Vo2max calculation

Thanks for all the replies.

As for the MaxHR test, is that an app or feature of the watch (like the lactate threshold test that you can run on the watch), or you refer to something like going all out on a 5K distance and looking at the peak HR?

An all-out 5K will probably give you a figure slightly above LTHR, but less than your MHR.

A simple way to test for MHR, is to find a hill that will take you at least 2 minutes to climb. Warm up for 10-20 minutes, then hit the base of the hill at about 85% effort (ie. fast, but a little below LTHR). Don't sprint, but try to hold your pace and let the gradient provide the extra intensity. Keep going until you feel you absolutely cannot hold that pace anymore.

Settings> Physiological Metrics> Autodetection> HRMax = On will then automatically update on the watch based on the highest value reached. If you have a HR chest strap, use that, as it is more responsive than OHR.

Be warned that testing for MHR hurts. A lot. But while MHR declines slightly with age, it is not affected by fitness level, so once you have an accurate figure, it is good for a couple of years, and not something you need to test for again anytime soon.

Actually, the same pace at a higher weight but with fitness unchanged will lead to a higher heart rate. Higher heart rate with more work done = unchanged maximum oxygen uptake.
Unchanged maximum oxygen uptake at higher weight = lower VO2Max per kg.

We are talking about a situation where heart rate is known.

So your example should be:
Higher weight, same pace, same HR -> More work done at current HR -> More work expected to be done at VO2Max HR -> Higher total VO2Max

...which cancels out that you need to divide by the weight to find your VO2Max pr. kg.

We can also use your example:
In your example, the VO2Max per kg has dropped. We both agree on that. But the important point is that this can be seen, just by looking at pace/HR combination and comparing it to an earlier pace/HR combination, exactly because of what I have described above. You don't need to know if the weight has changed. As soon as you run slower at the same HR, it is a sign of decreased VO2Max per kg, no matter if that decrease came from lower fitness or higher weight.

I took a look at all my training runs with HRM so far (about 4 months history, 80 runs). The max HR ever recorded was 181 (there were few runs around this figure, combination of hills and intervals), which is what I used to update the information on the watch. Yesterday I did an easy run and my vo2max stayed at 57, but the training status changed to unproductive. Today I did long interval session of 3 x 3k @ 4 min/km, after which the vo2max dropped to 56 (after virtually all intervals I did with the watch it always showed productive training status and increasing fitness). The race predictor is still way off with 1:24 prediction for HM - there is no way I could run that now, equally so for 5/10k predictions. But this figure is probably closer to reality. Will report back later how things develop. Maybe the training status/vo2max will be relevant for my training, maybe not. But I find it more reliable and helpful for training to train and assess progress based on race performance and Jack Daniels' VDOT values/paces.

Not directly answering your question, but you should probably take a real VO2Max test in your local sports center and compare it. That enough will give you confidence (or despair) on the accuracy of the method

It will not tell him how his VO2Max has developed over the previous months. And that is his main concern: That the change of VO2Max in the watch doesn't reflect the apparent change in his fitness.

But of course: He will probably have the same concern again at a later stage. So a VO2Max lab test now could be a good baseline for future VO2Max lab tests. But then it starts getting expensive.

Not going to do lab test. Vo2max is just one aspect of performance, you also need to train your lactate threshold, aerobic fitness etc. Interestingly enough the lactate threshold, another measurement the watch can give, is also off. It has me constantly at 4:15 pace since I bought the HRM in May this year. I can now hold this pace for HM whereas previously I struggled to do 5K.. Being a data / analytics oriented person this is pretty disappointing..

tomas,

Based upon your initial post I would say that the VO2max estimate is probably providing a reasonable evaluation of your relative fitness. I think you are looking at it as a relative measure of fitness, as in whether or not your fitness has improved or declined over time which probably the best way to view it. I would not use it as an absolute measure. The problem is the that VO2max estimate does not account for other factors that impact your pace at a given heart rate. First is weather. If you are in an area where you will see significant changes in temperature and humidity as the seasons change, your VO2max estimate will be impacted by the weather. Your VO2max will decline as things warm up and the humidity increases and will go increase as the weather cools. I also see a decline sometimes after a strenuous workout. Basically I am fatigued and can't perform as well and it shows up in the VO2max estimate.

It is really difficult to use those two races to evaluate the VO2max estimate since the VO2max estimate is more impacted by what you were doing prior to those races than how you performed during the race. Half marathons are on the road and no two races are the same due to differences in terrain and that could also impact your performance between those two races.

I ran a marathon this past spring and in the buildup for that marathon my VO2max peaked at 61 prior to the race. After a post race break of 2weeks I returned to training except now the weather is much warmer and more humid. During this time my VO2max declined because my ability to perform is reduced due to the warm weather. Over the summer months my VO2max dropped as low as 57 and has pretty much stayed there. I expect to see an increase soon as the weather cools.

Lastly, the Race Predictor is a joke. Do not pay any attention to it. VO2max estimate can provide a way of evaluating your relative fitness, but it does have some flaws in that it cannot account for weather.