# How pregnancy changes your body for exercise

> In pregnancy your heart works harder at the same pace, your balance and posture shift, and lying flat on your back becomes less suitable after about 16 weeks. Use the talk test, move steadily and choose propped-up or side-lying positions.

- Type: Guide
- Topic: Pregnancy & Early Parenthood › During Pregnancy
- Status: test content, not reviewed yet
- URL: https://twikka.com/learn/how-pregnancy-changes-your-body-for-exercise
- Updated: 2026-10-21

- **Your heart works harder:** resting heart rate rises by about 15–20 bpm, so the same pace can make your heart beat faster than before [1].
- **Use the talk test:** aim for an effort where you can talk but not sing [2].
- **Balance changes after the first trimester,** so take your time when you get up, turn or change direction [1].
- **After about 16 weeks, avoid lying flat on your back** for more than a few minutes [3].

## How does pregnancy change your heart rate and breathing during exercise?

Your heart works harder in pregnancy, so the same pace can feel more demanding than it did before. Resting heart rate rises by about 15–20 bpm over non-pregnant values [1]. At the same moderate effort late in pregnancy, your heart rate may be about 8 bpm higher than before pregnancy [4].

Breathlessness is common too, especially in late pregnancy, both at rest and after effort [1]. During steady exercise at a comfortable level, though, breathing tends to feel less of an effort [1].

A simple check works well. Moderate activity raises your heart rate, makes you breathe faster and feel warmer, and you can talk but not sing [2]. If you can't hold a conversation, slow down [3]. Brisk walking, water aerobics and stationary cycling at moderate effort are all examples [5].

How hard an effort feels doesn't track heart rate well in pregnancy, so you may be working at a much higher heart rate than it seems [1]. If you use a heart rate monitor, combining it with how hard the effort feels may be the best way to keep track of intensity [4]. Let the pace come down rather than pushing through.

If breathlessness or dizziness doesn't settle once you stop, get medical attention; the emergency signs are listed at the end of this page. If it is mild and passes, still mention it to your midwife or doctor.

> **Try this:** On your next walk, find a pace where you can talk but not sing. If you can't finish a sentence, slow down until you can.

## Why do your balance and joints feel different in pregnancy?

Pregnancy hormones such as relaxin make your ligaments softer and stretchier, and as your baby grows your posture and centre of gravity begin to change [6][7]. Relaxin together with changes in posture can lead to back pain [8]. As you gain weight, your tummy and pelvic floor muscles stretch and your balance shifts forward, so the joints of your lower back and pelvis work harder [6]. How much the hormones make joints unstable isn't clear yet, so don't assume your joints are loose or unreliable [1].

Balance is affected after the first trimester, and pregnant women are 2–3 times more likely to be injured by falling than non-pregnant women [1]. Walking changes as well: steps become slower and shorter, and your feet sit further apart, which seems to help keep you steady from side to side [9]. Weight through your feet also moves from the heel towards the midfoot and forefoot [9].

Pelvic girdle pain is common, reportedly affecting 20% of pregnant women [10]. Staying active may help: exercise in pregnancy reduces how severe low back and pelvic pain are, although it doesn't appear to reduce how often they happen [11].

What to do:

- Take your time when getting up, turning or changing direction.
- Choose activities with little risk of falling, on steady, even surfaces.
- Keep up gentle, regular activity.
- Mention new back or pelvic pain to your midwife, doctor or physiotherapist.

## Which positions become uncomfortable or unsafe as your bump grows?

The main one to watch is lying flat on your back, especially after about 16 weeks. The weight of your bump can press on the main blood vessel bringing blood back to your heart, which could cause low blood pressure and make you feel dizzy [3]. Resting on your back has been linked with symptoms of low blood pressure in up to 10% of pregnant women [12]. Standing motionless for long periods can have a similar effect in some women [1].

Most national guidelines advise against exercising on your back after 16 weeks, though that advice rests mainly on expert opinion [12]. How much risk it carries isn't clear yet, so the cautious choice is to avoid it.

What to do instead:

- **Skip sit-ups** and similar exercises that keep you on your back for more than a few minutes [3].
- **Prop yourself up with pillows or lie on your side.** Pelvic girdle pain exercises are safe throughout pregnancy, but positions may need adapting as your bump grows [13].
- **Try hands and knees** for gentle movements, with knees under hips and hands under shoulders [14].
- **Get up slowly.** You may feel faint after lying on your back or standing up quickly, and it's important to sleep on your side after 28 weeks [8].
- **On days when it all feels like too much,** do what you can and return to your usual routine when you're able [5].

If lying on your back makes you feel faint or dizzy, change position and get up slowly. Dizziness that keeps coming back should be checked by your midwife or doctor.

## When to check with a health professional

If you're starting exercise after a long break, it's always a good idea to see your doctor first.

