Healthy Habits

Running Pregnant: The Heart Rate Myth

Disclaimer: I am not a doctor, midwife or nurse. The information expressed in the series “Running Pregnant – By” should not be taken as medical advice. Please consult your doctor before running during pregnancy and postpartum.

So during my first Pregnancy I was told to keep my heart rate in check when running, ensuring that I do not over do it and somehow harm the baby. Till this day I have concentrated on my heartrate and tried to monitor it closely while I exercise during pregnancy. But after some research the past few days, I have discovered it is actually a little different.

The fact is, it is not actually an accurate measurement to go by. Using heart rate as a measure of exertion might be unreliable in pregnancy because of the many physiological changes that happen in order to support a growing Baby. When your pregnant your heart rate, blood volume and cardiac output all increases and because of all these changes, your heart rate may not increase in response to exercise in the same way that it did before pregnancy. So trying to monitor it, can prove to be false information at times.

So, What now? How do you know if your pushing too hard? According to my Dr and a few other articles I’ve read the best way t know if your pushing to hard is to use the talk test. Basically, as long as your breaking a sweat, raising your heart rate and can talk or carry a normal conversation your doing fine!

I still glace at my heart rate though, its kinda drilled into me now, and it still does give me an idea of how hard I’m pushing. What is also a fact is that what might be considered an easy run/exercise for a pregnant mom that ran miles everyday before he pregnancy and a mom that barely ever exercised is two completely different things. So, If you were not exercising or regularly running before your pregnancy then it’s probably not the best time to start a fitness routine while you are pregnant.

And for Moms that ran regularly before pregnancy, I’m not saying it won’t be hard, believe me your body is changing but it is still recommended to continue your exercise routing as much as possible but still scaling down and not over doing it.

Running or Exercise is beneficial to both you and baby. Not only can it reduce back pain, promote healthy weight gain during pregnancy, and strengthen your heart and blood vessels, but it may also decrease your risk of gestational diabetes, preeclampsia, and cesarean delivery. But every bodies journey is different, so take yours day by day, and remember , when in doubt – Call your doctor!

U P D A T E:

So after some discussions with a few others on the topic and a Family Dr, I have a little update. I thought about this previously as I was writing the article but refrained form motioning it because it is again so dependent from person to person, that you’ll have to discuss it with your Dr. and also see if it is something that works for you?

So before you were pregnant you had a baseline for your heart Rate – Mine was about 60 resting. and after becoming pregnant it is now about 70 -80 Depending on the day and according to my Polar watch.

So if you have decided to not try and push over 60-65% of your maximum heart rate then you should be safe, in my personal opinion, but check and discuss with your DR.

How to determine your target heart rate zone


Here’s a simple way to do the math yourself. If you’re aiming for a target heart rate in the vigorous range of 70% to 85%, you can use the heart rate reserve (HRR) method to calculate it like this:

  • Subtract your age from 220 to get your maximum heart rate.
  • Calculate your resting heart rate by counting how many times your heart beats per minute when you are at rest, such as first thing in the morning. It’s usually somewhere between 60 and 100 beats per minute for the average adult.
  • Calculate your heart rate reserve (HRR) by subtracting your resting heart rate from your maximum heart rate.
  • Multiply your HRR by 0.7 (70%). Add your resting heart rate to this number.
  • Multiply your HRR by 0.85 (85%). Add your resting heart rate to this number.
  • These two numbers are your average target heart rate zone for vigorous exercise intensity when using the HRR to calculate your heart rate. Your heart rate during vigorous exercise should generally be between these two numbers.

So my Personal calculation looks like this:

Pre-pregnancy Resting heart rate: 60

Pregnancy Resting Heart Rate: 70


Heart rate Zones: 50% and 65%



220-27 = 193 (Max Heart rate for age)

193+60 = 133 (Heart Rate Reserve)

133 x 0.5 (50% for HR) = 66,5

66,5+60 = 126,5 is my 50% heart rate zone.


220-27 = 193 (Max Heart rate for age)

193+70 = 123 (Heart Rate Reserve)

123 x 0.5 (50% for HR) = 63,5

63,5+70 = 133,5 is my 50% heart rate zone.

I hope this helps a little bit in monitoring your Heart Rate While running pregnant, I use this as a guide – but Like I said above, there are different variables for each person and the best is to talk to you Dr, and make sure your always training at an conversational pace.

Please feel free to Pop me any questions below and Have a look at the rest of my running series links below for all your Running Pregnant needs!

Happy Running



Links for Full Running Pregnant series:

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