There is a famous story about Pilates' inspiration for his unique apparatus. Before World War I he was touring England as a circus performer and professional boxer, and even teaching self-defense to the Scotland Yard police force. But when war broke out, he found himself interned in England as an enemy alien on the Isle of Man.
The health conditions in the internment camps were not great, but Pilates insisted that everyone in his cell block participate in daily exercise routines to help maintain both their physical and mental well-being. However, some of the injured German soldiers were too weak to get out of bed. Not content to leave his comrades lying idle, Pilates took springs from the beds and attached them to the headboards and footboards of the iron bed frames, turning them into equipment that provided a type of resistance exercise for his bedridden "patients."
These mechanised beds were the forerunners of the spring-based exercise machines, such as the Cadillac and the Universal Reformer, for which the Pilates method is known today.