Alysia Montano finishes in last place after falling during the 800-meter final at the U.S. Olympic track and field trials Monday in Eugene, Ore. (Marcio Jose Sanchez/Associated Press)

For four years, they work on technique, plot strategies, account for different scenarios, plan out their diet and schedules and every detail imaginable. And then with the finish line in sight, the slightest bump can render it all moot, deflating hopes with the subtlety of a sword piercing a children’s balloon.

At the U.S. Olympic track and field trials Monday, the two favorites in the women’s 800-meter race learned the fragility of dreams in the hardest way imaginable. Brenda Martinez was in second, making the final turn when Alysia Montano, running in fourth at the time, approached from behind. Martinez felt someone clip her foot, and she stumbled.

“I kind of just shut my eyes, like this is not happening,” Martinez said later.

She regained her footing but lost her position. Montano, meanwhile, tumbled to the track in disbelief, watching what could be her last shot at another Olympic team slip away. The expected 1-2 finishers instead were the last two across the line.

Kate Grace, a 27-year-old all-American from Yale, zipped by the commotion, her long strides carrying her from sixth to first. She won with a time of 1:59.10, followed by Ajee Wilson in 1:59.51 and Chrishuna Williams in 1:59.59.

“It’s surreal, and I’m ecstatic,” said Grace, who reached the podium for the first time at a national event.

As the Rio-bound runners celebrated, Montano was alone on the track. She made it to her feet and crept toward the finish line, her emotions both carrying her and thwarting her. Montano fell twice but finally crossed the finish line, where she again collapsed and cried. Her official time: 3:06.77, more than 1:07 away from qualifying.

Montano’s career has been star-crossed like few others. She’s been outspoken about doping in the sport and was determined to return to the Olympics and earn a spot on the medals podium. Montano competed at the London Games, where she was the fifth runner across the finish line. The two Russian medalists in her race were implicated last year in a widespread doping controversy, and if they’re disqualified, as many track observers expect, Montano eventually could be awarded the 2012 bronze.

Heading into the trials, she tried to block out doping whispers, the sport’s darkening cloud and everything beyond her control. “In order for me to move forward,” she said, “it was going to be to pretend like I wasn’t running in a sport that was so corrupt in the first place. Just not think about all that. It was my strategy to make it here today. I made it this far, and [there were] unfortunate circumstances. Somehow I’m going to have to find solace.”

Neither Martinez nor Montano was certain what happened. USA Track & Field officials ruled the contact was incidental, and no runners were disqualified. Montano said she wasn’t interested in assigning blame after the race but felt she got caught up in the commotion.

“I rehearsed this a thousand times. You can’t predict what happens with someone else,” said Montano, still distraught and in tears after the race. “I don’t know what happened to Brenda. She ended up tripping and I found myself jumping around her and someone kicked me out from behind. What can I do in that situation? I didn’t touch anyone.”

Said Martinez, 28: “I know I’m good enough to make the team. Some days it’s not going to go your way, and today that was me.”

Montano said she didn’t think she’d protest the result, asking, “What’s that going to do for me?”

The men’s 800 took place with similar stakes but markedly less drama. Clayton Murphy moved from fifth place to first over the final 200 meters, emerging from a pack and overtaking Boris Berian down the stretch to win with a time of 1:44.76. Berian finished 0.16 seconds behind Murphy, and Charles Jock finished in third with a time of 1:45.48.

“To be an Olympian and be able to represent Team USA is something I’ve dreamed of since I started running,” Murphy said. “I just can’t wait to get to Rio.”

In men’s pole vault, 23-year-old Sam Kendricks locked up a spot on his first Olympic team, easily topping the trials field while posting a personal-best mark. He successfully cleared 19 feet 4¾ inches, a new trials record that put him well in front of second-place Cale Simmons (18-6½ ) and third-place Logan Cunningham (18-4½ ), both of whom are also heading to Rio.

“There’s that thunder in your heart when you hear the crowd behind you,” Kendricks said, “especially when you look around. It’s funny, when you look to the left you hear them right there in your ear, and then you look to your right and hear that clap, you get that double heartbeat action. It made me feel like everyone was behind me, and that’s what I love about the pole vault.”

Americans used to dominate the pole vault at the Olympics, winning all 16 gold medals from 1896 to 1968. The United States has won just twice since, and none since Timothy Mack in 2004.

In the men’s javelin competition, Cyrus Hostetler will be returning to the Olympics after posting a top throw of 273 feet 1 inch on Monday. Curtis Thompson (271-11) and Riley Dolezal (261-4) are also Olympic-bound. Hostetler competed in London four years ago but failed to reach the finals there.