The last paragraph about marathons reminded me of a PBS Nova documentary about a dozen people who just picked up running to compete in the Boston Marathon starting off from basically couch potato status.<p><a href="http://www.pbs.org/wgbh/nova/marathon/" rel="nofollow">http://www.pbs.org/wgbh/nova/marathon/</a><p>I won't spoil it for you but it does not end like you expect.<p>I personally found that doing away with car and biking two hours a day has done me well. By combining exercise and commuting times I save a great deal of time.