 Non-disabled sprinters have calves and ankles that return and amplify the energy supplied by their hips and knees, while Pistorius compensates with additional work because he does not have calves and ankles with their associated tendons and muscles.An analysis published by "Engineering & Technology" magazine estimates that in using the blades, Pistorius must generate twice the power from his gluteal and quadriceps muscles that a normal sprinter would.Other sources also credit core abdominal muscles and a faster arm swing.