VO2 max is an intimidating word for an easy-to-understand biometric: It’s how well your body uses oxygen when you push yourself. That plateau marks your VO2 max, the upper limit of your aerobic capacity. That lingering doubt is part of what makes VO2 max such a maddening and compelling metric. Higher VO2 max levels correlate with a lower risk of cardiovascular disease, type 2 diabetes, stroke, and certain cancers. “There are certain intervals you can run based on VO2 max pacing and effort.”