Fitness Trend vs. Heart Rate Variability

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I love to look at fitness trends such as the one intervals.icu provides (or Levitate for Strava).
Think I understand the principle logic behind it (sorry if not and my ideas prove to be a big bullshit :-), but I was wondering:
Fitness trend calculations only take training load into account in summing up each training load on top of the previous, while taking regeneration over time into account.
What it does not take into account are other factors of daily life that I am sure influence your fitness as well, like stress from work, travel, illness, to name a few.
HVR analysis on the other hand side (like provided by Eilite HRV or hvr4training) provide a daily feedback based on measurements. I also understand that it is not as simple as “tell me your current HVR and I know your current fitness” but instead it involves some trend analysis over the past days, however in principle we seem to have two very different tools to analyse the same thing.
How could we bring both together in order to have a more accurate fitness / form estimation?
Cheers
Hauke

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The Fitness, Fatigue, and Form metrics aren’t really as all encompassing as their terms suggest. They are really just words to represent the Trainingpeaks metrics CTL, ATL, and TSB respectively without infringing on their trademarks. So you’re right that they are simply using your workout’s training loads to calculate them.

ATL (Fatigue) = Acute Training Load = Exponential rolling average for past 5 days
CTL (Fitness) = Chronic Training Load = Exponential rolling average for past 43 days
TSB (Form) = Training Stress Balance = CTL - ATL

But I like to think of Fitness and Fatigue as CTL and ATL because I think those terms imply that the metrics mean more than they really do.

I don’t know enough about HRV to suggest a way to include that in the ‘fitness’ metrics but I know that it varies from person to person so you would probably need some sort of machine learning to establish a person’s baseline to then infer whether it is depressed or elevated.

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You can plot HRV on the fitness page but as @Matt_Glowacki suggests quite a bit of work needs to be done with it to turn it into a “readiness” measure (like hvr4training does).

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Thanks for pointing me to “Readiness to perform” in hrv4training. I am a long term user of that app but seemed to have totally ignored that feature in the past :slight_smile:
However, contrary to what the main subject of hrv4training (which is HRV) might suggest, their readiness chart to me seems to be exactly the same as other form/fitness graphs: a comparison of Acute vs. Chronic training load. No HRV comes into play here…

What I was looking for in my original post was a way to re-adjust the training load graph from time to time based on the daily advice that tools like hrv4training give (e.g.“Your HRV is below your normal values… It might be a god idea to limit intensity today”