Kristin Armstrong of the United States crosses the finish line at Wednesday’s individual time trial. (Bryn Lennon/Getty Images)

Lucas wasn’t around for the 2008 Olympics and was not yet 2 years old at the London Games, so this all felt new. When the race was over, he approached his mother, who was still riding the emotional wave from exhaustion to elation. The 5-year-old tucked his head under her arm.

“Momma, why are you crying?” he asked. “You won.”

“Yeah,” Kristin Armstrong told him.

“So why are you crying?”

Someday he will understand. He will understand how the day before his mother turned 43 years old, she ripped through the time-trials course and became the oldest woman to win Olympic gold in cycling. How Armstrong shoved aside obstacles — be they age, skeptics, wind or the rain that drenched the Rio pavement. How she became the first cyclist to win the same event at three Olympics. And how Armstrong showed that you really can have it all: a family, a career, an Olympic legacy.

Armstrong’s golden years started at the 2008 Games and just keep going. Averaging nearly 25 mph, she won Wednesday’s race with a time of 44:26.42, a full 5.55 seconds faster than that of Russia’s Olga Zabelinskaya, who took silver.

“I have always loved that we were all born with the power to believe and to believe in ourselves,” Armstrong said later. “. . . You can set a goal and you can go accomplish anything you want. It doesn’t matter your age; it doesn’t matter where you’re from.

“I think that for so long we’ve been told you should be finished at a certain age. And I think there’s a lot of athletes out there that are actually showing that’s not true.”

Four years ago, even Armstrong couldn’t envision this. She thought the Beijing Games would be her lone Olympic appearance, but she kept going. She was certain she was done after London but just couldn’t walk away.

Why keep coming back? She’s asked this often and has tried to come up with a clever answer, but it’s pretty simple.

“Every time, it came down to: because I can,” she said.

Her secret weapon, she said, is balance. Back home in Boise, Idaho, most days are a juggling act. Armstrong works as a community health director for the St. Luke’s health system, and her small family keeps her both motivated and busy. It was important that they all did this Rio journey together.

Armstrong woke up early Wednesday morning to use the restroom and peeked out the window. Rain was falling; puddles were accumulating. When the time trials started a few hours later, it didn’t matter. Armstrong was so locked in, all she noticed was the pavement ahead of her.

“It was a blur,” she recalled later. “My husband was screaming at me, he said. I said, ‘Where were you?’ He said, ‘You about ran over me.’ ”

It took a while for the victory to settle in. The feeling was both familiar and new. She has won many big races before, starting with her first national road race championship in 2004. Much of her success has come in time trials, though, in which cyclists race solo against a clock. She has won two world championships, in addition to her Olympic titles.

Wednesday’s win was much more gratifying than the rest.

“I don’t have the words to describe it,” Armstrong said immediately after the race.

As for the Olympics in 2020, when Armstrong will be 46 years young, she insists a four-peat isn’t in the cards.

“I feel this time around, I have a different kind of closure than I did before,” she said.