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  • Writer's pictureJen Curtis

6 Biggest Misconceptions about Pregnancy Fitness

In my work I see not only a lot of pregnant and postpartum women that have been told all kinds of nonsense about pregnancy fitness, but also a lot of professionals who teach a lot of out-dated rubbish.

So I put together some of the top misunderstanding that I see and hear about exercising throughout pregnancy.

1. You can do whatever you did before pregnancy, just listen to your body. But don't do anything new.

While well intentioned, this one gets lots of women in trouble.

Some exercises are better suited to pregnancy, and others less so.

As you probably know, I'm not a big fan of black-and-white dos and don’ts, but, there are sports and exercise modalities that are down-right dangerous during pregnancy. Scuba diving, base jumping, MMA, acrobatics – it doesn't matter which way you spin it, you just can’t do this shit during pregnancy.

But this pregnancy black list is far shorter than most people think – then comes in the dark grey area, activities that do not lend themselves well to the physiology of pregnancy. Powerlifting, running, capoeira, Pilates (yes, Pilates) many aspects of CrossFit – yet we're getting mixed messages about these kinds of activities. We're either told "if you did it before getting pregnant, it's fine to carry on, but don't start during pregnancy" or we're told that we absolutely should not do any of these activities, right from conception.

As you've probably guessed, I don't sit in either of these camps. I'm a big fan of, as Jessie Mundell puts it, "modify over omit". We don't have to cut these activities out all together, rather we can modify them to make them more appropriate for the woman in question, at whatever stage of pregnancy, allowing for individual differences and preferences.

If you are a powerlifter, you can always lower the weight (check out my video on lifting weights during pregnancy), but the movements themselves are very appropriate for pregnancy (deadlift and squat in particular). You may want to add a different exercise modality to balance out your programme and better support your pregnancy (like an aerobic exercise – check out my post on a balanced pregnancy programme) and some kind of row variation to compliment your training. But it may not be appropriate (or even possible) to continue your powerlifting programme as you were doing before.

In capoeira, you might omit certain movements as your pregnancy progresses and it becomes uncomfortable, or there is concern for your core or pelvic floor. It's important to remember that pregnancy is not static – during your first trimester, you may be able to do all the bridges and back bends that your heart desires, but once you start to show this might stretch your abdominal wall in ways that doesn't feel good (and could potentially cause damage to these tissues).

The same goes for CrossFit – the first trimester may not present too many challenges (see my blog post about physiological changes during pregnancy), but as you start to show, exercises like pullups might cause bulging in the abdominal muscles that could cause or worsen a diastasis. Heavy weights, breath-holding and bearing down might cause pelvic floor problems – but we can modify all these things.

For example: I had 10 chinups before getting pregnant. During my first trimester, this went down to 5 pretty quickly, and it was around week 16 that I became concerned that there was some bulging through my abdominal wall – so I switched to rowing variations like ring rows.

We can lower weights to better suit pregnancy – we have pretty solid guidelines for that now, all the while you can continue to do something that looks like what you did before. If you have a habit and a community, we want to change the activity as little as we can to keep you active – but enough to avoid any injury. As with most things in life, there will be a sweet-spot.

Running may present problems for the pelvic floor as it creates a lot of intra-abdominal pressure. Ligaments holding pelvic organs in place may be a bit more elastic now, and may have less support. As the belly grows, weight-gain combined with more elasticity in joint ligaments may cause hip, knee or back pain. Most runners find they can run for 12-20 weeks, but that it doesn’t work for them after that point.

"Listen to your body" is tricky advice purely because most women don't know how to do this, and it may not lead to what is best for their body. Many keen exercisers will know how to push themselves hard through discomfort and even pain – but this might not be the right way to approach things during pregnancy. On the other side of the spectrum, many women hate exercise and if they "listen to their body" they won't move from the couch.

