High-intensity interval training safe for pregnant women and their babies

High-intensity interval training during pregnancy poses little risk to expecting mothers and their babies, according to recent research out of the University of Alberta that runs counter to traditional exercise recommendations for pregnant women.

The study, led by Jenna Wowdzia, a master’s student at the Program for Pregnancy and Postpartum Health, compared maternal and fetal cardiovascular responses to high intensity interval training as well as moderate-intensity continuous training.

“What was novel about this study is that we were looking at how the baby responded to high intensity exercise,” says senior-author Margie Davenport, a pregnancy researcher in the Faculty of Kinesiology, Sport, and Recreation. “We looked at responses in terms of the fetus’s heart rate and also the blood flow that was going to the fetus, so we can see if they were getting enough blood flow, oxygen and nutrients.”

High-intensity interval training is a top fitness trend, Davenport notes, with a growing number of people interested in continuing this type of training during pregnancy. For the study, high-intensity exercise was done through 10 one-minute bouts of interval workouts above 90 per cent of maximum effort with one minute of active recovery. Moderate-intensity exercise was measured with a 30-minute workout.

Davenport previously led the development of the 2019 Canadian Guideline for Physical Activity During Pregnancy for the Society of Obstetricians and Gynecologists of Canada and Canadian Society for Exercise Physiology. To develop the guideline, Davenport surveyed all available literature to look at whether exercise during pregnancy is safe and beneficial for both mother and baby.

“With those systematic reviews and with those guidelines we actually found really impactful information,” says Davenport. “Engaging in physical activity and exercise during pregnancy is associated with a 40 per cent reduction in the risk of developing major pregnancy complications such as gestational diabetes, pre-eclampsia and gestational hypertension, and there is no negative impact on the baby.”

Early small-scale studies that suggested longer-duration progressive exercise to maximal levels had some potential adverse effects led to a broad recommendation not to exceed 90 per cent of maximal exercise at any point during pregnancy, says Davenport.

“This (study) certainly opens up the area in terms of future research to be able to really look at this high-intensity exercise,” she notes. “Without that research, we really can’t change or evolve guidelines. This is the first key step to be able to re-envision what those physical activity guidelines look like.”

Reference:

Wowdzia, J.B., Hazell, T.J., Berg, E.R.V. et al. Maternal and Fetal Cardiovascular Responses to Acute High-Intensity Interval and Moderate-Intensity Continuous Training Exercise During Pregnancy: A Randomized Crossover Trial. Sports Med (2023). https://doi.org/10.1007/s40279-023-01858-5.