[BigAls87Z28]

Cardio wont "ruin" your hard earned work. Marathon runners's muscles dont look to ruined.
I dont know many wrestlers lost tallent by running constantly. If you have ZERO fat and ZERO sugars, yes your body will go to the 3rd and last source of energy, and that is protien which is muscle.
But that is not the case here.
Yeah, you sweat lifting, but you dont get your heart rate up high enough, long enough, to burn fat. Target heart rate is just something to guide you, to give you an idea where you need to be. Sweating from lifting is because you are lifting. You can sweat lifting boxes, but I dont see too many "in shape" UPS or any othe rtype of delivery guys.