Hi all, I have some curiosity about aerobic decoupling. I am somewhat familiar with its intending application to measure heart rate drift over a workout, but I have seen some odd behavior recently. The past few months nearly all of my rides have seen negative decoupling(my heart rate lowers at the same power as a ride progresses). Would there be any plausible explanation for this?
Thanks!
Several reasons including using it in the wrong way. Post an example screenshot.
I’m also interested to learn more, in particular analyzing specific intervals decoupling over multiple similar workouts, for example when you train for a marathon, checking HR Power performance on the “marathon pace” intervals in long runs. I understood that if there’s a drift of HR going up then probably the pace is little bit too high and cannot be sustained over marathon distance.
I don’t know if Intervals can perform such comparaison or if an AI tool would be needed.
You are warming up into the workout is one. As you warm up, your efficiency increases.
The power isn’t set high enough is another 
Could be digestion also, happens to me all the time
Hola,
El desacoplamiento se utiliza para determinar cuál es tu eficiencia aerĂłbica, es decir cuando se trabaja a ritmos bajos o medios. AquĂ es cuando se comprueba como responde tu base aerĂłbica viendo el desacoplamiento cardĂaco. Si tienes buena base, rodando en zona 2 no pasarĂa del 2-3%, incluso llegando a estar muy prĂłximo a 0.
Si nos fijamos en el desacoplamiento en entrenamientos con variabilidad de potencia y en partes determinadas de Ă©ste, puede que tengamos un desacoplamiento negativo. TambiĂ©n podrĂa ser, que empieces el entrenamiento con un pulso alto, por fatiga, y a lo largo de Ă©l se estabilice dando un desacoplamiento negativo.
I’ve noticed the same kind of “odd” decoupling (including negative values) pretty often when the route isn’t steady/flat. (Gravel & Road Cycling)
On hilly terrain, climbs + descents can skew the power↔HR relationship a lot:
- Downhills/coasting: power drops (sometimes to near-zero) while HR stays elevated for a bit → the overall math can get weird.
- Power surges on short climbs: HR lags behind power, then “catches up” later.
- Micro-variability (grade/wind/turns): makes it hard to interpret decoupling as a pure “HR drift” signal.
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I found this data field (“CHARGE”) yesterday; it might be helpful for anyone interested in live data, to pinpoint the moment. The description looks quite promising, though I haven’t had a chance to try it yet, using the Aerobic Decoupling - %HRR vs %6min MMP/Pace.
https://apps.garmin.com/apps/56480419-be66-42c5-92ad-6531fa6c130c
CHARGE is a scientifically advanced data field developed as part of a Master Thesis. It analyzes the relationship between external load (Power) and internal load (Heart Rate) in real-time to provide deep insights into your aerobic efficiency and autonomic nervous system status.
Key Features:
Real-time Cardiac Drift Analysis: Uses a hybrid algorithm (Linear Regression & Ratio models) to detect cardiac drift live during your ride. Helps identify fatigue, dehydration, or overheating before you feel it.
Aerobic Decoupling (Pw:Hr): Calculates long-term decoupling based on Joe Friel’s methodology. The algorithm automatically filters for Zone 2 efforts (56-75% FTP) and aggregates data into 3-minute buckets to ensure valid comparisons between the first and second half of your ride.
Heart Rate Kinetics (Tau): Performs active “Step Response” tests. Press the Lap Button before an interval to trigger the system. It detects power jumps (50W), waits for a plateau, and calculates Tau (the time constant to reach 63.2% of HR response) and the Step Amplitude to evaluate how fast your heart adapts to load.
Reactivity Score & Readiness: A smart algorithm that learns your individual heart rate response (slope/HRR) over time. It compares your current reactivity against a historical baseline (learning phase of 5 rides) to categorize your state as “Fresh,” “Normal,” or “Tired”.
Efficiency Metrics:
Physical: Joules per Beat (J/b) – Measures mechanical work per heartbeat .
Normalized: Efficiency Ratio (IF / %HRR) – Makes efficiency comparable across different athletes.
Full FIT File Support: All calculated metrics (Drift, Decoupling, Tau, Step Amplitude, Reactivity, Efficiency) are written directly to the FIT file for post-ride analysis in Garmin Connect or 3rd party tools .
Usage Note: For the most accurate Decoupling results, aim for steady-state endurance rides (Zone 2). For Kinetics testing, use the Lap button to signal the start of an interval.
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