I normally don't sit and read the warning signs before riding coasters. I know that nearly every coaster advises guests with heart, neck, or back problems to not ride. And nearly every thrill ride has a sign stating that pregnant women should not ride. However, I saw that Alpengeist's information signs said that guests with leg prostheses are not allowed to ride. It may seem a little harsh, but it makes sense that a loose prosthetic limb would be a hazard to other park guests. And since a rider with amputated limbs may not be adequately restrained by the car's harnesses, I understand the requirements imposed by the park.
Another sign states that "Guests of Exceptional Size" should attempt to sit in Row 5 as those four seats are designed for larger riders.