Some sharks have to keep swimming to maintain the flow of water through their gills. (It's true there are sharks who can lie still on the bottom, but not all sharks can do this.)
The point is: sharks move to live. And so should we.
Now I like to sit on the couch and watch sports as much as the next guy, but I've learned over the years that not only will exercise lengthen your life, it will improve the way you live it.
It's easy for people to get discouraged about exercising. After all, it's work. And the last thing you want to do after working all day...is more work. But the benefits are fantastic. If you have a sport that you love, great, go play that. But if you're not sure what exercise to choose, a strong case can be made for walking and running.
Walking or running is freedom. You can walk where you want, when you want. No worrying about whether the gym is open. You can go right out your front door. Some people prefer parks because you don't have to dodge traffic, so that's worth considering depending on where you live.
Walking is self regulated. When you're tired, stop. Sit down. You choose your distance and you set your own pace. Walking is not expensive. You really only need a decent pair of shoes. Comfortable clothes and a bottle of sunscreen are good, too. Depending on your health and fitness, you can gradually increase your pace until you're running, which opens up new possibilities in terms of distance and speed.
While activities like cycling and swimming are low impact and good for you, walking has an advantage in that it is 'weight bearing.' It will help maintain your bone density as you age because you are carrying your own body weight, versus a bicycle or water carrying your weight.
Physical fitness isn't the only benefit, either. The stress release you'll experience can be just as important. When you walk, you can set aside your problems (and turn off your cell phone) and be inside your own head. You can clear your thoughts and simply exist in the moment.
From the distant past when early humans were hunters and gatherers, we were made to move across the landscape on our own feet. To see new things, to feel the breeze in our faces, to sweat, to breath deep. To live.
So go take a walk. You'll feel a whole lot better.
(If you need some encouragement, call a friend and agree to meet up for a walk. Or pick up an issue of Runners' World for inspiration. Or visit Active.com or one of the many other fitness sites online. Or read Haruki Murakami's excellent book WHAT I TALK ABOUT WHEN I TALK ABOUT RUNNING.)
(The pic is from: dsc.discovery.com)