Training during the First Trimester

28/12/2015 20:00

At first, I felt just like my usual self, running every day, no food aversions, no symptoms at all, the only indication that I had a “passenger” was this plastic stick with two lines on it... and then...

Shortness of breath

During the first few weeks, I felt like I was puffing a bit more, having to breathe more deeply even when running slowly or going up a slight incline on my bike - apparently this is because the elevated progesterone increases breathing rate to get more oxygen into the blood. It can increase resting minute ventilation by up to 40% in the first trimester, and up to 50% at term. As a result of these changes, the body is processing oxygen and carbon dioxide better, so rather than this being a sign of a lack of oxygen to the developing foetus, it is a good thing because the increased is oxygen brought into the body is about 20% higher than the extra amount needed. So the body is actually breathing harder to bring in oxygen than required.

The extra puffing did make me consciously ease off the intensity.


When running, I dialled back significantly on any interval type training or hard efforts and stayed at an Easy (zone 1) heart rate level. It was actually very enjoyable! 

I joined the Park Run regularly from the second trimester once I no longer felt nauseous first thing every morning. The Park Run is a free, timed 5k run which happend every Saturday all over the world. The one in Singapore is less than 1km away from our house, so perfect for an easy short run.


Cycling consisted mainly of commutes to the office, and a few other rides much shorter than pre-pregnancy and much slower, with no hard efforts. Part of the reason why rides were generally shorter was because it’s difficult to finish a long ride before the sun starts getting higher in the sky and because the amount of water I could easily carry with my bike set up. I also found that I liked carrying something sweet to drink much more than usual.


In Singapore it is always hot and it's humid, so 

 getting sweaty is inevitable. When I'm not pregnant if I'm going for a long run, I can usually plan a route than includes a few public drinking fountains, a friend's house or a shop suitable for a quick pit stop... but now, I have started carrying elete (electrolyte charged) water with me in small bottles on a hydration belt all the time, even if I am only going out for 20 minutes! I still stop at the water fountains but having it with me all the time gives me a bit more peace of mind that I'll not run out and that I can keep myself and “Sprog” well hydrated and cool.


When reading about exercise during pregnancy, the vast majority of publications, websites and medical professionals say something along the lines of, “if you’ve been active before, carry on with what you’re doing as long as you feel comfortable, just make sure you don’t overheat.”

But that begs the question, “How hot is too hot?” and there are very few articles which precisely define “over-heating” or “hyperthermia”.

It is generally accepted that exercise dramatically increases body temperature, and the fetus can take on the mother's heat, possibly leading to birth defects. Yet to date, research has not proven any increase in birth defects when women exercise at high intensities (ACOG 1994). In fact, studies indicate that fit women actually have better ability to dissipate heat (ACOG 1994).  The conclusion of one study is: During submaximal exercise the temperature response seemed to provide thermal protection for the embryo and the foetus.

The most commonly recommended maximum temperature increase is of 1.6° Celcius (C) (3° Fahrenheit (F)) and a post-exercise temperature no higher than 39.2° C (102.6° F).

I took my temperature several times before and immediately after training and found a difference of 0.6 degrees at the most and a maximum of 38.0°C at my hottest, even in Singapore’s tropical climate.

However, I did (and will continue to do so whilst pregnant) do a lot more activities indoors in the air conditioning at Gym n Tonic. Using the gym has several advantages in addition to the cooler temperature: being always close to water, a loo and help!

Sport ID

I wear my ID bracelet all the time anyway, but I've modified the tag to include "PREGNANT - DUE 8 JUNE 2016" just in case! This would be important to know, but perhaps not immediately obvious until my bump is a lot bigger!


Usually I try to not eat grains and refined carbs to ensure my fuel efficiency is good and my body can use fat for fuel. During the first trimester, often the only things that I could stomach were crackers and bread. I also felt so nauseous a few times that I just didn’t feel like running/ cycling/ swimming/ moving in any way…


Then there were the tender boobs... I definitely felt more of a need to wear good bras. Sometimes (when not pregnant) I trained and raced with no bra when wearing very tight kit, it was enough. Not anymore!!


Once I found out I was pregnant I modified my practice quite significantly… I wrote about it: Yoga for the first trimester

Spreading the news

Although my husband and I agreed it was a little early to shout it from the rooftops, there were a few people who we told much earlier than the scan at the end of the first trimester. For example, ride leaders, Triathlon Coach, Swimming CoachYoga Teachers. All of these people needed to be aware that something was different – perhaps I wouldn’t be going as fast as usual, perhaps I would need to slightly modify the training session, and of course… if the worst happened, they needed to be able to tell any medical professional.