Testing for Aerobic Decoupling

if you never ride more than 2 hours then don’t bother going longer. Personally I think “aerobic fitness” is a loaded and ambiguous phrase, my preference is to think of it as basic aerobic endurance. If you can do 2 hours of z2 with low decoupling it means you have good basic aerobic endurance for 2 hours and its time to start doing more advanced aerobic work (tempo, sweet spot, threshold).


thanks - feels like I get it now. My target events are much longer duration GF’s and multi-day mountain trips etc, so more work needed to investigate 4-6hr fitness but at least I’m on the right track.

I’ve started a month block of tempo intervals now, building TiZ to lead into introducing longer SST work in Nov and through winter.

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@davidtinker Where can this decoupling stat be found? I can’t seem to find it.

  1. You need to open a ride/workout.
  2. Switch to the “Power” tab (lightning symbol) of that activity.
  3. Scroll to the bottom of that Activity Power page.


Awesome, thanks!

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One factor to keep in mind when looking at decoupling metrics - temperature/humidity matters. If you are doing long base rides in the summer, you might be starting the ride with temps in the 70’s and ending the ride with the temp over 100. Tough to read much into decoupling within the ride when you have big temp swings like that. Even comparing HR metrics on 2 outside efforts with similar temp can vary dramatically just based on humidity. I really only use my HR strap when doing inside trainer work because it’s a very controlled environment and I can look at HR metrics within a session and can also compare the same workout across time. Wearing it outside (particularly during the summer) isn’t that useful for me and the numbers can be really misleading.


If you take into consideration that your body core temperature will be rising and you sweat a lot more indoors in comparison with outside… Here where I live the temperature is lower then inside.
I find it very hard to compare aerobic decoupling outside but also inside

This is highly dependent on where you live and what your inside setup is. For me, it’s much easier to keep the engine cool indoors vs. out during the summer in Texas. Sweat rate is probably higher outside, but the main factor is cooling efficiency. It’s much better inside for me with low humidity and high air flow making evaporative cooling very effective. Sweat will be running off my body outside, but very little sweat hits the floor indoors because it’s evaporating as fast as it’s coming out. Extreme air movement and low humidity is key (see fan setup below). The fan on the right is the one I often see recommended on the TR forums, but the fans on the left and middle are the heavy hitters.


:smiley: That is a nice collections of fans! I only have one big fan, so maybe buying a second one could help… I do notice that the amount of sweat get less after 2h… I consume about 600ml/hour, so the hydratation should be ok.

Hi Guys,
Small question about the procedure of aerobic decoupling…
Today I created a custom workout to test my aerobic base, after a warmup of 10 minutes, I rode my indoor trainer at a steady 65% FTP for 3u10m and then a cooldown of 10minutes.
When I look at the data on interval.icu I have a negative decoupling… Am I doing the test wrong? Should I take more rest before completing such a test? I did another workout (Kennedy Peak) yesterday evening, so maybe I started the test with some fatigue

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It looks like your cadence drops a little during the test, and with it likely your HR. That could be it?

Over 3 hours on the trainer, and then you did a cool down?! Nice job!

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I rode my smart trainer in erg mode for an hour yesterday. Excluding the WU and CD, my HR during the 2nd half of the ride was about 11% higher than during the first half. Does that mean that the 5000 miles I have ridden in the last 6 months still isn’t enough, and I need to keep working on my “aerobic base”?

The warmup and cooldown is included in the workout… Both are 10 minutes.
The cadance was also my first assumption… but it seems about the same when I analyze the data

I was just wondering if I did something wrong with the test… I drank about 3 bottles liquid. One bottle contained isotone energy drink the other 2 just water… I also did my breakfast before the workout…

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If you’re going by the trainer power, it might actually be decreasing over time, causing your HR to fall.

No, nothing is wrong imo. I experience the same thing. I’ve seen numbers as low as -5% on some rides. If anyone has a theory to why I’m all ears.

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Maybe an hour is a bit short to make any assumption about your aerobic base?

In the article from TrainingPeaks they say that the intensity should be around 55% - 75% FTP… Maybe your workout was more intense?

Or it could just be that “decoupling” is nonsense.

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I m very new to this concept, but could that means that your FTP is too low? For example if I have a 8% AD on a 1H zone 2 interval (68%) I feel that would means either:

  • I need more aerobic work (this may be the case especially if decoupling happens more in last part of the session)
  • what I set up as 68% is actually a zone 3.

does this make sense or I m completely off track?

8% would be quite a bit. Your FTP could be set too high alright. I can’t remember the guidance but I think you’re aiming for less than 4% over 2 or 3 hours. Moving up to tempo you would expect it to push your HR up a bit higher.

Even at that though over the course of an hour that’s still a good rise. How much training have you been doing up to this point? Also do you have fans etc in place as heat and dehydration can have a huge effect.

I remember watching this a few months ago think there’s a workout idea 25 minutes in.