Dear Tester321,
Congratulations on your determination to get in shape, part of which is getting some muscle definition in your legs. I wish I had known at 20 what I now know at 56; I'd probably be in much better shape. You are off to a good start; don't let the nay-sayers ever distract you.
Almost all authorities, especially the ones who are in shape, will tell you that you need cardio, weights and good nutrition to get – and stay – in shape. They are right!
Jogging can certainly be a part of your program. So can other forms of cardio, some of which are not as high impact as jogging. No form of exercise is exclusively cardio or exclusively resistance. In fact, even using an elyptical trainer with adjustable tension can be viewed as resistance exercise and will build muscle.
Keep it up and have a happy new year 2010!