So here's the question: if this is about heart rate vs. gradient and pace (and I do pace myself properly on the gradients) - then why is my performance condition going down during the runs back home (training status is the same for now)?
There is something missing here.
It’s well known (and confirmed by a firstbeat rep) that gradient is not taken into account for VO2Max and performance condition. As mentioned, in contrast, the Garmin running power field does take gradient into account.
OK well that's good to know. Means that VO2Max in my case will continue to go down as I run in significantly more hilly terrain here than when away - which is to me bizarre as one would assume that VO2Max should go up when running in more challenging terrain. Ah well never mind...
When I read Firstbeats description of VO2max estimation (version 2.0, as used by Garmins most recent devices), my understanding is that elevation is taken into consideration.
I enclosed a picture from Firstbeats site.
I find this an interesting discussion. I have recently changed locale during holidays. My performance levels and VO2max went through the roof (6 points for Vo2 max in 10 days.)
There are two differences: the runs were on almost zero elevation gain/loss ground (at home it is hilly), and in rural areas (home is in the city).
Coming back, my VO2max is staying the same (but I expect it to drop any day now), and my performance condition is a disaster.
Good point. Changes in elevation are taken into account, but how this is achieved is probably quite different from how one might assume. The intelligence or smartness, if you will, upon which the Firstbeat analytics engine benefits has quite a bit to do with the ability to segment data and recognize when incoming data streams are representative of your VO2max and when it isn't.
A) Yes, if you go for a 10k run that is all downhill... then, ceteris paribus, yes, I would expect you'll have a higher than usual positive (+) Performance Condition - certainly during the earlier parts of the race. You are running faster than normal with less effort. So that's the first part. You could expect to get a similar result if you were running with a strong tail wind. Upon several occasion I've, personally, seen a few points difference in Performance Condition between running into the wind or against it.
How does this impact your VO2max? Well, that's a little trickier. Other than when you first start using your device, your VO2max calculation is never based entirely on a single run. So, unless you're always, only, running in downhill races (highly unlikely), your watch will likely recognize that particular as being non-representative and take that consideration into account as it looks to see if your fitness level has actually improved.