Your growing when your body is repairing it's self. If you don't let your muscles repair they will not grow. You just continue to break them down. Thus wasting your time. Also your whole body will grow much better if you train all of it. Especially legs. If you want to grow your upper body you must train your legs, and you must work your back. You only need to train each body part once a week. Use those 4 days to do

Day one Chest and tri's
Day 2 Legs
Day 3 off
Day 4 Back and bi's
Day 5 shoulders and traps
Day 6-7 off

If you want you can swap the arms
chest and bi's and back and tri's

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The Fool say in his heart "There is no God"