The 400 metres, or 400-meter dash, is a sprint event in track and field competitions. It has been featured in the athletics programme at the Summer Olympics since 1896 for men and since 1964 for women. On a standard outdoor running track, it is one lap around the track. Runners start in staggered positions and race in separate lanes for the entire course. In many countries, athletes previously competed in the 440-yard dash (402.336 m)—which is a quarter of a mile and was referred to as the "quarter-mile"—instead of the 400 m (437.445 yards), though this distance is now obsolete.
David Lekuta Rudisha, MBS is a retired Kenyan middle-distance runner who specialized in the 800 metres. He is a two-time back-to-back Olympic champion from the 2012 London and 2016 Rio Olympics, a two-time World champion from the 2011 and 2015 World Championships in Athletics, and a world record holder at the event with a time of 1:40.91, set at the 2012 London Games on 9 August 2012. Rudisha is the first and only person to ever run 800 metres under 1:41, and he holds the three fastest, six of the eight fastest, and half of the twenty fastest times ever run in this event.
Canada, represented by the Canadian Olympic Committee (COC), competed at the 2012 Summer Olympics in London, United Kingdom, from 27 July to 12 August 2012. Canadian athletes have competed in every Summer Olympic Games since 1900, except the 1980 Summer Olympics in Moscow because of the country's support for the United States-led boycott. Canada sent a total of 281 athletes to the Games to compete in 24 sports. With the initiation of its "Own the Podium" programme, the COC set a goal of finishing in the top 12 for total medals; but the nation came up short of this goal, finishing 13th in the medal standings. Canada matched its total medal count from Beijing 2008, finishing the event with 18 medals: two gold, six silver and 10 bronze.
Sheila Reid is a Canadian track and field Olympian who competes in cross country, middle and long-distance running events. She competed collegiately at Villanova University. Reid won the 2010 and 2011 NCAA Women's Cross Country Championship, and in June 2011 became the first woman to win the 5000 m and the 1500 m at the NCAA Women's Outdoor Track and Field Championship. She won the Honda Sports Award as the nation's top female cross country runner in 2011, repeated as the best female cross country runner in 2012, and also won the Honda Sports Award for Track and field in 2012.
Comoros competed at the 2012 Summer Olympics in London, England, which was held from 27 July to 12 August 2012. The country's participation at London marked its fifth appearance in the Summer Olympics since its début at the 1996 Summer Olympics. The delegation included two track and field athletes: Maoulida Darouèche and Feta Ahamada, and one swimmer, Ayouba Ali Sihame, all three qualified for the Games through wildcard places. Ahamada was selected as the flag bearer for the opening ceremony and Darouèche held it at the closing ceremony. Ahamada won her heat in the preliminary round of the women's 100 metres but was eliminated in the heat stages, while Darouèche and Sihame did not advance beyond the first round of their respective events.
Djibouti competed at the 2012 Summer Olympics in London, from July 27 to August 12, 2012. This was the nation's seventh appearance at the Olympics.
Equatorial Guinea competed at the 2012 Summer Olympics in London, which was held from 27 July to 12 August 2012. The country's participation at London marked its eighth appearance in the Summer Olympics since its début at the 1984 Summer Olympics. The delegation included two track and field athletes, Benjamín Enzema and Bibiana Olama who both qualified for the Games via wildcard places because their fastest times did not meet the required qualification standards. Olama was selected as the flag bearer for both the opening and closing ceremonies. Both athletes did not advance beyond the first round of their respective events.
Kathy Butler is a long-distance runner who competes in the 10,000 metres and marathon, as well as cross country running and road running. Born in Scotland, she has competed internationally for both Great Britain and Canada.
Lalonde Keida Gordon, HBM is a Tobagonian male track and field sprinter who specialises in the 400 metres. He won the bronze medal at the 2012 London Olympics with a personal best of 44.52 seconds. He is the third fastest 400 m runner from his country after Machel Cedenio and Ian Morris.
Malawi competed at the 2012 Summer Olympics in London, which was held from 27 July to 12 August 2012. The country's participation at London marked its ninth appearance in the Summer Olympics since its début at the 1972 Summer Olympics. The delegation included two track and field athletes; Mike Tebulo and Ambwene Simukonda, and one swimmer; Joyce Tafatatha. Tebulo and Simukonda qualified through wildcard places for their respective events. Tebulo was selected as the flag bearer for the opening and closing ceremonies. Tebulo finished 44th in the men's marathon, while Simukonda did not advance beyond the first round of the women's 400 metres. Tafatatha won her heat in the women's 50 metre freestyle but her time was not fast enough to allow her to progress into the semi-finals of the event.
