Aerobic Decoupling and Efficiency Factor

Aerobic Decoupling and Efficiency Factor (EF)

TrainingPeaks has the ability to track and measure your aerobic endurance using two different formulas: aerobic decoupling rate and efficiency factor. By comparing power (cycling) or pace (running) with heart for aerobic workouts or segments, you can track your level of endurance fitness.

Where are these metrics listed?

To see your aerobic decoupling rate, see the Pw:Hr for cycling and Pa:Hr for running metrics located on the expanded view at the right. The lower the decoupling rate, the better your aerobic endurance.

Your efficiency factor is listed directly to the right of your aerobic decoupling rate.



Why do you want to use Pa:Hr or Pw:Hr?

Aerobic endurance is the most critical factor in achieving success as an endurance athlete. Sports such as triathlon, road cycling, mountain biking and distance running are first and foremost dependent on the aerobic system-composed primarily of the heart, lungs, blood and the muscles' aerobic enzymes.

But how do you know if your aerobic endurance is progressing and how do you know when you've done enough such training to reach an optimal Aerobic threshold  fitness level? The answer to both of these questions may be found by comparing power or speed with heart rate or in other words, tracking your aerobic decoupling rate and your efficiency factor.


What is aerobic decoupling (Pa:Hr or Pw:Hr)?

Research indicates that when aerobic endurance improves there is reduced heart rate drift relative to constant outputs (power and speed). And, of course, the reverse of this is that when heart rate is held steady during extensive endurance training, output may be expected to drift downward. This parallel relationship between input (heart rate) and output (power or speed) is referred to as "coupling." When they are no longer parallel in a workout as one variable remains steady while the other drifts the relationship is said to have "decoupled." Excessive decoupling would indicate a lack of aerobic endurance fitness.


What is Efficiency Factor (EF)?

To determine EF the software divides normalized power or normalized graded pace by average heart rate for the workout or selected workout segment such as an interval. By comparing the resulting ratios for similar workouts over several weeks you can measure improvements in aerobic efficiency. If heart rate during an all-aerobic (below lactate/anaerobic threshold) workout rises while the intensity (power or pace) stays the same then the athlete is not operating efficiently and his or her aerobic endurance is questionable. The same is true if heart rate stays the same and
power decreases or the pace slows. If you are making good aerobic progress progress then your EF will rise over the course of a few weeks.


What do you need to measure these metrics?

Cycling- Heart rate and power time series data
Running- Heart rate and speed/pace time series data

How is the efficiency factor calculated?

Your efficiency factor is determined by measuring your normalized power or pace against your average heart rate a for a selected aerobic workout or segment.

Normalized power/ average heart rate = Efficiency factor

For more detailed information on Aerobic Decoupling and Efficiency Factor please see these articles:


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