Finally, "don't do anything you didn't do before" is the mother of crappy advice. Many women (like me) may benefit from picking up a lower-impact form of exercise, like swimming or yoga. Women who weren't exercising before should definitely consider doing an activity like this, or even some gentle strength training. The truth is, pregnancy may require that you pick up a new activity, since your body is different now and your current activity, while usually modifiable, might not serve you as well as a new activity. This is ok too.

2. Do not let your heart rate go above 140 bpm

This guideline has been around for some time, and refuses to die! I want to set the record straight, there is nothing magical about the number 140 bpm, you will not cause any damage if you go over this number, and it is likely highly individual.

The concern always was that if you increase your heart rate, you will increase your body temperature, and this can disrupt the development of the foetus, especially in the first trimester. The other major concern is that blood flow will be directed away from the uterus, and the baby will not get enough blood.

Scary stuff.

While this is technically true about body temperature, these guidelines were not created from observation and studies, but from extrapolation and huge amounts of speculation. There are a few truths we need to unpack first:

  1. Your body becomes extremely effective at dispersing heat during pregnancy

  2. Your pregnant body has many built-in mechanisms to ensure blood flow to the uterus above all else

  3. 140 bpm will look very different on different women

  4. Your environment will play a very big role

The entire cardiovascular system adapts to ensure that heat is dissipated effectively. Blood vessels dilate and there is more blood flow to the skin (which is why pregnant women "glow"). The volume of blood itself increases by some 40%. Your body will prioritize blood flow to the uterus even in very extreme conditions.

If you are interested in this topic, the book Exercising Through Your Pregnancy by James Clapp is the best resource I have come across.

All that aside, 140 bpm looks very different from woman to woman. Someone who has excellent cardiovascular fitness might feel that 140 bpm is an "easy" pace, whereas someone who has been sedentary and is overweight might feel that this is intense. This is why individualization is so important, and why a scale like the Borg Scale can be very useful.

For some bizarre reason, this scale goes up to 20 and starts at 6 – rather than just a simple 1-10 rating, but however you chose to grade it, pregnant women want to train up to "somewhat hard" if they are untrained and maybe "hard" if they are trained. You should be able to talk, and shouldn’t be panting. This is still a cautious approach to cardiovascular fitness, but is more flexible, and grades effort more according to individual differences, rather than some arbitrary number.

Finally, if we are worried about body temperature, heart rate might not be a good indication. Consider this: swimming at a hard pace, getting your heart rate up to 160 in COLD water in a cool climate, verses walking at a gentle pace with your heart rate around 100-110 but in a hot climate of 40 degrees centigrade. This simply illustrates that controlling one variable like heart rate might be quite arbitrary and ultimately not control what we are hoping to control.

3. Don't lift more than 3kg

This is one of the most infuriating ones. If a woman already has small children at home, she will regularly be lifting more than this (or any other arbitrary weight that you assign). Some pregnant women have 5 year olds that weigh 20kgs or more. If it's their first pregnancy, they still pick up laundry baskets and shopping that weigh more than this.

Not lifting some weight in the gym and doing some strength training means that we are not preparing our pregnant clients for real life scenarios. We must prioritize keeping her back, legs and core strong in as "functional" a way as possible. This means deadlifts, squats, rowing and pressing variations.

I wrote a detailed blog post on strength training for mums.

4. You must contract your pelvic floor or engage your core on every rep

This topic is HUGE and there is no consensus in the fitness community about how best to cue.

Until recently, the focus has been on "engaging the core" and pre-contracting the pelvic floor. Many professionals teach ALL women to contract their pelvic floors before every rep. This has been the standard for decades and is particularly prevalent in Pilates. Most pre- and postnatal fitness professionals cue this way.

However there is a growing school of thought that this is not the way the core or pelvic floor work. Yes, there should be a pre-contraction before movement, but this should be automatic (does your 5 year old contract his pelvic floor before he lifts up his toy or gets out of a squat?)

While there may be some scenarios in which it is beneficial for the individual to perform a voluntary contraction of these muscles prior to movement, it is not a helpful blanket rule.

