One athlete's "psych-up" ritual may psych out an opponent. And even treatments that lack hard evidence of benefit, scientists say, might provide a competitive edge if the athletes believe they work.
There are 205 countries competing in Rio, many for decades, and most of them can't match Phelps' total of 23 golds.
Violence erupted and businesses were set aflame after an officer shot and killed a 23-year-old man during a foot chase, Saturday. Police say the man was fleeing a traffic stop and armed with a gun.
Do you know how long the longest earthworm is? Or how people might contract a parasitic worm?
Violence erupted and businesses were set aflame in protest across the city's north side after an officer shot and killed a 23-year-old man. Police say the man was fleeing a traffic stop and was armed.
Michael Phelps captured one last gold, his 23rd in his staggering career. On the track, Jamaica kept its stranglehold on the women's 100 meters as Elaine Thompson became the world's fastest woman.