Cardiovascular fitness refers to the efficiency of the heart, lungs, and blood vessels in delivering oxygen to muscles during sustained physical activity. It can be measured using various tests, including the VO2 max test, which assesses the maximum oxygen uptake. Other methods include the 1.5-mile run, step test, or heart rate monitoring during exercise. Improving cardiovascular fitness can lead to numerous health benefits, such as reduced risk of heart disease, improved stamina, and enhanced overall physical performance.