China Athletics Worlds(01 of11)
Open Image ModalJamaica's Usain Bolt, left, looks across as he goes all out to win a men's 100m semifinal at the World Athletics Championships at the Bird's Nest stadium in Beijing, Sunday, Aug. 23, 2015. (AP Photo/Lee Jin-man) (credit:ASSOCIATED PRESS)
APTOPIX China Athletics Worlds(02 of11)
Open Image ModalJamaica's Usain Bolt celebrates after winning the gold medal in the men's 100m ahead of United States' at the World Athletics Championships at the Bird's Nest stadium in Beijing, Sunday, Aug. 23, 2015. (AP Photo/Lee Jin-man) (credit:ASSOCIATED PRESS)
APTOPIX China Athletics Worlds(03 of11)
Open Image ModalJamaica's Usain Bolt is interviewed after winning the gold medal in the men's 100m at the World Athletics Championships at the Bird's Nest stadium in Beijing, Sunday, Aug. 23, 2015. (AP Photo/Darron Cummings) (credit:ASSOCIATED PRESS)
China Athletics Worlds(04 of11)
Open Image ModalJamaica's Usain Bolt, centre, races to win the gold medal in the men's 100m ahead of United States' Justin Gatlin, 2nd left, at the World Athletics Championships at the Bird's Nest stadium in Beijing, Sunday, Aug. 23, 2015. (AP Photo/Lee Jin-man) (credit:ASSOCIATED PRESS)
China Athletics Worlds(05 of11)
Open Image ModalJamaica's Usain Bolt, right, wins the gold medal in the men's 100m ahead of United States' Justin Gatlin, left, at the World Athletics Championships at the Bird's Nest stadium in Beijing, Sunday, Aug. 23, 2015. (AP Photo/Lee Jin-man) (credit:ASSOCIATED PRESS)
China Athletics Worlds(06 of11)
Open Image ModalJamaica's Usain Bolt is interviewed after winning the gold medal in the men's 100m at the World Athletics Championships at the Bird's Nest stadium in Beijing, Sunday, Aug. 23, 2015. (AP Photo/Darron Cummings) (credit:ASSOCIATED PRESS)
China Athletics Worlds(07 of11)
Open Image ModalJamaica's Usain Bolt smiles after winning the menâs 100m final at the World Athletics Championships at the Bird's Nest stadium in Beijing, Sunday, Aug. 23, 2015. (AP Photo/Ng Han Guan) (credit:ASSOCIATED PRESS)
China Athletics Worlds(08 of11)
Open Image ModalJamaica's Usain Bolt crosses the finish line to win the menâs 100m final at the World Athletics Championships at the Bird's Nest stadium in Beijing, Sunday, Aug. 23, 2015. United States' Justin Gatlin, left, was second. (AP Photo/David J. Phillip) (credit:ASSOCIATED PRESS)
China Athletics Worlds(09 of11)
Open Image ModalJamaica's Usain Bolt, right, wins the gold medal in the men's 100m ahead of United States' Justin Gatlin, left, at the World Athletics Championships at the Bird's Nest stadium in Beijing, Sunday, Aug. 23, 2015. (AP Photo/Lee Jin-man) (credit:ASSOCIATED PRESS)
China Athletics Worlds(10 of11)
Open Image ModalJamaica's Usain Bolt celebrates after winning the menâs 100m final at the World Athletics Championships at the Bird's Nest stadium in Beijing, Sunday, Aug. 23, 2015. (AP Photo/Ng Han Guan) (credit:ASSOCIATED PRESS)
APTOPIX China Athletics Worlds(11 of11)
Open Image ModalJamaica's Usain Bolt, right, crosses the line to win the gold medal in the men's 100m final at the World Athletics Championships at the Bird's Nest stadium in Beijing, Sunday, Aug. 23, 2015. (AP Photo/Mark Schiefelbein) (credit:ASSOCIATED PRESS)