According to the material, which factor contributes to a higher VO2 max in males than in females?

• A. Higher hemoglobin concentrations
• B. Larger body size
• C. Both higher hemoglobin concentrations and larger body size
• D. Neither factor contributes

Answer: (C)

VO2 max depends on how much oxygen is delivered to and used by working muscles. Two factors that differ between males and females help explain why males often have higher absolute VO2 max: the oxygen-carrying capacity of the blood and the size of the body.

Higher hemoglobin concentration means each liter of blood can carry more oxygen, so arterial oxygen content is greater. With more oxygen available in the blood, more can be delivered to muscles during maximal effort, increasing VO2 max.

Larger body size typically comes with more muscle mass and a bigger heart, which supports a higher maximal cardiac output. A greater cardiac output means more oxygen-rich blood is pumped to the muscles at peak exercise, further elevating VO2 max.

Since VO2 max is the product of cardiac output and the oxygen extracted by tissues, both a higher oxygen content (from more hemoglobin) and a greater delivery capacity (from larger body size) contribute to higher VO2 max in males. When VO2 max is expressed relative to body mass, the difference can lessen, but these factors still explain the higher absolute values typically seen in males.