Returning a favor from earlier in the race, Nikki Hamblin helps Abbey D'Agostino off the track in the women’s 5,000 meters. (Ian Walton/Getty Images)

They were strangers at the starting line, a 24-year-old Dartmouth graduate who barely qualified for these Olympics and an English-born runner who transplanted to New Zealand seven years ago. Less than 20 minutes later, they found themselves eternally linked — by circumstance, by action, by benevolence.

In a sport measured by a running clock and at a global event where only the victors are awarded shiny medals, the display of sportsmanship Tuesday morning resonated far beyond the track.

“That girl is the Olympic spirit right there,” New Zealand runner Nikki Hamblin said later.

Hamblin and Abbey D’Agostino, a runner from Topsfield, Mass., collided on the track during the women’s 5,000-meter race. The two seemingly sacrificed any chance at an Olympic medal to help each other reach the finish line, picking each other up, urging each other to continue, pushing each other to the finish.

“I’m never going to forget that moment,” Hamblin said. “When someone asks me what happened in Rio in 20 years’ time, that’s my story.”

Here are 10 members of the U.S. track and field team you should know as they compete in the Rio Olympic Stadium. (Lee Powell/The Washington Post)

[Update: A day after indelible moment, reality hits with news of knee injury]

The 5,000-meter race is a grueling slog, requiring runners to make 12 1/2 laps around the track. About two-thirds of the way through Tuesday morning’s round one heat, Hamblin and D’Agostino found themselves crammed together with more than a dozen other runners, the entire group moving as one around the track. That’s when the long-distance races can be the most dangerous.

In the men’s 10,000-meter final two days earlier, Britain’s Mo Farah tripped and tumbled to the track. He bounced up and somehow still managed to cross the finish line first and defend his Olympic title. Not everyone gets up so easily.

“When you’re in a tight bunch, you have to watch the legs in front of you,” Hamblin said.

[Simone Biles caps her Olympics by winning fourth gold medal]

The New Zealand runner didn’t see what happened and wasn’t sure who was at fault, but she crashed onto the blue track and lay there still on her side for a couple of seconds. She thought right away, “What’s hit me? Why am I on the ground?”

“And then suddenly there’s this hand on my shoulder,” she explained later, “like, ‘Get up, get up! We have to finish this!’ ”

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The hand and the voice belonged to D’Agostino. She’d been right on Hamblin’s heels and tumbled over the Kiwi runner, badly twisting her right knee in the process. But D’Agostino popped right up, urging Hamblin to do the same.

“I was like, ‘Yep, you’re right. It’s the Olympic Games. We have to finish this,’ ” Hamblin said.

D’Agostino, no doubt, was just grateful to be in the field. With seven NCAA titles, she’s the most decorated long distance and cross-country runner the Ivy League has ever seen. But at the U.S. Olympic trials, she finished fifth in the 5,000 meters. Only the top three earned a ticket to the Rio de Janeiro, but when two other runners — Molly Huddle and Emily Infeld — decided to skip the 5,000 to focus on other Olympic events, a spot opened for D’Agostino.

“It’s been a privilege, and I’m so thankful,” she told the Valley News in Lebanon, N.H., earlier this month.

Finally on the track at Olympic Stadium, D’Agostino wasn’t about to stay down. Both runners were on their feet and continuing in the race, but the American was clearly hurting. She didn’t make it far before collapsing again. This time Hamblin was there to lend a hand.

While the leaders raced ahead, both D’Agostino and Hamblin sacrificed valuable seconds to help a competitor. It was instinct, a natural act and something that doesn’t usually earn medals or recognition.

“Everyone wants to win, and everyone wants a medal. But as disappointing as this experience is for myself and for Abbey, there’s so much more to this than a medal,” Hamblin said immediately after the race when her hopes of advancing in the Olympics appeared to be dashed.

[Olympic ring: Will Claye wins silver medal, then takes knee and makes biggest leap of all]

Both runners staggered their way through the remaining laps, each step drawing them closer to the finish. With no hopes of posting a time fast enough to qualify, D’Agostino was compelled, putting one foot in front of the other until she’d completed the remaining 4 1/2 laps.

Hamblin was well ahead of her and crossed the line in 16:43.61. She was exhausted, in pain and about to experience a touch of shock. She turned around and was surprised to see that D’Agostino had not given up, that the young American was still trudging down the track. “Wow,” she thought.

“I’m so impressed and inspired that she did that,” Hamblin said.

D’Agostino finally crossed the line with a time of 17:10.02, last place, more than two minutes slower than her personal best and more than two minutes after the race’s winner, Almaz Ayana of Ethiopia.

Both runners’ faces expressed utter relief. D’Agostino’s knee was clearly a problem. Still, in that quick moment at the finish line, there was no disappointment in not winning — just relief, gratitude and admiration.

“When you’re at this level, you know how hard it is to get here, so there’s just a mutual understanding of how much everyone puts into it,” Hamblin said. “You might finish last in your heat or something like what just happened, but you should still be proud that you’re here.”

[Jerry Brewer: Emma Coburn wins bronze, and something more precious than medal]

D’Agostino told officials at the finish line that she was having trouble putting weight on her leg, Hamblin said. The American needed a wheelchair to leave the track.

Meanwhile, both countries filed a protest on behalf of the runners, contending that the unintentional mishap impacted their result. Race officials agreed. D’Agostino and Hamblin found out after the race that despite being the last two competitors across the finish line, they had advanced and would be allowed to compete in the 5,000-meter final Friday.

The extent of D’Agostino’s injury wasn’t immediately known. She was treated by medical staff on-site after the race but was not made available to reporters. Officials with U.S. Track and Field did not offer an update on her health Tuesday evening.

If her knee allows, she’ll line up at the starting line Friday. Hamblin will be nearby, strangers no more.

“Regardless of the race and the result on the board, it’s a moment that you’ll never, ever forget for the rest of your life,” Hamblin said. “There’s going to be that girl shaking my shoulder, saying, ‘Come on, get up.’ ”

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