Performance Condition - not very useful

I think it does account for hills as firstbeat does some filtering to measure only at comparable conditions. 

no it doesn't. i am pretty sure i get consistently bad numbers if i run in hilly terrain. This is the official documentation which also doesn't indicate that this is taken into account: https://support.garmin.com/en-US/?faq=A28UA4k16v1qjjGuvSFgo8

Heikoo said:

So neither gradient, altitude, temperature, humidity.

This isn't correct.  It takes into account every metric you mentioned in your original post and heat and altitude are fairly recent additions. You'll find this information (BobMiles is correct) in the graph under the "VO2Max Fitness Level" and "Heat and Altitude Acclimatization" tabs. I hope you find the attached link helpful. For further assistance, send HermanB from FirstBeat a private message. He's very helpful. 

www.firstbeat.com/.../

Hi tess! Thanks for your input. I know that firstbeat offers advanced fitness metrics which take into account more parameters. However, i am talking about the "performance condition" metric and according to the best of my knowledge and experience this is still rather primitive. 

(Update: I stand corrected: https://www.firstbeat.com/en/consumer-feature/real-time-performance/ --> "Firstbeat reveals your Real-time Performance level using the same analytic tools and methods used to detect your VO2max fitness level." I will ask HermanB because this contradicts my experience)

Hi Heikoo - I saw this thread as I was scrolling the forum and wanted to jump in for a second.

Performance Condition is a bit primitive, but consider it an advantage. Think of it as a clear window into what's happening, and the value comes from your own awareness and context that you provide to make sense of the numbers.

It is - as has already been mentioned above - a marker driven by the relationship between how fast you are running compared to how hard your body is working to produce that result. If you are chugging up a long hill and notice that your PC is, say, -2 then it's probably safe to say that you are working harder than normal and the reason is (based on the context you provide to explain the data) is the fact that you are on a long up hill.

At the same time, if you are out running on a nice flat surface and you're at PC -2 and you've been out running for like 40+ mins, then, well there's a good chance you are looking at the onset of fatigue. If you are at PC -2 about 10 mins into your run you may be suffering from a lack of adequate recovery from your last workout, perhaps struggling under an excessive Training Load, or maybe starting to get sick... or maybe it's a really hot day or you are in Colorado Springs or something like that.

For me, sometimes a little rawness in your data is a good thing. 

HermanB said:

For me, sometimes a little rawness in your data is a good thing. 

Bingo.

Many of the metrics and datafields we use are built on black-boxes. I agree having raw data available can be enlightening.

Similarly, Body Battery is driven by HRV stress. Your Body Battery may be way low but if you can look at raw HRV stress and see you're "at rest," you can infer your Body Battery will climb without waiting for it. (it's a lagging indicator)

"All models are wrong; some models are useful." - George Box.

I appreciate knowing how the models work.

Herman: I know FirstBeat publishes white papers but I think it would be helpful to have a graphical flow-chart showing how each FirstBeat metric drives the other metrics. Maybe a hard line showing direct links, and dotted line showing correlations. (example: HRV directly impacts Body Battery; sleep is only loosely correlated in that you may have lower HRV while asleep, but possibly not)

I would really love a link to some definitive resource, perhaps with a few examples, to help us mortals make use of the metrics provided.