It's dynasty time on the opening two days of track and field at the Olympics.

As of Friday morning (12 August) , three athletes will each try to become the first woman to win three straight individual titles at the Summer Games.

Athletics schedule - Rio 2016

New Zealand shot putter Valerie Adams stands the best chance, while the odds don't look that great for 10,000m great Tirunesh Dibaba and 100m sprinter Shelly-Ann Fraser-Pryce. And if none of the three succeed, there still is Czech javelin double champion Barbora Spotakova on 18 Aug. Here is a look what opposition and odds they face.

Valerie Adams: Shot put

The New Zealand star knows how to fight back. Two years ago, after being untouchable at major championships from 2007 to 2014, with four world and two Olympic gold medals to show for it, she underwent elbow and shoulder surgery. It is tough enough to return, but to come back with another Olympic gold would be outstanding.

Recovery didn't come easy as the tall Kiwi struggled until early this year. Slowly though, she found her groove again and has championship experience. "My preparations have been going really well," she said as she arrived in Brazil from her training base in Switzerland.

Adams is the second-best performer of the season, behind China's Gong Lijiao. Christina Schwanitz of Germany, who took over Adams' world title last year, could well be her toughest opponent on Friday.

Adams knows how elusive Olympic gold can be. The London 2012 Games were already over when gold medalist Nadezhda Ostapchuk was caught for doping and Adams belatedly won her second title. This weekend, she wants to hold her third gold in the Olympic Stadium.

Tirunesh Dibaba: 10,000m

Dibaba is already considered the greatest female distance runner in history with her five Olympic medals (three gold) and five world championship golds. The 31-year-old has fought back from major injuries several times in her career and just finished a yearlong break after the birth of her son.

Tirunesh Dibaba (right) in the women's 5000m final at London 2012 (Photo: Getty Images/Ryan Pierse)

Dibaba's toughest opposition is likely to come from fellow Ethiopian Almaz Ayana, 24, who is doing the long-distance double in Rio after winning the 5,000m at the world championship last year and has the top 10,000m performance of the year so far.

Dibaba is a massive celebrity in Ethiopia and leads a family of runners, including sisters Genzebe, who will compete in the 1,500m, and Ejegayehu, who won silver in the 10,000m in the 2004 Athens Games.

Shelly-Anne Fraser-Pryce: 100m

For years, sprinting was a US-Jamaican duel, but Fraser-Pryce will also have to keep an eye on Dutchwoman Dafne Schippers, who was already breathing down her neck when the Jamaican won her third world title in Beijing last year. And a toe injury has hampered Fraser-Pryce this year.

Shelly-Ann Fraser-Pryce after winning gold in the Women's 4x100m relay final at the World Athletics Championships Beijing 2015 (Getty Images/Andy Lyons)

Like Dibaba, she will need to heed her own compatriots. Eileen Thompson leads the charge with a season's top time of 10.70 seconds. Three Americans have all run faster than Fraser-Pryce this season. None however, has proven it at major championships.

Fraser-Pryce carried her nation's flag at the opening ceremony, with her long hair dyed yellow and green, colors in both the Jamaican and Brazilian flags.