Testing for Aerobic Decoupling

Another post! Sorry! I wondered if anyone on here knows of any workout that would be ideal for testing aerobic decoupling.

I’m very much a complete amateur on this subject but would think it’s very handy for Ironman and especially to test the 0.70-0.75 intensity target. So ignoring cardiac drift that could happen during indoors due to heat and excursion.

Would a longer step test be a good way of testing and perhaps seeing HR rise too much over a given power target? I know over a certain power zone we are essentially burning more of our energy store than we can replace.

Hope this makes sense or am I completely off the mark with this?

single power target over a “long” period of time.

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Two articles worth review to get your head around it:


Yes perhaps I’m over thinking it. So target race power, so say Ironman watts on non erg mode and watch for when it goes into say out of the desired zone

Oh thanks, perfect. Will give this a read

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Here is a 90 minute workout I used a year ago during early base:

WKO5 is being used for graphing, but there are other tools out there like TrainingPeaks and Intervals.icu.

Here is a 2 hour segment from an outdoor ride at tempo (78% FTP):

see how the HR trend line and power trend line are parallel like a set of railroad tracks? That is 0.05% decoupling, essentially no decoupling.

And here is a 2.5 hour / 4500 foot (1370m) climb where I rode to HR (~154bpm) and let power drop as elevation went from 1350’ to 5850’

decoupling is about 7.5% and you can see the power trend line is falling while the HR trend line is almost flat.

Hope those examples help.


Yes thankyou, a lot to absorb.

I think you are right, best to start at 60% first and watch HR plus cadence as not all power is created equal

This is one way to do it lol joking of course but I’m always going to be happy about getting about 4% on a 100 mile ride

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gets easier, helps to start out looking at a workout at constant power (60% or 65% or 70% or whatever). After initial warmup (mine are about 20-30 minutes), look at decoupling for 30 minutes or ideally longer.

Another decoupling question…

Those first five minutes my heart rate is coming up to match the workload. Including those 5 minutes make about a 2% difference in the decoupling rate. Do you all consider that when analyzing this information?

I generally leave out the warm up period when I look at that

I would chop off that little HR ramp. That is when you seem to stabilize to the load and is a better “start” for the DC calc’s.


I’ll take it a step further and say its common for a body to need a full 15-30 minutes to warmup, so I leave that out of the decoupling calculation as well.

So chop off this:

and you’ll have a better idea of decoupling. And yes that means you should be riding at least 90 minutes to have a good first cut at decoupling.

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That’s where I was considering making my calculation as well.

Thanks for your input you guys!


Eyeballing it I’d say 20-25 minute warmup. Toss that out of decoupling. If less than 5% then you should have ridden longer. I’m assuming that’s aerobic endurance / zone2.

What do you mean by this?

The 60min interval was at 90%.

Decoupling is often used in early or mid base as a measure of your aerobic endurance while riding in zone 2 (or maybe zone 3). On zone 2 rides if decoupling is less than 5-6% then keep riding longer to find your limit. Or the other way around, if I’m targeting 5-6 hour events then I want to see my decoupling under 5-6% on long 4-5 hour zone 2 ride.

I’ve seen some coaches use decoupling at higher intensities, but at those training intensities the typical assumption is that you’ve already developed a strong aerobic base.


Oh, I gotcha! I’ll have to find time to try the long zone 2 ride to assess it.

Intervals.icu has a specific stat for this “Power / HR in Z2” that you can plot over time to see how your base is improving. It only counts time spent in HR Z2. There is also a slider under the Intervals.icu decoupling charts to exclude warmup and cooldown time which also applies to related stats like “Power/HR Z2”.

This is the best decoupling chart IMO:

It shows HR as a percentage of HR reserve (max HR - resting HR) overlapped with 60s power as a percentage of eFTP. It adjusts the scales so the traces start out overlapped so as decoupling kicks in they start diverging (more bpm required to get the same watts). It saw this in a Dr Stephen Seiler video (link).


Thanks for this clarification.

I only recently started adding HR to my power data again after just using power for many years. I have been doing some longer z2 intervals in some weekday rides and see a -0.3% pwr:hr over 2hrs, so if I interpret that correctly, then its saying I’m very aerobically fit for those durations so I need to go longer and find out out at what point the ratio >+5%?

I’ve also been doing some longer tempo intervals recently (as steady as is possible outdoors) and seen 3%, so again, does that mean go longer to find the point where ‘fitness is running out’ ?