Some of my fondest memories with my YF was when he would sit close to me and practically beg me for a back rub. He loved them, I loved them, and it was always a wonderful time of closeness between us. There was never anything sexual or wrong about those back rubs, and we enjoyed them so much, I can't imagine our friendship without them. By all means, do the back rub, you will love it! (So will he!)