Hi, I live in Netherlands, so usually I’m training at sealevel (or below …). In summer I go to the Alps and suddenly I’m cycling at +2 km (or higher …), with less oxigen. I have the impression that cycling at this altitude costs me 10% of my power, i.e. when my FTP is 220w at sealevel, only 200w is left on high altitude.

I have not been in the Alps with Xert on my Garmin yet, so I am curious if & how Xert deals with altitude?!

You can adjust your signature for your activities at altitude to ensure you properly account for xss. You can reset it after your return. It doesn’t yet dynamically change your signature variables based on altitude.

Thanks Armando. I am not sure if you are right - or maybe I misunderstand you.

Let me give an example: last year I did the climb of the Passo del Stelvio from Prato in Italy. My threshold power at that moment was 235 watt. The climb starts at 950 meter, the top is on 2758 meter. At sea level the air contains 20.9% oxygen, at 950 meter appr. 18.5%, on top of the Stelvio only appr. 14.8% is left.

If I can make the assumption that my FTP from 235 watt at sealevel goes linear down with oxygen percentage, my FTP at the start is (18.5/20.9)*235 = 208 watt and on top of the Stelvio only 70% or 166 watt is left from my original FTP (14.8/20.9*235).

Of course I can adjust my signature, but that is only correct if I ride on a constant altitude. My Garmin knows the actual height and can adjust it “on the fly”.

With this calculation in mind, I had a look at my actual data. In the last part of the climb I had an average wattage of appr 180 watt, with a heartrate of appr 140 bpm. My lactate threshold is reached with a heartrate of appr. 163 bpm, so in fact I did a worldclass job at that moment, which is not reflected in the Xert analysis.

Possibly the weak point in my calculation is that FTP does not go linear down with altitude. But if it is, it is easy to implement in your algorithm I think?!

Variable TP in our calculation of MPA would not be *easy* unfortunately. It is something we are considering, but not until we are able to put in place some more computing power. As is with the effects of longer rides where TP is also dynamic, it will require quite a bit more in place in order to make it work.

Thank you Armando. “Some more computing power” - on the Garmin you mean?

Thanks Frank

Extractions

Great topic, looking forward to future features that would adjust for altitude.

If I get it correctly, I can tweak for instance the FTP value for that specific activity and see the metrics for that activity updated in real time?

Thanks.