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HMS, BM EQ-Bank 64 MC

During exercise at high altitude (3000 m above sea level), which of the following adaptations occurs first in the body?

  1. Increased production of red blood cells
  2. Increased breathing rate and depth
  3. Increased cardiac output
  4. Increased capillarisation
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\(B\)

Show Worked Solution

Consider Option B:  Increased breathing rate and depth

  • The immediate response to high altitude is hyperventilation to compensate for lower oxygen partial pressure

Other Options:

  • A is incorrect: RBC production (erythropoiesis) takes several days to weeks
  • C is incorrect: While cardiac output increases, it’s secondary to respiratory changes
  • D is incorrect: Capillarisation is a long-term adaptation

\(\Rightarrow B\)