Katrina Delgadillo didn’t mean to run her first marathon. A high school soccer player, she started running a few miles daily in college. She was on a treadmill in the Mansion House when Island runner Allyson Metell approached her and asked if she would like to train together outside.

“Before I knew it, my three miles became a six-mile run, and then I was accompanying her up to 10 miles,” Ms. Delgadillo said. “She started encouraging me to train for a marathon. She said, you’re already halfway there.”

Thirteen marathons, several triathlons and more than a decade later, Ms. Delgadillo is in her last week of training to run another marathon in Boston on Monday. She’s been training all winter with Marylee Schroeder and Chantal Desgagne.

Today a path in Vineyard Haven, next stop: starting line in Hopkinton on Monday. — Mark Alan Lovewell

The Boston Marathon is unlike other marathons because for most participants, it requires a qualifying time, meaning runners have to prove they can complete the course within a certain time frame ahead of the race.

“What makes Boston most satisfying is you actually have to qualify on a certified course, then you get to register. It’s a huge accomplishment,” said Ms. Schroeder, who has run about 30 marathons (she’s lost count).

This will be the 122nd Boston Marathon. More than 26,000 runners completed the race last year. Ms. Schroeder said the atmosphere in Boston makes the event one of her favorites. “The fans in Boston cheer for everybody,” she said. “In [the] New York [marathon], they only cheered for the people they knew.”

Ms. Delgadillo said training for a marathon affects all aspects of being: nutrition, sleep schedules, social life.

“Any spring marathon is difficult because you’re training all winter long,” she added. “In the cold frigid morning, you still have to get up and train.”

That’s often before the sun comes up.

“We start off dark,” said Ms. Schroeder. “We’ll have our headlamps on and our reflectors.”

“We live in a beautiful place, and I love to get up early and see the sun rise,” said Ms. Desgagne. She isn’t bothered by the cold. “I’m from Quebec City, so.”

The three runners do distance training up-Island, hill training on Skiff avenue in Vineyard Haven and speed training at the high school track.

Ms. Schroeder said if you’re training for a marathon on the Island, finding hills can be a challenge. You are also eventually going to run all the up-Island roads. One of her favorite runs starts out at the Agricultural Hall in West Tisbury, then follows Middle Road down to Tabor House Road, then back up to North Road and across Tea Lane. The first time she ran Tea Lane about two years ago, she found the uneven dirt surface and series of hills really challenging.

“I had to stop and walk part of it. I thought, what is this road? Every time I thought it would end, it just kept going,” she said. That first time she ended up having to walk part of the way.

“I thought, I have to conquer this road.”

That mentality is shared among all three athletes. Ms. Desgagne persists even with a stress fracture in her right foot, an edema and a hamstring injury in her right thigh.

“I’m just sucking it up because I want to finish Boston, and I didn’t work this hard to not do it,” she said. “My time’s not going to be good, but I’ll do my best.”

She said after Boston she will take time to rest and heal, then start training for a half iron man.

This will be Ms. Desgagne’s fourth Boston marathon, but she estimates she’s run about 10. She pointed out that at a certain point, counting doesn’t make sense anymore.

“I ran 48 miles last week, basically two marathons,” she said.

Monday will be a culmination of months of work and training. The women have spent a lot of time together as they prepare.

“Marylee is my inspiration,” said Ms. Desgagne. “She scared the crap out of me the first time she asked me to go run with her, because she’s fast.”

“You have three and a half to four hours of talking when you’re on your runs,” said Ms. Schroeder. “It’s definitely brought us all closer together.”