Endurance training can increase VO2 max in part by increasing which of the following?

Endurance training can increase VO2 max in part by increasing which of the following?

• A. Increase maximal arteriovenous oxygen difference
• B. Decrease maximal arteriovenous oxygen difference
• C. No change in arteriovenous oxygen difference
• D. Increase capillary density

Answer: (A)

VO2 max at peak exercise depends on two things: how much blood can be pumped (cardiac output) and how much oxygen is extracted from that blood by the working muscles (arteriovenous oxygen difference). Endurance training raises VO2 max partly by boosting the muscle’s ability to extract oxygen. Training makes muscle tissue more oxidative: more mitochondria, higher oxidative enzyme activity, and more capillaries around fibers. These adaptations allow muscles to take up more oxygen from the blood during max effort, increasing the arteriovenous oxygen difference. While greater capillary density supports oxygen delivery and utilization, the most direct impact on increasing VO2 max in this context is the larger arteriovenous oxygen difference driven by improved oxygen extraction.