Fitness level?

My Forerunner 245 sometimes shows my fitness level increasing during a training session (eg +2, +3 etc). My vo2 max stays the same. Where do these fitness levels go?

    • The +2 and +3 etc you see during a run are your condition (I think it measures heat rate variation). This is affected by how rested you are I think. It hasn't really got much to do with vo2 which only changes slowly following say a few weeks/month of training
    • The +2 and +3 etc you see during a run are your condition (I think it measures heat rate variation). This is affected by how rested you are I think. It hasn't really got much to do with vo2 which only changes slowly following say a few weeks/month of training