Sorry for the triple post. Some context on fluid loss, plasma volume loss, performance and dehydration:
What is also noteworthy from this study was that the crampers had an average loss of body weight of 2.9%, compared to 3.6% for the non-cramping controls. In otherwords, the people who DID NOT cramp lost more weight than the people who did. It goes further than this, because Schwellnus et al were able to measure the change in plasma volume as well – a more direct measure for what is happening to fluids. Here, they found that the crampers actually gained a small amount of 0.2% during the race. The non-cramping control subjects LOST 0.7%. So the sum effect of this data is that it suggests very strongly that cramping is not associated with dehydration, or with lower serum electrolyte levels, which is what we have had drilled into us for many years!
Talking about cramping, but gives some context on what kind of blood volume loss is normal for performance to be maintained. In Paula's case, that of winning a world championship by the largest margin ever, she definitely maintained her performance,
In 1979, Ethan Nadel published a study [1] where he compared exercise in the heat to exercise in the cold, specifically to look at the circulatory system. In that paper, he showed that the challenge to the circulation as a result of plasma volume contraction was more than adequately met by a redistribution of blood from the splanchnic, renal and gastro-intestinal circulatory systems.
Is there a challenge to the circulation whenever plasma volume is reduced (be it high temperatures or fluid loss)? Yes, but the body is more than capable of adjusting to this ‘stress’. A number of other studies by scientists in Denmark particularly (Savard, Nielsen, Nybo) confirmed this for exercise in the heat.
this quote touches on the mechanisms that the body uses to maintain plasma volume. The body needs to maintain a pretty constant volume, just for regular function. The kind of volume loss that Paula is claiming is responsible for such a change in HGB could not be possible if her body compensated for her dehydration in such a way observed by Nadel.
The extra HGB had to come from somewhere. Too much is observed for it to have increased due to changes in blood vlume (even the extreme changes of dehydration, which it should be said, Paula did not face an extreme case of severe dehydration: she would not have been able to dominate in such a way if she had.)