No, you take your own blood out, to reinfuse later, giving you a performance boost. It’s very difficult to detect, whereas it’s much easier to detect the use of someone else’s blood.
Am I right in thinking Preidler was providing his blood for others?
No, it would have been for autologous transfusion. Take your blood out when you don't need it, recover as usual, put it back in later and improve your oxygen transport capacity.
Am I right in thinking Preidler was providing his blood for others? I'm not sure I understand what it means by 'blood extraction'