VO2 Max vs. Fitness state

By fitness state - do you mean the Performance Condition metric that is estimated throughout each run?

If yes, here's a possible explanation to what you are seeing:

Performance Condition is comparing your performance "live" during a run versus your current recorded VO2max value.
Your initial VO2max of 47 was probably too high, and therefore your performance condition was showing -15.
Continous negative values on performance condition means that your fitness is actually decreasing - or more probably in your case: The initial VO2max value was over-estimated.
As your recorded VO2max drops over time (adjusts towards your real VO2max), the gap between your recorded VO2max and your real VO2max decreases, hence the Performance Condition shows a better value (-3)

47-15 = 32
36-3 = 33

Based on the numbers you provided they indicate that your real VO2max have increased by 1 point during the period. And, once the PC numbers starts changing from negative to positive figures - you should expect the VO2max value to start increasing as well, just give it some time.

By fitness state - do you mean the Performance Condition metric that is estimated throughout each run?

If yes, here's a possible explanation to what you are seeing:

Performance Condition is comparing your performance "live" during a run versus your current recorded VO2max value.
Your initial VO2max of 47 was probably too high, and therefore your performance condition was showing -15.
Continous negative values on performance condition means that your fitness is actually decreasing - or more probably in your case: The initial VO2max value was over-estimated.
As your recorded VO2max drops over time (adjusts towards your real VO2max), the gap between your recorded VO2max and your real VO2max decreases, hence the Performance Condition shows a better value (-3)

47-15 = 32
36-3 = 33

Based on the numbers you provided they indicate that your real VO2max have increased by 1 point during the period. And, once the PC numbers starts changing from negative to positive figures - you should expect the VO2max value to start increasing as well, just give it some time.

Thank you so much for the good explanation. It makes sense to mee now. Of course i meant Performance condition. It was translated from german to english. So i will give it some Time. Thx

Also, VO2 max is a "best potential" metric, it's the amount of O2 your muscles can in theory process when your body's performing at its best. Therefore, once Garmin Connect has had chance to work it out relatively accurately, it'll pretty much stay the same with just slight increases as you get fitter.

However, performance condition relates to how well your body is actually performing, so that will vary all the time based on how tired your body is, temperature, if you're ill etc.

You should also check and make sure you have everything set up correctly on the watch. Make sure your weight and heart rate zones are correctly entered. If they are wrong, all of the calculations will be wrong and you will get bad data out.

Browner40 is right - having all user properties set correctly is important to get the most accurate outputs.

However, I want to point out one thing that people tend to confuse on this topic: Setting the MaxHR value correctly is crucial, but changing how the pulse zones are set up will not affect the VO2max calculations.

While the zones might not effect the VO2Max measurement, they have an effect on everything else. You need to have Max HR and whatever other metric you use to determine your zones set up correctly in order to get meaningful data. I let the watch determine my Resting HR automatically and set my Max HR and lactate threshold through testing. You should try to ensure you are updating these values every couple weeks/months depending on how much you train. I use %LTT to determine zones on my watch and make sure I do enough of a threshold run to trigger a new detection every couple weeks.

Sometimes a software update will reset the zones and it always shows up on my first run when all of a sudden I have a huge recovery time and training effect when I know I shouldn't.

I don’t know what you mean by «have an effect on everything else»

I agree it’s important to keep HRmax (wont change short term), LT and HRrest up to date, but you can set the zones to whatever you like without them affecting any FirstBeat performance/fitness/effort metrics.

If I for example set my zone 5 to start at 120bpm instead of 170 bpm I’m pretty sure that won’t affect anything else than the Time in Zone graph. (and of course my ability to follow any given zone based training plan or philosophy)

I think that Training Effect uses HR zones to work out whether you're training aerobically or anaerobically. Theoretically, it would use your LTHR to determine threshold but as LTHR isn't always present I'd guess that it would just base TE on your HR zones, specifically 4 and 5 (which is ultimately the same thing if you set your HR zones based on your LTHR).

Not sure if other metrics such as recovery time, IF and TSS take into account an/aerobic split.

HRMax is definitely the most important one to get right though, and it's really best to avoid the formulas for estimating it (such as 220 minus your age) as the margin of error is massive (e.g. I'm 50 with a HRMax of 200 - if I used 170bpm then my VO2Max would be meaningless). You might need to use a formula when you start out training, but once you get a better feel for what your heart's probably capable of reaching then you should definitely update it. That said, if you're just starting to get into shape then you shouldn't be trying to push your heart to it's maximum just to find your HRMax.

I believe the FirstBeat algorithms is basing intensity on a percentage of the set MaxHR, not the user defined pulse zones.
If a value for LTHR is present - detected or set manually - it probably (hopefully?) takes that value into account to determine aerob vs anaerob TE.

If you read through the information on the different metrics in the manual, and how to obtain those metrics, there's really no mention on how pulse zones might be set to increase/decrease accuracy - it only talks about MaxHR.

There's a million ways to set your pulse zones based on different philosophies and training goals and no setup is more "correct" than the other.
MaxHR, LTHR and Resting HR on the other hand is either right or wrong.

If you were to make the FirstBeat algorithms - which inputs would you choose to take into account? The zones based on how each user prefers their setup - or the values (if set correctly) that is universal and directly says something about a persons physical properties?

I know HermanB from FirstBeat is sometimes chiming in on these discussions - maybe he's able to shed some light on the topic :)