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  • Writer's pictureJen Curtis

Exercising in early pregnancy - what you need to know

At least once a week I get a message from someone saying:

"I'm pregnant! How should I change my training programme"

You don't need to change ANYTHING. In the beginning.

Exercise in the first trimester doesn't increase OR decrease the risk of miscarriage or complications or birth outcomes in any way.

And exercising in your FIRST trimester massively increases the chances that you will exercise in the second and third trimesters - it’s much easier to “keep going” than it is to “start”.

And THIS will have positive outcomes for you and your baby: working out throughout your pregnancy is healthy for both of you, will make it easier to get back into postpartum, and will help you maintain a healthy weight AND mood.

(note: it probably won’t make birth easier)

BUT WHAT YOU DO NEED TO KNOW about exercise in the first trimester:

The one thing that I think is SUPER important to know, but almost no-one does....

is a concept called UNDERFILL


This is a NORMAL physiological process that has a MASSIVE impact on your cardiovascular system.

Basically, a cascade of hormonal changes cause your smooth muscle to relax.

Smooth muscle is in the walls of your blood vessels.

So blood vessels dilate.

Therefore blood pressure DROPS because there is now more space inside your blood vessels and cardiovascular system than there is blood to fill it.

This means that the heart has to work harder to increase blood pressure.

Which means more beats per minute - approximately 10 bpm.

So if your resting heart rate is 60 normally, within the first few weeks of pregnancy it will increase to 70.

You won't feel or notice this, EXCEPT when you start to exercise (or go up the stairs) - your heart rate shoot up much faster than it usually does at the same intensity.


So many women get upset and say "I've already lost fitness" - calm down, you haven't.

So what should you do about it?

All you need to do is to adjust the intensity level at which you're working to achieve the same heart rate as before.

That's literally it.

That might mean running or swimming or crossfitting at a slower pace.

Or having more breaks in the workout to bring your HR down.

If you lift weights, you might need to rest more in between sets.

DON'T STOP EXERCISING ALL TOGETHER - this is dumb. So many women do this because they feel like they can’t run the same pace as before.

The number one rule of pregnancy exercise: MODIFY BEFORE YOU OMIT.

This is a good exercise for pregnancy and postpartum, and then motherhood because it's ALL about adapting not just your workouts, but EVERY ASPECT OF YOUR LIFE.

You might feel weaker

You’ll likely lose some strength during the first trimester, because even though you don’t have a bump yet and no anatomical changes have taken place (yet), your connective tissue may become more elastic.

This includes the tendons that connect your muscles to the bone. If these become more elastic, your muscles will produce less force.

This means that your actual strength levels will decrease (i.e. it isn’t just “in your head”)

If you do lift weights, it’s best to reduce the weights to where you can exhale on the effort (rather than holding your breath) - this is more important later on for safeguarding your pelvic floor, but it’s a good habit to get into in your first trimester, and in any case, you will likely be feeling tired, so this will make your weight training more enjoyable.

Remember: Stimulate, don't annihilate.


You may also notice that you are more tired now than before you were pregnant. This is also normal, your body is doing a lot of work metabolically (and, let's face it, you might be drinking less coffee)

The modifications that I’ve recommended in this blog post apply here: go a bit slower, rest a bit more and lift lighter weights. It’s really that simple. Above all, this will make your workouts more enjoyable and lower the barrier to entry.

If you find yourself dreading your workout because you feel tired, lower the bar, do less, modify to your current energy levels rather than either pushing yourself really hard, or not working out.

Don’t fall into the all or nothing mindset - something is always better than nothing.


If you found this helpful, join my FREE 4-day course, "How to Exercise During Pregnancy"

And check out my online programme: Strong Pregnancy for realistic, safe and effective exercise during pregnancy - the course includes a training programme designed for each month of pregnancy as well as guidelines around how to train safely and how to modify for each stage of pregnancy.


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