Having been a long-distance runner for nearly all of my life, it has surprised me how little respect cardio gets these days. Trust me, I love my cardio...but there are some downsides to cardio that can't be avoided. While it has always been a great stress reliever in many ways in my life, research also shows that is creates lots of oxidative stress (which makes us age faster) and can be tough on the joints. And I wouldn't want to forget that it also tends to be less effective as a fat loss tool for most of us than lifting weights. Why weights?