* Sprint rivals Jamaica and US to face off in Rio * Bolt looking for triple threat *Rivalry extends to women's races too * Yohan Blake looking to come out of Bolt's shadow
By most measures, like economics, technology or military might, Jamaica does not rival the United States. Not so on the track, where they stand as the superpowers of sprint.
All eyes will be on the two nations when the athletics programme starts on Friday, with Jamaican superstar Usain Bolt looking to tie an Olympic record with a historic "triple-triple" of gold medal performances in the 100 metres, 200 metres and 4 x 100 metres relay.
The three-time Olympian, due to turn 30 on August 21, the last day of the Rio Games, has vowed that this will be his last Olympics and arrived in characteristically combative form, vowing that his US rivals will "feel my full wrath."
"They have not learned over the years that the more you talk, the more I will want to beat you," said Bolt, who won the three sprint events at the 2008 Beijing Games and 2012 in London.
The Jamaican will need to match that brash talk with his best performance of the season to top two-time Olympian Justin Gatlin, 34, and 21-year-old Trayvon Bromell on his Olympic debut. Gatlin has clocked a 9.8 seconds for the 100 metres this year, while Bromell has notched 9.84 seconds, both better than Bolt's 9.88 seconds, well off the world record of 9.58 seconds he set at the world championships in Berlin in 2009.
That could interfere with the Jamaican's goal of tying the Olympic record of nine Olympic golds in athletics held by "Flying Finn" Paavo Nurmi, in the 1920s, and American Carl Lewis, a generation ago.
The rivalry isn't limited to the men.
Four-time US Olympian Allyson Felix, 30, said it provides a powerful motivation for both sides.
"It's a highlight for us," said Felix, who has four career gold medals and aims to become the first woman to win five in athletics in Rio, where she has three chances in the 200 metres, 400 metres and the 4 x 400 metres. "We bring out the best in each other. It will be another great showdown."
Standing in the way of Felix's medal goals will be Jamaica's Veronica Campbell-Brown, with six career Olympic medals after a string of appearances dating back to Sydney in 2000.
One more in Rio will see Campbell-Brown become only the second competitor to medal at five Olympic Games.
Jamaican athletics fans got a taste of what their post-Bolt team could look like at the country's Olympic trials in Kingston last month, which the Olympic champion skipped due to injury.
That proved to be 26-year-old Yohan Blake's moment to shine, narrowly edging Nickel Ashmeade, also 26, to win the 100 metres. Blake, who claimed silver in the 100 metres and 200 metres in London behind his more famous countryman, will be looking for his chance to step out from Bolt's shadow.
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 "Rio 2016, Rio Olympics 2016, Rio Olympic Games, Sprint, Athletics, Usain Bolt, Jamaica, USA, Justin Gatlin, Allyson Felix, Trayv")
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