High heart rate during exercise but not out of breath

This question crops up all the time! You are out for an easy run, but when you get home and check the heart rate data from your sports watch, it looks very high. How can this be? Am I ill? Do I need to see a doctor? Why is my heart rate so high while running? Or more specifically, why is my heart rate high on easy runs? How is it possible for my heart rate to be that high when it seemed like I was going for a really slow run with low effort?

For example, at an easy, conversational pace, you’d expect the average forty year old runner’s heart rate to be around 140-150bpm (beats per minute). At this effort level, you’d be able to say a sentence of about this length without having to gasp for breath in the middle. But when you look at the data, it says 170-190 heart rate when running! That’s a high BPM when running, no matter how good you are, and would be more appropriate to a Zone 5, max effort 5K or interval session! Weird right? If you have a high heart rate when running but feel fine, this may solve it for you.

Firstly, let’s state that if the data is correct, and your heart rate really is very high while running at an easy effort, you should definitely get yourself checked out out by a doctor. Perhaps your brain can’t regulate your heart rate properly, leading to Tachycardia Arrhythmia. It’s rare, but possible.

However, before you get too excited and rush to get an appointment at the clinic, do a few sanity checks on the data next and understand how easy it is for the data to be completely wrong!

After you’ve read the solutions below, you should check out our course on improving your running form (link opens in new tab) so that you can be faster and more relaxed on your runs.

Look at the heart rate graph more closely!

Exhibit A:

Does your heart rate look like Exhibit A above most times you run? Does it shoot up at the beginning and stay high the whole way?

Exhibit B:

Or does it look like the Exhibit B above, where the heart rate rises gradually throughout the run?

Exhibit C:

Or perhaps it jumps around erratically like in Exhibit C above, suddenly going from a low heart rate to a high heart rate (see the “shelf” around 22 minutes to 27 minutes), even though you were maintaining the same pace throughout?

Assuming you are running at the same pace throughout the run, you’d expect to see something like Exhibit B. So why are you seeing something different?

Problems normally caused by optical wrist-based heart rate monitors

Most of the problems I see in this area stem from people using the optical heart rate monitor on their sports watch without setting the watch up correctly.

There is a sensor inside the watch with strong LED lights either side of it. The sensor looks at changes in the reflected light level caused by the blood pulsing past it. For this to work properly, the watch needs to be set up correctly on the arm. If it’s not, it can start measuring your cadence instead!

Cadence monitor instead of Heart Rate monitor!

What happens to your wrist when you run? Your arm is counter-balancing the movement of your legs and thus your wrists are moving forwards and backwards at the same rate as your feet are taking steps. The number of steps you take each minute is called Cadence. This normally doesn’t change much throughout your run.

When you are using a wrist based heart rate monitor instead of a chest strap sensor, the watch needs to be snug against your wrist, otherwise slight movements in the watch position caused by the arm movements are determined to be changes in light levels. Since that’s exactly what the sensor in the watch is looking for, it can easily lock on to these instead. In this case, the graph will look just like Exhibit A above. Or if perhaps it will get confused and jump between the two, like in Exhibit C, with a few minutes showing real heart rate and few minutes showing cadence instead. Note that I’ve included the cadence readout in Exhibit C and you can see it exactly matches the false heart rate value.

How to get a more accurate reading from an optical heart rate monitor.

Here are your options to fix this.

First, try tightening the strap. If you can quickly and easily slide your finger under the strap, it’s too loose. Tighten it until your finger gets a bit stuck when trying to slide under the strap. This will mostly likely fix the issue.

If the strap is already tight, but you are still measuring your cadence, or getting erratic readings, try shoving the watch up your arm a bit towards the elbow. This will move it on to a thicker bit of flesh, with more blood flow and a snugger fit.

Another option is to switch the watch to the other arm. Most people are right handed, but wear their watch on the left. However their left wrist will be slightly thinner due to less strength from the hand bias. See if your other wrist gives a more reliable reading.

Oddly, if your strap is too tight, it will prevent your blood flow from being measured properly and might measure too low, for example during a hill session, you’d expect it to be really high, but it’s not reacting and is staying low, so it appears your heart rate is low while running fast.

Finally, if you still can’t get a reading that looks right, apart from seeing a doctor, you could try a chest strap sensor instead. Most decent sports watches will support one. They need to be wet to work well, so soak the strap before you leave, but they are generally accepted to give a good reading, especially at the high effort levels required in 5K races, interval sessions or Maximum Heart Rate Stress Tests that help you determine your heart rate training zones.

I hope you found that useful. If it has helped you answer the question why you have a high heart rate during exercise but not out of breath, or why is my heart rate so high while running, please comment below.

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