Peter Kline was 53 before he ran his first marathon in 2006. Since that time he has run races all over the country — Washington, San Diego, Chicago, even Boston.

That doesn’t include the 100-mile ultra-marathons. And earlier this year he ran rim-to-rim and back along treacherous snow-covered trails at the Grand Canyon, you know, for kicks.

Some mornings he is up at 4 a.m. churning out miles before the sun has even thought about rising.

And while all that would be enough for even the most avid running fanatic, what has brought Kline the most joy is pushing children with various disabilities — rider-athletes, he calls them — along 26.2 mile marathon courses.

Francisco Kjolseth | The Salt Lake Tribune The Salt Lake Tribune staff portraits. Robert Gehrke.

“I love it. I love the kids and the excitement of the family, the excitement of the children and the happiness they get,” Kline said last week, as he prepared to run the Salt Lake City Marathon on Saturday. “It just changed me and I don’t want to go back to anything other than that.”

Over the past seven years, Kline has run about 40 marathons with rider-athletes, including four ultra-marathons.

“They get to feel included and involved and special,” he said. “Other runners will come by … they’ll want to give them high fives. They’ll talk to them. It’s their Super Bowl. ... They get that medal around the neck and tell [friends] they ran the race, and it’s true.”

On Saturday, Kline’s companion for the day was Brianna Heim, or Bri, an exuberant 13-year-old born with glutaric acidemia type I, a rare disorder that means her body is unable to break down certain proteins, causing amino acids to build up in her brain.

Her mind is sharp. She’s a straight-A student, but she is unable to walk and talks mostly with the help of the speech program on her iPad.

“She’s an adrenaline junkie. She’s been paragliding a couple times, indoor skydiving,” Wendy Heim said of her daughter, who was the 2015 National Miss Amazing Preteen Queen. “She has the need for speed.”

How did the Heims and Kline connect? It started at a Utah Grizzlies hockey game. The Heims are big fans and they sat next to a man who worked for Bank of America, the firm Kline works for in Bellevue, Wash.

“Bri was pretty excited about the idea of being in a marathon,” Wendy Heim said.

Before the race Saturday, Bri Heim said she looked forward to “running and going fast.” Kline sheepishly said he hoped she was OK with “old man fast.”

No, they didn’t break any world records. Even with a new, lighter, $5,000 chair Kline bought not long ago, he still pushed a 50-pound chair holding an almost-grown person up and down hills on a course that snakes all across the city, and at an elevation that is about 4,100 feet higher than his home.

(Rick Egan | The Salt Lake Tribune) Peter Kline pushes 13-year-old Brianna Heim, as they warm up for the Salt Lake Marathon on Saturday, where Kline will be pushing Hieim in the race. Thursday, April 11, 2019.

Kline is responsible for keeping his riders hydrated on the journey. Oftentimes the kids have feeding tubes and some have needed to have their throat suctioned. Potty breaks are not uncommon.

It’s not easy for the rider-athlete, Kline said.

They are “physically invested in the sport,” he said. “It’s not a smooth ride. There’s no suspension system on this jogger. You may be in the elements, it may be raining, it may be cold. They’re using their mind and they’re using their bodies.”

Still, Kline usually averages between 12- and 13-minute miles, so he’s certainly not the last to finish. In fact, he said, near the end of the race an interesting thing happens: Runners who have hit the wall and are struggling get a second wind when they see Kline and his passenger approach. Often, they run those last miles together.

On Saturday, Kline and Bri started out in a dark morning chill. Bri was bundled in a blanket and gloves and a hat but it warmed up as the day went on, aside from a light rain that hit around mile 15. They finished the race at about 1 p.m., covering the course in a little over six hours.

“I loved being in my first marathon. It was so much fun! I loved how all the people cheered and congratulated me,” Brianna wrote afterward. “Being in that big awesome chair was comfy.”

But was it fast enough?

“It’s never fast enough for this adventurous girl!” she said. “But I really liked the speed we were going.”

(Rick Egan | The Salt Lake Tribune) Peter Kline pushes 13-year-old Brianna Heim, as they warm up for the Salt Lake Marathon on Saturday, where Kline will be pushing Hieim in the race. Thursday, April 11, 2019.

“We had a great time. … Brianna was fabulous. A lot of fun. It was a perfect day,” Kline said. “A lot of runners ran with me and afterwards they would come up and tell me they were inspired by the run.”

Kline is flying home Sunday (he pays all of the expenses — the chair, hotel, airfare, meals, race registration — himself) to prepare for his next race, the San Diego marathon in June. Then Seattle a couple of weeks later. Then Chicago. Then Charlotte. Then an ultra-marathon in Florida in December, with different rider-athletes in each city.

But for Peter Kline, it’s not about the expense or time or all those countless miles of pavement. It’s about going the extra mile to put a smile on the face of a kid like Bri who gets to feel the joy of “running and going fast.”