vo2 max does not increase.

Hello everyone...

Does anyone here know which segments of a run are included in the calculation of the Vo2 value?

Background... I started 2 years ago with the Fenix... the first runs at 51/52 since then I'm at 48... Yesterday I ran a race again for a long time..10k cross, in 43min... Vo2 max 48...I got a lot of awards..fastest mile, fastest 5k, fastest 10k...

But why doesn't the Vo2 max value go up?

Thanks ...