A quick recap on VO2 max: it’s a measure of how good your body is at using oxygen during exercise — basically how well your heart, lungs, and muscles work together. You can get it from certain smartwatches or from a treadmill test. You can also get a quick estimate using your max heart rate (maxHR). A simple rule: 220 – your age. So if you’re 40, your maxHR is ~180 bpm. Once you know that, you can see what “intensity zone” you’re in. Example: If you’re 40 and your heart rate on a walk is around