The most common test used to assess cardiovascular fitness is the VO2 max test. This test measures the maximum amount of oxygen the body can utilize during intense exercise, indicating aerobic capacity and endurance. During the test, an individual typically performs incremental exercise on a treadmill or cycle ergometer while their oxygen consumption is monitored. A higher VO2 max indicates better cardiovascular health and fitness level, making it a valuable measure for athletes and individuals seeking to improve their fitness.