For an injury or a health condition, see a health professional, such as your doctor or a physio.

If you feel uncomfortable or sore in a muscle or joint, stop or ease off, and get advice from your midwife, doctor or physiotherapist if it persists or gets worse.

In pregnancy, bleeding from the vagina, fluid leaking, regular painful contractions, the baby moving less than usual, pain or swelling in a calf, or a bad headache or changes in vision need your midwife, doctor or maternity unit straight away, even if they seem mild.

Call your local emergency number for chest pain or pressure (or pain spreading to the arm, neck, jaw or back, especially with sweating or feeling sick), severe breathlessness, fainting or collapse, signs of a stroke, a serious injury, or someone who isn't safe. In pregnancy, heavy bleeding is also an emergency.

If you have thoughts of self-harm, contact a local crisis line (findahelpline.com lists free services in every country), or call your local emergency number if you are in danger.

## Quick answers

### How much activity should I aim for in pregnancy?

Women with no medical reason not to should aim for at least 150 minutes of moderate aerobic activity a week, with a variety of aerobic and muscle-strengthening activities; gentle stretching may also help. Activity of any length counts, so short walks add up. If you were regularly active before pregnancy, you can carry on.

### Is it safe to lift weights or strength train while pregnant?

Strength work is part of a varied routine, but heavy lifting with breath-holding (the Valsalva manoeuvre) raises blood pressure and may temporarily reduce blood flow to the baby. Check with your midwife or doctor before trying heavy strength training, and breathe steadily through any lifting you do.

### Is it safe to start exercising for the first time when I'm pregnant?

Physical activity in pregnancy is not linked with miscarriage, stillbirth, preterm birth or birth defects. Start with small amounts, such as short, easy walks, and build up how often and how long over time. Some activity is better than none, and any length of activity counts.

## Sources

1. Bø K et al. (2016). Exercise and pregnancy in recreational and elite athletes: 2016 evidence summary from the IOC expert group meeting, Lausanne. Part 1-exercise in women planning pregnancy and those who are pregnant. British Journal of Sports Medicine. https://doi.org/10.1136/bjsports-2016-096218
2. NHS. Exercise in pregnancy. https://www.nhs.uk/pregnancy/keeping-well/exercise/
3. NHS. Exercising in pregnancy - Best Start in Life. https://www.nhs.uk/best-start-in-life/pregnancy/exercising-in-pregnancy/
4. Evenson KR, Hesketh KR (2023). Monitoring Physical Activity Intensity During Pregnancy. American Journal of Lifestyle Medicine. https://pmc.ncbi.nlm.nih.gov/articles/PMC9830234/
5. Mottola MF et al. (2018). No. 367-2019 Canadian Guideline for Physical Activity throughout Pregnancy. Journal of Obstetrics and Gynaecology Canada. https://doi.org/10.1016/j.jogc.2018.07.001
6. Whittington Health NHS Trust (2026). Pelvic girdle pain (PGP) and low back (lumbar) pain in pregnancy. https://www.whittington.nhs.uk/mini-apps/leaflet/Default.asp?id=601&print=1
7. Plymouth Hospitals NHS Trust. Antenatal exercises (patient information leaflet). https://www.plymouthhospitals.nhs.uk/display-pil/pil-antenatal-exercises-3961
8. Health New Zealand. Common issues in pregnancy. https://www.healthnz.govt.nz/health-topics/pregnancy-maternity/health-problems-in-pregnancy/common-issues
9. Forczek W et al. (2018). Gait assessment of the expectant mothers - Systematic review. Gait & Posture. https://doi.org/10.1016/j.gaitpost.2018.02.024
10. Sward L et al. (2023). Pelvic Girdle Pain in Pregnancy: A Review. Obstetrical & Gynecological Survey. https://doi.org/10.1097/ogx.0000000000001140
11. Davenport MH et al. (2019). Exercise for the prevention and treatment of low back, pelvic girdle and lumbopelvic pain during pregnancy: a systematic review and meta-analysis. British Journal of Sports Medicine. https://doi.org/10.1136/bjsports-2018-099400
12. Mottola MF et al. (2019). Is supine exercise associated with adverse maternal and fetal outcomes? A systematic review. British Journal of Sports Medicine. https://doi.org/10.1136/bjsports-2018-099919
13. Dynamic Health. Pelvic girdle pain in pregnancy. https://dynamichealth.nhs.uk/help-and-advice/pelvic-health/pelvic-girdle-pain-in-pregnancy/
14. Cambridge University Hospitals NHS Foundation Trust. Pelvic girdle pain (PGP) in pregnancy. https://www.cuh.nhs.uk/patient-information/pelvic-girdle-pain-pgp-in-pregnancy/

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Source: Twikka (https://twikka.com/learn/how-pregnancy-changes-your-body-for-exercise). General information about physical activity, not medical advice.