Plenty of research touts the importance of cardiorespiratory fitness (CRF)—also known as cardio fitness, cardiovascular endurance, and aerobic fitness—as a health marker, as well as an athletic ...
Photo illustration: Graham Bower/Cult of Mac Apple’s VO 2 max metric measures the performance of your heart and lungs when you push yourself to the limit. Up until now, though, it’s only been useful ...