Off Track ..... Li Na has a secret weapon: Her shoes

Li, who defeated Japan's Ayumi Morita in straight sets yesterday to advance to the third round of the Olympic tennis competition, wears a space-age shoe from Nike which may be the lightest ever.

According to the manufacturer, the Zoom Court Luna weighs just 8 ounces (227g) per shoe, compared to 16 ounces (454g) for a normal tennis shoe. And Li is the only player who wears it.

The superlight shoe combines two proprietary technologies - Flywire and Lunarlite Foam.