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Trimester One - Changes to your body, how it might make you feel and how to adapt exercise

Physiological changes to your body, how you might be feeling and how to adapt your exercises

Changes to your body & how you might be feeling in trimester one

Like anything in pregnancy, if it doesn't feel right speak with your doctor or maternity nurse. I am not a doctor and will stay firmly in my lane of personal training, however I hope I can shed a bit of light on WHY you might be feeling the way you do.

Nausea and sickness - This is the most common pregnancy symptom and can vary pregnancy to pregnancy - so even if you avoided for baby one, doesn't mean you are clear for subsequent pregnancies. It does however, usually subside by the end of trimester one but can go into month 4 and occasionally beyond although often not as severe. This is thought to be caused by a host of reasons including, lower blood pressure, vascular underfill (described later) giving you a feeling of vertigo and being lightheaded. Another cause of nausea can be fluctuating levels of hormones estrogen and progesterone which tend to level out by trimester two.

Chronic tiredness - Its exhausting growing a baby, but your body is working hard, making changes for the growing baby. Tiredness can be caused by many factors including fluctuating hormone levels (mentioned earlier), but a main cause is quite a fascinating reason. Our blood volume increases by up to 50% by the end of pregnancy to cater for the demands of oxygen for both mother and baby. To make room for this increase in blood volume, our blood vessels have to dilate and get bigger. Tiredness occurs when the blood vessels have dilated and grown in size, but the blood volume hasn't yet, so this 'shortfall' in blood volume results in tiredness. This is because the blood is taking longer to flow around the body due to the larger blood vessels. This can also cause a slightly reduced blood pressure, again another cause of tiredness.

Breathlessness - You may feel like you have to catch your breath now and again when you didn't before and without a large bump, this might be a bit disconcerting. Again this can be down to vascular underfill and the numerous changes in your circulatory and respiratory system. Its also your body’s way of saying calm down, so don't push past it, listen to your body and do not overwork it.

Sweating faster - Another amazing adaptation our bodies do for temperature regulation is lowering your sweat threshold, so you sweat quicker than before. Even doing the simplest of tasks like walking for ten minutes can make you sweaty. This is to ensure you don't overheat and your body stays at a suitable temperature. But an increase in sweating means you need to take on more water than usual.

Relaxin - This is a hormone which is released throughout pregnancy and up to 6 months postnatally as well, sometimes longer if you are breastfeeding. Relaxin affects every single joint in the body from your fingers to your toes, but amazingly allows joints, like the pelvis, to move and change to accommodate the growing baby and during birth. This doesn't mean however, its the time to get the deepest squat possible with this new found flexibility. Overextending the muscles and pushing them past their normal range of motion can make them more susceptible to injury. Avoid overloading with resistance if you're training and keeping at a moderate weight. I'll touch on this in exercise adaptations too.

Exercise adaptations in trimester one

Tiredness - As I mentioned earlier, tiredness is very common in trimester one so reduce the length and intensity of your workouts/exercise and increase rest periods - an example would be reducing from 30/45 mins to 15-20 mins. Your body is working harder to circulate the blood so fatigue kicks in quicker, its important to change your intensity according to fatigue levels. This can also mean reducing your weights, there is no magic number, but keep the weight low or even bodyweight if you are particularly tired or bring exercises to seated/kneeling. There is no prescribed heart rate you should/shouldn't do, so use the talk test, you should still be able to hold a conversation as you exercise, if you cant tone it down!

Avoid overheating - So this goes without saying, avoid hot yoga and make sure you workout in a ventilated room. Hot rooms will dehydrate you quicker by making you sweat more and faster than in a ventilated room. Make sure you wear light clothing and not heavy jumpers or clothes to keep you nice and cool. Take on lots of water in your rest periods and afterwards too.

Avoid breath holding and use your breath properly during the exercises to avoid feeling lightheaded - Inhale on the eccentric phase, exhale on the concentric phase. So use a squat as an example, inhale as you squat down, exhale as you come back up. Avoid holding your breath in exercises, so reduce the weight down and you'll be less tempted too. Holding your breath will put undue strain on the pelvic floor muscles, respiratory and cardiovascular systems.

Isometric holds (eg. plank) are ok to do in trimester one but approach with caution - You can hold plank for up to 15 seconds but I personally would advise no longer. Again this places undue stress on the cardiovascular systems by increasing the blood pressure. Naturally if you feel tired or lightheaded, this will make it worse so avoid them entirely. Again just listen to your body.

