Alise Post may be the closest thing to a constant in the ever-evolving world of BMX cycling, the winner of four consecutive national titles in one of the most chaotic of Olympic sports.

On Sunday, the 25-year-old rider from St. Cloud, Minnesota, will try to make it five in a row.

Post will be joined by other Olympic hopefuls for the final day of the Gator Nationals in Oldsmar, Florida, which doubles as the U.S. championships. The winners of the elite men's and women's events will earn crucial points that help determine who makes the U.S. team for the Rio Olympics in August.

"I guess I've been pretty successful every year," said Post, a member of the 2012 team that failed to medal in London. "Ever since 2011, when we started to have these races on Olympic-style tracks, I've won every year. So it's hard to say it's been good luck or anything."

Well, maybe just a little bit of luck.

After all, crashes are a big part of BMX racing, and avoiding them sometimes boils down to little more than good fortune. Post need only recall her semifinal ride during the London Games, when she wiped out so hard — missing the finals — that she doesn't remember anything that happened afterward.

"There's probably 20 minutes of stuff I don't remember," she told The Associated Press. "My parents came to see me right after I crashed. I was physically fine. But yeah, they were the ones — I told them, 'I have to go race,' and they said, 'No, no, no. You're done.'"

Post doesn't like to highlight the crashes, writing them off as part of the sport. But that element of danger is a big reason so many fans have packed the grandstands since the races, lasting 40 seconds or less, were added to the Olympic program for the 2008 Beijing Games.

Large crowds are expected this weekend in Florida, where Post will be pushed by Brooke Crain — her teammate on the London team — rising star Felicia Stancil, and several other Rio hopefuls.

The men's race figures to be a two-man chase between Connor Fields and Nic Long, who have combined to win the last four national championships. They're the top two riders in USA Cycling's BMX power rankings, well ahead of Justin Posey, Corben Sharrah and Jared Garcia.

"On paper, Nic and myself and Corben would be the three favorites," Fields said, "if you were a betting man. But all it takes is one 'BMX event' to happen — something quick off the start, two guys bump, someone holds someone up at a turn. There's so many guys that would be so close to pounce, it's hard to discount all those other guys."

The same could be said of the competition for the three-man team for the Rio Olympics.

The final squad will be decided primarily on results of the world championships in May, points accrued at competitions such as the national championships, and an invitation-only Olympic trial in June.

"In a BMX race, it's so quick. Anything can happen," Fields said. "It just takes the smallest of mistakes and that could be the end of your race. The end of your Olympic hopes."