On Saturday, my son and I both competed in a local sprint triathlon. Mine was a traditional sprint with a 325-yard swim, 11.5-mile bike, and 5K run. His was shorter but no less intense: a 25-yard swim followed by a half-mile bike and quarter-mile run. Most kids his age are unable to do anything but go all out, so it’s a pretty serious event.

I’ve been doing these for several years. In 2009, our local gym decided to add a kids’ triathlon event to their regular events for adults. It promotes family fitness and is fun for the kids — many of whom have just watched their parents compete in the “big” triathlon.

Why do I do triathlons? I like the sport because it’s fun and challenging and because I like to exercise toward a goal. The bigger question is…Why do I exercise?

I do it for a couple of reasons. Part of it is cosmetic, of course. I like to eat and my metabolism has started slowing down, so I have to work harder to stay in shape.

But another big chunk of it has to do with parenting. First, for me, it’s important to be as active a parent as my kids want me to be. I want to be healthy enough to chase them around the yard, jump on the trampoline with them, play basketball with them, climb with them up a mountain, or throw them around in the pool. And I want to be healthy enough to enjoy doing stuff with them for as long as possible. (Some of the most frustrating times in my life have been when I was injured and unable to really play hard with them.)

Second, I want to be a good example for them. Kids who see their parents committed to good health are more likely to live healthier lifestyles. If kids see running and biking and swimming as part of their dad’s life, it’ll become an important part of theirs, too. In fact, I look forward to the day when my son is old enough to participate in an adult triathlon (there were some 12 and 13-year-olds on the “real” course this weekend). I’d love to train together and compete together.

But I want it to be natural, too. Something they choose to do on their own, because they see it modeled for them.

I don’t want to be the kind of dad who pushes his kids to play outside, or participate in sports, but spends all weekend watching TV and never does those things himself. Like most kids, my own children are much more likely to do what I do than do what I say. So I try to do stuff they can aspire to.

Ten years ago, triathlons seemed like some crazy thing that ridiculous athletes did. It was something I wouldn’t have imagined ever attempting. Today, my kids think triathlons are those things their dad does every summer. They think it’s something they can do, too. In fact, they have done them. I’m proud of that — that working hard and playing hard and accomplishing things is becoming just a regular part of their life, an example they can see and hopefully emulate.