How do you get stronger?

i run track but its come down to my strength. Im a sprinter. i have been working out almost all summer doing all sorts of powerlifts and crazy stuff. We lift alot of weight too normally over 230 for squats...but my upperbody and hamstrings never get anystronger no matter what. Doing upper body work is so unnatural feeling and very painful for me. How can i see some improvements?