Aerobic Decoupling

Aerobic decoupling compares the efficiency factor (EF) of the second half of a ride or run, against the EF of the first half.

Thanks for the question Mark.

To be clear for everyone (including myself):

Efficiency Factor is a ratio of the external (power, speed) to internal (HR) response for the session. We need to correct the way that is written currently.

Cycling: EF = normalised POWER / avg HR. Unit is watt/bpm, but we don't currently show units.

Running:EF = NGP speed / avg HR. Unit is yard/minute/bpm. Also don't show units.

Example calculation for running (see chart): moving NGP 4:31 min/km -> 3.69 m/s -> 241 yard/minute. Moving HR 124. => EF ~ 1.94.

So back to your question: To me, we should recognize that EF will be specific to you. Higher is generally best. So your cycling EF for your example was 1.63. I pulled a random similar 2 hour aerobic bike session from Athletica ambassador pro triathlete Andi Boucherer and it reads 2.01.

So learn and become familiar with your own EF, and keep tabs on it. Rises in the EF suggest enhanced fitness, while reductions might indicate detraining or overtraining. Just one of a number of factors to keep tabs of.


Aerobic decoupling compares the efficiency factor (EF) of the second half of a ride or run, against the EF of the first half. When aerobic decoupling number is low, towards zero or even negative, this indicates good 'durability'. Conversely, when you begin a training program and you are less durable, we typically observe higher decoupling numbers (%).


@dave-yuill the Normalized Graded Pace (NGP) we use for run pace calculation takes gradient into account... It probably won't be perfect but its the best we can use at this point for run calculation of decoupling across different run course phases.

Normalized Graded Pace (NGP) is the adjusted pace reported from a global positioning system (GPS), or other speed/distance device, that reflects the changes in grade and intensity that contribute to the physiological cost of running on varied terrain. It was inspired by the normalized power concept built by Dr Andy Coggan.

@dave-yuill Wouldn’t the heart rate data influence it? If I’m running uphill at +>5% my HR will be quite high, if I then head downhill, it will go down (depending obviously on distance, but I’m assuming if you’re doing one length/segment that is one pa

What is Aerobic Decoupling I can see in my session data?

Does this take into account elevation? For example if the 1st half is less hilly than the second half, intuition says that Aerobic Decoupling % will be higher?

@airforceken Aerobic Decoupling would take both pace/power and HR into account. As @Prof mentioned with NGP used as the pace/power variable then this will to some degree account for elevation changes.

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