Cardio

What I have found the best to do for toning up your muscles and getting defined is swimming.  I swim a quarter mile every day, not all at once though.  I like to do one lap at a time, pretty intense speed, then rest, then do another.  This is a great form of cardio for all weightlifters because it takes a solid 30 seconds a lap .  When you do a set of benching or deadlifting or whatever exercise you may do, you push yourself really hard for about 10 to 15 seconds usually, sometimes more, and sometimes less depending on your rep range.  Well, this type of swimming is perfect for that, because it conditions your heart to work very hard for a shorter period of time, whereas long distance running or long distance swimming will make your heart healthier for the long haul.  I definitely am not gonna say that a long swim and a long run will not help you, but weightlifting wise, the proper way to do cardio should be in short fast movements.  Like sprints for example.  Another short but very intense form of cardio training.  Personally I don't like doing them because, after a while, they start to tear on your knees, but everyone is different.  Personally I have found that short quick swims are the best way to make gains in the weight room as far as cardio endurance.  Any form of cardio is bound to get you lean though, because you are burning calories.  It;s common sense, the more cardio you do, the more calories you burn.  You burn more calories with short quick motions than you do with a long slow cardio session.  Let's not forget that your heart is the biggest muscle in your body.  You have to make sure you work it just as much as every body part.  A simple 15 20 minute cardio session after every workout is all you need.