What’s the best way to accurately measure one’s VO2 max, or at least ballpark it sufficiently so that you can track improvement over time without it being lost in measurement noise?
Do you need to measure VO2 max specifically? If your form of exercise is jogging/running, you will easily be able to tell if you're improving by tracking distance and time of your runs. If you want to be precise, you can e.g. race a timed 5k once per month under the same conditions. But if you're a beginner, you won't need that to be able to tell you're improving, just the feel of difficulty to maintain a certain pace will change noticeably.
As someone else mentioned, a classic poor man's test of VO2 max is simply to time trial a set amount, such as seeing how far you can run in 10 minutes, and use a calculator. So the same thing with extra steps.
