Off Track ..... New shoes spring into Olympic action

Two athletes in Sunday's marathon will have an extra spring in their step - quite literally.

Angola's Joao N'Tyamba and Ecuador's Franklin Tenorio have both opted to race in the controversial Spira Stinger shoe that has a two stainless steel springs bedded in its sole.

US track and field authorities have banned the distinctive yellow footwear, saying it gives athletes an unfair advantage, while the international athletics federation has yet to rule on the issue, opening the way for the Spira's debut at an Olympics.