You CAN Lift That: New Research on Safe High Intensity Exercise for Pregnancy

“She’s going to hurt her baby.”

“That’s just wrong.” 

“Irresponsible and Dangerous”

When cross-fit athlete Tia Clair Toomey shared videos of her participating in a gruelling cross-fit session at 8 months pregnant, amidst the positive comments from her legions of fans, there was of course the backlash.

Toomey is not alone. Elite athletes that continue to train at a high level during pregnancy are often plagued with criticism and admonishment. Take US athlete Alysia Montano who was called 'ridiculous' for competing in sprint events at 8 months pregnant for example.

To blame (in part) is the fact that for a long time, we were sold the message that pregnant women are fragile and need protection. Historically, pregnant women were given a long list of exercises to avoid -  and these lists were often based on expert opinion, rather than actual research and evidence.

However, recent research emerging out of Canada and Australia is challenging these misconceptions and providing new insights into the upper limits of exercise during pregnancy.

As co-founders of the Empowered Motherhood Program, including a Pelvic Health Physiotherapist (Lyz) and a former professional athlete (Kimmy) a former professional athlete), we are incredibly passionate about helping women to feel informed, empowered and strong through every stage of their pregnancy. 

Thank you to researchers Lori Forner and Margie Davenport for providing their insights for this post.

Changing the Status Quo

In Australia, up until 2020, the Royal Australian College of Obstetricians and Gynaecologists (RANZCOG) recommended that pregnant women experiencing a low-risk pregnancy should aim to complete between 150-300 minutes of moderate-intensity exercise (moderate intensity being a level where they are able to maintain a conversion) including two strength-based sessions per week.

For a lot of women, this represented a significant regression from their pre-pregnancy routine. As researcher Margie Davenport points out, women who would continue to engage in high-intensity exercise during pregnancy would often experiencing feelings of anxiety or stress over whether the exercise they were doing was safe for their baby.

In 2020 the RANZCOG guidelines were updated to include 150-300 minutes of moderate-intensity exercise OR 75 to 150 minutes of vigorous exercise, or some combination of the two. (Vigorous exercise is at a level where you need to pause for breath during a conversation).

Not only is this change representative of the growing trend towards acknowledging that some women will come into pregnancy with years of training behind them but of the fact that often a woman’s exercise routine is part of her mental, social and emotional well-being - and often the exercise she enjoys is at a level beyond moderate.

The benefits of exercise in pregnancy are numerous. A research paper authored by Margie Davenport and others (Prenatal Exercise for the Prevention of Gestational Diabetes Mellitus and Hypertensive Disorders of Pregnancy: A Systematic Review and Meta-analysis 2018) shows that just 9 minutes of exercise a day can result in a 25% reduced risk of pre-eclampsia. Or just 19 minutes of exercise a day can result in a  25%  reduced risk of gestational diabetes. 

So it is vital that we help pregnant women to keep moving safely and in a way that they find motivating and rewarding.

What are the upper limits of ‘safe’ exercise in pregnancy?

The RANZCOG Exercise during Pregnancy Guidelines states that due to ‘limited research regarding exercise at higher intensities there is no evidence-based safe upper limit for the intensity of exercise”.

Davenport, says that this may be because “the vast majority of research that has been conducted during pregnancy has been in the moderate intensity range. Until recently we have had very limited information about vigorous to near-maximal exercise intensities during pregnancy."

With female professional sports expanding every year (for example AFLW has expanded from 8-18 teams in the last 7 years and W-League has expanded from 8-11 teams over the last 15 years) defining the upper limits of safe prenatal exercise is becoming more and more important.

Davenport’s recent paper published in the Journal of Sports Medicine and with lead a Jenna Wowdiza and other co-authors (Maternal and Fetal Cardiovascular Responses to Acute High Intensity Interval and Moderate Intensity Continuous Training Exercise during Pregnancy 2023) surveyed 15 participants who had previous experience with HIIT exercise found that 30 minutes of moderate intensity continuous exercise and a standard HIIT protocol (10 × 1-min intervals ≥ 90% maximum heart rate [HRmax]) were well tolerated by both mother and fetus, the research team did not observe any adverse effects of either acute bout of exercise.

