RIO DE JANEIRO (AP) — In the unpredictable sport of BMX cycling, where races last just about 40 seconds, a strong start means a lot.

Get to the front after the first turn, and there’s a good chance a rider will be able to avoid the kind of wreck-filled chaos that marked the action in the men’s quarterfinal round at the Rio de Janeiro Olympics on a breezy afternoon.

“It’s always the key,” Australia’s Sam Willoughby said, “but especially … when it’s windy like this and there’s carnage out there.”

An early lead will come in handy for riders in the men’s and women’s semifinals beginning Friday afternoon, with the medal races later in the day.

Willoughby is on a roll headed into the semis after winning all three of his heats in the quarters on Thursday . Australian teammate Anthony Dean also had a strong quarterfinal round, while the United States and the Netherlands each sent all three of their cyclists into the men’s semis.

“We don’t have lanes and it’s a full-contact sport, so the start is very important,” Willoughby, the 2012 silver medalist, said this week. “To get out front at the first corner, you can run your own race from there and create your own destiny a bit.”

It’s tough enough just to have a chance to lead the pack after the first turn.

The action begins with cyclists released from a starting gate at the top of a ramp three stories tall. They pedal furiously down the ramp and pick up speed to jump hills and maneuver through turns on the roughly quarter mile-long course.

U.S. rider Alise Post said she thinks riders reach a speed of 35 to 40 mph just a few seconds into the race. There’s no suspension on the bikes, either.

“It’s very demanding for sure,” Post said.

The series of jumps after the starting ramp leads into the wide first turn. Inside position is important. Stay out in front and there is a greater likelihood that a rider won’t get caught up in the pack of cyclists desperately trying to catch up.

And this all might happen in a span of 10 seconds, maybe less.

The alternative is to scramble from behind, which isn’t uncommon, though less desirable.

A contender’s day can end in a hurry. In the quarterfinals on Thursday, two-time gold medalist Maris Strombergs barely missed the cut after getting set back from a crash in his first heat that also involved Britain’s Liam Phillips. Joris Daudet of France, the reigning world champion, also got knocked out after crashing.

“There’s still 800 feet of track that you can’t mess up on … because seven guys will pass you, no problem,” U.S. rider Nic Long said. “It’s never easy. But yeah, winning to the first jump, the winning to the second jump, then winning the first turn, makes winning to the finish line that much easier.”

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