Lactate and epinephrine during exercise in altitude natives

Area of Science:

• Exercise Physiology
• Altitude Adaptation
• Human Physiology

Background:

• Altitude natives are reported to have low blood lactate accumulation during exercise.
• It is unclear if this low lactate accumulation is resistant to changes in oxygen availability (hypoxia-normoxia transitions).

Purpose of the Study:

• To test if acute changes in inspired oxygen fraction affect blood lactate vs. power output relationship in altitude natives.
• To investigate if changes in blood lactate vs. power output are related to changes in blood epinephrine concentration.

Main Methods:

• Altitude natives (n=8) in La Paz, Bolivia (3,600 m) performed incremental exercise (one- and two-leg) under chronic hypoxia and acute normoxia.
• Measured blood lactate accumulation ([La]), blood epinephrine concentration ([Epi]), and oxygen uptake (Vo2) relative to power output (W).

Main Results:

• Blood lactate vs. power output relationships in altitude natives were similar to unacclimatized lowlanders.
• Acute normoxia shifted the lactate-power output relationship to the right, reducing maximum blood lactate by 7-8%.
• Blood epinephrine and blood lactate were tightly correlated (r=0.81) independently of oxygen availability.

Conclusions:

• Altitude natives' response to acute changes in inspired oxygen fraction during exercise is not fundamentally different from lowlanders.
• Normoxia attenuated increases in both blood lactate and epinephrine with exercise intensity.
• The findings suggest a loose linkage between glycolysis and oxidative phosphorylation influenced by epinephrine.