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Resilience and Survival in Extreme Environments 145

The ancestral physiological phenotype

Oxygen-sensing mechanisms

Carotid Pulmonary General Kidney, Many tissues
body vasculature vasculature liver and organs

Altered
Hypoxic Redistributed VEGF1 EPO and expression of
ventilory pulmonary and metabolic
response circulation angiogenesis erythropiesis enzymes and
transporters

Blunted
Fuel
Blunted hypoxic Expanded Expanded preference
blood
HVR pulmonary RBC mass
vasoconstriction volume adjustments

“Downstream” consequences

Increased Dampened
Increased reliance on heart rate for CHO as
reliance on slow twitch a given preferred
aerobic fibers−tighter submaximal fuel for heart Blunted
metabolism coupling of work rate and muscle catecholamine
(low lactate energy (due in part metabolism response to
accumulation demand and to increased (increased exercise
during supply O -carrying ATP/O )
exercise) 2 2
pathways capacity)

Figure 7.1 Hochachka et al.’s conceptual schema of ancestral physiological

phenotype influenced by adaptation to altitude and its close relationship to
characteristics of individuals who are well-adapted to endurance performance.
Lowlander endurance performers differ primarily by upregulation of mitochon-
drial function (mitochondrial metabolic enzymes and transporters). (Redrawn
from Hochachka, P.W., Gunga, H.C. & Kirsch, K., Proc. Natl Acad. Sci., 95, 1915–
1920, 1998. With permission.)

then level off (Burse, Cymerman & Young, 1987). Insulin levels rise and then

return to sea-level values after 2 weeks (Young et al., 1987). Blood lactate

levels, which initially rise sharply after exercising at 14,000 ft ., return toward

sea-level baseline after 2 weeks. Plasma glucose levels remain unaff ected by

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