I have a totally ruptured L4-L5. Can't sit in chairs nor car or airline seats. An upright bicycle would leave my left side numb and in pain: all bumps would be transmitted directly up my spine. I ride a Roubaix road bike with bars nearly level with the saddle and lean forward 40-45 degs, I think. Do multiple centuries in a row with this setup. Lower bars wouldn't make the disk problem worse. I just don't have the flexibility anymore for lower bars.