How is cardiovascular endurance defined?

Cardiovascular endurance is fundamentally defined as the body's ability to sustain physical activity over an extended period. This concept emphasizes the efficiency of the cardiovascular and respiratory systems in delivering oxygen to working muscles during prolonged exercise. When an individual has high cardiovascular endurance, they can engage in activities such as running, cycling, or swimming for longer durations without excessive fatigue, making option B the most accurate definition.

While strength training and muscle power (as referenced in the first option) are important components of overall fitness, they do not relate to cardiovascular endurance. Likewise, the speed at which someone can run pertains to performance metrics and may not accurately measure endurance itself. Finally, flexibility of the heart muscles is not a recognized factor in determining cardiovascular endurance, as it is more about the overall capacity of the heart and lungs to support continuous physical activity rather than the flexibility of the heart's structure.