I am an unofficial 3.0 player returning to the game after 15 years away. My father-in-law is a former state and conference champion (he played in both HS and NCAA). He was kind enough to hit some balls with our family on Saturday morning. I did my best and he said I did fine but man, my back is hurting. My mid/lower back hurts and I am leaning forward to compensate. I am thinking it started to hurt when I had a bunch of mishits, given that his shots were tough for me to handle. Is it possible that the shock from the mishits traveled up through my arm to my back? I play with a 24-year-old Prince oversize racket that was a hand-me-down from a family member. I have no idea what kind of strings are on it or what tension it is. The grip is kind of large since I over gripped it with some Prince splatter tape. Thanks in advance for any help!