Avoid anything that ‘bumps the bump’ - Yes your bump in trimester one is teeny tiny, but its still the home for your little one so avoid anything that could bump the area - this would include something like chest to floor burpees, a leg press where if you lost control, it could fall onto you. Use rowing machines with caution through trimester one.

Avoid anything that puts you at risk of falling or unbalanced - Anything single leg like steps ups, if you lost balance you could fall and not only injure yourself but also bump the bump. As relaxin is flowing through your body, it will make your joints less stable and increase the risk of toppling over.

Focus on maintaining strength in areas that weaken - As your belly grows, your centre of gravity shifts forward which means some muscles can 'switch off' working that would normally be working. The most common affected areas are the back, core, glutes & hamstrings, so ideally focus on keeping them strong throughout trimester one and subsequent ones.

Stretch out muscles that often tighten through pregnancy - This includes muscles like your hip flexors, quadriceps, pectorals and your back. As your belly gets bigger and your centre of gravity and posture changes, your lower back/lumbar spine can often be 'pulled' inward (this is called lordosis), so its important to keep the whole back strong through pregnancy. This will also help to avoid back pain.

You can lie on your back for a few more weeks - If you feel well enough to do so, it's perfectly safe to lie on your back when performing exercises in trimester one. As the fetus grows, if you are in a lying position it can push down on your vena cava (main vein carrying blood to the heart) making you feel light headed as it reduces the blood flow around the body. In trimester one however, the fetus is so small its unlikely to put any pressure on the vena cava, but if you do feel light headed, again just stop and try seated/kneeling exercises.

You can still work you core in pregnancy - Standing, seated, kneeling and side lying are all good ways. Also just simple breath work and engaging the core can help, especially for the lower abdominals, specifically the transverse abdominals. Avoid crunches or anything that creates pressure into the abdominal wall, so change to something like a standing knee crunch.

Continue what you were doing - Now is not the time to start changing your workouts regime wildly. If you feel well in yourself to continue working out how you did prior to pregnancy, then it is generally safe to continue this into the first trimester however I would advise to:

  • Lower the intensity

  • Increase rest periods and drink more water

  • Decrease any resistance if you need too or feel tired

  • Reduce the length of time if you need too

  • Aim for seated/kneeling positions if you feel tired, rather than standing

Some days you may have more energy but you know your body better than anyone, so just go with what feels right.

Activities to avoid - This would generally be contact sports such as rugby, boxing, horse riding, martial arts as you are at risk of bumping the bump.

Activities to approach with caution - HIIT (see next paragraph), cross fit, box jumps (or any type of explosive work due to relaxin and joint instability), powerlifting, overhead presses and barbell work (as it can bump the bump).

High Intensity Interval Training (HIIT) - Generally if you were doing this prior to pregnancy it is safe to continue it in trimester one however it is strongly advised to approach HIIT with caution! Make sure you are cutting back on intensity, so shorten the work time and increase the rest time. Avoid exercises that could bump the bump (so no chest to floor burpees) and avoid jumping/explosive work as the relaxin levels in your body mean joints are unstable, so things like jump lunges could make you topple over. Change it up to stepping - so step lunges, and stepping onto boxes rather than box jumps. Make sure you can still maintain a conversation too using the talk test throughout.

Preparing for later trimesters and postnatally

Start deep diaphragmatic breathing now - Get your body used to it now for postnatally and beyond. As pregnancy progresses and the baby pushes the diaphragm up breathing can become very chest orientated, this helps to send the breath down and around into the abdomen. Practice this by lying on your back and placing a hand on your tummy, from there inhale and send your breath into your belly, inflating it and then as you exhale, sending the breath out of the belly.

Work that pelvic floor - It's never too late to start your pelvic floor exercises. You can incorporate them into your workout or you can do them separately, there are loads of ways to do them so mix it up a bit! If you need advice or new ideas, get in touch at

Interval training - This is good way to prepare the body for things like labor as its time of work and a time of rest so mimics contractions during labor and birth. Try 30 seconds of work with 30 seconds of rest, a great way to get short, effective workouts done too!

It goes without saying this is just my advice, and if anything doesn't feel right - stop, move on and change it up and always here for questions of queries. Feel free to email me. Hope this helps you mummas and keep up the amazing work!

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