Well...the thing is that most forms of cardio focus on the legs, so the other mucles that are not in use (i.e. upper body) are just waiting around for nutrition...most of which are going to the legs and heart in order for you to do the cardio. If you *really* want to do cardio on a lifting day, the best thing is to do them on opposite end of the day. For example, I have a combined day on Thursday...I run in the morning and lift in the evening. Of course, I'm training for a half-marathon so it's more of a case that I *really* want to lift. It's completely optional and doesn't really help me that much with the running. In some ways, if I don't do it right, it will work against me (i.e. extra weight and bulk I have to run around with.) By the same token, cardio in a weight lifting regimen is optional and can work against you if not done right. If you really are doing it to keep weight down, you are better rewarded by focusing on your caloric intake. The weight lifting will take care of the rest. Better still, don't do cardio for the sake of doing cardio, but as a component of a sport or activity you love that you can practice on the weekend...you know...like paintball.

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