VO2 refers to the volume of oxygen that the body can utilize during intense exercise. It is a key indicator of cardiovascular fitness and aerobic endurance. Higher VO2 levels suggest that the body is more efficient at delivering and using oxygen, which is essential for sustained physical activity. VO2 is typically measured in milliliters of oxygen used per minute per kilogram of body weight (ml/min/kg). Athletes often aim to improve their VO2 through training, as it can enhance performance in endurance sports like running, cycling, and swimming.