Olympic triathlon preview

The three-discipline event, which made its Olympic debut in Sydney in 2000, includes a 1,500-meter open water swim, a 40 km bike ride and a 10,000-meter run, a grueling test of endurance for the 55 men and 55 women competing in London. It's expected to draw sizable crowds, as it will be one of the best free-to-view events in the program. The course, which begins and ends in Hyde Park, a venue that will largely be open to the public, loops through the picturesque Knightsbridge neighborhood, and competitors will pass such famous landmarks as Wellington Arch and Buckingham Palace.

SPORTS EXPLAINERS: TRIATHLON

The athletes likely won't get to appreciate the views, but the scenic backdrop should be rather television-friendly.

Alistair Brownlee, Great Britain: In 2008, the then-20-year-old youngster faded in the final kilometers in Beijing, finishing 12th, but he has since proven to have serious staying power. In 2009, he won all five world championship series events he entered, and despite being hampered by injuries in 2010, he has still gone on to win six more events, including the London test event last August. Brownlee tore his Achilles tendon earlier this year, but he won his first race back in Kitzbuehel, Austria, in late June. He's a favorite to stand atop the podium, but his biggest competition might be his teammate and brother ...

Jonathan Brownlee, Great Britain: Two years younger than Alistair, Jonathan stepped into the void left by his brother's injury this year, winning world triathlon series events in San Diego, Calif., and Madrid. In Kitzbuehel, Jonathan came in second, less than a minute behind his big brother, and he has quickly become a favorite to stand on the podium as well.

Helen Jenkins, Great Britain: On the women's side, fellow Brit Helen Jenkins remains a strong favorite to cross the line in Hyde Park first. The 2008 and 2011 world champion has had 10 podium finishes since 2009, including a win at the London test event (on the Olympic course) last year.

After a fifth-place finish in San Diego in May, Hunter Kemper qualified for his fourth Games, making him one of two athletes to compete in every Olympic triathlon. (Canada's Simon Whitfield is the other.) But the 36-year-old Kemper, whose best Olympic finish was seventh place in Beijing, will have to have the race of his life to see the podium in London.

On the women's side, the American field is a bit deeper, led by Sarah Groff, who finished the 2011 season ranked third in the world, and Gwen Jorgensen, who competed in her first triathlon in March 2010. The 26-year-old Jorgensen, a strong runner, finished the test event in London last August just eight seconds behind Jenkins. Laura Bennett, who narrowly missed out on a bronze medal in 2008, fills out the U.S. team.

Brownlees vs. the world

The brothers are the overwhelming favorites, and with a nation rooting them on, it will be up to the other 53 competitors to try and unseat them.

To consider a former gold medalist an underdog may be ridiculous, but Canada's Simon Whitfield is relishing the role. At 37, the Sydney gold medalist and silver medalist in Beijing knows his chances of catching the likes of the Brownlee brothers or Spain's Javier Gomez, much stronger runners, are slim, but that's not stopping Whitfield from trying for one more medal.

The first modern triathlon took place in 1974 in San Diego, and the first official world championship was held in 1989. ... Elite men typically finish the triathlon in about 1 hour, 50 minutes, while the best women finish at just about 2 hours. At the 2011 Chicago triathlon, the average finish of the more than 3,000 participants was 3:15.

Aug. 4: Women

Aug. 7: Men