A few weeks ago I was jogging on a treadmill in a hotel and a light bulb went off. Why was I running a drab hotel workout room, when I had beautiful San Francisco right outside my door? I hopped off the treadmill and ran outside. A few days later I ponied up for proper running shoes, shorts and shirt. I've been running a few times a week ever since, and I'm loving it. I've been riding my mountain bike hard for a couple of decades, and it's still the love of my athletic life, but I must say I'm enjoying a new kind of exercise. I travel a fair amount, so exercise is critical else I fall victim to stagnation on the road. Big meals, confined spaces are not conducive to good life.
A huge upside is that I can run anywhere in the world without having to deal with a lot of equipment, or workout room roulette at a hotel (does the hotel have one, is it full???). Running gear fits simply into my already small travel bag. I'm really glad I've found a portable way to move my body and work my lungs.
Onto the physics and biology. My body had become accustomed to biking. All of my muscles and joints had figured out the movement of the bike, and everything just settled in about ten years ago. The result was my chest and stomach got lazy, while my legs and arms got solid. Running is mixing all of that up again, and I'm psyched. While it's not as good as focused anaerobic exercise on my chest and stomach, they're at least engaged when I run. I'm finding running to be more of a dense exercise. I burn calories at about a 33% increased rate which is cool, and I suspect the result of not ever "coasting downhill" as one does when biking; it's non-stop.
The first several runs left me with some hip and back-of-the-knee pain, but that has subsided and I suspect was simply my body getting used to new, jarring, movement. Here's to a more cross-trained exercise regimen!