What is one reason some people struggle to sustain cardiovascular activity?

One reason some individuals struggle to sustain cardiovascular activity is due to a lack of oxygen delivery to the muscles. During aerobic activities, the muscles require a significant and continuous supply of oxygen to generate energy efficiently. When the body is unable to deliver enough oxygen, muscle fatigue sets in quickly, limiting stamina and performance.

This physiological process is crucial during sustained cardiovascular activities such as running, cycling, or swimming, where the heart and lungs work together to supply oxygen-rich blood to the working muscles. Factors such as cardiovascular fitness levels, respiratory health, and overall efficiency of the circulatory system can all impact oxygen delivery. If any of these systems are compromised, aerobic performance can suffer, leading to difficulty in maintaining prolonged physical activity.

The other options highlight separate factors affecting physical performance but do not directly address the critical aspect of oxygen delivery, which is central to sustaining cardiovascular activity. Hydration, muscle mass, and coordination are important in their own rights but are not as directly related to oxygen delivery during sustained aerobic exertion.