When your decoupling is a sign of fitness vs overtraining?

I remembered a bit over a year ago, I listened a podcast with Dr. Stephen Seiler about polarized training. He mentioned something that caught my attention about a low HR in a hard session cannot be totally associated with fitness. It can also be a sign of fatigue…

Now, I listened today the latest podcast in Athlete’s Compass (Fat Adaption and Training Acronym Overload). I have read in the past the decoupling term but my question here is: when is a sign of your fitness vs a sign of your fatigue?

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Hey @js.lopez116
You bring up a great point about decoupling and fatigue.

I don’t think decoupling alone can tell you whether you’re overreaching per say, but combined with your own subjective measures of feel, fatigue and how fresh you feel and how fast you recover from your training sessions. Remember external factors like heat, humidity, altitude, and hydration, how well you’ve slept and overall life stress can affect your heart rate. So just because it’s a humid session, your decoupling can be higher than expected as your hr increases the second half of the session. Remember decoupling is looking at your external output (pace or power) to your internal output (hr) from first half to second half of the session. As HR increases during the second half, so does aerobic decoupling.

When doing hard efforts and your heart rate is unexpectedly low, and you feel trashed, I would personally go to recovery mode. Take a few days easy, sleep, pay attention to your hrv and eat nutritious food. If fatigue continues, do few days very easy aerobic work, nothing too long either.

If you listen to the Training science podcast Dr. Laursen did with Gordo Byrn; it’s full of wisdom from Gordo ‎Training Science Podcast: The MAGIC Ingredients That Makes ULTRA Athletes ULTRA - with Gordo Bryn & Prof. Paul Laursen on Apple Podcasts

When is decoupling sign of fitness…. As Dr. Laursen mentioned, when he sees athletes with negative decoupling rates, he is confident the athlete is truly ready for performance. Maybe Prof can answer better than I can…

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I might have asked the wrong question earlier: while decoupling doesn’t directly measure overtraining, it’s tempting to assume that a negative decoupling value indicates good fitness, suggesting readiness for an event. However, if decoupling is negative (meaning your heart rate remains steady in the second half of your workout), this could be misleading. Dr. Stephen Seiler points out that your heart rate can also stay low if you’re overtraining.

The question is: How to know that the negative decoupling is “good fitness” and not something related to overtraining? (besides how you feel)

Would it not be amazing if there was a test to prove overtraining eih?!

Here’s a great article by Dr. Maffetone and Dr. Laursen that talk directly about being fit- but unhealthy… Athletes: Fit but Unhealthy? - PubMed

Speaking from my own experience, it is really difficult to tell you are overtrained.
But here’s what I experienced:
Excessive fatigue - feeling of trash
Had to nap - there was no way I could have gone through a day without an hour nap and woke up groggy
Upset stomach
Night sweats
Brain fog
Swelling, bloating and weight gain (I thought I was perimenopausal)
Low performance - (opposite reaction - my HR was sky high and stayed really high for a long time when doing tempo and threshold efforts, it can also go other way, depressed heart rate … )
Lack of progression despite volume or hiit increase (yes was over doing it)
Increase inflammation markers
low libido :flushed:

I went through endocrinologist (tested my HPA axis, did brain MRI scan and concluded I had exhausted my HPA axis. . Still didn’t believe I could be overtrained until my sport med doc looked at all the lab work, hormone test, brain scan and said., yeah, I think overtraining is the correct diagnosis…

My point is, if you think you are overtraining, you better listen to your intuition and back off a little so you don’t have to sit on your coach exhausted and sick wondering if you’ll ever race/train again. My journey took 6 months and I am luck AF to be back in racing and going to IM worlds!

Best of luck


A great question @js.lopez116. With no absolute answer but will give it a shot.

  1. When we train, we adapt, and our muscle cells work more efficiently to produce the same power at a lower HR.
  2. When we get fitter, our parasympathetic nervous system (rest and digest) works harder to make adaptations in us, seen as a higher HRV (Plews et al. 2013).
  3. In athletes really training a lot, we see the combo of 1 and 2 mask the effect of 1, and even though we have a really low HR, we are actually in a state of parasympathetic overtraining.
  4. You can tell you are in this state when you are doing HIIT work and you can’t reach the power and HR level that you want to. You can also observe your HRV. Together, these can help you to know its time to go easier. Change HIIT sessions to easy aerobic training (L1/2) and/or take a day off until your freshness returns.