Endurance training can increase diffusion capacity, aiding oxygen delivery to muscle. Which statement best describes this relationship?

Endurance training can increase diffusion capacity, aiding oxygen delivery to muscle. Which statement best describes this relationship?

• A. It reduces diffusion capacity.
• B. It has no effect on diffusion capacity.
• C. It increases diffusion capacity, aiding oxygen delivery to muscle.
• D. It increases diffusion distance.

Answer: (C)

Endurance training improves diffusion capacity for oxygen from the blood into muscle, boosting delivery to working muscles. This happens mainly because repeated aerobic work stimulates the growth of more capillaries around muscle fibers (angiogenesis). More capillaries increase the surface area available for gas exchange and shorten the average distance oxygen must diffuse from capillaries to mitochondria. With a greater rate of oxygen diffusion and better extraction by mitochondria, muscles receive the oxygen they need to sustain aerobic metabolism during prolonged exercise. In short, increased capillarization and shorter diffusion distances make oxygen transfer into muscle more efficient, enhancing endurance performance.