What is a primary determinant of aging-related VO2 max decline?

What is a primary determinant of aging-related VO2 max decline?

• A. Reduced maximal cardiac output.
• B. Increased lung capacity.
• C. Increased heart rate with age.
• D. Increased muscle glycogen stores.

Answer: (A)

The main idea is that VO2 max at peak exercise is driven by how much blood the heart can pump, i.e., maximal cardiac output. VO2 max equals maximal cardiac output times the arteriovenous oxygen difference (VO2 max = Qmax × a-vO2 difference). In aging, the capacity to increase cardiac output during maximal effort drops because both the heart’s rate response and its stroke volume are reduced, and arteries may stiffen, all limiting how much blood can be delivered to working muscles. When delivery declines, oxygen extraction by muscles can’t fully compensate, so VO2 max falls primarily due to reduced maximal cardiac output.

Increased lung capacity isn’t a driver of aging-related VO2 max decline; in fact, lung function tends to worsen with age rather than improve, and it usually isn’t the primary limiter at maximal exercise. An age-related rise in heart rate is also inaccurate—maximal heart rate tends to decrease with age, not increase. Increased muscle glycogen stores don’t determine VO2 max, since it’s about oxygen delivery and utilization rather than fuel reserves.