The newest guidelines from the American College of Obstetricians and Gynecologists reaffirmed in 2019 suggest a pregnant woman should use her rate of Perceived Exertion (see image below) or the Talk Test.
A pregnant woman’s heart rate fluctuates throughout gestation, therefore making it
difficult for you to determine from a number on a heart rate monitor just how hard your body is actually working. As a woman’s heart rate response changes throughout pregnancy, the past overall recommendation was to keep your heart rate to a maximum of 140 beats per minute (BPM) during exercise. This guideline assumed that all pregnant women with a heart rate of 140 BPM are exerting the same amount of effort during physical activity.
In 1985, ACOG conducted a study that resulted in their recommendation of 140 beats per minute as the maximum heart rate for a pregnant woman who is exercising. In 1996, the ACOG rescinded this guideline. A pregnant woman is not simply pumping blood through her own body, but also her unborn child’s, a circumstance that leads to a lower volume of blood circulating than when she is not pregnant and thus, a faster heart rate to compensate. FYI: If you have are a regular exerciser, you could recognize you are pregnant because your normal routine has her heart rate going higher than usual. The use of perceived exertion can be a more effective way to determine intensity during pregnancy (unless you are an athlete with longer training sessions – more on that below). Recent research suggests pregnant athletes should use a heart rate monitor, reason being athletes tend to “push” through.
It’s important to pay attention to how hard you are working during pregnancy exercise, or your rate of perceived exertion. Use the Talk Test, speaking a full sentence while exercising. Or the Borg Scale.
Please note that your doctor’s recommendations always supersede this advice. So, if your OB recommends you stay under 140 BPM, then that is the protocol that you should follow.
ACOG recommends the 20-point scale, while other research recommends a 10-point scale. For moderate intensity exercise you should be between 13-14 or “somewhat hard” on the Borg scale.
Measuring exertion through the talk test is one of the easiest ways to determine what’s too much and what’s too little. As long as you can carry on a conversation while exercising you are likely in the sweet spot and not overexerting yourself.
Takeaway: You should avoid using a heart rate monitor to determine the right heart rate for your body during pregnancy exercise. A pregnant woman’s heart rate fluctuates throughout gestation, therefore making it difficult for you to determine from a number on a monitor how hard your body is actually working.
Please see the Prenatal Exercise Do’s & Don’ts before beginning prenatal exercise.
Download our Prenatal & Postnatal Starter Pack.