The weather was fantastic over the weekend, clear, bright, and just a little cool. Not being one to waste a rare opportunity like that, I took advantage of it and went for some extended kicking sessions on both Saturday and Sunday. The exercise was great. I put a lot of miles on my kickbike and hopefully did my body a lot of good in the process.
As I expected after all that exercise, I could feel the impact on my body. By Sunday evening I could feel muscles I didn't know I had, or at least muscles I hadn't paid any attention to for a long, long time. They felt warm and stretched. They weren't in pain, and they weren't crying out for attention. It felt extremely satisfying.
The thing that really struck me was how different the feeling was compared to times that I had gone jogging or for an extended bicycle ride. I knew from bitter experience that when I had jogged or cycled putting out a similar amount of effort for a period of hours I would be in a world of hurt. My muscles would have been ready to go on strike, or close to it. After a long jog my knees, ankles, and especially my feet would be in severe pain. If I went for an extended cycling session, my feet and ankles would be okay, but my knees and my butt would be doing the complaining. Yet I didn't experience any of this after using my Kickbike for hours, two days in a row. Obviously there was something very different going on.
This got me to thinking about my high school physics classes, especially about how force vectors can be broken down into their horizontal and vertical components. I sketched out a few simple diagrams, and tried to get a handle what happens when I jog versus kick. I've gone through this particular analysis before, but my weekend experience made it even more obvious and relevant.
When I jogged a large part of the force applied by my body went into keeping me from crashing to the ground, decelerating then accelerating with each step, and pushing off from the ground to launch myself forward. Not only was there a lot of vertical motion, there was also a lot of force and physical work that my body had to generate. All the vertical motion and effort did nothing to actually move me forward - it just served to keep me erect.
With kicking, in contrast, the vast majority of the effort I expend goes into forward motion. My body is supported by the non-kicking leg, and to a lesser extent by my hands and arms. My muscle movements and the force I apply goes into horizontal forward motion, not into wasted vertical motion. And I don't have the shock of constant vertical acceleration and deceleration. My hips go up and down a bit while kicking, but nowhere near as much as when I jog. Yet I get plenty of exercise - a real aerobic workout for my whole body.
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