That little burst of speed may have done more than shave a few seconds from her race time.
In a video image taken at 4:09:44, Boren is seen running along the left side of Boylston Street, her eyes fixed on the finish line. There is a flash, and smoke billows from the spectator area that Boren has just passed. Behind her, a runner crumples to the pavement. In the seconds that follow, video shows Boren, clad in a green T-shirt and black-and-white striped shorts, putting her hands over her ears and turning to look over her left shoulder as she keeps running.
"At first, I didn't know if it was a celebratory boom, like fireworks, but as I was running along I thought, 'That has to be a bomb,' " the St. George resident said Tuesday. "It was a sound that was unbelievable."
As Boren looked back, all she could see was smoke. Debris rained down on her as she ran those last yards.
The official time clock shows Boren crossed the finish line at 4:09:50, about six seconds after the first of two bombs exploded along the final blocks of the marathon.
Another image shows Boren running beyond the finish line, a perplexed look on her face. By then the second blast had gone off.
"That is when things really sank in," she said. "I was so caught up in everything. It was just kind of shocking, very shocking."
Cory Walker Maxfield was not far behind Boren. The Holladay resident had made a third trip to Boston to run the marathon, which Maxfield calls the "biggest party and parade in the world."
"The whole city of Boston makes it so special," said Maxfield, who has now competed in 20 marathons.
She was on Boylston Street, too, and could see the finish line down the road. Maxfield figured she had about a minute of running to go.
"At that point," she recalled, "I'm running on sheer willpower alone, trying to put one foot in front of the other."
Slightly ahead of her was 78-year-old Bill Iffrig, in an orange tank top and black running shorts. They'd been in the same pack of runners for the past half mile or so.
It was noisy. Maxfield was listening to her iPod, relying on music by her son's band Fictionist to rock her home and could still hear the roar of the crowd. Then she heard a blast about 25 yards ahead of her.
"My initial reaction was, 'What in the heck was that? Was that a cannon [for] Patriots' Day, some sort of festivity going on?' "
But then, as the course filled with smoke and people began screaming, Maxfield had another thought: "That can't be a bomb."
Iffrig, of Lake Stevens, Wash., had been knocked to the ground by the first blast.
Maxfield, 54, was running along the right side of Boylston Street and someone a race official, she believes grabbed her shoulder and tried to steer her off to a side street on the right.
Just then, from behind her, the second bomb exploded.
"I couldn't see what was happening," Maxfield said. "People were screaming, the smoke, and suddenly everybody that had Boston Marathon volunteer jackets was rushing toward these two areas, tearing down barricades, and it was just pandemonium."
Amid the chaos, she could not see those who had been injured. Startled and unsure where to go or what to do, Maxfield kept doing what marathoners do: running. She crossed the finish line 4:11:17 after the race's start.
Maxfield was shivering a combination of exertion, shock and the brisk wind as she made the long walk to a pickup spot where runners reclaim gear bags. Meanwhile, her husband, Larry, made his way to their pre-arranged meeting place at the intersection of Stuart and Berkeley streets, south of Boylston.
Larry Maxfield was sure of two things: Thanks to a text alert, he knew his wife had crossed the finish line, which meant she was probably OK, but other runners who had finished ahead of her spread word of the bombs and the many people hurt.
By the time Maxfield connected with her husband, she was so physically and emotionally distraught, she could barely walk.
"We slowly ambled our way toward our hotel," she said, at one point stopping in a restaurant to get some soup and watch the news.
"It took a while for it to sink in. It was unimaginable. It was hard to process. It was difficult. ... I can't even stand it," said Maxfield, who returned to Utah on Tuesday. "It's just such a special occasion to be here, and it just makes me so sad and so sick that anyone would target such an event."
As Boren rushed from the course, police, medical staffers and volunteers raced the other way to help the injured.
"It was really unbelievable, the quickness of how they responded," she said. "They were just on the ball."
A family friend, seated in the spectator seats directly across from the first bomb, witnessed the carnage, she said, and was greatly shaken. Boren's husband was supposed to meet her at the finish line but, in what turned out to be fortunate, got stuck in traffic.
Boren was able to text her friend before cell service cut out. She borrowed someone else's phone to reach her husband. She got little sleep Monday night, calling what happened a shame and expressing sorrow for the victims and their loved ones.
"Everything kept going over and over in my mind," said Boren, who traveled home to Utah on Tuesday. "It is all just kind of sinking in. It just seems like a horrible dream. I am counting my blessings today."
And she's grateful for those few precious seconds.