news conference in Charlotte, N.C., Thursday, May 15, 2014. (AP Photo/Chuck Burton)

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Michael Phelps, second from left, and his coach, Bob Bowman, left, talk as Phelps prepares for the Charlotte Grand Prix swimming event in Charlotte, N.C., Thursday, May 15, 2014. (AP Photo/Chuck Burton)

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Michael Phelps warms up before the upcoming Charlotte Grand Prix swimming event in Charlotte, N.C., Thursday, May 15, 2014. (AP Photo/Chuck Burton)

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Michael Phelps smiles as he warms up before the upcoming Charlotte Grand Prix swimming event in Charlotte, N.C., Thursday, May 15, 2014. (AP Photo/Chuck Burton)

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Michael Phelps climbs from the pool as he readies for the Charlotte Grand Prix swimming event in Charlotte, N.C., Thursday, May 15, 2014. (AP Photo/Chuck Burton)