Why is my power staying steady, yet my heart rate continues to climb?
Most of us have experienced this first hand. This is known as cardiovascular drift or heart rate decoupling. But why does it happen? Should we care? If so, what can we do to help mitigate it?
Although some athletes may interpret this higher heart rate as getting a better workout, according to Dr. Ed Coyle of the University of Texas, this extra stress is not beneficial It is a negative type of stress.
Take a look at the graph from one of my athletes doing some long (15 minute) sweet spot intervals:
Key: Red: HR in BPM; Purple/Pink: Power in Watts; Blue: Target Intensity in Watts
For each interval the power was very steady as you can see, but their heart rate rose over each successive effort. By the numbers, interval #1 was a 144 average HR, #2 was 151, and #3 was 155. An 11 BPM jump from the first to the last. Part is due to fatigue, but this workout was done indoors and heat played an issue.
That's a great graphical example of what cardiovascular drift looks like using data.
So what's the deal?
If you’re not interested in reading the article or listening to the talk, the biggest take-aways are:
What about heat adaptation? Science has shown that our bodies actually do adapt to the heat with physiological changes, but purposely making yourself hot during exercise can be detrimental to the quality of your workout at best, and possibly dangerous. Better to stay cooler and nail your workout. I’ll take a look at heat adaptation in another post.
Here are two great resources that dive into why this happens, why it is indeed negative, and what you can do to help minimize your CV drift.
Fasttalk Labs Podcast: Cardiovascular Drift with Dr. Ed Coyle
And if you really want to nerd out:
So while getting your heart rate up during exercise is often the desired response and a good thing for our fitness development, take the necessary steps to avoid that cardiovascular drift.
Have you ever experienced CV drift? Have you learned any tricks for staying cooler while riding indoors? Post up questions and comments below!
Drink up and get that fan firing!
Coach B.L. is the head coach at BJL Coaching and an avid racer and cycling enthusiast himself.