Well, as a professional athlete, you are not allowed to use any "foreign" blood, or even your own blood for a transfusion, especially not before a competition. That gives you an advantage to other athletes, which is doping! Those are the rules, I did not invent them...
Pretty shady and very dangerous, athletes have died because they used blood that wasn't cooled well or just was not their blood type, and it is performance enhancing, so...
Well, as a professional athlete, you are not allowed to use any "foreign" blood, or even your own blood for a transfusion, especially not before a competition. That gives you an advantage to other athletes, which is doping! Those are the rules, I did not invent them...
Pretty shady and very dangerous, athletes have died because they used blood that wasn't cooled well or just was not their blood type, and it is performance enhancing, so...