2016 Rio Olympics - Artistic Gymnastics - Preliminary - Women's Qualification - Subdivisions - Rio Olympic Arena - Rio de Janeiro, Brazil - 07/08/2016. Oksana Chusovitina (UZB) of Uzbekistan competes. REUTERS/Dylan Martinez

2016 Rio Olympics - Tennis - Preliminary - Men's Singles First Round - Olympic Tennis Centre - Rio de Janeiro, Brazil - 07/08/2016. Novak Djokovic (SRB) of Serbia in action against Juan Martin Del Potro (ARG) of Argentina. REUTERS/Toby Melville

2016 Rio Olympics - Swimming - Final - Women's 100m Butterfly Final - Olympic Aquatics Stadium - Rio de Janeiro, Brazil - 07/08/2016. Sarah Sjostrom (SWE) of Sweden celebrates REUTERS/David Gray

2016 Rio Olympics - Swimming - Final - Women's 100m Butterfly Final - Olympic Aquatics Stadium - Rio de Janeiro, Brazil - 07/08/2016. Sarah Sjostrom (SWE) of Sweden celebrates after setting a new world record. REUTERS/Stefan Wermuth

2016 Rio Olympics - Swimming - Final - Women's 100m Butterfly Final - Olympic Aquatics Stadium - Rio de Janeiro, Brazil - 07/08/2016. Sarah Sjostrom (SWE) of Sweden and Emma McKeon (AUS) of Australia compete. REUTERS/Michael Dalder

2016 Rio Olympics - Swimming - Victory Ceremony - Men's 400m Freestyle Victory Ceremony - Olympic Aquatics Stadium - Rio de Janeiro, Brazil - 06/08/2016. Mack Horton (AUS) of Australia poses with his medal. REUTERS/David Gray

2016 Rio Olympics - Swimming - Victory Ceremony - Men's 400m Freestyle Victory Ceremony - Olympic Aquatics Stadium - Rio de Janeiro, Brazil - 06/08/2016. Gold medallist Mack Horton (AUS) of Australia shakes hands with silver medallist Sun Yang (CHN) of China (PRC). REUTERS/Marcos Brindicci

Rio Olympics - Swimming - Olympic Park - Rio de Janeiro, Brazil - 02/08/2016. Michael Phelps (USA) of United States visits the Olympic swimming venue. REUTERS/Stefan Wermuth