MARYSVILLE — A warning: what Tory Klementsen is teaching can become highly addictive.

A runner’s high starts out simple enough, coming after the first mile or so, but then it gets harder to attain — and the chase begins.

“Once you go longer, you find that it comes after the second or the third mile,” she said.

Working with the city of Marysville, Klementsen teaches running classes that range from beginners to Marathon Maniacs, a national organization that inducts runners who run three marathons in as many months.

One of Klementsen’s pupils, Megan Reuther of Everett, has obtained membership in the club after starting to run approximately a year ago.

“I wanted to lose weight and running seemed like the best way to do it,” Reuther said. “I heard about Tory’s story and she went with me in my first 10K, pointing out where this marathon went over this bridge and that half marathon went up that hill and I said, ‘Okay, I’ll give it a try.’”

Klementsen has lost 100 pounds since she started running, and has completed more than 40 marathons. Her experience with all kinds of runners helps her personalize a training regimen to each of her runners’ needs.

The class starts out with a three- or seven-mile run for half or full marathoners, respectively. Then every Saturday, the class meets at Jennings Park to run a progressively longer course — all the way up until 21 miles.

Between those meetings, however, Klementsen also has four days of homework, or training sessions planned out for her students.

One of the adjustments Klementsen said runners have to get used to is how much time the training takes.

“It’s like everybody in the family is training,” she said of marathoners who have families. “I think at first, they don’t realize how much time it takes, but they have to understand that they can do it.”

Reuther, who just finished her 12th marathon, underwent such a transition, but said she has made it a routine with her 3-year-old son Colton.

“Now I take my little boy to the park with me so he can play while I run,” she said. “I take him home when he’s done and keep running.”

Many of her students are training with a specific goal in mind, to run in either the Nike Women’s Marathon or the Seattle Marathon (Nov. 27).