Mauritania competed at the 2012 Summer Olympics in London, which was held from 27 July to 12 August 2012. The country's participation at London marked its eighth appearance in the Summer Olympics since its debut in the 1984 Summer Olympics. The delegation included two track and field athletes, Jidou El Moctar and Aicha Fall, who were selected to the team by wildcard places, as the nation had no athletes that met either the "A" or "B" qualifying standards. Moctar was selected as flag bearer for the opening ceremony while a LOCOG Games Maker carried it for the closing ceremony. Neither of the two athletes progressed beyond the heats.
Eswatini (Swaziland) competed at the 2012 Summer Olympics in London, which was held from 27 July to 12 August 2012. The country's participation at London marked its ninth appearance in the Summer Olympics since its debut at the 1972 Summer Olympics. The delegation included two track and field athletes: Sibusiso Matsenjwa and Phumlile Ndzinisa, and one swimmer, Luke Hall; the first two competitors qualified for the Games through wildcard places while Hall was awarded a universality place by FINA. Hall was selected as the flag bearer for the opening ceremony and Matensjwa held it for the closing ceremony. All three competitors did not advance further than the heat stages of their respective events.
Damian David George Warner is a Canadian track and field athlete specializing in decathlon. He is the 2020 Olympic champion and a four-time World medallist. Warner also won the bronze medal at the 2016 Summer Olympics and was the 2014 Commonwealth champion and the two-time and reigning Pan American champion from the 2015 and 2019 Games. Warner holds the Pan Am Games record and the Canadian record for the decathlon and the fourth-highest decathlon score in history. Warner also holds the Olympic Games Record for the Decathlon at 9018 points. Competing in the heptathlon, he is the 2022 World Indoor champion.
Julie Labonté is a Canadian track and field athlete competing in shot put and discus.
Tyler Daniel Harper is a Canadian track and field athlete competing in the 400 metres. He came in third in the 2012 Canadian National Championships in Calgary, earning an Olympic "B" standard. He finished 7th at the 2008 IAAF World Junior Championships in Bydgoszcz, Poland. His personal best time is 45.60 seconds, achieved May 5, 2012 in Lubbock, Texas.
Katarina Mary Johnson-Thompson is an English athlete. A multi-eventer, she is primarily known as both a heptathlete and an indoor pentathlete. In heptathlon she is a double world champion and double Commonwealth Games champion. In indoor pentathlon, she is a world and double European champion.
Xie Zhenye is a Chinese sprinter. He is the current Asian record holder of the 200 metres with a time of 19.88 seconds. In 2018, Xie ran a personal best of 9.97 seconds in the 100 metres, making him the second Chinese sprinter to record a time below the 10-second barrier, after his compatriot Su Bingtian. Xie represented China at the 2012 Summer Olympics, 2016 Summer Olympics and 2020 Summer Olympics where he became the first Chinese athlete to have ever qualified for a semi-final of men's 200 metres at any Summer Olympic Games. In 2023, in the absence of his injured compatriot Su Bingtian, Xie became the 2022 Asian Games champion in the 100 metres event, with a time of 9.97 seconds.
Geofrey Kusuro is a Ugandan long-distance runner. He competed at the 2008 Summer Olympics in the men's 5000 m, not reaching the final. At the 2012 Summer Olympics, he competed in the Men's 5000 metres, finishing 37th overall in Round 1, failing to qualify for the final. He also represented Uganda at the 2009 and 2011 World Championships.
Taylor Milne is a Canadian middle distance runner. Milne made his official debut at the 2008 Summer Olympics in Beijing, where he competed in the 1500 metres. At the 2016 Olympics he was eliminated in the heats of the 3000 m steeplechase.
Carline Muir is a Canadian sprinter, who specialized in the 400 metres. She won the bronze medal for the 400 metres, and ultimately, led her national team to claim the sprint relay title at the 2009 Summer Universiade in Belgrade, Serbia. She is also a three-time junior national champion, a two-time silver medalist at the Canadian Track and Field Championships.
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