American swimmers Katie Ledecky and Michel Phelps each broke records while capturing gold medals for the U.S. team at the 2016 Summer Olympic Games in Rio de Janiero, Brazil on Sunday. Their victories helped the U.S. surge to sole possession of the lead in overall medals on the second day of competition. Here’s a recap of the day’s action at the Olympics:

U.S. Finally Strikes Gold in Swimming

Swimming - Olympics: Day 2
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After missing out on gold medals in the pool on Saturday, the U.S. swimming team nabbed two firsts on Sunday with Ledecky winning the 400-meter freestyle in 3 minutes, 56:46 seconds — nearly two seconds better than her own world record and more than four seconds ahead of silver medalist Jazmin Carlin of Britain. American Leah Smith took the bronze.

Phelps, the most successful Olympian in history, added to his Olympic record by winning a 19th gold medal on Sunday night in the 4 x 100-meter freestyle relay, along with teammates Caeleb Dressel, Ryan Held and Nathan Adrian. Phelps’ strong second leg gave the Americans an edge they held on to over the silver medalists of France. Australia claimed bronze. The gold was Phelps’ 23rd overall medal — also a record.

Adam Peaty of Britain set a world record in the men's 100-meter breaststroke, with Cameron van der Burgh of South Africa placing second and American Cody Miller taking the bronze.

Similarly, Sarah Sjöström of Sweden set a world record in the women's 100-meter butterfly, with Penelope Oleksiak of Canada claiming silver and American Dana Vollmer capturing a bronze medal.

Simone Biles Helps U.S. Women’s Gymnastics Team Dominate

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Three-time reigning world gymnastics champ Simone Biles dominated in all four events of the qualifying round — floor, vault, balance beam and uneven bars — far surpassing teammates Aly Raisman, who finished a distant second, and defending all-around gold medalist Gabby Douglas.

The American team, which is favored to defend the team gold they won in London in 2012, led after the qualifying round. China and Russia were considerably behind in second and third, respectively.

Huge Tennis Upsets

Tennis - Olympics: Day 2
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Unseeded Argentinian Juan Martin del Potro defeated world No. 1 Novak Djokovic in the first round of men's tennis singles in Rio, 7(7)-6(3), 6-4. The shocking defeat for Djokovic was the last of a day filled with upsets on the hard courts of Brazil.

The U.S. women’s doubles team of Serena and Venus Williams lost to Lucie Safarova and Barbora Strycova, of the Czech Republic. The three-time gold medalist sisters were 15-0 in Olympic play prior to the match, but they were bested by the relatively inexperienced Czechs.

Serena Williams did win her first-round singles match over Australia’s unseeded Daria Gavrilova, 6-4, 6-2.

More American Medals

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American Corey Cogdell earned a bronze medal in women’s trap shooting, as Australian Catherine Skinner defeated New Zealand’s Natalie Rooney for the gold medal.

U.S. fencer Alexander Massialas settled for a silver medal in individual foil, as he was bested by Italy’s Daniele Garozzo. Timur Safin of Russia took the bronze.

Breanna Stewart, Diana Taurasi and Sylvia Fowles each had 15 points as the U.S. women’s basketball team routed Senegal, 121-56, breaking their own record for most points scored in the Olympics.

Medal Leaders

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The U.S. grabbed sole possession of the medals lead with its productive day.

United States: 12 | 3 gold; 5 silver; 4 bronze
China: 8 | 3 gold; 2 silver; 3 bronze
Italy: 7 | 2 gold; 3 silver; 2 bronze
Japan: 7 | 1 gold; 0 silver; 6 bronze
Australia: 6 | 3 gold; 0 silver; 3 bronze

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