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Originally Posted by pgardn
There have been some trainers that say the better long distance horses have large spleens. They claim that the spleen releases a large amount of extra RBC's when horses are put to longer running tests.
Having been a runner for sometime, I never encountered any information of this type for humans. The spleen does hold large amounts of excess RBC's but they are usually released during trauma involving blood loss, not during running. I had never heard about making sure you train long enough so that your spleen releases blood.
So whats the deal with the horses spleen?
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The spleen stores red blood cells. Release is dependent upon catecholamine release and sympathetic nervous system stimulation (fright, flight, exercise, suffocation/asphyxia, excitement, bleeding/hemorrhage, etc).
Horses are better at it than humans (being prey animals), able to increase the number of red blood cells in circulation quite quickly and markedly. This aids oxygenation (along with other physiologic changes happening concurrently).
Appropriate exercise and training regimines cause metabolic adaptations that make such processes more efficient. The metabolic adaptations required by and ideal for sprinting vs long distance exercise vary.
I sent you something in more detail privately.
