Explain why the greatest benefits to cardiorespiratory fitness come from sustained physical activities like running walking an cycling

Sustained physical activity lets the body to put effort in its muscles while giving out oxygen to the muscle groups. This activity progresses the muscle groups as well as to the cardiovascular and respiratory systems that transport oxygen to the muscles through blood flow. Sustained physical activity maneuvers all these systems in concert and increases cardiorespiratory fitness levels.

Running, walking, and cycling are great ways to increase your cardio respiratory  fitness because they make your lungs work harder and heart beat faster so they can keep up with your muscles, which helps you get or stay fit.