When you have grown out of being the only girl in an otherwise all-boys rugby league in Scotland but not out of fiercely competing in the mud, where do you go to find your life’s biggest athletic challenges?

If you are the still-rambunctious Lesley Paterson, you work your way, swimming, mountain biking and trail running, with several hundred others from 44 countries to the 23rd Xterra World Championship in Kapalua, Maui.

Paterson, who pursues her third Xterra Women’s title and a piece of the $100,000 in prize money Sunday, says the 1-mile roughwater swim, 20-mile mountain bike race up to the 3,500-foot level of the West Maui Mountains and 6.5-mile trail run, provides a demanding but alluring duality.

“It is the grittiness of it — it is a tremendously challenging course — and the unbelievable beauty of Hawaii and, yet, (something) so painful,” Paterson said. “It is this bizarre contrast where you are literally in paradise and, yet, you are in hell.”

For the 38-year-old known as the “Scottish Rocket,” who won on Maui in 2011 and ’12, as well as a world ITU Triathlon title in 2012, sports has been filled with travails beyond the trails. She was diagnosed with chronic lyme disease in 2011 and suffered through a pelvic stress fracture last year. She still managed to finish fifth at Kapalua.

But except for 2014, a year in which the fatigue brought on by the debilitating lyme, a tick-borne illness, parked her career to a competitive standstill, she has not only pressed on but won titles in Europe, the U.S. and elsewhere.

“Many times” she said she has considered walking away from the sport. “It has been a roller coaster, for sure. I’ve gone from having some amazing performances to really struggling. It has been a real pendulum,” Paterson said. “To be honest, coming into (this) season I wasn’t sure if I’d even race. But I did well, trained hard and got more and more motivated and it has probably been one of the best seasons I’ve had in the last (few) years. It is just part of the ups and down.”

You could write a book about her persistence and drive in staring down those tribulations. And, in fact, she and her husband, Simon Marshall, a sports psychologist, have authored, “The Brave Athlete. Calm the (Bleep) Down and Rise to the Occasion.”

The book is about mental discipline and surmounting challenges. The title, undoubtedly, derives from her own experiences. “I’m crazy,” she says frankly of her all-out, high-energy existence.

In periods when she is not competing, the routine at her San Diego home consists of rising at 4 a.m. to train until nearly noon. Then she moves to her side job, training and coaching others, including actress Sylvia Hoeks of “Blade Runner 2049” before working on projects for her film production company, Sliding Down Rainbow Entertainment Inc.

It is a full load and then some, but the drive to return to Maui has her competing in a half dozen or more Xterra events each year to earn her way back to the world championships.

“A lot of Xterra (Worlds) is about family,” Paterson said. “It is like this tribe where people from all over the world come together each year for the camaraderie and the competition, a very positive (spirit).”

Reach Ferd Lewis at flewis@staradvertiser.com or 529-4820.