If you are in a gaining phase it would be advisable to not do cardio the day following leg training. This is when you are recovering. Although you are recovering for the entire week, you still have to live. Start cardio the second day after legs unless you are cutting for a show.
I'm sure you are aware that you can't gain and cut at the same time, so is your cardio for general fitness or to lean up?
MsFit
I never do aerobic exercises with my legs right after i workout hard with my legsdue to the fact that I destroy my legs and they need lots o time to recover.
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