There is no one motive prompting someone to get off the couch and do a triathlon, but it's different than committing to one's first footrace. To be a triathlete means a lifestyle not just of grunt work but of competency. A personal equipping. The commitment to constant learning, skill and technique, life balance, patience, perspective. Triathlon isn't just the smooshing together of several single sports. It makes its own weather.

Who are the multisporters today who capture my imagination? Those who know where they want to go, know it is not easy and devise skills, products and methods to get there. One is Don Bowie. I don't know Don, have never spoken to him. I don't know if he's ever even done a triathlon, narrowly construed.

Besides being a very tough fellow, he's an example of how the combining of multiple sports makes something greater than the sum. “In 2012 I was introduced to road cycling and immediately became addicted,” writes Don. “How far can I bike and run in 24 hours? How many vertical feet can I climb?” He created his own sport, the Altathlon. Yeah, baby! (Both images here are of Don doing what he does).

Here are Don's first words about himself, from his website: “I train hard, I climb hard, I ride hard, I have an abysmal diet with a penchant for children's sugar-cereal. I periodically live in Harvey-the-RV, my 1978 Foretravel classic motorhome, which is usually parked around the open spaces of Bishop, California.”

Another of my favorites is Kilian Jornet, whom I also do not know. Kilian is by summer this generation's great skyrunner, by winter a consummate ski mountaineer.

Here are the first words Kilian writes about himself on his website: “I define myself as a lover of mountains. I like competing, as it is a way to meet friends and to self-improve. But, above all, I conceive sport as a way to discover landscapes both inside and outside you.” Is this an endurance athlete writing, or John Muir?

Both Don and Kilian are mountaineers. What we consider mountaineering – the notion of wanting to ascend a peak just because it's there, and it's high – dates from roughly 1500. I have a hard time believing the urgency to ascend for the sake of the ascent is only 500 years old.

Multisport is not simply getting from A to B in the shortest elapsed time. Read what motivates these guys, in their own words. Curiosity of the natural world combined with a spirit of overcoming, achieving, and surviving is square in the circle scribing their concepts of sport.

The English Channel was first crossed by swimming in 1875. The sport of competitive swimming, at least in Europe, only predates this by 30 or 40 years. (It took Native Americans to teach the English that the front crawl was a faster and more efficient means of swimming than the breaststroke.) Striking to me about this first Channel swim is the marriage of two notions: the “game” of competitive swimming and the overcoming of a geographic obstacle. This swim, as I imagine it, feels and tastes very much like the first Hawaiian Ironman.

This is my sport. It has very few fences. In fact, I'm in the process of breaking my “human powered locomotion” rule by adding horses to the allowable methods of conveyance, just, at the end of the day I've got to be at least as whipped as the horse or it doesn't count. This is my rule. If Don Bowie can make up his own sport with its own rules then I can too.

Mind, I'm not against organized sport and obviously neither is Kilian, who is a several-time skyrunning and ski mountaineering world champion. He would not be were there not associations providing a foundation for these events. But I think you can see that Kilian does not do what he does only because there are races to win.

The self-defining words of Don Bowie and Kilian Jornet are Big Ideas that can carry you through a lifetime lived up-mountain, out of doors.

But look, these two guys, they're up there, you and I are down here, working our jobs, loving our spouses, raising our children, protecting those under our care and these are Big Ideas too. How do you cram all these Big Ideas into one life? How do all these Ideas make space for themselves in one person's heart? I don't know, but they do. All these Ideas can be substantial, with heft. The trick is for these Ideas to defy physics, to have mass but not weight.

This is all easy to write. Circling back to the Forum member I wrote about in the first installment of this series, sometimes the early mornings, the long sessions, the cold, the heat, the exhaustion, the jam-packed schedule, the equipment that needs expensive replacement, is a rough go. If you discount the numbing routine, paralyzing regrets, and grinding bereavements, life is a bowl of cherries. Sometimes it seems the only thing worse than the weight and toil of marriage, the heavy responsibility of parenthood, the treadmill of work, and the maintenance of endurance lifestyle would be your life without any of those things.

But when it's good it's very good, and the sublime happens often enough.

[This is the 5th of 5 blog entries on the subject: Letters to a Friend; No Skill for Living; Who is an Athlete? Subversive Tri; The Boundary of Sport]