It’s the end of an era: Dick Hoyt will not be running the Boston Marathon today.

As the marathon’s Grand Marshal, the 74-year-old retired lieutenant colonel in the Air National Guard will be driving along the route in a truck instead of pushing his son, Rick, in his running chair.

Over the course of 32 marathons, the Hoyts have become synonymous with the race. Dick and Rick, who is a spastic quadriplegic with cerebral palsy, first got into running in 1977 at Rick’s request. He wanted to partake in a charity run for a lacrosse player who had been paralyzed. His son, said Dick, has been his main motivating factor through all the races — more than 1,000 in total. Their best marathon time came in 1992, when they completed the Marine Corps marathon in 2 hours and 40 minutes.

Dick recalled how spectators along the marathon route have told he and his son that they wait to see the duo race by, then go home and watch them finish the marathon on TV.

It wasn’t always like that. When they first started running country’s oldest marathon in the early 1980s, the race organizers “didn’t know what to make of us,” said Dick.

“They really didn’t want us in the marathon; they thought ‘What is this?’” said Hoyt. “It’s changed. Now when people see us coming down the street they say ‘You guys are the Boston Marathon.’”

The marathon organizers apparently agree.

“Year after year, Dick and Rick Hoyt toed the starting line in Hopkinton to celebrate the Boston Marathon, showing millions of runners and spectators they could achieve anything and that there are no limits,” said Tom Grilk, Executive Director of the Boston Athletic Association in a statement. “Although he will not be racing this year, Dick will continue to be at the head of the field, leading 30,000 runners on their trek to Boston. Dick and Rick Hoyt will forever be synonymous with the Boston Marathon and the sport of running.”

Since that first marathon, they’ve missed the race just twice, according to a spokeswoman for Hoyt. Once when Dick was hospitalized with cellulitis in his leg and once when he was recovering from a heart attack.

This year Bryan Lyons, a Billerica dentist, will be pushing Rick instead. At 74, Dick is done with longer distance races like marathons.

The duo’s last Boston Marathon was supposed to be in 2013. However, the bombings prevented them from finishing. They pledged to come back the next year and did just that. Dick ran through back pain so sharp “I could barely pick up an empty cup at one point.”

“My body is starting to tell me to slow down,” said Dick, who lives in Holland, Mass. — a small town near Sturbridge on the Connecticut border — and grew up in North Reading.

Dick admits he doesn’t weather the New England cold as well as he used to, either.

“It’s tough training, getting out there in the cold weather, especially this winter, the snow, the piles are everywhere and you have the cars going by,” he said. “Before it didn’t bother me. Now that I’m older, I get cold.”

Dick still plans on doing between 15 and 20 races a year with Rick, but those races will be shorter than marathons — 5ks or 10ks. He still wakes up, has a healthy breakfast of yogurt and fruit then goes down to his local health club for two and half to three hours to swim run or bike. He travels across the country working as a motivational speaker.

What’s he going to miss about running the race?

“Everything,” he said. “All the people. The crowds are just unbelievable.”

His advice for first time marathoners is simple: start off slow. The beginning portions of the race are all downhill.

“A lot of people take off,” he said. “That’s the toughest part. I’ve had blood blisters at six or seven miles. It’s not fun.”

He also says people should hydrate themselves. Start off with water, then switch between water and Gatorade in the latter stages of the race.

He’s asked if there’s any silver lining to not running the marathon.

“This year, I’m going to beat Rick for the first time,” he joked.