If the muscles of your core are balanced, everything will contract as it needs to, and actively and forcefully doing a voluntary contraction may mess the system up.

What's more, some women have a tendency towards overactivity of the pelvic floor, and adding voluntary pelvic floor contractions on to that may exacerbate the issue. Check out this video about Goldilocks and the 3 Pelvic Floors for more about this topic.

Pulling your belly in is also problematic. Most instructors teach that to "stabilize your core" you need to pull your navel to spine, or some variation of that theme. The reality is that the core simply does not work like that. It is a dynamic system that will respond to movement and changes in intra-abdominal pressure.

With all my clients I cue the breath – this involves assessing proper breathing mechanics from the get-go and then reinforcing that through our training. For a deeper look at this I highly recommend the work of Julie Wiebe.

5. Too much core work

Most pre-natal programmes have a HUGE focus on the CORE. Crunches, planks, or variations of these, and very little work on anything else. In large part this is due to the fact that most pre-natal exercise programmes available are Pilates-based, which is generally considered "safe" to do during pregnancy. (I would debate that. I feel that the over-emphasis on the core and pelvic floor may create more problems than it solves, and the lack of work on other body parts, like the back, glutes and legs, creates an unbalanced programme that is unlikely to meet the needs of most women).

I emphasize a balanced full body approach that involves, pushing, pulling and leg exercises, with a slight bias towards the posterior chain, rather the anterior, or core. This means back, bum and legs. I cannot stress the importance of having a strong back during pregnancy. Most women would benefit greatly from learning how to do a proper hip-hinge, and then performing comfortable sets of deadlifts, rather than a core-focused exercise.

Check out this video on exercise selection during pregnancy for more information.

6. Dangerous for your baby? Or dangerous for you?

It makes total sense that the highest priority is keeping your baby safe and not causing him or her any harm through your exercise routine.

However, we do need to differentiate between exercises that COULD do your baby harm, and those that are perfectly safe, as it is a shame to stop doing those that are safe and could improve your health (like aerobic exercise or moderate strength training).

Then we need to understand that there are some activities that are perfectly safe for your baby, but potentially could cause harm to you and your body.

This is usually in the shape of damage to the pelvic floor, core (diastasis) or some other musculo-skeletal complaint (back or hip pain, for example).

Examples of this are high-impact exercises: running, jumping, box jumps, wall balls, full range of motion Olympic lifts… I think it is important that we understand WHY we may choose to stop doing a certain activity – and it's important that we don't scare women into stopping by telling them that it could damage their baby in some way when this is untrue.

It's important that we understand the implications of particular exercises.

High impact activities could damage your pelvic floor, for example, or put a lot of pressure on joints that are undergoing changes and potentially have a little less support.

(I also agree that we need to stop telling women that their joints are "loose" or "unstable" but it may be important to understand that pregnancy hormones can and do affect the strength of our connective tissues and we may feel less strong at this time. Musculoskeletal aches and pains can and do arise from this type of activity in some, if not most, women).

Likewise, lifting heavy weights does not cause miscarriage, this is an old-wives tale. Lifting even heavy weights doesn't really have any impact on your baby, but it could put a lot of pressure on your pelvic organs and connective tissues like the linea alba, especially if you are breath-holding under high loads.

High intensity exercise like CrossFit or hard HIIT sessions may not impact your baby at all, but they may wipe you out and cause you to feel extreme fatigue that may be hard to cope with later in the day.

In Conclusion...

Ultimately, exercise is important during pregnancy, but most advice is misguided, or lacks proper understanding about a) the physiology of exercise, b) the physiology of pregnancy and c) how they interact.

Most advice also completely ignores individual differences and usually falls into one of two emotionally-driven camps – either "just rest, walk and do yoga, don't exert yourself in the slightest" or the "badass mama" camp that "pregnant women can do anything" The truth and reality rarely falls neatly into one of these two camps, but falls on a spectrum in between.

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