2016 Rio Olympics - Athletics - Final - Men's 400m Final - Olympic Stadium - Rio de Janeiro, Brazil - 14/08/2016. Wayde van Niekerk (RSA) of South Africa runs towards the finish line on his way to setting a new world record. REUTERS/Fabrizio Bensch

2016 Rio Olympics - Athletics - Final - Men's 400m Final - Olympic Stadium - Rio de Janeiro, Brazil - 14/08/2016. Wayde van Niekerk (RSA) of South Africa and Kirani James (GRN) of Grenada celebrate. REUTERS/David Gray

2016 Rio Olympics - Athletics - Final - Men's 400m Final - Olympic Stadium - Rio de Janeiro, Brazil - 14/08/2016. Wayde van Niekerk (RSA) of South Africa competes to win the gold. REUTERS/Lucy Nicholson

2016 Rio Olympics - Athletics - Final - Men's 400m Final - Olympic Stadium - Rio de Janeiro, Brazil - 14/08/2016. Wayde van Niekerk (RSA) of South Africa reacts after setting a new world record and winning the gold medal. REUTERS/Kai Pfaffenbach

2016 Rio Olympics - Sailing - Preliminary - Men's Windsurfer - RS:X - Race 1/2/3 - Marina de Gloria - Rio de Janeiro, Brazil - 08/08/2016. Ricardo Santos (BRA) of Brazil competes. REUTERS/Brian Snyder

2016 Rio Olympics - Athletics - Semifinal - Women's 400m Semifinals - Olympic Stadium - Rio de Janeiro, Brazil - 14/08/2016. Christine Day (JAM) of Jamaica, Shaunae Miller (BAH) of Bahamas and Allyson Felix (USA) of USA compete. REUTERS/David Gray

2016 Rio Olympics - Athletics - Semifinal - Men's 100m Semifinals - Olympic Stadium - Rio de Janeiro, Brazil - 14/08/2016. -Usian Bolt (JAM) of Jamaica crosses the finish line in the Men's 100 m Semifinals. REUTERS/Carlos Barria

2016 Rio Olympics - Athletics - Semifinal - Men's 100m Semifinals - Olympic Stadium - Rio de Janeiro, Brazil - 14/08/2016. Justin Gatlin (USA) of USA competes. REUTERS/Kai Pfaffenbach