base2 

If my understanding is wrong, I'll be the first to admit that I am about to learn a new thing. Having said that: My understanding is that EPO is a hormone excreted by the kidneys that tells the body to make more blood. This increases the blood amount in people. My understanding is there is a limit to how effective it is. At some point there just isn't room in your body for more. At that point no additional amount of hormone is going to have the desired result. The body becomes non-responsive to it in the same way a diabetic may stop responding to insulin. You can get there by 2 ways. Driving your kidneys to make it through an elite training program until you obtain peak physical fitness, at the same time as also being in top form. The other way is to add it to your body in some way. Either way, when peak fitness/form is reached, the additional hormone ceases to have the desired result.

What Lance did was add more blood to himself. An extra pint or 2 meant his blood was under 1/8 less stress or could deliver 1/8 more oxygen/nutrients to his muscles & could take 1/8th more products of metabolism away.

Now his body had to process out that extra pint or 2, and that is a different discussion in term of human physiology. But nothing a healthy human couldn't sustain. But adding blood is a different animal than EPO even though for regular people the results are the same. More blood. For elite athletes, like Lance though, I always thought adding blood starts where EPO ends.

I am genuinely curious if there is a doctor or other medical professional here in this forum that could chime in. I'd actually like to know if my understanding is correct & if not, what nuance I missed.