Cielo propped himself up on a lane rope, looked up at the scoreboard and began sobbing.

Last week, Cielo was cleared of wrongdoing by the Court of Arbitration for Sport following an emergency hearing here in China.

"It's been a tough time for me, something that I didn't expect at all for my career," Cielo said. "But I had to deal with it and it feels like the biggest relief of my life to overcome something like that and be able to compete."

Cielo, who will also attempt to defend his 50 and 100 freestyle titles later this week, finished his race in 23.10 seconds. Matthew Targett took the silver in 23.28 and Australian teammate Geoff Huegill, who has come out of a four-year retirement, took the bronze in 23.35.

Cielo and three teammates tested positive for furosemide, a banned diuretic, at a meet in Rio de Janeiro in May. After the Brazilian swimming federation gave Cielo a warning, swimming governing body FINA appealed the decision to the CAS, which upheld the Brazilian ruling.

Cielo said he consumed the drug in a contaminated batch of a food supplement he regularly uses.

The ruling prompted an outcry from other swimmers, who called it unfair, and there were some whistles in the crowd after his victory.

"This gold medal has a different feeling from the other ones," Cielo said. "This was the hardest I've had in my life. It was a time to test not just my talent in swimming but how much I could take and still stand up so I'm really proud of myself for being able to do so."

Cielo cried again during the medal ceremony, and the capacity crowd at the Oriental Sports Center responded by applauding in encouragement.

"It's difficult for him," Targett said. "I'm not going to speak for my friend, but I lived with the guy and I know exactly what he's going through. At times like this, you find out who your real friends are."

Targett called Kenyan racer Jason Dunford, who finished seventh, a "sore loser" for allegedly putting his thumbs down after the race.

"I'm really happy for him," Targett continued. "And if I was ever to get beaten by anybody I would want it to be a friend."

Vollmer won her race in 56.87, just 0.07 ahead of Australia's Alicia Coutts, with Lu Ying of China 0.19 back in third.