Which term describes the ability of the lungs and heart to deliver oxygen to working muscles?

The term that accurately describes the ability of the lungs and heart to deliver oxygen to working muscles is cardio-respiratory endurance. This concept refers to the effectiveness of the cardiovascular system and respiratory system in providing oxygen to the body during sustained physical activity. High cardio-respiratory endurance indicates that the heart can pump blood efficiently, and the lungs can oxygenate that blood adequately, allowing the muscles to perform at optimal levels over extended periods.

In the context of overall health and fitness, good cardio-respiratory endurance is essential as it is linked to improved performance in physical activities, better recovery after exercise, and enhanced overall well-being. The other options, while relevant to various aspects of fitness, do not specifically address the combined functions of the heart and lungs in oxygen delivery. Muscular power focuses on the maximum force produced in a single effort, muscle flexibility pertains to the range of motion in the joints, and overall fitness encompasses a broader range of components including strength, endurance, flexibility, and body composition, making cardio-respiratory endurance the most precise term for this specific physiological function.