Joe Friel (author of The Cyclists Training Bible) coined the term ‘the decoupling dance’ to describe what happens to heart rate and power when you are riding for extended periods. Although he didn’t write about it in the aforementioned book, he has written extensively about the subject in his blog.
The effect can actually be seen in as little as twenty minutes of indoor riding if you have the right tools to ‘couple’ or monitor two vital pieces of information: watts and heart rate. There are numerous studies that show the intricate relationship between these two fitness factors, especially when a rider begins to reach their threshold heart rate.
Put simply, your heart rate rises as your body fatigues, and your power declines. This can happen either together or separately, depending on which of the two is your focus, and on how fit you are. Let’s look at each one separately.