Cardiovascular fitness can be assessed using various tools such as VO2 max testing, which measures oxygen consumption during exercise, and heart rate monitoring during intense physical activity. Other methods include treadmill stress tests and predicting fitness levels through field tests like the 1.5-mile run or the step test. Wearable technology, such as fitness trackers and smart watches, can also provide valuable data about heart rate variability and overall activity levels, contributing to a comprehensive evaluation of cardiovascular health.