John Register’s Olympic dreams were crushed while he was training for Atlanta in 1994. An improper landing from a hurdle jump hyper extended his knee, severing a leg artery and ultimately leading to an amputation. Register was faced with a choice between confinement to a wheelchair or a prosthesis followed by intense therapy and rehabilitation. The desire to be independent and mobile led him to opt for the latter. Register was fitted with an above-knee prosthetic leg. The limb consisted of soft, flexible plastic and carbon graphite with openings to allow the thigh muscles to grow. This was revolutionary compared to ordinary prosthetics, with their hard, rigid sockets. Non-pliable materials confine the muscles, causing them to atrophy. Prosthetic composition was a necessary consideration for John Register; compliant substances absorb the impact of heel strike, and the muscles can generate the necessary energy to move the knee and proceed through the stride. If the material is too compliant, there is not enough reaction force to propel the leg forward into swing phase. In this situation, the knee and hip must generate a large amount of force to continue the motion, costing the amputee a great amount of extra energy and work.

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