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What is heart rate decoupling?

Updated: Oct 26, 2021

You may have heard about Heart Rate decoupling being used as a performance metric but never really understood how and why it is used. In running, heart rate decoupling has been used for some time for training evaluation. However the latest wearable devices have the ability to combine both heart rate and your actual running power data much the same way we do with cycling .

Heart Rate decoupling is actually not much more than an equation. You divide your training into two parts and calculate the ratio between power and heart rate for both halves. Then you divide the ratio of the second half by the ratio of the first half. The number you get from this is the number that represents the difference between these two ratios.

Relationship power heart rate

This number shows the decrease in power at the same heart rate. This helps one identify when the body gets tired and has to work harder to deliver the same wattages. The idea of heart rate decoupling is that there is a relationship between heart rate and power. With the aforementioned equation you can see whether heart rate and power are parallel to each other or whether the heart rate differs from the power.

Heart rate decoupling shows the effect of fatigue

This value shows the heart rate at which your body is tired. Now that you know this, you can compare different workouts to see if you are getting better. But before you compare all workouts, you have to look out for some pitfalls. To start with, the relationship between heart rate and power is quite reliable up to your aerobic threshold. Above this point where fat burning is at its maximum, the relationship becomes less reliable. Your aerobic threshold is normally between 80 and 95% of anaerobic threshold or FTP. Heart Rate decoupling should not be used for training sessions with many intervals above the aerobic threshold and that makes heart rate decoupling especially suitable for analyzing endurance rides.

The heart rate delay

There is also a delay in the heart rate when the intensity changes where power shows an acute difference. So if the intensity is very variable you can see this in power but is less clear in heart rate. For this reason, for heart rate decoupling you will need to use workouts that are uniform without too many intervals and changes in intensity. Also, the training should have a certain length to be able to oversee the deceleration of heartbeat. In order to get a reliable picture, the training should last at least one hour.

Heart rate can be misleading

Another pitfall are the conditions under which heartbeat can vary that are not due to fatigue. Coffee or other products containing caffeine can lead to a higher heart rate at the same power levels. So if you stop halfway through your workout for a tasty espresso, this can be distorted. A few nights of poor sleep can also lead to a higher/lower heart rate. During your workout this will increase and your heart rate will drop again. But because the heart rate was high in the beginning, this can lead to a negative value for heart rate decoupling. Dehydration has an even greater effect on heart rate. When your body has too little fluid, the heartbeat and power will no longer run in parallel. But this also works the other way around. If you suspect dehydration you can use the value from heart rate decoupling to determine the degree of dehydration.

What is a good heart rate decoupling?

So if you keep these in mind, what numbers are we looking at? Normally a value below 5% for heart rate decoupling during an endurance ride is considered good. Of course, the length of the workout has a big influence on the value from the heart rate decoupling. The duration of the ride should match your personal goals. If you train for a particular race or ride that lasts longer than four hours, the first step is to achieve a heart rate decoupling of less than 5% over an endurance ride of three hours. Once that has been achieved, your endurance capability is at a level that it’s time to add some more intensive workouts to your schedule. But if you don’t reach that 5% yet, it’s advisable to train a bit more on your endurance first. Heart Rate decoupling is very useful at the beginning of your training plan. By means of heart rate decoupling you can determine whether you are ready for the second phase of training which contains more intensive training, or whether it is better to work on your basic condition in the first phase of your training plan. Always keep in mind that you use low-intensity workouts for your analysis that are at least one hour long. And when you want to compare two workouts to determine your progress, compare two workouts with more or less the same intensity and under the same conditions.

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