Testing for Aerobic Decoupling

Slightly diverged topic, but is anybody playing with the HRV analysis which appears to be able to highlight when your effort exceeds the aerobic threshold in real-time during a workout?

I’m going to play with it tomorrow during my endurance session…

What interface are you using for this? I’ve only heard of Marco Altini’s HRV Logger app which is apparently only available for iOS.

That’s what I’m using. Tested briefly last night and it works well, tomorrow is the big test

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Dang. Wish I had something for Android or Windows. I’d be interested to give it a try as well.

So what to do once you have that data? In view of working on aerobic decoupling, is it better to do your Z2 rides close to AeT/LT1, rather than down at 60-65%FTP (likely lower than LT1)? That’s what I thought I gathered from skimming that Friel article, but I might have read too fast.

(Is AeT==LT1 a valid equivalency? Or close? Or am I misusing terms?)

My thinking is work at the just below aerobic threshold for as long as possible. Power will drop as time extends. Over time the power output will go up as the engine develops. I’ll report back

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I don’t think a 1H Z2 (Coggan) ride is very suitable for determining AD, it is just to short. I would aim for about two hour’s or longer depending on what length of the event you are preparing for. According to Friel you should aim for a decoupling of less than 5%.

I agree, it’s in the end of workout any substantial fatigue sets in.

If you are referring to HR zone 3 I’d try not to, even if an occasional drift into HR Z3 is OK as it does not inflict any severe fatigue. If you’re referring to PWR zone 3 imo that is the goal.

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LT1 is the top of Seiler’s Z1. I’ve used that HRV app this week and using the suggested protocol it put my LT1 at 78% of my max HR. I’ve been doing my easy at 67% of max. I do wonder about working closer to this 78% figure. I’ll do it again next week to see if the protocol delivers consistent results for me.


Reporting back on the use of HRV4Training’s HRV Logger and their DFA analysis to identify the aerobic threshold. Last night I did a slow aerobic 8k run, and the whole run was apparently above the .75 threshold of DFA as indicated by their research. 0.75 is the threshold they believe indicated the aerobic threshold.
This morning I did Petit with the logger running and the live display. Attached is the screen shot from the end of the ride. It does appear to show that as the ramps increased I did get closer to the aerobic threshold. This matches with both the heart rate data from the ride and power data from the ride - both which I have reference values from laboratory testing 9 months ago.
There was one outlier which is that single reading at 0.85, assume that is the sort of data foible that can occur; although it did occur at the second ramp when I was really only starting to warm up; but it was gone 2 minutes later.
Tomorrow I have threshold intervals and VO2 max intervals. Let’s see how it works then…but so far so good.


second report on the HRV Logger. It appears not to really work on short intervals like VO2Max. Probably not a surprise, the intervals were 2 minutes and the sampling period is set at two minutes. It did show increased workload and getting closer to aerobic threshold but didn’t register any of the intervals as over threshold.

Today was a short progression run.

I’ve attached the aerobic/anaerobic contribution chart from WKO along with the HRV Logger screen. It does align fairly well and of course it is real-time where as WKO is after the fact.

I’m pretty pleased with it so far and for steady state endurance rides when you want to ensure you are staying aerobic this seems close to perfect…

@Nate_Pearson or @ambermalika this almost fits into the branding of ‘Adaptive Training’… Any chance you could calculate DFA (alpha 1) in TrainerRoad and use it to control intensity of long endurance rides??


Looks like the HRV Logger app is now out for Android users: https://play.google.com/store/apps/details?id=com.asma.hrvlogger


I messed around with the HRV logger app for android this morning a bit, without fully reading the instructions :slight_smile: Initially it looks like my LT1 may be lower power than I thought, but I need to do a few more experiments. My HR was higher than ‘normal’ for the power I was doing today, not sure why it was different.
From reading the paper this is based on it sounds like 0.75 is likely a rough approximation, and more work will need to be done to firm up a cutoff, but that it is definitely higher than 0.5. Sounds like it is still early days for this, but all very interesting.

What’s the conclusion when decoupling is negative?

Don’t think there is a conclusion.

I’ve seen negative values on rides where I struggle early on and don’t warm up properly. Heart rate goes through the roof and then settles down. I usually see that with larger percentages. A negative value for a fraction of a percentage might be a good thing. Or maybe not. I’ll consider how I felt throughout the ride if I get an odd AD value.

It was a fairly normal endurance ride, steady Z2. I felt good. Perhaps what I can say is that 2h is not enough observe decoupling at this intensity.

Basically anything below 4% (including negatives) just means you haven’t pushed enough to find your breaking point - so you need to increase intensity or duration to find where you start to decouple.

Two hours is the minimum, but people with a strong base need more time to find the actual break point. Just as a reference, below are some of my endurance ride durations and decoupling from the last two weeks

3:15 0.8%
3:05 -0.4%
3:45 2%
3:00 0.1%
2:00 -4.3%

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Agree, but I would add, it’s a good maintenance session. You didn’t waste your time.

My Wednesday 2hr Z2 always looks like that. I push it on the weekend rides.

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Yeah I didn’t mean to imply it was a wasted session, you don’t have to push to your breaking point every ride…a

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I hesitate to bring this up but I’ve been exploring IN_EX score lately. It is more sensitive (and seemingly more useful) than measuring decoupling with Pw:HR first half last half, which is quite crude.

It’s an attempt by Seiler to quantify stress / strain. I’m still getting wonky graphs occasionally so I’m not completely fluent yet.

:+1: Oh yeah, and not directed at you (even though I quoted…my bad). I know you know your stuff. Some people might come across that and go “shouldn’t I be getting a ‘high score’ if I want improvement?” Well, yeah. Sometimes :grinning:

I went out today for another Z2 ride, this time 3 hours and outside. I pace these rides by heart rate. Had to battle some crazy wind, ended up with same HR, more watts and 5.5% decoupling.