Erythropoietin (EPO) gained notoriety in 1998 when a bunch of cyclists in the Tour de France got caught in possession of it.
EPO increases RBC in the blood. This will basically raise your energy levels (Cancer. 2003 Sep 1;98(5):1072-9), and thus will improve recovery, etc... A50 was developed for a very similar purpose as EPO, and I suspect that a lot of the muscle enhancing effects/potency of A50 (increased muscle fullness, etc...) can be attributed to the much of same mechanisms which are at work in EPO. Its worth noting that EPO increases protein synthesis, just like A50 as well. Primarily, though, its effect is to increase RBCs.
Having more RBCs, thus having more oxygen delivered to muscle tissues is directly associated with a substantial improvement in athletic performance, i.e speed, endurance, strength, etc...(Sports Med. 2003;33(3):187-212.). EPO is associated with improved bodyweight, exercise capacity, oxygen uptake, respiration, whole body metabolism and energy efficiency (Semin Oncol. 2002 Jun;29(3 Suppl 8):69-74) In addition, cognitive function (learning, etc...)is also improved with EPO(Clin Breast Cancer. 2002 Dec;3 Suppl 3:S116-20).
Ok... so how much do you take? I´d say you´ll need about 8,000-10,000IU for 2 weeks. That´s it. You take it all at once over 2 weeks (maybe a little over 1,000IU or so per day for 14 days) and then that´s it. Then, sometime in week 3, you´ll start feeling the results...which will last...for 3-6 months! Yeah, you read that right.
Watch your BP, and don´t let it get out of hand, because that could mean your hematocrit is getting too high... and remember to keep well hydrated to avoid any possible issues with clotting & keep some aspirin on hand just in case you find that you need to thin your blood out a bit.