I had a ruptured disk repaired, but it could not be totally corrected, so I have to be extremely careful with rides that jerk side to side or stop/start quickly. I can still do Kali. There's really only one spot that causes me any discomfort and that's at the end when you bump into the sides and people in front of you. As long as I know it's coming, I can be prepared. I've been able to do it without hurting my back. Space Mountain is an absolute no for me. One side is worse than the other. It even bothers my 19 year old when she's on that side. Her neck hurt for quite a while after getting off a couple of trips ago. I can do Splash with no problem. The water at the drop keeps things fairly smooth. I can do KS now. When they were doing that chase the poachers scenario, I had to stop riding it, but now I can ride again. 7DMT is smooth, but the way it swings out did bother me. I won't be doing it anymore either. I didn't do TT after my surgery for fear of the braking and the curvy track, but I tried it last trip and was able to do it without a problem. However, I do these rides knowing how to lean or brace which keeps me fairly safe. My daughter rode with me and warned me when anything that might bother me was coming up. Actually, one of the worst rides for jerking is TSMM. I am still able to do it. Just be aware that it does jerk quite a bit.