Outdated Pregnancy Exercise Advice? Here’s What the Research Really Says
At Back Bay Health, we hear it all the time:
“My OB said not to lift more than 20 pounds.”
“I was told to keep my heart rate under 140.”
“A trainer said crunches will cause Diastasis Recti.”
If you’ve been handed a list of blanket “don’ts” for exercise during pregnancy—especially during a healthy, uncomplicated one—it’s time for a second opinion.
Because the truth is: most of these restrictions are not backed by current research.
Common (But Outdated) Pregnancy Exercise Myths
Let’s break down a few of the most common myths we hear:
🚫 Don’t lift more than 20 lb.
🚫 Avoid getting your heart rate above 140 BPM.
🚫 Crunches cause Diastasis Recti.
🚫 Running is bad for your pelvic floor.
🚫 Don’t exercise on your back.
🚫 It’s unsafe to start a new exercise program during pregnancy.
If your provider or trainer is handing you advice like this with no consideration of your individual health, fitness level, or symptoms—that’s a red flag. 🚩
Here’s What the Research Actually Shows
Current evidence paints a very different picture. Lifting weights, even heavy ones, is considered safe during a normal pregnancy, and there's no data supporting an arbitrary 20lb limit. In fact, strength training can be an important part of staying strong, mobile, and pain-free throughout pregnancy.
The idea of keeping your heart rate under 140 beats per minute is outdated and no longer recommended by major health organizations. Most people can safely tolerate increased heart rate during exercise, and monitoring for symptoms like dizziness, breathlessness, or pain is far more helpful than sticking to a rigid number.
When it comes to core work, crunches and ab exercises do not cause Diastasis Recti. DR is a normal and expected part of pregnancy for many, and exercise (including targeted core work) can actually help manage it. Similarly, running isn’t inherently bad for your pelvic floor, especially if it was part of your routine before pregnancy and feels good to continue.
Even exercising on your back is often fine in the second and third trimesters, particularly for short periods of time and if you're asymptomatic. And starting a new exercise program during pregnancy? That’s often a great idea, especially for those who were previously sedentary and are now ready to move in a safe and supportive way.
The takeaway? The "better safe than sorry" approach to pregnancy exercise often leads to unnecessary fear and deconditioning. What’s actually safer is staying active.
What Do Good Exercise Recommendations Look Like During Pregnancy?
So what should modern pregnancy exercise guidance include?
The current guidelines recommend aiming for at least 150 minutes of moderate to vigorous activity per week, ideally spread over 3 to 5 days. But it’s not just about the numbers. The type, intensity, and structure of your workouts should reflect your unique fitness level, symptoms, preferences, and lifestyle. There’s no ‘one size fits all’ approach here… just smart, adaptable movement that supports both you and your baby.
Need Help Modifying Your Workouts for Pregnancy?
Whether you're feeling uncertain about your current exercise routine, wondering how to make smart modifications, or dealing with symptoms that make movement tough, you're not alone.
📍 You can work with us in person at our Boston clinic, Back Bay Health, or virtually from anywhere.
💬 Have a question right now? Book a free discovery call or reach out directly, we’re here to help you move with confidence during pregnancy and beyond.
Pregnancy Exercise Reference List:
Mottola MF, Davenport MH, Ruchat S, et al 2019 Canadian guideline for physical activity throughout pregnancy British Journal of Sports Medicine 2018;52:1339-1346.
Moolyk AN, Wilson MK, Matenchuk BA, et al Maternal and fetal responses to acute high-intensity resistance exercise during pregnancy British Journal of Sports Medicine 2025;59:159-166.
ACOG committee opinion number 804 April 2020: Physical Activity and Exercise During the Pregnancy and Postpartum Period.
Prevett C, Kimber ML, Forner L, de Vivo M, Davenport MH. Impact of heavy resistance training on pregnancy and postpartum health outcomes. Int Urogynecol J. 2023 Feb;34(2):405-411. doi: 10.1007/s00192-022-05393-1. Epub 2022 Nov 4. PMID: 36331580.
Cooper DB, Yang L. Pregnancy And Exercise. 2023 Apr 17. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan–. PMID: 28613571.
Hicks LE, Graf MD, Yeo S. Prenatal exercise and its effects on postpartum mental health: systematic review and meta-analysis. Arch Womens Ment Health. 2024 Nov 7. doi: 10.1007/s00737-024-01525-2. Epub ahead of print. PMID: 39508925.
