I tried riding a bike for my back (a human-powered 12 speed). I have scoliosis and I tried to strengthen my back muscles to stand upright. After a few miles, the muscles fatigue and worse posture occurs. I actually got asked if I was in pain on a group ride, the questioner looked hurt for me. He offered advice to help me, but I literally couldn't get my back to be straight the way requested. I must need more stamina. I can't imagine putting that compression upon a damaged back! You guys must either be tough or stubborn!