by Yvonne McKenny & Caitlin Stannard
How hard can you go? And for how long? What do you need to look out for and when should you stop? You've asked for it, we've been eagerly awaiting it and it's finally here. The team at Evoker physiotherapy have kindly written us this exclusive two-part article on a well-debated topic: running in pregnancy and postpartum. Here is part 1: on running in pregnancy. Look out for part 2 coming very soon, on running in postpartum.
It's not news to many that exercise in pregnancy is encouraged. Most are also aware of the common advice, that if you are a regular runner before pregnancy, you are generally able to continue this throughout your pregnancy. But does that also apply to the half marathon, marathon and ultra runners amongst you? Where do we draw the line? And what is really at stake? We know that there are many benefits to exercise and it’s important, now more than ever, when embarking on the life changing journey of pregnancy and childbirth that you make an educated and informed decision about how to exercise confidently and safely through this time.
Unsurprisingly, the majority of new mothers are most concerned about fetal health when considering exercise during pregnancy. And it’s a great place to start. We’ve got some pretty good research on the impacts of moderate, vigorous and high exertion on fetal health, with the consensus on the need to avoid ‘high exertion’ as this can cause alterations in your growing bubs heart rate (fetal bradycardia).
So what does “high exertion” entail? High exertion was considered to be working at HR levels of >90% Max HR **. Therefore the research indicates that exertion should be limited to <90%HR max for previously active women. There have been no research to the effects above this point and should therefore be avoided. This serves as a clear HR ceiling to limit how hard you should push exercise through pregnancy.
**Important to note this guideline is more like 60-80% Max HR for the sedentary woman but I’m unlikely to find many of you here.
However this is not without its own limitations. The somewhat inaccurate means of calculating HR Max, the changes of HR in pregnancy, that is, an increase in resting and submaximal heart rate and ultimately the lack of research on the specifics, means that using HR alone can be insufficient.
For this reason, heart rate monitoring is recommended and best used in combination with the talk test. Simply put, if your breathing is strained such that you’re unable to hold a conversation or say more than a few words, you are likely working too hard and your baby is too.
This combined approach has been discussed in various papers (O’Neill 1991 and da Silva 2020) as the best way to navigate this somewhat grey area safely.
Therefore to avoid going where research can’t recommend safely, lets make it clear:
With high exertion aside, we have a very good review of the evidence from 2019 (Beetham et al), that looked at vigorous exercise (Talk test, vigorous = can talk but need to pause for breath) in late pregnancy which found that birth outcomes weren’t compromised for most low-risk pregnancies (premature birth, low birth weight or risk of an adverse event). In fact there was a small reduction in risk of prematurity with those who do vigorous exercise. Interestingly they didn’t find any benefit of vigorous vs moderate intensity in the weight gain of healthy weight women in pregnancy. They concluded that we don’t have the research to confirm the safety of exercising at very high heart rates (>90% HR max), and thus it should be avoided.
Ok, so we’re ruling out “high” exertion exercise, but we’re giving the relative green light for the less intense “vigorous exercise” with regards to the baby’s health. So by those definitions, running for most regular runners would fit that category. That is, you’re working out, but not out of breath, and can still hold a conversation. Your regular 5-10km runs may fit that criteria nicely. Right?
But hold up! Things may sound a little different when we switch the focus to the mother’s health. The stoic inside you may dismiss any concerns for yourself, but let’s talk about the things that you can’t necessarily feel or see, and what things should perhaps be on your radar that are not there yet.
During pregnancy the pelvic floor tissues soften to prepare for childbirth. Large hormonal changes mean that the ligaments and other support structures around the pelvis also stretch. Then you have to consider that women will put on anywhere from 10-30kg by their third trimester.
The pelvic floor is now not only relaxing, but it has the increased strain and pressure from the mothers increasing body weight and that of the growing baby. This is likened to 100kg of weight on your pelvic floor! And that’s without the added impact of running.
To best understand what this means, it’s important to remember that the pelvic floor is not just muscular.
A large, integral part of the pelvic floor support system is connective tissue or ‘fascia’. This is something you cannot train. No amount of pelvic floor strengthening will make your fascia ‘tighter’.
Therefore it is something that needs to be maintained and protected throughout pregnancy for best function later in life. Unfortunately, damage to pelvic floor fascia is irreversible and can lead to pelvic organ prolapse during or after pregnancy.
So what does this mean for your running ambitions through pregnancy?
It is safe to say, pregnancy is not the time to take up running if you haven’t previously been a runner. For those who have a healthy lifestyle prior to pregnancy and have an ‘uncomplicated’ pregnancy, the guideline is that you may be able to safely continue running during your first and second trimesters - so long as you are not having pain or trying to increase your load/distance/intensity.
By the third trimester, there will be some women who can still manage to run, but for most it will likely be too much to bear to continue running, and/or detrimental to your health and comfort. If you do choose to run through the later stages of your pregnancy, you will need to accept that your running will change - you will need more rest breaks and you will need to slow down and increase your fluid intake.
Should you choose to continue running through any stage of your pregnancy, you need to please consider the below 7 points in order to reduce strain on your pelvic floor;
Our guidelines are exactly that. They can’t account for every case scenario, so with all of this considered, it’s important to know the signs of when your body is ‘doing it tough’, and ultimately – when do you need to stop running? This includes;
If you experience any of these symptoms, it's important to stop running and seek specific medical advice from your health care professional.
With all pelvic floor concern aside, all of the bodily changes that are associated with pregnancy are likely to have an impact on your biomechanics too, and this can lead to other aches and pains. It has been observed that pregnant runners display increased side to side pelvic motion, as well as increased lumbar extension, all of which may serve to create overloaded tissues and pain. This will also slow you down, so it’s important to listen to your body if this occurs.
We are physiotherapists. Both runners ourselves. We are pilates instructors and we’re trained in women’s health, with experience through private clinics and maternity wards. So, believe us when we say that we’ve seen a bit of it all. The reality is - there is massive differentiation between each woman, and it's not a predictable case of she who is fittest pre- pregnancy will be able to handle the most during or after pregnancy. Nonetheless, we have outlined some of the main points for your consideration - the guidelines, the evidence and the information that can help you to have confidence in your body as it changes through this very special time.
Should you need more specific tailored advice, there really is no substitute for getting assessed and seeing a pelvic floor physiotherapist.
And how about running post birth? Check out our next blog, part 2, coming soon!
Images with kind permission from athletes Ellie from @Ellie_Living_Healthy and Ankita Gaur from @thecookie_runner.
Beetham KS, Giles C, Noetel M, Clifton V, Jones JC, Naughton G. (2019). "The effects of vigorous intensity exercise in the third trimester of pregnancy: a systematic review and meta-analysis." BMC pregnancy and childbirth. Dec 1;19(1):281.
da Silva, Danilo F.; Mohammad, Shuhiba; Hutchinson, Kelly Ann; and Adamo, Kristi B. (2020) "Cross-Validation of Ratings of Perceived Exertion Derived from Heart Rate Target Ranges Recommended for Pregnant Women," International Journal of Exercise Science: Vol. 13 : Iss. 3, Pages 1340 - 1351.
O’Neill M. E., Cooper K. A., Mills C.M., Boyce, E.S., & Hunyor, S.N. (1992). "Accuracy of Borg’s ratings of perceived exertion in the prediction of heart rates during pregnancy." British Journal of Sports Medicine. 26(2), 121 -124.