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Usain Bolt of Jamaica celebrates after his win gold in the Men's 100m Final on Day 9 of the London 2012 Olympic Games at the Olympic Stadium at Olympic Stadium on August 5, 2012 in London, England. - 

So the Olympics continued over the weekend, and one of the big stories was Usain Bolt of Jamaica's win in the 100 m race, his second Olympic gold in the event. Jamaica and other island nations have become know for their sprinting power, in the same way that countries like Kenya are known for their strength in distance running.

Here to talk with us in today's Mid-day Extra about how countries come to specialize in certain sports and events is Scott Douglas, news editor of Runners World.

Follow Jeff Horwich at @jeffhorwich