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What to Know About Exercise Heart Rate During Pregnancy

Don't Let This Heart Rate Myth Impact Your Pregnancy Workouts

woman doing yoga while pregnant watching her heart rate during pregnancy exercise

During pregnancy, your body is going through lots of changes to support the growth of your baby. They can cause fatigue and some aches and pains, so it makes sense why many pregnant people might be hesitant to expend any bit of their energy on exercise. However, there are plenty of perks to working out during pregnancy, including a lowered risk of gestational diabetes and reduced backaches, constipation, bloating, and swelling, per the Mayo Clinic. In fact, the American College of Obstetricians and Gynecologists (ACOG) recommends doing at least 150 minutes of moderate-intensity aerobic exercise each week when you're expecting.

But, as trainer Anna Victoria recently pointed out on Instagram, there's a lot of information out there about what's safe for prenatal workouts, and it can be confusing to navigate. Specifically, there's a common misconception that your heart rate should stay below 140 beats per minute (bpm) during pregnancy exercise. Victoria isn't the only one wondering about it; TikTokers are also calling out this outdated advice, claiming it's a myth.

So do you really need to pay attention to your heart rate during pregnancy workouts, and if so, how do you go about doing that? Here's what experts have to say.

Do You Need to Keep Your Heart Rate Under 140 BPM?

The short answer is no. "The heart rate limit of 140 beats per minute is an outdated number," says Rachel Trotta, a NASM-certified personal trainer who specialises in pre- and post-natal fitness.

These recommendations were the standard once upon a time because it's believed that getting your heart rate up too high can potentially affect blood flow and oxygen levels for your baby, says Megan Gray, MD, obstetrician-gynecologist at Orlando Health Physician Associates. However, there isn't enough research to make a recommendation on an ideal heart rate while exercising during pregnancy, she says.

Not to mention, "a blanket heart rate precaution is a bit tricky since everyone's max heart rate is so different and can be different day to day," wrote Amy Schultz, a physical therapist for Victoria's Fit Body app, in a comment on Victoria's Instagram post. "Instead, knowing your own personal max heart rate and basing your training off a percentage of that would be more ideal. Also, going off of RPE is a great/research backed way to stay active safely during pregnancy!"

Trotta seconds that. "More current recommendations are based on a [person's] rate of perceived exertion [RPE] during exercise," she says. "This means that, instead of monitoring heart rate, most pregnant [people] can use the talk test to self-assess." More on how to do that, below.

Can You Work Out at High Intensities During Pregnancy?

If you're a seasoned athlete and have trained at high intensities pre-pregnancy, you can continue to do so while pregnant, granted you modify as needed as your pregnancy progresses.

"While research is lacking, people with low-risk pregnancies who previously performed high-intensity exercise may continue this level throughout their pregnancies," says Stephanie Hack, MD, a board-certified obstetrician and gynecologist and host of the Lady Parts Doctor Podcast. "However, they should monitor for symptoms, such as vaginal bleeding, abdominal pain, fluid leakage, regular painful contractions, etc." In general, it's a good idea to discuss your workout routine with your healthcare provider especially if you hope to continue intense exercise while pregnant, she says.

More good news: Even if you aren't already active, it's safe to start exercising — even up to moderate or vigourous intensities — while you're pregnant. According to a small 2012 study in "Obstetrics & Gynecology," when inactive and active pregnant people did moderate- and vigourous-intensity exercise for 30 minutes, it was well-tolerated by the mother and baby, suggesting that you can safely start or maintain a workout routine at vigourous intensities while pregnant.

"Unfortunately, we don't have much information about the effects of exercise at higher levels (over 85 percent capacity)," Dr. Hack explains. "Theoretically, there could be negative effects if too much strain is placed on the maternal heart, which would ultimately affect the fetus." To make sure you're staying below that threshold, keep reading to learn about the talk test, below.

How to Use the Talk Test to Gauge Workout Intensity

The talk test is an accessible way to gauge just how intensely you're working during exercise. It's simple: During exercise, how well you're able to speak out loud can help demonstrate where you are on an intensity scale. For example, during moderate-intensity exercise, you're raising your heart rate and likely sweating but can still speak to someone in short sentences, Dr. Gray says. Meanwhile, during vigourous or intense exercise, you're only able to say one or two words. If you're so winded that you can't carry a conversation, you could consider decreasing the intensity to lower your heart rate, Trotta says.

If you know your maximum heart rate from wearing a smartwatch or fitness tracker, ideally, the upper limit of your exercise heart rate should be less than 85 percent of your maximum heart rate, says Dr. Hack.

How to Safely Exercise While Pregnant

For starters, it's always a good idea to consult with your healthcare provider about your workout routine while pregnant, especially if you have complications. "Exercise should be avoided in people with complications, such as unexplained vaginal bleeding, incompetent cervix, and preeclampsia. Your doctor can help you determine what type of activity is best for your pregnancy," Dr. Gray says.

When training at high intensities, make sure to drink plenty of water before and during your workout and enjoy a pre-workout and post-workout snack or meal, Trotta says. These meals or snacks should be high in carbohydrates and protein to support your performance and muscle repair after your workout. Pregnant people who work out at high intensities need to ensure that they're consuming enough calories to fuel their workouts and support their pregnancy and overall health.

It's important to note that when it comes to tracking heart rate with the talk test, you're primarily doing this only with cardio and HIIT exercises. If you're strength training, you want to be more mindful of your blood pressure versus your heart rate.

"I advise weightlifting pregnant women to not hold their breath during strength training. Holding your breath for a few seconds during very heavy lifts is called the Valsalva maneuver, and it is normal and common for barbell training and powerlifting," Trotta explains. Holding your breath for a few seconds while lifting can raise your blood pressure, which can be harmful to your baby. That's why she recommends pregnant people lighten the weights they use so that they are able to lift with smooth, unbroken inhalations and exhalations. "For an experienced weightlifter who's pregnant, this means she still might lift heavier weights than the average person, but it's light enough (relative to her own skill) that she can be more aware of breathing and form," Trotta says.

While there are generally no limits on the type of exercise to engage in during pregnancy, you should definitely avoid high-risk activities, like skiing, softball, flag football, sky diving, and scuba diving, Trotta says. The ACOG also recommends avoiding hot classes because you can become overheated, which can put you and your baby at risk.

If you ever feel dizzy or experience any bleeding or contractions during your workout, stop exercising completely and reach out to your doctor.

The bottom line is that exercise during pregnancy has many benefits and there's no real reason to stop your workout routine as long as your doctor gives you the green light.

"If exercising intensely triggers someone's fear that something bad will happen to the baby, it's important to remember that moderate (or easy) workouts still count! You can always scale down exercise to feel less challenging, especially if that helps you stay more consistent and have more peace of mind," says Trotta.

Maybe pre- or post-natal training will usher you into your Pilates girl era — and there's no better time for that!

Image Source: Pexels/Pavel Danilyuk
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