hey dude you may find it hard to put on mass training 4 days a week as a natty-
you may also find that you`ll grow quicker just using compound exercises till you are big enuff to NEED to shape a muscle.
what are you doing for legs bud?
btw i only train 2x a week and usually only do 1 exercise per body part
whilst concentrating heavily on legs.(squats and deads are THE biggest growth exercises for the whole body)
einsteins mind was the key to all things...to understand more than to know.
www.englishmuscle.co.uk
www.extremenutrition.co.uk