Even though she sailed with the Polynesian Voyaging Society three times before, Heidi Kai Guth knew that earning a spot on the worldwide voyage of Hokule‘a and Hikianalia was not going to be easy. She would have to be fitter than ever.

Guth, the society’s 44-year-old chief operating officer, is comfortable in the ocean. She surfs, paddles canoes and swims.

But this global sailing expedition is a massive undertaking: 36 months to complete, 50,000 miles at sea, multiple legs that can last up to a month at a time and more than 300 crew members vying for spots.

The high-stakes adventure prompted the voyaging society to place a greater emphasis on personal health. The society even created a rigorous fitness screening that proved so hard that nearly half of the crew member applicants failed when the test was first given in December.

The difficulty inspired everyone who wanted to be part of the journey, Guth included, she said.

"We want to be ready," Guth said. "I think a lot of people are training extra hard."

When she leaves with Hokule‘a on its second leg, from Tahiti to American Samoa on or about Saturday, she’ll be well prepared. For weeks, Guth had a fitness routine worthy of an Olympic hopeful.

She paddled her own one-person canoe whenever she could.

She paddled in a two-person canoe with a friend.

She regularly joined other potential crew members to paddle a six-person canoe around Kailua Bay for several hours.

She swam three miles at a stretch, once or twice a week.

She surfed along the south shore.

She bodysurfed off Kuliouou.

She rode her bike for errands around her home in Hawaii Kai. Sometimes Guth parked her car at Ala Moana Beach Park and pedaled to her office on Sand Island.

And she climbed the stairs at Koko Crater, which she considers the best way possible to prepare for life aboard canoe at sea. The stairs help improve balance and strengthen her hips.

Even when she took a break, she worked out.

"If I let myself watch TV, I have to be doing some kind of core workout," Guth said. "That’s when I lift free weights or do pull-ups. That’s my isometric and weight-training time. This is how I squeeze in everything."

The training was geared toward passing the crew member fitness screening, which she completed in early June: 20 pushups, 10 triceps dips, five pull-ups from a complete extension, a range-of-motion test called Turkish get-ups, running or walking a mile in 15 minutes and swimming a nautical mile in 90 minutes.

"I really had to up my game for the fitness requirements," Guth said. "The five pullups was not a problem because I use those muscles in paddling. But the tricep dips were."

(There’s also a more challenging test for crew members who want to become rescue swimmers: a five-mile swim from Sandy Beach to Maunalua Bay, but with fins.)

THE NEW fitness screening is very different from the one given by the voyaging society in the past. In the early years, the crew members were drawn from a small pool of qualified applicants, said Bruce Blankenfeld, who served as Hikianalia’s captain and navigator on the first leg of the global voyage from Hawaii to Tahiti.

"When we first started sailing in the ’70s and ’80s it was mostly men but these people were oriented toward the ocean and the water by the things they did," said the 57-year-old Blankenfeld. "They were rescue people and firemen. They were fit. And they were younger. Now we have a whole age range — 20s to 60s. And we’re expecting that everyone has a degree of fitness."

Dr. Ben Tamura, a Kaiser Permanente physician who was on four Hokule‘a voyages dating back to the early 1990s, said potential crew members on those early voyages were judged primarily on their ability to tread water.

"We never emphasized personal fitness on previous voyages," he said. "In the past they had to jump off Portlock Point and in groups swim to Niu Valley. That would take about an hour. It was basically tread water and drift with the current. Can you stay afloat until the canoe can get you?"

Still, fitness was — and remains — a critical asset because it can enhance safety at sea, Tamura said.

"If you are physically fit you can endure an injury and come back from it," he said. "People strain things. They pull things. The sea gets rough and you are bouncing around. There are a lot of slips and falls. That canoe rocks and rolls when the wind picks up."

Daily life on a voyaging canoe requires good upper-body strength to raise sails and booms and to use the giant steering sweep, said the 58-year-old Tamura, who stays fit by paddleboarding and walking.

But it wasn’t Tamura’s shoulders that were sore after his first voyage, to Tahiti.

"The parts of my body that hurt were my stomach muscles, my butt and my thighs," said Tamura, who lost 40 pounds on that trip. "You are constantly adjusting your posture when the canoe moves. When you are sitting, you are constantly doing crunches, rocking back and forth. I would say 10,000 crunches a day."

Guth never doubted her ability to be ready for the voyage. She had a desire fueled by what she knows is out there — what every crew member knows is out there, she said: the freedom of the sea.

"I really love the possibilities of just seeing the horizon," she said. "Just knowing you can go anywhere and being able to focus on exactly where you are at that given moment and what is necessary right then. It’s such a gift."