What best defines cardiovascular fitness?

Cardiovascular fitness is fundamentally defined as the ability of the heart and lungs to supply oxygen effectively during sustained physical activity. This aspect of fitness is crucial because it indicates how well the cardiovascular system can deliver oxygenated blood to working muscles, which is essential for endurance activities like running, cycling, or swimming. When cardiovascular fitness is high, the body can perform prolonged physical activities with greater efficiency and less fatigue, as the heart can pump blood more effectively, and the lungs can facilitate better oxygen exchange.

This definition encompasses not just the strength but also the efficiency of the cardiovascular system, making it a vital component of overall fitness. Improving cardiovascular fitness can significantly enhance an individual's performance and overall health, lowering the risk of various diseases.