The first time Tai Blechta competed in the XTerra World Championships on Maui, he hated every minute of it.

The accomplished triathlete wasn't prepared for the grueling course — a 1-mile swim, 20-mile bike and 7-mile run — along challenging terrain and in humid conditions.

Never mind that he doesn't mountain bike much or that he had just competed in the Ironman in Kona the week before.

"It was horrible," said Blechta, 29, of Manoa, who cramped up during the race. "There were big rocks, big drops; you could crash."

He paused, the added, "But you get to like it pretty quickly."

Blechta is one of more than 550 athletes from 20 states and six countries participating in the inaugural XTerra Trail Running World Championship on Sunday at Kualoa Ranch.

This is the last race in the 50-race XTerra Trail Running Series held in 15 states and seven countries.

This off-road half-marathon will start in Ka'a'awa Valley. Runners will navigate the length of the valley, around the front of the ranch and into Hakipu'u Valley, over the ridgeline and back into Ka'a'awa.

The course is littered with hills, valley trails, stream crossings and some twisting sections that have become a signature of the XTerra races.

The XTerra started with an off-road triathlon on Maui 12 years ago and grew into a worldwide series of more than 100 races in 15 countries and more than 50 trail runs in seven countries.

About 30,000 athletes compete in XTERRA events all over the world, with another 40 million tuning in to its TV show every year.

Despite its challenging terrain and course design, more than 30 competitors in Sunday's race are also signed up for the Honolulu Marathon, scheduled for the following Sunday.

Including Blechta.

"It's probably not the smartest thing to do if you want to get a good time," said Blechta, who's hoping to qualify for the prestigious Boston Marathon. "You can get hurt, you can break an ankle, you can fall. You're pushing so hard up the hills; it's a harder intensity. It's pretty easy to pull something or over-strain yourself."

But this trail run was scheduled purposely around marathon season in Hawai'i, when most runners are in shape and training for the races leading up to the 26.2-mile race.

And while Sunday's trail run is half the distance of a marathon, it's no less difficult.

In fact, some say it's harder.

"The terrain is very unforgiving and very unexpected," said Blechta, who's competing in his sixth XTerra race and second marathon. "It's just a really, really challenging course to get through. Though it doesn't take as long (as the marathon), the effort and frustration and excitement are a lot higher. It's a lot more challenging race in a shorter period of time."

His plan for recovery and preparation for the Honolulu Marathon?

"I'm going to do a couple of short runs," he said. "And get a massage."