After moving to the United States at age 18 to train at Auburn University, César Cielo Filho quickly developed into the world’s fastest freestyle sprinter. He missed out on the podium at the 2007 worlds, but made his mark at the Beijing Olympics, first coming third in the 100 free (in a tie with Jason Lezak), prior to winning the 50 free in a time narrowly outside the world record. At the 2009 World Championships in Rome, he won the sprint double (50 and 100 metres), crowning his performance with a world record in the 100. Cielo’s 46.91 was the first official time under 47 seconds, as Alain Bernard’s earlier 46.94 was not recognized. Later that year, just before the super-fast polyurethane swimming suits were banned, he also lowered the 50 free world record to 20.91. After two more titles at the 2010 short-course championships, Cielo made the news in 2011 due to a failed drug test. In May 2011, he was found to have used furosemide (a diuretic and potential masking agent). Cielo claimed not to have used the substance – or at least not to enhance performance – due to cross-contamination of a caffeine supplement. This explanation, which according to FINA regulations leads to a warning, was confirmed in a ruling by the Court of Arbitration for Sport, amid much confusion and anger from fellow competitors. Seemingly unaffected, Cielo proceed to defend his 50 freestyle title at the 2011 World Championships, while also winning the 50 metre butterfly. Later in the year, he added four golds to his Pan American Games tally, which already had three golds and a silver from 2007.