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What’s a Safe Intensity to Work at During Pregnancy?

Have you ever heard the guideline to “keep your heart rate below 140 beats per minute” during pregnancy? If so, you’re certainly not alone. This is an outdated guideline from 1985 — which was actually eliminated in 1994 — but somehow STILL persists today. So, if that guideline isn’t correct, then what is? How do you gauge what a safe level of exertion is for you during pregnancy? How do you even know who, or what source, to trust?

These are all great questions, and rest assured, we have the answers (and the evidence-based support) in this post. Let’s begin by looking at what the official guideline is (and who sets it). Then, we’ll discuss how to use this guideline during cardio and strength training.

What are the “Official” Guidelines and Who Sets them?

Currently, there is no global consensus regarding exercise recommendations during pregnancy. Each country generates its own guidelines. In the United States, the American College of Obstetricians and Gynecologists (ACOG) is the body that provides the official medical guidelines for exercise during and after pregnancy. ACOG published its very first set of guidelines in 1985 — when almost no research existed about exercise during pregnancy. In the absence of data, ACOG set a blanket guideline to “keep heart rate below 140 beats per minute during pregnancy.”

In the years following, research showed that heart rate is NOT an accurate gauge of exertion during pregnancy. There are a few reasons for this:

  1. Resting heart rate progressively increases throughout pregnancy
  2. Heart rate response to exercise is variable throughout pregnancy, and from one individual to another
  3. Blunted, exaggerated, and normal linear responses may all be seen at different stages during the same pregnancy (ACE, 2011)

Because of this learning, ACOG eliminated the heart rate guideline in 1994, and replaced it with the guideline to use Rate of Perceived Exertion (RPE) instead. This relies on listening to your body and gauging intensity by how you feel, which is a much more accurate method. This guideline continues today, which you can see here in the latest version of the ACOG Guidelines, updated in 2020.

So, now that you understand that you should be using RPE to gauge a safe level of exertion, let’s talk more about how to use this tool.

How to Use RPE to Gauge Your Exertion

“Rate of Perceived Exertion” or RPE is an easy tool to use because it’s all about how you feel. While there are different RPE scales, we like to use a 1 – 10 scale because it’s the simplest:

  • 1 = Extremely Easy: This is minimal-to-no exertion, like gentle walking.
  • 10 = Extremely Difficult: This is maximal exertion, like sprinting or lifting something so heavy you could only do 1 repetition.

In general, a good guideline for pregnancy is to work between a 6 – 8 on the RPE scale. This means that on a scale of 1 – 10 (with the parameters noted above), you work in what feels like a 6 – 8 range for YOU. If you are accustomed to higher intensity exercise, you can go up to an 8.5, provided that feels ok for you. Please note, however, that you should always follow your doctor’s guidance. There is no research to date at RPE levels higher than 8.5.

It is very important to note that RPE will vary highly by individualand for each individual at different stages of pregnancy. For example, what feels like a 7 for a person who is used to high-intensity exercise will feel much higher for someone who is just beginning their fitness journey. Moreover, what feels like a 6 earlier on in your pregnancy will feel much higher later in pregnancy when you are carrying an additional 25 – 35+ lbs of weight. Finally, given the many fluctuations during pregnancy, your RPE can vary day-to-day. That same set of squats that felt like a 7 on Tuesday might feel like an 8 on Friday!

The final thing to note is that there are other considerations to ensuring the cardio exercise you are doing is safe, such as managing intra-abdominal pressure and alignment shifts. Many traditional cardio moves should be modified as pregnancy progresses. To help you with this, check out these Cardio Modifications for Pregnancy. You’ll find several modifications for the most common cardio exercises — from jumping jacks, to burpees, and more.

What about the “Talk Test”?

You may have heard of using the Talk Test. This is another tool that ACOG references as an option for gauging a safe exertion level. This means that you are able to carry on a conversation while exercising. This can be helpful for those newer to exercise but, if you are well-conditioned, you can stick to the same RPE guidance as was given above: 6 – 8 (or up to 8.5). So, while working at an “8,” you may not be able to carry on a conversation, but this is still within a safe range in which to work.

Looking for More Support?

If you are pregnant and looking for more guidance in safe and effective exercise, check out our Prenatal Training Programs & Services.

If you are a health and fitness professional interested in learning more about working with pre & postnatal clients, explore our Pre/Postnatal Professional Education. 

Sources:

ACOG Committee on Obstetric Practice (2020, April).  Physical Activity and Exercise During Pregnancy and the Postpartum Period. American College of Obstetricians and Gynecologists. Opinion 804.

American Council on Exercise. (2011). ACE Group Fitness Instructor Manual: A Guide for Fitness Professionals. San Diego, Print.