Running Through Pregnancy

There’s a lot of miscommunication and mis-understanding out there about exercise and pregnancy.  Is it okay? Will it hurt your baby?  How much is too much? And what about running…that’s a lot of impact, right?

Even worse than the miscommunication is the ridiculous amount of JUDGEMENT out there.  We’ve all heard the stories about pregnant women at the gym or on the running trails getting lampooned by their non-pregnant peers about all the “damage” they’re doing to their baby.  Maybe you’ve even been that judgy person, if only in your own head.


Let’s clear up some of the misunderstanding.

First – in general, EXERCISE WILL NOT HARM YOUR BABY. There is no definitive research to suggest that exercise is detrimental to the health of your future child. None. Zip. Nada. If you are having a healthy pregnancy with minimal symptoms…well there just isn’t sound reason to refrain from physical activity.

The general guidelines for exercise during pregnancy, according to ACSM, are that pregnant women should be getting 30 minutes of mild to moderate physical activity at least three times per week.  This is less than the guidelines for non-pregnant, healthy adults (30 minutes of moderate-to-vigorous exercise five times per week, or 75 minutes of vigorous intensity exercise per week), but keep in mind that it’s also a minimum value. The American College of Obstetrics and Gynecology (ACOG) recommends that women exercise at an intensity of 12-14 – “somewhat hard” – on the Borg RPE scale (which ranges from 6-20).


So….that raises the question of intensity.  Recommendations of “somewhat hard” or “mild to moderate” exercise are what’s been published.  But does that mean you shouldn’t train hard?  Not necessarily.  In general, if you’re a runner, pregnancy is probably NOT a good time to start a hardcore training cycle for a marathon, especially if the intensity is not typical for you, or if this is your first time training for that distance.  HOWEVER….if you are well accustomed to hard workouts and are elite/very highly trained…that’s different.  We’re all familiar with Alysia Montano racing while pregnant, and Paula Radcliffe continuing her training throughout her pre-partum period.  My point is, it’s all relative. These women are simply continuing to train in a way that they’re accustomed to – they’re not increasing intensity or volume beyond their “envelope of function”.  If you get the OK from your physician – i repeat, IF you get the okay from your physician -it is likely safe to continue to train at the intensity and volume you’re accustomed to, provided you don’t experience any adverse symptoms. It’s okay to keep doing what you’re doing and what’s well within your capacity, but in general, pregnancy is likely NOT a good time to double down and train harder than ever for a new event (especially true for those of us who are not highly trained enough to get paid for our running!)


On the other hand, if you’re sedentary….pregnancy IS actually a good time to start an exercise program!  Even if you’ve never exercised a day in your life, pregnancy is an ideal time to start.  Again, it’s important to watch the intensity – a gentle walking program, swimming, or prenatal yoga is a good place to start.  400m intervals on the track? not so much.  You can, however, increase intensity during pregnancy AS TOLERATED, but do so gradually, and do not START at high intensities.

Lastly – whether or not you can run during your pregnancy ultimately depends on the health of the baby and what your physician says (provided your physician is up to speed on the literature…).  In general, the higher risk category your pregnancy falls into, the less physical activity you will be able to do.  You may also experience physical symptoms like pain and nausea that prevent you from exercising.  There’s really no way to predict this – being an elite athlete doesn’t mean you’ll have a smooth, flawless pregnancy.  The best course of action for your own health and the health of your baby is to chill, and follow your physician’s advice.

Pregnancy also leads to some pretty significant physical changes that can impact your running.  Some things to pay attention to:

1.Your ligaments become lax. 

This is a NORMAL adaptation to pregnancy – the ligaments at your pelvis (especially at the pubic sympysis and sacroiliac joints)  have to relax so that, you know, the kid can fit in there and whatnot.  This is accomplished with a hormone called relaxin.  The trouble with hormones is that they travel through the blood, and so their effects are not localized to just the pelvis.  Most other ligaments in your body will be affected.  Most commonly, women complain of issues at the feet – arches dropping – and the low back (SI joint and lumbar instability).  Your knees may also be affected.  This is one reason why you don’t want to increase intensity or volume of running too much during pregnancy, and why you may have to stop at some point due to pain.  Be mindful of symptoms in these areas – ligamentous laxity could be a reason you’re hurting, and if you push through, it could lead to bone and joint injury.


2. You’re going to gain weight.

Pretty obvious, right? and kind of unavoidable.  It’s completely normal, and actually recommended, for women to gain 20-35 pounds during pregnancy.  HOwever, all that extra weight is going to alter your posture – your pelvis will likely be more anteriorly tilted (which can affect the alignment of your femoroacetabular joints) and your lumbar spine will be more extended.  This can create discomfort, sure, but if you load yourself too much in these new positions, you could create an orthopedic injury – most notably intra-articular hip pathology and muscle strains around the hips and low back.  Another reason why you may not want to increase volume and intensity of your running during pregnancy.


3.  You may experience Diastasis Recti either during or after pregnancy.

Regardless of how fit you are….babies are big.  If they press against your abdomen a little too hard, your rectus abdominus (the “six pack” muscle) can physically separate.  Please don’t panic – THIS IS COMPLETELY 100% TREATABLE WITH PHYSICAL THERAPY.  A good rule of thumb is just to not do crunches, either during or after your pregnancy.  I would also recommend seeing a physical therapist AT LEAST every trimester, and then more frequently postpartum so that you can monitor and treat this, if it happens. Again, this is relatively common and it has no relation to your pre-pregnancy fitness level.


4. You will need to monitor your vital signs more closely.

During pregnancy, your blood volume increases (you have to bleed for two now, so to speak), which means that your cardiac output increases – by about 40-60% – your stroke volume will increase by about 30%, and your heart rate will increase by about 10-15% (both your resting heart rate and your max).  This may make a given level of exercise feel a little harder than it used to – that’s okay.  It also means that it may be best to judge your exercise intensity on PERCIEVED EXERTION (which research shows actually corresponds quite well with lactate threshold), not on a heart rate measurement. Additionally, the added blood volume is mostly plasma, not red blood cells – which can lead to anemia, especially in runners (you’re already more susceptible than the general population).

One last thing about vitals – your blood pressure should NOT change.  if it rises, that’s considered a medical emergency.  Monitor yourself closely!


Overall, it is perfectly safe to exercise during pregnancy, even to run!  Your best bet is to consult with your physician and come to an agreement as to what works best for you.  This is going to look different for everyone and it really depends mostly on the state and risk level of your pregnancy, not necessarily on your level of fitness. That’s why it’s SO IMPORTANT not to judge other women for what they are or are not doing during their pregnancy!


Special thanks to Dr. Carol Figuers, PT, Ed.D at Duke University for the content!  

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