Important Canadian Study Suggests High-Intensity Training Might Be Safe for Pregnant Women After All

December 14, 2023 by
Photo Credit: @cassidy_lancemcwherter/
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Keep exercising, but not too hard: That has been the general advice to pregnant women for decades now. The thinking is that too much intensity is dangerous.

As a long-time CrossFit athlete who was recently pregnant and gave birth to a healthy baby boy in September, I found myself torn about what was safe and what wasn’t on more than one occasion. Eventually, I just went with the listen-to-my-body approach when it came to fitness.

This resulted in people giving me grief (and sometimes skeptical glares at the Globo gym) for pushing sleds aggressively, jacking my heart rate, and doing burpees well into my third trimester.

I knew, though, the intensity others perceived I was doing was just that: a perception. So instead of letting it get to me, I chose to take comfort in knowing that, despite continuing with some degree of intense training during much of my pregnancy, I was working at a much lower capacity than what my non-pregnant body could normally do. And I felt good about it.

This just in: If new research out of the University of Alberta, and published in Sports Medicine Journal, is on track, then it appears I might have been onto something with my pregnancy fitness regime. In the study, research found that bursts of intense physical activity during pregnancy might just be safe for both the mother and baby, after all. 

The details: The participants in the study included 15 pregnant women in their late 20s to mid-30s in their second or third trimesters. 

  • They were put through both 30-minute moderate-intensity workouts and shorter high-intensity intervals. The latter involved 10 one-minute efforts on a spin bike at around 90 percent of their maximal heart rate. 
  • Researchers monitored the mothers’ and the babies’ heart rates, as well as other health metrics, including blood flow to the fetus, changes in glucose levels, lactate production, and blood pressure during the training sessions. Both tolerated the high-intensity training well.

One big thing: This study is especially rare because many countries don’t allow research on pregnant women working at a maximal heart rate. Canada is one of the only countries that does.

The big picture: While the sample size in this study is small—just 15 women, plus I’ll throw myself into the mix, as well as hundreds of other CrossFit athletes, including the six-time Fittest Woman on Earth Tia-Clair Toomey-Orr—it’s important research that could be the impetus for updated fitness guidelines for pregnant women.

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