Kaplan really emphasizes this curve is super important, but i don't understand it that well conceptually...can someone briefly explain why it shifts what the shifts mean etc (in layman's terms)
I'm pretty sure it's the other way around, left-shifted is more saturated (hence more affinity) and right-shifted is less saturated (less affinity)
does an altitude increase= left shift? and why do athletes sometimes train in high altitudes?
I thought those people just have more RBC's and are more 'barrel-chested' (Quechas)The answer to your first question is quite difficult, as it depends on what stage of acclimatization you are at. Simply put, people who have lived at altitude for long periods of time usually have some sort of respiratory alkalosis, which would be a left shift. If you want to know more, I'd love to discuss it with you.
As for the second part of your question, athletes train at altitude because the PO2 causes an increased production of red blood cells. More RBCs = increased oxygen carrying capacity, etc.
It's interesting that you mention the barrel chest trait. Generally people with a barrel chest have a harder time ventilating, so I am curious as to how it provides an advantage to those at altitude.
Heritability studies in the Andes
In the mid-1800s, Denis Jourdanet, an early researcher into high-altitude adaptation, described the high-altitude native as having a ‘vast chest [that] makes him comfortable in the midst of this thin air' (Houston, 1987). This is one of the earliest descriptions of what may be the most commonly cited characteristic of New World high-altitude natives: the relatively large ‘barrel chest'. Alberto Hurtado (Hurtado, 1932) commented on this characteristic in Andean populations and postulated that the enlarged chest could allow for increased lung volumes and thereby increase oxygen uptake. Whether this chest morphology is a genetic characteristic has been the subject of numerous studies.