Which component of health-related fitness includes both aerobic capacity and stamina?

The component of health-related fitness that encompasses both aerobic capacity and stamina is cardiorespiratory fitness. This aspect of fitness is particularly crucial as it refers to the ability of the heart, lungs, and vascular system to deliver oxygen to working muscles during sustained physical activity. A well-developed cardiorespiratory system allows an individual to engage in aerobic exercise over extended periods, which directly relates to both aerobic capacity—how much oxygen the body can use during exercise—and stamina—the ability to maintain prolonged physical effort.

Improving cardiorespiratory fitness involves activities that elevate the heart rate for an extended duration, enhancing overall endurance and energy levels during various forms of physical activity. This is why choices related to flexibility, muscular endurance, and body composition do not fit the criteria outlined in the question. Flexibility pertains to the range of motion in joints, muscular endurance relates to the muscle's ability to perform repeated contractions over time, and body composition refers to the proportions of fat and non-fat mass in the body. None of these directly measure an individual’s aerobic capacity or stamina as cardiorespiratory fitness does.