Which component of fitness involves prolonged exercise capacity?

The component of fitness that involves prolonged exercise capacity is cardiovascular endurance. This aspect of physical fitness is crucial because it reflects the body's ability to sustain moderate to high-intensity exercise over an extended period. Cardiovascular endurance is largely determined by the efficiency of the heart, lungs, and blood vessels in delivering oxygen to working muscles during sustained physical activity. Activities such as running, swimming, or cycling test and improve this type of endurance.

Muscle strength, while important for overall fitness, pertains to the maximum force that a muscle or muscle group can exert in a single effort rather than the duration for which that effort can be sustained. Flexibility relates to the range of motion around joints and does not specifically involve prolonged exercise. Balance involves the ability to maintain body position and stability but is not focused on the capacity for sustained physical activity. Thus, cardiovascular endurance is the most relevant component to prolonged exercise capacity.