How is cardiovascular endurance defined?

Cardiovascular endurance is specifically defined as the ability of the heart, lungs, and blood vessels to supply oxygen to the muscles during prolonged physical activity. This ability is crucial for sustaining activities that require continuous effort over an extended period, such as running, cycling, swimming, or playing sports. It reflects the efficiency of the cardiovascular system in delivering oxygen-rich blood to muscle tissues, which is necessary for maintaining activity and enhancing overall physical performance.

The other options do not accurately describe cardiovascular endurance. Lifting heavy weights pertains more to muscular strength rather than endurance. Stretching effectively is related to flexibility, and performing high-intensity interval training focuses on short bursts of intense effort, which can incorporate endurance but does not encompass its full definition. Therefore, the focus on oxygen delivery during extended activities distinctly identifies option B as the correct understanding of cardiovascular endurance.