Muscle Gain During Pregnancy: What To Expect

Can you BUILD muscle during pregnancy?

A lot of women (and trainers) have asked me if this is a reasonable goal during pregnancy. As always, the answer starts with “it depends” - MOSTLY it will depend on whether you are already trained or not.

So let’s first talk about women who are TRAINED - i.e. they already lift weight and have muscle mass.

(Scroll down to the next section to learn about UNtrained pregnant women, if you want to start lifting weights during your pregnancy, or if you are a trainer and want to know for a trainee)

In short, no, it isn't reasonable to expect to BUILD muscle during pregnancy. (Sorry, I know that’s not what you wanted to hear).

While it may theoretically be possible to MAINTAIN (and our goal should definitely be to maintain as much as we can) it is unlikely and one should expect to LOSE muscle mass and strength over the course of pregnancy.

This is due to physiological and anatomical changes; the hormonal milieu affects the elasticity of our connective tissue, so force production in the muscles decreases.

Think: if the connective tissue attaching the muscles to the bones are more elastic, the muscles have to work much harder to produce the same force.

Therefore, it isn't reasonable to expect to load the muscles as much as before pregnancy, and since mechanical load is one of the mechanisms of hypertrophy, it will affect our ability to gain muscle while pregnant.

The other two mechanisms of hypertrophy are muscle damage and metabolic stress, both of which will be harder to achieve under the hormonal (and anatomical) changes of pregnancy.

Anatomical changes will also affect your ability to produce force, especially in large, compound movements that allow you to mechanically load the muscles, like squats, deadlifts and pullups.

You’ll also want to consider your pelvic floor... and while you might be able to lift heavy loads, it probably isn’t ideal for your pelvic floor.

Some training guidelines specific to lifting weights that you should consider if you are pregnant:

1. You want to learn to EXHALE on the EFFORT. Many of you will be chronic breath holders, and if you lift heavy, you’ll be used to “bracing” - this isn’t recommended during pregnancy because the best information we have suggests that it puts a lot of pressure down on the pelvic floor and pelvic organs. Breath holding (and/or valsalva) can increase blood pressure and may have a negative effect on foetal heart rate.

2. So you’ll want to select weights that you can lift while EXHALING - this helps regulate intra-abdominal pressure and may help the pelvic floor support the pelvic organs.

3. You’ll also want to work to an RIR of 1-3 reps, so leave a couple of reps in the tank, rather than maxing out or reaching failure.

4. Some guidelines recommend lifting in a higher rep range of 8-15 reps, rather that 5 rep maxes or 1 rep maxes- although it may still be safe to lift for 5 reps if you leave a couple in the tank.

You can of course manipulate other training variables like time under tension or reps and sets to increase overall training volume, producing more metabolic stress to compensate for the reduced load BUT your ability to recover will also likely be compromised during pregnancy.

Remember, your body is doing a lot of metabolic work to build a human at the moment! Reserves are low and training load and volume will likely need to decrease over the course of your pregnancy.

You should also be eating adequate calories and protein (around 0.6-1.2g per POUND of bodyweight (kg x 2.2) - this is important for pregnancy, not just muscle mass.

Muscle Loss During Pregnancy: Mindset Shift

A final word about mindset - it can be incredibly difficult for very fit women to accept the changes and limitations to their routine, and the prospect of losing hard-earned gains can be really scary. It is really important though to embrace the physical changes and to adapt to them. This might involve some grief and letting go for you (it did for me) but not all the changes are permanent. If you train right, you can return to previous levels of strength and fitness, but remember, that proper (and safe) pregnancy exercise is your postpartum PRE-hab.

Although you will most likely lose strength and muscle mass throughout pregnancy and the postpartum period, one of your training goals absolutely should be to maintain as much muscle mass as you can (strength is most likely going to decline, no matter what you do, #sorrynotsorry).

Losing Body Fat While Pregnant: Starting From Zero

The way we approach UNtrained individuals is different.

If you would like to start lifting weights during your pregnancy or want to know what you can expect from a new client starting resistance training during pregnancy, this half of the blog post is for you.

For some women, I would say, yes, it is possible to gain muscle mass during pregnancy if you START a resistance training regimen (with sufficient load) during that time.

Caveat: I'm basing this on anecdotal evidence, I have seen it happen - I'm not aware of studies that confirm this.

It is important to note that, the current ACOG guidelines recommend 2x resistance training sessions per week for untrained individuals.

So forget the old chestnut “don’t do anything you didn’t do before pregnancy” - that’s a myth, there is such a thing as programming for pregnancy - although you probably do want to do this with a trained professional.

HOWEVER, their guidelines are very vague when it comes to SAFE or EFFECTIVE loading during pregnancy.

So here are some guidelines that are widely used in INFORMED, evidence-based prenatal training certifications:

Getting Fit While Pregnant

The trainee should EXHALE on the EFFORT, so "bracing" and breath holding through the movement is not appropriate during pregnancy. (As above, this is to regulate intra-abdominal pressure, activate the recoil of the pelvic floor AS WELL AS to prevent increase in blood pressure)

An untrained individual should be training in a 8-15 rep range, with a RIR of 2-3 reps (with the subjective feeling that they could do 2-3 more reps) - this means that 5RM are not appropriate.

In theory, this is great - BUT, in practice, most UNtrained women during pregnancy will not be able to train to this load - they will be using load far below their actual “8RM” - so they might be squatting with a 5kg dumbell, but they could actually do way more than that.

This isn’t the time to push.

Partly because most untrained women will be fearful of lifting weights.

But also, they will tire easily (as will many trained women). Most of us are in a different mindset when it comes to exercise and pregnancy. It’s about feeling good, not doing the most you can possibly squeeze out of a session.

(Again, many trained women will find it hard to make this mindset shift, but it is important)

You can absolutely utilize other training variables like TUT and increased volume (reps AND sets) to "maximize" her muscle growth during this time - but she is likely to fatigue before you get to that.

(This is all, of course, as long as she isn’t experiencing hip pain and/or symphysiolysis - which will massively limit the kinds of exercises she can do and how she can load her lower body)

She should also be consuming adequate protein to the tune of 0.6-1.2g protein per POUND of bodyweight, regardless of resistance training.

However, loading is going to be limited MAINLY by what we consider “safe” for her pelvic floor (so, not being able to max out or breath hold) but also by:

1. The elasticity of her connective tissue and

2. Her ability to recover (another reason why high volume might be detrimental to her).

(Looking for some more pregnancy training tips? Start here...)

Is it harder to build muscle when pregnant?

I hope this blog post helps guide you in training yourself or pregnant individuals - and answers a few of your questions. I offer online consulting services for both trainers who wish to troubleshoot and learn more and pregnant and postpartum women who want to train under the instruction of a prenatal fitness specialist. Please send an email to info@jen-curtis.com

If you are a trainer and want to work with pregnant women, it is VERY important to get qualified. I highly recommend the Girls Gone Strong Pre & Postnatal Coaching Certification

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About Jen…

Jen Curtis is a pregnancy and postpartum fitness specialist who is passionate about helping women transform their bodies in a sustainable way.

The creator of The Complete Postpartum Programme, she is well-known for her no-BS approach, her dedication to facts, science and evidence and for debunking myths around nutrition and exercise.