Veteran sprinter Tyson Gay is making a bid to force his way onto the US bobsled team after entering this week's National Push Championships in Canada.

Usain Bolt beats Justin Gatlin by one hundredth of a second to retain the 100m title at the World Athletics Championships in Beijing.

Gay, who last summer completed a one-year ban for a 2013 positive doping test and had been mentored by Lance Brauman for years, began working with Smith's sprint group this week.