I am trying to apply a torque load to the inside of a circular shaft. Let me try to describe my analysis.

I am analyzing a component that would go on the shin of a prosthetic leg. An aluminum bar runs from the ankle and then inserts about a quarter of an inch into my cylindrical component. I would like to simulate someone walking with an alternating force applied to the heal then toe of a foot. I hope to do this with a torque load applied to the inside of my cylindrical component, but do not know a valid way of applying it.

Does anyone know and appropriate way to define the torque on the inside of my component? I appreciate your input!