Read an article in a Reader's Digest while waiting with my daughter for an app't this afternoon. It mentioned a study where one group of women walked or jogged 5 times a week. Another group replaced two of those workouts with strength training. Even though the ones who did strength training actually did 30% less cardio, they did 7% better on cardio endurance tests and lost 2% of their body fat. Those who did only cardio LOST NONE! (Emphasis mine.) There was some other info, but I can't remember the rest of what it said. Something about your muscles continuing to burn calories after the workout is done. Yadda yadda, we should all know that by now. I was tempted to tear out the page, but my conscience won that battle. ;-)
So when you hear again and again and again that you need to add strength training, not just do cardio every day, BELIEVE IT! And just DO IT!