why do cardio on strength days??

do i really need cardio on the strength days?

i am a magazine junkie and love fitness related mags. so many of them encourage cardio all week long. i think this makes sense for someone who divides strength/weights between upper and lower body.

but for someone like me, who does full body strength/weights every other day...and cardio on off days. do i really need cardio on the strength days?

i ask this because i really challenge myself with strength so my heart rate is UP for 45min during the workout. doesn't that give me enough calorie burning (actually--i think i may burn more).

anyone have any knowledge to drop on me in this area?

thanks!!! :)

My understanding is that cardio is defined by keeping your heartrate in the correct zone for an extended period of time, it doesn't matter what you're doing (walking, running, swimming, biking, mountain climbing, lifting weights).

that could make sense, where would interval cardio fit into that?