This device for the training of a human body extremity in the practice of a specific physical activity, is comprised of a concave mould that, made up of at least a rolled piece of light and substantially rigid material, the first part is shaped on the inside which is adjusted and substantially wraps around the extremity and its joint to a limb. This being the part where the immobilisation is kept held to the optimally correct position for a piece of equipment for the exercising of the type of action in the specific physical activity, and a second part that is adjusted and substantially wraps the part of the member next to the joint.