Summer football training?

I play middle linebacker/fullback for my highschool and im 6-2 215. I run a 5-1 forty. My freshman year all my coach wanted us to do was lift weights....i dont dont understand what the problem is.....it makes you less likely to get injured, makes you stronger, makes you faster????i still dont get it. Run run run, if you not brawney then you gota be able to run like crazy....if cant break 'em out run 'em. you either have to be really fast like you or really big and be able to power run... what position are you trying out for? wide reciever?running back? you should think about this. with you present size probably one of them, to be a lineman you get start eating now and lifting to build that.d tackles have to be big in order to fill their gaps.....good luck with football!!!!