HIIT Workouts and Pregnancy ( Do’s, Don’ts, and Modifications!)

Do you get-it-ON at the gym? Always giving your all at boot camps, aerobics classes, CrossFit, Orange Theory, and running + lifting circuits?

I am. (But I seriously don’t judge anyone who isn't!)

I’ve always wondered why I love these classes so much.  Especially once I learned not everyone is hardwired that same intense-energy way. I remember being shocked when my youth-league soccer teammates dreaded our conditioning practices. Whereas for me--if conditioning was the sport itself, I’d have been quite content. Perhaps I’m drawn to high-intensity workouts because I have such a mild temperament. It’s a space where I can feel strong and fast without worrying about the emotional sequelae of others. Or maybe it’s my brain, so strongly calibrated toward efficiency, that leads me to want to get “the most” out of a workout.

My sister (who is a daily morning runner) and I laugh at the things bystanders will yell out as we jog past. Things like "You're so brave!" or "You're an industrious soul!"

These people mean well. They want to say something encouraging and supportive. But it comes out awkwardly, as we run by. And it's hard to respond when you're so out of breath!

So, if you put yourself in this type of exercise category. Whether you're a runner, weight lifter, or CrossFitter. Let’s take a minute to look at what’s safe and advisable while pregnant.

Good News for Pregnant Athletes:

The simplest way to double-check if you are in a safe heart rate zone while pregnant is if you can still talk while working out.

This is called the “Talk Test” and generally ensures that you are staying within the recommended “moderate” intensity.

Here are some other guidelines:

  • It’s extra important to incorporate 5-10 minutes of warm-up and cold down. This helps your heart regulate blood flow.
  • Your core body temperature should not exceed 100 Fahrenheit.
  • Apply the RPE (rate of perceived exertion) tool. RPE is a scale of 6-20.  6 is how you feel when lying in bed with “little to no effort”. 20 is the hardest workout you’ve ever done. While pregnant, you should stay below a 16, which is “Very Hard” status.
  • Heart Rate Monitoring. A safe heart rate is different for everyone. It's based on your maternal age and BMI. But generally, while pregnant, your target heart rate should be 20-30% less than your target heart rate when not pregnant. Your resting heart rate has already increased 10-20 beats per minute simply by being pregnant! It takes a lot of oxygen to build a baby. So we have to respect that!

The best combo is to combine monitoring your Heart Rate + Rate of Perceived Exertion + the Talk Test.

Also, be aware that your blood pressure and blood sugar levels might be extra sensitive, too.

While pregnant you are turning a HIIT workout into a MIIT workout. Moderate intensity interval training.

It’s wise to modify your workouts, especially in the third trimester.

Pregnancy is not the time to compete with yourself. Take a maintenance approach. All athletes have “down-time” and/or cross-training seasons. While pregnant, your body is adding fluid, pressure, and more of an extra human being every day. So even though you may feel like you’re doing less...the amount of load you’re carrying is more. At times, less “work” is challenging your body just as much as if you were doing more reps.

We are modifying for a few reasons:

  • Your cardiovascular system has an increased load while pregnant. It has more blood to circulate.
  • Your diaphragm is in a compressed and elevated place. As the uterus grows, it presses upward onto the diaphragm. This causes it to ascend further into the ribs. This means it’s not quite working as effectively as usual and it’s harder to breathe.
  • Load management. Having a healthy pelvic floor is just as much about load management as it is religiously doing pelvic floor activation exercises. Think about it this way. Would you lift a gallon of milk with a sprained wrist? Likely not. Your pelvic floor is already working hard to support the increased pressure of your womb. Adding even more pressure, especially if not in an intentionally graduated way, can make it harder for the pelvic floor to lift against gravity over time. Just because you might not be experiencing incontinence now, doesn’t mean you’re doing things to predispose you to experience it even just 3-5 years down the road.

Specific Workout Modification Suggestions:

  • Instead of doing double-unders... do side shuffles. 
  • Instead of doing reps for time... do reps for quality. Slow and controlled.
  • Instead of doing pull-ups...do bicep curls with free weights.
  • Instead of doing loaded squats or box jumps... do air squats and step-out jacks
  • Instead of doing sprints...jump on the rower or stationary bike
  • Instead of doing burpees...shuffle backward
  • Instead of doing a rope climb... have a dance party!

You can also think about this time as a time to cross-train. Hop into a yoga class. Find a pool. Go for a walk in a new neighborhood. Ride a stationary bike.

Have Any Sport-Specific Questions?

Feel free to reach out to me at [email protected] if you have any specific questions about how to modify your workout while pregnant. I’ll do my best to brainstorm with you and come up with the most evidence-based options we can!


Please clear all exercises while pregnant with your doctor and/or healthcare team. If you experience any signs of dizziness, shortness of breath, contractions, bleeding, or pain stop immediately.  

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