"I read a saying once that if you have to ask, you'll never know. It's a very internal thing," Viesturs says. "Most of the climbers I know, we don't have a death wish. We don't seek danger. We seek to challenge ourselves."
The Physical Challenge
But the inability to find all of the right words doesn't stop him from trying to explain his passion. Part of the allure of high-altitude climbing for Viesturs is the physical challenge of doing it without supplemental oxygen. It's a standard that sets him apart from most of the mountaineering world and an extreme feat that's physically impossible for most climbers.
"Using oxygen takes away from experiencing the mountain for what it is or challenging yourself and seeing what you can do physically," Viesturs says. "To climb to 29,000 feet (8,800 meters), what's that feel like? Can I push myself that hard? Am I strong enough physically? Those are the things I want to test myself with."
When Reinhold Messner and Peter Habeler stunned the world in 1978 by making the first ascent of Everest without oxygen, Viesturs, who was just getting into climbing, decided to follow suit.
"It inspired me, and I thought if I ever had the chance to go to Everest or some other Himalayan peak, I didn't want to use oxygen just so I could get to the summit," he says.
On May 8, 1990, at 1 p.m., Viesturs finally realized that aspiration. Relying on his lungs, he stood on top of Everest for the very first time. While a schedule based on training up to seven days a week, year round, helps him to keep functioning at high altitudes, Viesturs also has a rare physiology to thank.
Clinical laboratory studies have confirmed that the 5'10", 165-pound (75-kilogram) climber processes oxygen faster and in bigger volumes than the average person. While most people's lungs have the capacity to hold 4.5 to 6.5 liters of oxygen, depending on their size, Viesturs' can hold seven. He's also been blessed with a high anaerobic threshold—the point at which lactic acids start accumulating in muscles, causing cramping—which gives him the raw endurance to climb longer.
Playing the Mental Game
The mental challenges of climbing have also played a big part in Viesturs' drive to get to the top ever since he came across the book Annapurna in his school's library at age 15. He was inspired by the true account of the 1950 French expedition and its dogged efforts to find and climb the 26,503-foot (8,078-meter) Himalayan peak Annapurna, the tenth highest in the world.