Will US racial tensions be reflected in Rio?

America’s hot summer of racial tension, violence and politics has spilled on to the basketball court, the track and the Twitter feeds of some of the country’s top sports stars.

Now, as athletes head to the Olympic Games in Rio de Janeiro will they take the debate over America’s racial divide onto the world’s biggest global sports stage with them?

What comes to mind is another summer in which sports and race collided spectacularly: in 1968 at the Olympics in Mexico City.