FILE - Alise Willoughby, of the United States, puts her hands on her head after crashing in the BMX Racing semifinals at the 2020 Summer Olympics, Friday, July 30, 2021, in Tokyo, Japan. (AP Photo/Ben Curtis, File)
FILE - Connor Fields, of the United States, center, who later crashed, is followed by Romain Mahieu of France, center-left, and Vincent Pelluard of Colombia, left, as they compete in the men's BMX Racing semifinals at the 2020 Summer Olympics, Friday, July 30, 2021, in Tokyo, Japan. The American was racing into the first corner in a semifinal when he clashed wheels with a French rider, sending him down. Two more riders fell on him. Fields briefly tried to sit up, then lost consciousness, and would not wake again for three days. (AP Photo/Ben Curtis, File)
FILE - Colombia's Carlos Mario Oquendo Zabala crashes during a BMX cycling men's quarterfinal run at the 2012 Summer Olympics in London, Thursday, Aug. 9, 2012. The most dangerous event at the upcoming Paris Olympics might well be BMX, where broken bones, concussions and even paralysis occur with scary regularity. (AP Photo/Christophe Ena, File)
FILE - Medics prepare to carry Connor Fields, of the United States, away on a stretcher after he crashed in the men's BMX Racing semifinals at the 2020 Summer Olympics, Friday, July 30, 2021, in Tokyo, Japan. His injuries were numerous: torn shoulder ligaments, a torn bicep, broken ribs, a collapsed lung. But most serious was what was diagnosed as a subarachnoid hemorrhage and subdural hematoma — essentially, bleeding on the brain. (AP Photo/Ben Curtis, File)
FILE - Felicia Stancil, of the United States, center, looks ahead as the bike of teammate Alise Willoughby flies in the air after she crashed in the BMX Racing semifinals at the 2020 Summer Olympics, Friday, July 30, 2021, in Tokyo, Japan. BMX racing has been described as NASCAR on two wheels, only stock car racing is probably a whole lot safer.(AP Photo/Ben Curtis, File)
FILE - Connor Fields, of the United States, bites his gold medal during a victory ceremony for the men's BMX cycling final during the 2016 Olympic Games in Rio de Janeiro, Brazil, Friday, Aug. 19, 2016. “There's no way to check this," Fields said, “but I might be the only athlete to both win the Olympics and nearly die at one.” (AP Photo/Patrick Semansky, File)
FILE - Cyclists, front from right, Carlos Ramirez Yepes, of Colombia, Sam Willoughby, of Australia, and Amidou Mir, of France, compete in the BMX cycling quarterfinals during the 2016 Summer Olympics in Rio de Janeiro, Brazil, Thursday, Aug. 18, 2016. In the background left is Kyle Evans of Britain. Sam Willoughby made a mistake during practice, doing something he did every day for 10 years prior, and broke his back. (AP Photo/John Locher, File)