What might be the significance of a sudden drop in estimated V02 Max as measured by a Polar Vantage M fitness watch?

Question

Many of Polar's fitness watches, to include the Vantage M model, have the capability to estimate V02 using heartrate variability as a proxy. There are at least a few peer reviewed papers that have concluded that these estimates are sufficiently precise to be used to track trends in a user's fitness over time even if they are not completely accurate. Indeed, in my own experience the estimates appear internally consistent in that the values produced don't vary much over the short term, but do vary in an explainable way over long periods of time during which my fitness regime has changed. That observation is based on years of data.

However, I recently have observed that my estimated V02Max has dropped dramatically. It had for several years been reporting a values in the mid to high 60s. It now reports values in the high 30s. There's a startling inflection when graphed over time. My exercise regime was consistent over the period when I observed this change.

I concede that values in the mid to high 60s are probably an overestimate, so either the heart rate sampling or the proprietary algorithm used to deduce V02 Max (or both) probably have something wrong. Even, so I'm inclined to believe that something has dramatically changed and I'm not sure how to account for this. Are there any conclusions to be drawn? Where should I look for explanations?

Answer 1

From the comments, I do think that your problem is that your fitness status is stagnating.

That is because your training input and stress levels basically remained the same. If that happens, your body does adapt to these inputs.

Therefore, your body does not even reach its maximum power levels. These levels adapted to your training. Thus, if your training does not become harder, you train at levels your body adapted and got used to. Where, I ask you, should your device get the data to derive your max VO2 from, then?

VO2Max is a measurement taken for the maximum power output level your body can possibly have. If you do not push your body to these levels because you stopped to make your training routine progressively harder, the device lacks the data for your maximum output level to derive the measure from. Therefore, it would not be surprising that the measure it takes out of the data it has is faulty.