This data is the first to demonstrate that brief bouts of near-maximal exercise is well tolerated by both mother and fetus, providing reassuring safety data for those who wish to continue this type of exercise during pregnancy and who are not experiencing any contraindications (medical reasons why physical activity might not be recommended during pregnancy).

Davenport notes that for those with absolute the above findings may not be applicable to those who have not done HIIT previously. If you are interested in finding out more, Davenport and her team have developed an exercise per-participation screening tool, the Get Active Questionnaire for Pregnancy (https://csep.ca/2021/05/27/get-active-questionnaire-for-pregnancy/) which helps women determine if they need to speak to their health care provider before continuing or beginning exercise during pregnancy.

You Shouldn’t Be Lifting That.....Changing the way we think about Pregnancy and Weights 

As more money is invested into female sport, we are going to see more and more women who want to continue to exercise and compete at the highest level during their pregnancy, with the view to returning to elite sport as soon as possible. And this includes lifting (often heavy) weights.

Professional athletes, will often have a team of healthcare professionals ensuring that they are exercising at a level that is optimal for their longevity as an athlete and for the health of their baby.

However, for everyday athletes who want to continue to train at a high level, is it safer just to drop the barbell and stick with ‘pregnancy-safe’ movements?

Not according to Christina Prevett and the team of researchers who recently published a paper on the ‘Impact of Heavy Resistance Training on Pregnancy and Postpartum Health Outcomes in the International Urogynecol Journal (2022). Prevett and her team surveyed 675 women and found that “those with experience in heavy lifting prior to pregnancy were not found to have adverse pregnancy, delivery, and pelvic floor outcomes if they continued heavy weightlifting, holding their breath during lifting skills, or performing exercises on their back during pregnancy.”

Previously, lifting heavy weights, performing exercises that cause you to hold your breath or perform valsavla and exercising whilst lying on your back beyond the 16 weeks gestation were all contra-indicated for pregnant women.

Co-author Lori Forner shares that this research “found that women who continued to lift throughout their pregnancy had better health outcomes than those who stopped lifting when they became pregnant. One extremely important finding in our study was the beneficial impact of heavy weightlifting in pregnancy on perinatal depression. We observed much lower rates of postpartum/postnatal depression and anxiety in women continuing to lift in pregnancy compared to the general population.”

However, Forner also cautions that “pregnancy is not the time to start Olympic or high-intensity weightlifting.” She also notes that “more research is needed to look deeper into mother-baby responses to heavy weightlifting during pregnancy.”

We believe it is important to note that whilst there was no adverse outcomes, approximately 57% of the women surveyed experienced urinary incontinence following pregnancy. Which is slightly above the rate of urinary incontinence experienced by the general population. (Thom et al 2010).

So why modify at all?

It is clear that was is considered ‘safe exercise’ in pregnancy is changing. However, whilst we want pregnant women to continue to exercise and to feel strong and empowered in their pregnancy, we also want to do so in a way that: 

• Supports their long-term pelvic health;
• Prepares their body for birth; and 
• Sets them up for optimal postnatal recovery.

Therefore it is really important that women are supported to exercise in a way that is safe for their pregnant body and which takes into account their exercise history, their fitness levels, the physiological changes that are occurring (including changes to connective tissue, structural changes, hormonal changes and changes to weight distribution) and their long term exercise goals.

While these studies provide encouraging insights, it's important to acknowledge that every woman is different. If you wish to continue to participate in Olympic Weight Lifting, Cross Fit, Elite Sport or HIIT, it is important to seek guidance from healthcare professionals, including Pelvic Health Physiotherapists. 

Ideally the exercise you do in pregnancy, not only supports you physical and mental health, but your long term pelvic health, preparation for birth and postnatal recovery.

In the Empowered Motherhood Program, our week by week pregnancy program is designed for just this. We are here to help you to feel strong and confident through every stage of your pregnancy with physio-led at-home workouts that include strength, cardio, and pilates and are designed in accordance with the RANZCOG Exercise During Pregnancy Guidelines. 

Thank you to the research teams involved

We are incredibly grateful to the above research teams for investing so much time and effort into prenatal exercise in this way. It is incredibly inspiring and empowering to have research that helps us to understand the ways that high level exercise impacts a mother and her baby during pregnancy.