Anatomical Heart Illustration
Black and line anatomical line drawing of a human heart.

Why Heart Rate Pacing

As ME patients, we know that pacing is one of the hardest parts of illness management. Quite frankly, I think the premise goes against human nature. And it is in total opposition to the social rules of capitalism, and of many families and communities. It is hard.

While heart rate pacing doesn’t cover everything, it doesn’t always tell us when we’ve done too much mental exertion, for example, it can really help us get a handle on our physical activity. We can learn a lot about our bodies and what is tolerated and what isn’t. We can use an objective tool to tell us when it’s too much. And we can understand a bit about when we’ve overdone it, to know we need to rest more.

It is the number one thing that I wish someone had told me about early in my experience living with ME.


What is it?

In ME patients, we have a greatly reduced anaerobic threshold. This means that our body is often engaged in a hard core workout, just from the basics of daily living. When you have a severely impaired energy system, you can’t do that repeatedly without paying for it. And we pay for it in the form of post exertional malaise (PEM).

In short, heart rate pacing is a tool to help us stay below our anaerobic threshold and reduce our experience of post exertional malaise. It is not a cure for ME/CFS. But it is a management tool that can help you reduce the impact of day to day living, and can for some people expand their capacity to do things.

Here are two articles from some solid sources:

Using A Heart Rate Monitor To Prevent Post-Exertional Malaise In ME/CFS is a great overview of heart rate pacing.

Pacing by Numbers: Using Your Heart Rate To Stay Inside the Energy Envelope from ME/CFS and Fibromyalgia Self-Help.


What’s My Magic Number?

There are several ways to get at this answer, and most of them will involve trial and error.

1, CPET: I am one of the people who actually mostly knows my number. And that’s because I have done the exercise test that determines this. The test is called a 2-Day CPET (Cardio Pulmonary Exercise Test). This test is both difficult to access, and depending on the level of illness severity, can be very difficult to physically do. There are people who have experienced illness decline after doing the test, so it is a very personal choice whether to pursue it.

I found it incredibly helpful, both for being approved for SSDI, and for learning about my anaerobic threshold and learning my pacing number.

I am always happy to share more about my experience of this with any patients considering doing it. I can be reached at chronicallyrebecca at gmail dot com, or through the usual social channels.

2, Calculation: In absence of a 2-day CPET, many folks start with a formula. Healthy people can estimate their anaerobic threshold at (220 – age).  So, I had my CPET done when I was 44. If I were healthy, my anaerobic threshold at that time would have been estimated at a heart rate of 176 bpm. ME/CFS patients aren’t healthy, and the decline depends on how severe you are. So many people take a percentage of what would be their age calculated number, often 50%, 55%, or 60%.

So, the formula would look like: (220 – age) x .5

or (220 – age) x .55

or (220 – age) x .6

What would that have been for me when I was 44? 88 bpm at 50%, , 97 bpm @ 55%, 106 @ 60%

(My actual tested AT was 86. They all would have been to high.)

3, Starting with 100: The most basic of all. Try to stay under 100. If you can do that successfully and don’t have PEM, god job! Who knows? Maybe you can go higher? Still getting PEM? Go lower until you don’t.


If you use method 2 or method 3, you will need to experiment. The real truth is in when you reach a low enough number under which you activity does not cause PEM. If you’re getting PEM from activities where your heart rate is 90, try going lower.

One reason we need to be even more conservative when calculating pacing numbers, is that many of us also have Chronotropic Incompetence. Chronotropic Intolerance: An Overlooked Determinant of Symptoms and Activity Limitation in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome?


Working with Devices

First, many folks will tell you that the most accurate way to do this is with a chest strap. I have a chest strap, and due to my chronic pain, I am unable to use it. On the occasions that I have tested my wrist devices against my chest strap, they have done pretty well. Your mileage may vary.

Most of the fitness trackers out there are not a good fit for this endeavor. There are several challenges, like accuracy or responsiveness. But the biggest challenge is that in order to do this well, you need an alarm to tell you when your heart rate is too high. This is not a standalone feature on any device that I’m aware of. So the way that heart rate pacers do this, iby typically by pretending they are performance athletes. In order to do this, you need the kind of device a performance athlete might use.

Here’s a little primer I wrote on how to work with devices for heart rate pacing. It can be confusing, and I recommend reading this before looking at a device to buy.

Fitbits are popular fitness trackers. Fitbit does not have the feature needed. There is a work around that a few folks use, but it involves a third party phone app, and I’m not familiar with all the ins and outs. Folks have been asking Fitbit to add the feature for years, with no success.

As I understand it, Apple watch and some Garmin devices can work well for folks. I’m an avowed Android devote, so I know nothing of Apple watches. I haven’t personally used any Garmin products, but they are my next try if I decide to switch product manufactures. I would personally probably try the Vivoactive 4. Someone I know reported that she doesn’t find the vibration alarm strong enough. Others seem to like it.

I ended up in the Polar Family.

The Polar A360 and A370 watches are very popular across the heart rate pacing community. I used the Polar A370 for two years, then switched to the Polar M430, which I greatly prefer. Here’s a bit of a comparison between the two devices: Polar A370 vs Polar M430 Watch for HR Pacing for ME.

Most of these devices are all set up the same way, in the Polar Flow app. But setting the watches up for heart rate pacing can be a confusing process. If you skipped over my link above to my primer, please read it now.

If you have a Polar device, an acquaintance put together a guide of how to do it, and told me I was free to share broadly and she didn’t need credit: Polar watches setting HR zones, vib alert and annotating print screens- a370

Support for Heart Rate Pacing

ME/CFS Pacing With a Heart Rate Monitor 2 on Facebook

ME/CFS: Below the Threshold on Facebook is an information resource maintained by Angela Flack, who also manages the Holistic Myalgic Encephalomyelitis site mentioned below. It is more structured than most FB groups. This group is structured as a learning resource. Within the group, the information is organised into master threads. Please post your questions on the related master threads: the intro content is in the unit posts, and other master threads are pinned in the announcements.

Holistic Myalgic Encephalomyelitis : Angela’s site has lots of information, but what makes it really special is the information on heart rate pacing and using heart rate variability data.  Anyone interested in trying this approach to manage their ME/CFS should start with her HRM Master Page.